Metallicity of M dwarfs I. A photometric calibration and impact on the mass-luminosity rela
应用光伏学题库
一、选择题（在下列每题的四个选项中，只有一个选项是符合试题要求的。
请把答案填入答题框中相应的题号下。
每小题1分，共10分）二、填空题（本大题共10小题，每小题1分，共10分）§01. ★Photovoltaics (often abbreviated as PV ) is a simple and elegant method of harnessing the sun's energy.2. ★PV devices (solar cells) are unique in that they directly convert the incident solar radiation into electricity , with no noise, pollution or moving parts, making them robust, reliable and long lasting.3. ★Photovoltaics is the process of converting sunlight directly into electricity using solar cells .4. ★The first photovoltaic device was demonstrated in 1839 by Edmond Becquerel, as a young 19 year old working in his father‘s laboratory in Fra nce.5. ★The first practical photovoltaic device was demonstrated in the 1950s.6. ★★Research and development of photovoltaics received its first major boost from the space industry in the 1960s.§11. ★A photon is characterized by either a wavelength, denoted by λ, or equivalently an energy, denoted by E.2. ★★There is an inverse relationship between the energy of a photon (E ) and the wavelength of the light (λ) given by the equation: ，.3. ★★The photon flux is defined as the number of photons per second per unit area.4. ★★★The total power density emitted from a light source can be calculated by integrating the spectral irradiance over all wavelengths or energies of interest.5. ★★In the analysis of solar cells, the photon flux is often needed as well as the spectral irradiance.6. ★The blackbody sources which are of interest to photovoltaics, emit light in the visible region.7. ★★★The spectral irradiance from a blackbody is given by Plank's radiation law.8. ★★The peak wavelength of the spectral irradiance is determined by differentiating the spectral irradiance and solving the derivative when it equals 0. The result is known as Wien‗s Law: ()2900p m T λμ=.9. ★★★Solar radiation in space: sun H D R H ⨯=220.H sun =5.961×107W/m 2.10. ★The solar radiation outside the earth's atmosphere have been defined as a standard value called air masszero (AM0) and takes a value of 1.353 kW/m 2.11. ★The spectral irradiance from a blackbody at 6000 K (at the same apparent diameter as the sun when viewedfrom earth); from the sun‘s photosphere as observed just outside earth‘s atmosphere (AM0); and from the sun‘s photosphere after having passed through 1.5 times the thickness of earth‘s atmosphere (AM1.5G).12. ★★The Air Mass is defined as: θ is the angle from the vertical (zenithangle).13. ★★When the sun is directly overhead, the Air Mass is 1.14. ★The standard spectrum at the Earth's surface is called AM1.5G (the G stands for global and includes bothdirect and diffuse radiation) or AM1.5D (which includes direct radiation only), these calculations give approximately 970 W/m 2 for AM1.5G 。
河南省平顶山市叶县高级中学2024-2025学年高二上学期9月月考英语试卷
河南省平顶山市叶县高级中学2024-2025学年高二上学期9月月考英语试卷一、听力选择题1．What did the woman buy for her mum?A．A hat.B．A coat.C．A T- shirt.2．What does the man like doing?A．Travelling alone.B．Joining a guided tour.C．Backpacking with friends. 3．Why is the woman broke at the end of the month?A．She likes shopping.B．She doesn't work hard.C．She earns little money. 4．What time will the man’s party probably start?A．At 7: 30 p.m.B．At 8: 00 p.m.C．At 11: 00 p.m.5．Where are the speakers probably?A．In a hospital.B．In the police office.C．On the street.听下面一段较长对话，回答以下小题。
6．What should the woman do to order checks?A．Wait in a line.B．Fill in a form.C．Check the mail.7．When will the woman probably get the check?A．In two days.B．In four days.C．In a week.听下面一段较长对话，回答以下小题。
8．What is the man’s attitude towards art class?A．Favourable.B．Unconcerned.C．Worried.9．What does the woman mean about talent?A．She wants to be a painter too.B．She knows how to draw and paint.C．She hopes she could have some kind of talent.10．What are the speakers mainly talking about?A．The man’s hobby.B．The talent of the woman.C．The woman’s favourite class.听下面一段较长对话，回答以下小题。
高三英语艺术批评深度分析方法单选题30题
高三英语艺术批评深度分析方法单选题30题1. In the context of art criticism, the term "aesthetic value" refers to _____.A. the financial worth of a work of artB. the artistic quality and beauty of a pieceC. the popularity of the artistD. the historical significance of the art答案：B。
“aesthetic value”意为美学价值，指的是艺术作品的艺术质量和美感。
选项A 指的是艺术作品的经济价值；选项C 指的是艺术家的受欢迎程度；选项 D 指的是艺术的历史意义。
均不符合“aesthetic value”的含义。
2. When analyzing a painting, one should pay attention to _____.A. the price it was sold forB. the colors and compositionC. the number of people who like itD. the materials used to create it答案：B。
分析一幅画时，应关注颜色和构图。
选项A 指的是其出售价格，不是分析绘画的重点；选项C 指喜欢它的人数，与对绘画的专业分析无关；选项D 指创作所用材料，不如颜色和构图重要。
3. In art criticism, the phrase "formal analysis" involves _____.A. studying the artist's personal lifeB. examining the style and structure of the artC. researching the art market trendsD. looking at the social impact of the art答案：B。
2022年考研考博-考博英语-燕山大学考试全真模拟易错、难点剖析B卷(带答案)第84期
2022年考研考博-考博英语-燕山大学考试全真模拟易错、难点剖析B卷（带答案）一.综合题(共15题)1.单选题______ she realized it was too late to go home.问题1选项A.No sooner it grew dark thanB.Hardly did it grow dark thatC.Scarcely had it grown dark thanD.It was not until dark that【答案】D【解析】【试题解析】考查倒装句。
句意：直到天黑，她才意识到太晚了，不能回家了。
A、B、C选项意思为“一……就”；A选项no sooner…than置于句首，前面部分倒装；B选项hardly…when“”和C选项scarcely…when是固定搭配。
D选项it is not until…that“直到……才”用法正确。
因此D选项正确。
2.单选题The ______ of Confucius built the temple in memory of their ancestor.问题1选项A.descendantsB.predecessorsC.correspondentsD.opponents【答案】A【解析】【试题解析】考查名词辨析。
A选项descendants“后代，晚辈”；B选项predecessors“前任；前一代”；C选项correspondents“通讯员”；D选项opponents“对手”。
句意：孔子的______建造这座庙来纪念他们的祖先。
根据语境，在这里孔子的后代纪念孔子比较合理，A选项descendants“后代，晚辈”符合题意。
因此A选项正确。
3.单选题He felt ______ of what he had done in school.问题1选项A.shyB.ashC.advisableD.ashamed【答案】D【解析】【试题解析】考查词义辨析。
备战高考英语名校模拟真题速递(江苏专用)专题06 阅读理解之说明文10篇(第六期)(含解析)
备战高考英语名校模拟真题速递(江苏专用)第六期专题06 阅读理解之说明文10篇（2024·江苏南通·模拟预测）Mark Temple, a medical molecular (分子的) biologist, used to spend a lot of time in his lab researching new drugs for cancer treatments. He would extract DNA from cells and then add a drug to see where it was binding (结合) along the chemical sequence(序列). Before he introduced the drug, he’d look at DNA combination on a screen to see what might work best for the experiment, but the visual readout of the sequences was often unimaginably large.So Temple wondered if there was an easier way to detect favorable patterns. I realized I wanted to hear the sequence,” says Temple, who is also a musician. He started his own system of assigning notes to the different elements of DNA — human DNA is made of four distinct bases, so it was easy to start off with four notes — and made a little tune out of his materials. This trick indeed helped him better spot patterns in the sequences, which allowed him to make better choices about which DNA combinations to use.Temple isn’t the first person to turn scientific data into sound. In the past 40 years, researchers have gone from exploring this trick as a fun way to spot patterns in their studies tousing it as a guide to discovery. And the scientific community has come to realize that there’s some long-term value in this type of work. Temple, who from that first experiment has created his own algorithmic software to turn data into sound, believes the resulting music can be used to improve research and science communication.So Temple decided to add layers of sound to make the sonification (可听化) into songs. He sees a clear difference between “sonification” and “musification”. Using sound to represent data is scientific, but very different from using creative input to make songs. The musical notes from DNA may be melodic to the human ear, but they don’t sound like a song you’d listen to on the radio. So when he tried to sonify the virus, he added layers of drums and guitar, and had some musician friends add their own music to turn the virus into a full-blown post-rock song.Temple sees this work as an effective communication tool that will help a general audience understand complex systems in biology. He has performed his songs in public at concert halls in Australia.1．What is Mark Temple’s purpose in turning DNA data into sound?A．To help him fight boredom.B．To develop his creative ability.C．To make his drug more powerful.D．To aid the process of his experiments.2．What can we learn about Temple’s system?A．Its effect remains to be seen.B．It failed to work as expected.C．It is too complicated to operate.D．It has produced satisfying results.3．Why did Temple try to make the virus sound like real music when sonifying it?A．To get rid of public fear of the virus.B．To show h1s talent in producing music.C．To facilitate people’s understanding of science.D．To remind people or the roe or Science in art creation.4．What does the text mainly talk about?A．Why scientists are turning molecules into music.B．How scientists help the public understand science.C．Why music can be the best way to present science.D．How music helps scientists conduct their research.（2024·江苏南通·模拟预测）Phonics, which involves sounding out words syllable (音节) by syllable, is the best way to teach children to read. But in many classrooms, this can be a dirty word. So much so that some teachers have had to take phonics teaching materials secretly into the classroom. Most American children are taught to read in a way that study after study has found to be wrong.The consequences of this are striking. Less than half of all American adults were efficient readers in 2017. American fourth graders rank 15th on the Progress in International Literacy Study, an international exam.America is stuck in a debate about teaching children to read that has been going on for decades. Some advocate teaching symbol sound relationships (the sound k can be spelled as c, k, ck, or ch) known as phonics Others support an immersive approach (using pictures of cat to learn the word cat), known as “whole language”. Most teachers today, almost three out of four according to a survey by EdWeek Research Centre in 2019, use a mix of the two methods called “balanced literacy”.“A little phonics is far from enough.” says Tenette Smith, executive director of elementary education and reding at Mississippi’s education department. “It has to be systematic and explicitly taught.”Mississippi, often behind in social policy, has set an example here. In a state once blamed for its low reading scores, the Mississippi state legislature passed new literacy standards in 2013.Since then Mississippi has seen remarkable gains., Its fourth graders have moved from 49th (out of 50 states) to 20th on the National assessment of Educational Progress, a nationwide exam.Mississippi’s success is attributed to application of reading methods supported by a body of research known as the science of reading. In 1997 experts from the Department of Education ended the “reading war” and summed up the evidence. They found that phonics, along with explicit instruction in phonemic (音位的) awareness,fluency and comprehension, worked best.Yet over two decades on, “balanced literacy” is still being taught in classrooms. But advances in statistics and brain imaging have disproved the whole-language method. To the teacher who is an efficient reader, literacy seem like a natural process that requires educated guessing, rather than the deliberate process emphasized by phonics. Teachers can imagine that they learned to read through osmosis(潜移默化) when they were children. Without proper training, they bring this to classrooms.5．What do we learn about phonics in many American classrooms?A．It is ill reputed.B．It is mostly misapplied.C．It is totally ignored.D．It is seemingly contradictory.6．What has America been witnessing?A．A burning passion for improving teaching methods.B．A lasting debate over how to teach children to read.C．An increasing concern with children’s inadequacy in literacy.D．A forceful advocacy of a combined method for teaching reading.7．What’s Tenette Smith’s attitude towards “balanced literacy”?A．Tolerant.B．Enthusiastic.C．Unclear.D．Disapproving.8．According to the author what contributed to Mississippi’s success?A．Focusing on the natural process rather than deliberate training.B．Obtaining support from other states to upgrade teaching methods.C．Adopting scientifically grounded approaches to teaching reading.D．Placing sufficient emphasis upon both fluency and comprehension.（2024·江苏泰州·一模）A satellite is an object in space that orbits around another. It has two kinds — natural satellites and artificial satellites. The moon is a natural satellite that moves around the earth while artificial satellites are those made by man.Despite their widespread impact on daily life, artificial satellites mainly depend on different complicated makeups. On the outside, they may look like a wheel, equipped with solar panels or sails. Inside, the satellites contain mission-specific scientific instruments, which include whatever tools the satellites need to perform their work. Among them, high-resolution cameras and communication electronics are typical ones. Besides, the part that carries the load and holds all the parts together is called the bus.Artificial satellites operate in a systematic way just like humans. Computers function as the satellite’s brain, which receive information, interpret it, and send messages back to the earth. Advanced digital cameras serve asthe satellite’s eyes. Sensors are other important parts that not only recognize light, heat, and gases, but also record changes in what is being observed. Radios on the satellite send information back to the earth. Solar panels provide electrical power for the computers and other equipment, as well as the power to move the satellite forward.Artificial satellites use gravity to stay in their orbits. Earth’s gravity pulls everything toward the center of the planet. To stay in the earth’s orbit, the speed of a satellite must adjust to the tiniest changes in the pull of gravity. The satellite’s speed works against earth’s gravity just enough so that it doesn’t go speeding into space or falling back to the earth.Rockets carry satellites to different types and heights of orbits, based on the tasks they need to perform. Satellites closer to the earth are in low-earth orbit, which can be 200-500 miles high. The closer to the earth, the stronger the gravity is. Therefore, these satellites must travel at about 17,000 miles per hour to keep from falling back to the earth, while higher-orbiting satellites can travel more slowly.9．What is Paragraph 2 of the text mainly about?A．The appearance of artificial satellites.B．The components of artificial satellites.C．The basic function of artificial satellites.D．The specific mission of artificial satellites.10．What is the role of computers in artificial satellites?A．Providing electrical power.B．Recording changes observed.C．Monitoring space environment.D．Processing information received.11．How do artificial satellites stay in their orbits?A．By relying on powerful rockets to get out of gravity.B．By orbiting at a fixed speed regardless of gravity’s pull.C．By changing speed constantly based on the pull of gravity.D．By resisting the pull of gravity with advanced technologies.12．Why do satellites in higher-earth orbit travel more slowly?A．They are more affected by earth’s gravity.B．They take advantage of rockets more effectively.C．They have weaker pull of gravity in higher orbits.D．They are equipped with more advanced instruments.（2024·江苏泰州·一模）The human body possesses an efficient defense system to battle with flu viruses. The immune system protects against the attack of harmful microbes (微生物) by producing chemicals called antibodies, which are programmed to destroy a specific type of microbe. They travel in the blood and search the body for invaders (入侵者). When they find an invasive microbe, antibodies attack and destroy any cell thatcontains the virus. However, flu viruses can be a terrible enemy. Even if your body successfully fights against the viruses, with their ability to evolve rapidly, your body may have no protection or immunity from the new ones.Your body produces white blood cells to protect you against infectious diseases. Your body can detect invading microbes in your bloodstream because they carry antigens in their proteins. White blood cells in your immune system, such as T cells, can sense antigens in the viruses in your cells. Once your body finds an antigen, it takes immediate action in many different ways. For example, T cells produce more antibodies, call in cells that eat microbes, and destroy cells that are infected with a virus.One of the best things about the immune system is that it will always remember a microbe it has fought before and know just how to fight it again in the future. Your body can learn to fight so well that your immune system can completely destroy a virus before you feel sick at all.However, even the most cautious people can become infected. Fortunately, medical scientists have developed vaccines (疫苗), which are weakened or dead flu viruses that enter a person’s body before the person gets sick. These viruses cause the body to produce antibodies to attack and destroy the strong viruses that may invade during flu season.13．Why does flu pose a threat to the immune system?A．Microbes contain large quantities of viruses.B．Antibodies are too weak to attack flu viruses.C．The body has few effective ways to tackle flu.D．It’s hard to keep pace with the evolution of viruses.14．What does the underlined word “antigens” refer to in Paragraph 2?A．The cell protecting your body from viruses.B．The matter serving as the indicator of viruses.C．The antibodies helping to fight against viruses.D．The substance destroying cells infected with viruses.15．How do vaccines defend the body against the flu viruses?A．They strengthen the body’s immune system.B．They battle against weakened or dead viruses.C．They help produce antibodies to wipe out viruses.D．They expose the body to viruses during flu season.16．Which of the following is a suitable title for the text?A．Antibodies Save Our Health.B．Vaccines Are Of Great Necessity.C．Infectious Flu Viruses Are Around.D．Human Body Fights Against Flu Viruses.（23-24高三下·江苏扬州·开学考试）A recent study, led by Professor Andrew Barron, Dr. HaDi MaBouDi, and Professor James Marshall, illustrates how evolution has fine-tuned honey bees to make quick judgments while minimizing danger.“Animal lives are full of decisions,” says Professor Barron. “A honey bee has a brain smaller than a sesame (芝麻) seed. And yet it can make decisions faster and more accurately than’ we can. A robot programmed to do a bee’s job would need the backup of a supercomputer.”Bees need to work quickly and efficiently. They need to make decisions. Which flower will have a sweet liquid? While they’re flying, they face threats from the air. While landing, they’re vulnerable to potential hunter, some of which pretend to look like flowers.Researchers trained 20 bees to associate each of the five different colored “flower disks” with their visit history of reward and punishment. Blue flowers always had sugar juice. Green flowers always had a type of liquid with a bitter taste for bees. Other colors sometimes had glucose (葡萄糖). “Then we introduced each bee to a ‘garden’ with artificial ‘flowers’. We filmed each bee and timed their decision-making process,” says Dr. MaBouDi. “If the bees were confident that a flower would have food, they quickly decided to land on it, taking an average of 0.6 seconds. If they were confident that a flower wouldn’t have food, they made a decision just as quickly. If unsure, they took on average 1.4 seconds, and the time reflected the probability that a flower had food.”The team then built a computer model mirroring the bees’ decision-making process. They found the structure of the model looked very similar to the physical layout of a bee brain. “AI researchers can learn much from bees and other ‘simple’ animals. Millions of years of evolution has led to incredibly efficient brains with very low power requirements,” says Professor Marshall who co-founded a company that uses insect brain patterns to enable machines to move autonomously, like nature.17．Why does Professor Andrew Barron mention “a supercomputer”?A．To illustrate how a honey bee’s brain resemble each other.B．To explain how animals arrive at informed decisions fast.C．To demonstrate how a robot could finish a honey bee’s job.D．To emphasize how honey bees make decisions remarkably.18．Which of the following can best replace “vulnerable to” underlined in paragraph 3?A．Easily harmed by.B．Highly sensitive to.C．Deeply critical to.D．Closely followed by.19．What influenced the speed of trained bees in making decisions?A．Their judgments about reward and punishment.B．Their preference for the colors of flower disks.C．Their confirmation of food’s presence and absence.D．Their ability to tell real flowers from artificial ones.20．What message does Professor James Marshall want to give us?A．The power of bee brains is underestimated.B．Biology can inspire future AI.C．Autonomous machines are changing nature.D．AI should be far more efficient.（23-24高三下·江苏扬州·开学考试）Are you frequently overwhelmed by the feeling that life is leaving you behind, particularly when you look through social media sites and see all the exciting things your friends are up to? If so, you are not alone.FOMO, or Fear of Missing Out, refers to the perception that other people’s lives are superior to our own, whether this concerns socializing, accomplishing professional goals or generally having a more deeply fulfilling life. It shows itself as a deep sense of envy, and constant exposure to it can have a weakening effect on our self-respect. The feeling that we are always being left out of fundamentally important events, or that our lives are not living up to the image pictured by others, can have long-term damaging psychological consequences.While feelings of envy and inadequacy seem to be naturally human, social media seems to have added fuel to the fire in several ways. The reason why social media has such a triggering effect is tied to the appeal of social media in the first place: these are platforms which allow us to share only the most glowing presentations of our accomplishments, while leaving out the boring aspects of life. While this kind of misrepresentation could be characterized as dishonest, it is what the polished atmosphere of social media seems to demand.So how do we avoid falling into the trap of our own insecurities? Firstly, consider your own social media posts. Have you ever chosen photos or quotes which lead others to the rosiest conclusions about your life? Well, so have others and what they’ve left hidden is the fact that loneliness and boredom are unavoidably a part of everyone’s day-to-day life, and you are not the only one feeling left out. Secondly, learn to appreciate the positives. You may not be a regular at exciting parties or a climber of dizzying peaks, but you have your health, a place to live, and real friends who appreciate your presence in their lives. Last of all, learn to shake things off. We are all bombarded daily with images of other people’s perfection, but really, what does it matter? They are probably no more real than the most ridiculous reality TV shows.21．What can frequently experiencing FOMO lead to?A．Harm to one’s feeling of self-value.B．A more satisfying and fulfilling social life.C．Damage to one’s work productivity.D．Less likelihood of professional success.22．What does the author suggest in the third paragraph?A．The primary reason for FOMO is deeply rooted in social media.B．Our own social media posts help us feel much more confident.C．People who don’t share posts on social media are more bored.D．Social media’s nature enhances envious feelings and self-doubt.23．Why does the author mention reality TV shows in the last paragraph?A．To emphasize how false what we see on social media can be.B．To indicate how complicated social media has turned to.C．To figure out how popular and useful social media has been.D．To point out how educational value reality TV shows reflect.24．Which is the best title for the text?A．Myths and misconceptions about FOMO B．FOMO: what it is and how to overcome itC．How FOMO is changing human relationships D．We’re now all in the power of “FOMO addiction”（23-24高三上·江苏泰州·阶段练习）While Huawei’s official website does not call Mate 60 Pro a 5G smartphone, the phone’s wideband capabilities are on par with other 5G smartphones, raising a related question: As a leader in 5G technology, has Huawei managed to develop a 5G smartphone on its own?The answer is not simple. Huawei, as a pioneer in global 5G communication equipment, has played a leading role in the commercialization of 5G technology, with its strong system design and fields such as baseband chips (基带芯片), baseband processors and 5G modems.However, basebands and modems are not the only aspects that define 5G wireless communication. The stability and high-quality signals of a 5G smartphone also depend on other critical components such as RF transceivers (射频收发器) and RF front ends and antennas (天线) . These components are largely dominated by four US high-tech giants—Qualcomm, Avago Technologies, Ansem and Qorvo—which account for a surprising global market share.Huawei has faced significant challenges in getting critical components because of the sanctions imposed by the United States which are primarily responsible for the inability of the Chinese company to launch 5G smartphones in the past three years. However, Mate 60 Pro, despite not being labeled a 5G device, exhibits mobile network speeds comparable to Apple’s latest 5G-enabled devices, offering a stable communication experience. This suggests Huawei has, over the past three years, overcome the 5G development and production limits due to the US sanctions by cooperating with domestic partners, and establishing an independent and controllable stable supply chain.Considering that Huawei has not explicitly marketed this device as a 5G smartphone, it is possible that it isyet to fully overcome some key core technological and componential shortcomings. For the time being, we can consider Huawei’s Mate 60 Pro as 4.99G. But when combined with the satellite communication capabilities of Mate 60 Pro, it is clear Huawei has been trying to find more advanced wireless communication solutions for smartphones and making significant progress in this attempt. This should be recognized as a remarkable endeavor, even a breakthrough.25．What do the underlined words “on par with” mean in Paragraph 1?A．as poor as.B．as good as.C．worse than.D．better than.26．Why was it tough for Huawei to develop a 5G smartphone three years ago?A．Its system design and fields needed to be updated.B．It only focused on the commercialization of 5G technology.C．It was unwilling to cooperate with high-tech giants in America.D．It lacked critical components mainly controlled by US high-tech giants.27．What does Paragraph 4 centre on?A．The US sanctions.B．Critical components.C．Apple’s latest 5G-enabled devices.D．Progress in Mate 60 Pro.28．What is the text mainly about?A．Huawei faced with significant challengesB．Huawei’s Mate 60 Pro—a 5G smartphoneC．Huawei’s Mate 60 Pro—a remarkable breakthroughD．Huawei leading in global 5G communication equipment（23-24高三上·江苏无锡·期末）Blue-light-filtering glasses (滤蓝光眼镜) have become an increasingly popular solution for protecting our eyes from electronic screens’ near-inescapable glow — light that is commonly associated with eyestrain (眼疲劳). In recent years they’ve even become fashion statements that are recognized by celebrities and ranked in style guides. But a recent review paper shows such glasses might not be as effective as people think.The paper, published last week in Cochrane Database of Systematic Reviews, analyzed data from previous trials that studied how blue-light-filtering glasses affect vision tiredness and eye health. The study’s authors found that wearing blue-light-filtering glasses does not reduce the eyestrain people feel after using computers.“It’s an excellent review,” says Mark Rosenfield, a professor at the State University of New York College of Optometry, who was not involved in the study. “The conclusions are no surprise at all. There have been a number of studies that have found exactly the same thing, that there’s just no evidence that blue-blocking glasses have anyeffect on eyestrain.” He adds that the new review reinforces the fact that there is virtually no evidence that blue-blocking glasses affect eyestrain despite them being specifically marketed for that purpose. As for using blue-light-filtering eyeglasses for eye health, for now, Rosenfield says, “there’s nothing to support people buying them”.The strain we may feel while staring at our phone or computer screen too long is likely to be caused by multiple factors, such as bad habits or underlying conditions, an associate professor of vision science at the University of Melbourne, Downie says. She argues that how we interact with digital devices contributes more to eyestrain than screens’ blue light does. Changing the frequency and duration of screen usage and distancing one’s eyes from the screens might be more important in reducing discomfort, Downie says. She adds that people who experience eyestrain should see a doctor to assess whether they have an underlying health issue such as far-sightedness or dry eye disease.29．What can we know about blue-light-filtering glasses from the text?A．They can improve eyesight.B．They may not reduce eyestrain.C．They can promote eye health.D．They can help to cure eye diseases.30．What can we infer from paragraph 2?A．A great many professors were involved in the study.B．Blue-blocking glasses on the market are harmful to eyes.C．The finding of the study comes as a surprise to the public.D．Data from previous trials help the study a lot.31．What does the underlined word “reinforces” mean in paragraph 3?A．Denies.B．Opposes.C．Strengthens.D．Evaluates.32．What should we do if we suffer from eyestrain according to Downie?A．Wear blue-light-filtering glasses.B．Have an examination in the hospital.C．Stop staring at the screen for ever.D．Focus on the frequency of phone usage.（2024·江苏连云港·一模）Not all birds sing, but several thousand species do. They sing to defend their territory and croon (柔声唱) to impress potential mates. “Why birds sing is relatively well-answered,” says Iris Adam, a behavioral neuroscientist. However, the big question for her was why birds sing so much.“As soon as you sing, you reveal yourself,” Adam says. “Like, where you are and where your territory is.” In a new study published in the journal Nature Communications, Adam and her co-workers offer a new explanation for why birds take that risk. They may have to sing a lot every day to give their vocal (发声的) muscles the regular exercise they need to produce top-quality songs. To figure out whether the muscles that produce birdsongsrequire daily exercise, Adam designed an experiment on zebra finches-the little Australian songbirds.She prevented them from singing for a week by keeping them in the dark cage almost around the clock. Light is what galvanizes the birds to sing, so she had to work to keep them from warbling (鸣叫). “The first two or three days, it’s quite easy,” she says. “But the longer the experiment goes, the more they are like, ‘I need to sing.’” At that point, she’d tap the cage and tell them to stop singing.After a week, the birds’ singing muscles lost half their strength. But Adam wondered whether that impacted the quality of songs. When she played a male’s song before and after the seven days of darkness, she couldn’t hear a difference. But when Adam played it to a group of female birds, six out of nine preferred the song that came from a male who’d been using his singing muscles daily.Adam’s conclusion shows that “songbirds need to exercise their vocal muscles to produce top-performance songs. If they don’t sing, they lose performance, and their songs get less attractive to females.” This may help explain songbirds’ continuous singing.It’s a good rule to live by, whether you’re a bird or a human-practice makes perfect, at least when it comes to singing one’s heart out.33．According to Iris Adam, birds sing so much to ______.A．warn other birds of risks B．produce more songsC．perform perfectly in singing D．defend their territory34．What does the underlined word “galvanizes” in Paragraph 3 mean?A．Prepares.B．Stimulates.C．Forbids.D．Frightens.35．What do we know about the caged birds in the experiment?A．They lost the ability to sing.B．They strengthened their muscles.C．Their songs showed no difference.D．Their songs became less appealing.36．What may Iris Adam agree with?A．The songbirds live on music.B．The songbirds are born singers.C．Daily exercise keeps birds healthy.D．Practice makes birds perfect singers.（23-24高三上·江苏扬州·期末）Sometimes called “Earth’s twin,” Venus is similar to our world in size and composition. The two rocky planets are also roughly the same distance from the sun, and both have an atmosphere. While Venus’s cold and unpleasant landscape does make it seem far less like Earth, scientists recently detected another striking similarity between the two, the presence of active volcanoes.When NASA’s Magellan mission mapped much of the planet with radar in the 1990sit revealed an。
High-excitation OH and H_2O lines in Markarian 231 the molecular signatures of compact far-
a r X i v :0711.2281v 5 [a s t r o -p h ] 24 D e c 2007Draft version February 2,2008Preprint typeset using L A T E X style emulateapj v.10/09/06HIGH-EXCITATION OH AND H 2O LINES IN MARKARIAN 231:THE MOLECULAR SIGNATURES OFCOMPACT FAR-INFRARED CONTINUUM SOURCES ∗Eduardo Gonz ´alez-Alfonso Universidad de Alcal´a de Henares,Departamento de F ´ısica,Campus Universitario,E-28871Alcal´a de Henares,Madrid,SpainHoward A.SmithHarvard-Smithsonian Center for Astrophysics,60Garden Street,Cambridge,MA 02138,USAMatthew L.N.AshbyHarvard-Smithsonian Center for Astrophysics,60Garden Street,Cambridge,MA 02138,USAJacqueline FischerNaval Research Laboratory,Remote Sensing Division,Washington,DC 20375,USALuigi SpinoglioIstituto di Fisica dello Spazio Interplanetario,CNR via Fosso del Cavaliere 100,I-00133Roma,ItalyandTimothy W.GrundySpace Science &Technology Department,Rutherford Appleton Laboratory,Chilton,Didcot,Oxfordshire,OX110QX,UKDraft version February 2,2008ABSTRACTThe ISO/LWS far-infrared spectrum of the ultraluminous galaxy Mkn 231shows OH and H 2O lines in absorption from energy levels up to 300K above the ground state,and emission in the [O I]63µm and [C II]158µm lines.Our analysis shows that OH and H 2O are radiatively pumped by the far-infrared continuum emission of the galaxy.The absorptions in the high-excitation lines require high far-infrared radiation densities,allowing us to constrain the properties of the underlying continuum source.The bulk of the far-infrared continuum arises from a warm (T dust =70−100K),optically thick (τ100µm =1−2)medium of effective diameter 200-400pc.In our best-fit model of total luminosity L IR ,the observed OH and H 2O high-lying lines arise from a luminous (L/L IR ∼0.56)region with radius ∼100pc.The high surface brightness of this component suggests that its infrared emission is dominated by the AGN.The derived column densities N (OH) 1017cm −2and N (H 2O) 6×1016cm −2may indicate XDR chemistry,although significant starburst chemistry cannot be ruled out.The lower-lying OH,[C II]158µm,and [O I]63µm lines arise from a more extended (∼350pc)starburst region.We show that the [C II]deficit in Mkn 231is compatible with a high average abundance of C +because of an extreme overall luminosity to gas mass ratio.Therefore,a [C II]deficit may indicate a significant contribution to the luminosity by an AGN,and/or by extremely efficient star formation.Subject headings:galaxies:abundances —galaxies:individual (Mkn 231)—galaxies:ISM —galaxies:starburst —infrared:galaxies —radiative transfer1.INTRODUCTIONThe peculiar ultraluminous infrared galaxy (ULIRG,L IR ≥1012L ⊙)Markarian 231(Mkn 231,12540+5708)is the most luminous infrared galaxy in the local universe,with a 8-1000µm luminosity of 3.2×1012L ⊙(Sanders et al.2003),and may be a representative ex-∗BASEDON OBSERVATIONS WITH THE INFRARED SPACEOBSERVATORY,AN ESA PROJECT WITH INSTRUMENTS FUNDED BY ESA MEMBER STATES (ESPECIALLY THE PRINCIPAL INVESTIGATOR COUNTRIES:FRANCE,GER-MANY,NETHERLANDS,AND THE UNITED KINGDOM)AND WITH THE PARTICIPATION OF ISAS AND NASA.Electronic address:eduardo.gonzalez@uah.es Electronic address:hsmith@ Electronic address:mashby@ Electronic address:jackie.fischer@Electronic address:luigi.spinoglio@ifsi-roma.inaf.it Electronic address:t.w.grundy@ample of the link between AGNs and nuclear starbursts (Scoville 2004).A QSO-like nucleus is evident from many observations:optically it is classified as a Type 1Seyfert (Boksenberg et al.1977;Cutri,Rieke,&Lebofsky 1984;Baan,Salzer,&Lewinter 1998),it exhibits UV through IR polarization and broad absorption lines (Smith et al.1995),it has compact X-ray emission (e.g.,Gallagher et al.2002)and extremely compact mid-infrared emission (Soifer et al.2000),and in the radio it is variable and possesses a parsec scale jet (Ulvestad,Wrobel,&Carilli 1999;Taylor et al.1999).Nevertheless,there is also evidence of a compact star-burst in these results as well as in VLA observations of H I 21cm absorption (Carilli,Wrobel,&Ulvestad 1998),near-infrared observations (Tacconi et al.2002),and millimeter CO interferometry (Bryant &Scoville 1996;2Gonz´a lez-Alfonso et al.Downes&Solomon1998,hereafter DS98).Estimates for the starburst luminosity range from1/3to2/3of the bolometric luminosity(Davies et al.2004,DS98). Molecular observations have provided important clues about the concentration and kinematics of the gas in Mkn 231.DS98showed the presence of an inner nuclear disk of radius∼460pc in CO(2-1),and a more extended disk with lower brightness.Most of the molecular gas has been found to be dense(∼104cm−3)and warm (∼70K)from recent observations of CO and HCN sub-millimeter lines(Papadopoulos,Isaak,&van der Werf 2007,hereafter PIW07).Lahuis et al.(2007)have in-ferred embedded starburst chemistry in Mkn231and other ULIRGs based on mid-IR Spitzer observations of ro-vibrational bands of warm/hot HCN and C2H2,while Graci´a-Carpio et al.(2006)and Aalto et al.(2007)have inferred XDR chemistry and/or radiative pumping based on anomalous intensity ratios of millimeter lines of HCN, HNC,and HCO+.The bulk of the luminosity in ULIRGs is emitted at far-infrared(FIR)wavelengths,where a number of molecular tracers are detected,mostly in absorption. Prominent lines of OH and H2O were detected using ISO/LWS in the FIR spectrum of Arp220,along with absorption features by radicals such as NH and CH, revealing a chemistry that may be indicative of PDRs with plausible contribution by shocks and hot cores (Gonz´a lez-Alfonso et al.2004,hereafter Paper I).How-ever,those species are also expected to be enhanced in XDRs(Meijerink&Spaans2005),so that the dominant chemistry in the nuclear regions of ULIRGs remains un-certain.In Paper I,the ISO/LWS FIR spectrum of Arp 220was analyzed by means of radiative transfer calcula-tions,which included a non-local treatment of the molec-ular excitation by absorption of FIR photons.Paper I showed that the population of high-excitation OH and H2O rotational levels,in evidence from absorption in high-lying lines,is pumped through absorption of FIR continuum photons,a process that requires high FIR ra-diation densities.The detection of these lines thus not only reveals the chemical and excitation conditions in the absorbing regions,it also sheds light on the size and characteristics of the underlying continuum FIR source in spite of the low angular resolution currently available at these wavelengths.In this paper we extend our approach of Paper I to the ISO/LWS FIR spectrum of Mkn231,and show that this galaxy spectrum presents striking similarities to that of Arp220.Specifically,strong absorption in the high-excitation OH and H2O lines is also seen in Mkn231.Rotationally excited OH in Mkn231has been previously detected via the2Π1/2Λ-doublet transitions (Henkel,Guesten,&Baan1987).VLBI observations of the mega-maser OH emission at18cm wavelength trace an inner torus or disk of size∼100pc around the AGN (Kl¨o ckner,Baan,&Garrett2003),and MERLIN obser-vations were able to map essentially the whole single-dish mega-maser OH emission with angular resolution of ≈0.3′′(Richards et al.2005).We analyze here both the FIR continuum emission and the high-excitation OH and H2O lines,as well as the[C II]158µm and[O I]63µm emission lines.In§2we present the ISO spectroscopic observations of Mkn231.In§3wefirst analyze simple models for the FIR continuum emission from Mkn231, and then examine how well those models reproduce the observed FIR emission and absorption lines.§4summa-rizes our results.We adopt a distance to Mkn231of170 Mpc(H0=75km s−1Mpc−1and z≈0.042).2.OBSERVATIONS AND RESULTSThe full43-197µm spectrum of Mkn231(first shown and discussed by Harvey et al1999),was obtained with the LWS spectrometer(Clegg et al.1996)on board ISO (Kessler et al.1996).In Fig.1,it is compared with that of Arp220(Paper I)re-scaled to the same distance(170 Mpc).The grating spectral resolution is∼0.3µm in the 43–93µm interval(detectors SW1–SW5),and∼0.6µm in the80–197µm interval(detectors LW1–LW5),corre-sponding to∆v 103km s−1.The lines are thus unre-solved in velocity space.The≈80′′beam size ensures that all the FIR continuum and line emission/absorption from Mkn231(CO size∼4′′,DS98)lie within the ISO/LWS aperture.The data(TDT numbers5100540,18001306,and 60300241)were taken from the highly-processed data product(HPDP)dataset(called’Uniformly processed LWS01data’),and reduced using version10.1of the OffLine Processing(OLP)Pipeline system(Swinyard et al 1996).We performed subsequent data processing, including co-addition,scaling,and baseline remov-ing,using the ISO Spectral Analysis Package(ISAP; Sturm et al.1998)and our own routines.In order to obtain a smooth spectrum throughout the whole LWS range,theflux densities given by each detector were cor-rected by multiplicative scale factors.Corrections were less than25%except for detectors LW2and LW3(100–145µm),for which the corrections were30%.We thus attribute an uncertainty of30%to the overall continuum level,as well as for the linefluxes.Figure1shows that the FIR spectra of Mkn231and Arp220are similar in key aspects(see also Fischer et al. 1999),in particular the prominent molecular absorptions mostly due to OH doublets(that will be referred to here-after as lines)and the lack of strongfine-structure line emission typically seen in less luminous galaxies.A closer inspection of the pattern of line emission/absorption in both sources is shown in Fig.2,where the continuum-normalized spectra are compared.Of particular inter-est are the clear detections in both sources of the high-excitation OHΠ3/27/2−5/284µm andΠ3/29/2−7/2 65µm lines,with lower level energies of120and290 K,respectively(see§3).The330→221and331→220 H2O66-67µm lines,both with lower levels at195K, are also detected in Mkn231,as well as the tentatively identified220→111line at101µm.It is likely that the increased noise level atλ 160µm is responsible for the non-detection of the high-excitationΠ1/23/2−1/2 OH line in Mkn231,which is seen in strong emission in Arp220.While the high-excitation OH and H2O lines at65-67µm are of similar strength in Mkn231and Arp 220,the H2O lines at longer wavelengths are undoubtly weaker in Mkn231,as seen for the322→211,220→111 and221→110H2O lines at90,102,and108µm,re-spectively.The weakness of the latter lines in Mkn231 suggests that the region where the high-lying H2O lines are formed is relatively weak in the far-IR continuum at λ=90−108µm.The Mkn231spectrum thus suggestsHigh-excitation OH and H2O lines in Mkn2313that a warm component,with relatively weak contribu-tion to the far-IR continuum atλ 80µm,is responsible for the observed high-excitation absorptions(§3.3).Ta-ble1lists the linefluxes,continuumflux densities at the corresponding wavelengths,and equivalent widths for the lines detected in Mkn231.In the case of Arp220,we used high-spatial resolution continuum measurements available in the literature to infer that Arp220is optically thick even in the submil-limeter continuum(Paper I;see also Downes&Eckart 2007).The steeper decrease of theflux density with in-creasing wavelength in Mkn231,however,suggests that it has lower FIR continuum opacities(Fig.1).This ex-pectation is further reinforced by the detection in Mkn 231of the[N II]122µm line,a feature not seen in Arp 220(Fig.2).Other notable differences between both sources are that the[O I]63µm line is observed in emis-sion in Mkn231but in absorption in Arp220,and that the ground-state119,53,and79µm OH lines are signifi-cantly weaker in Mkn231(Fig.2).In modeling Arp220, we were forced to invoke an absorbing“halo”to account for these lines;in Mkn231,no such halo is required(§3). In the spectrum of Mkn231,the main119.3µm OH line appears to be slightly blue-shifted relative to the expected position,an effect we attribute to the prox-imity of the line to the edge of the LW3detector. There is a nearby weaker red-shifted feature,at120µm, which coincides with the expected position of the ground Π3/25/2−3/218OH line,and appears as a marginal fea-ture in both the“up”and“down”grating scans.How-ever,the limited signal-to-noise ratio((1.0±0.4)×10−20 W cm−2),the narrow appearance of the feature(≈0.42µm),and the fact that it is not blue-shifted as the main line,make that assignment only tentative.In Arp220, the main OH line is not shifted because it does not fall so close to the edge of the detector,as a consequence of the lower red-shift of the source.In Arp220,a red-shifted shoulder appears at120µm,suggesting the possibility that18OH may be responsible for it(Paper I).We can-not however be certain that18OH is detected in any of these sources,but given the high16OH column densities we derive in some of our models below(§3.3)and the fact that values of the16OH/18OH ratios below the canonical value of500may be expected in regions where the ISM is highly processed by starbursts(Paper I),our tenta-tive identification should be followed up with future Her-schel Space Observatory observations with higher spec-tral resolution and sensitivity.Finally,the spectrum of Mkn231shows a broad feature at the position of the Π1/2−Π3/23/2−3/2OH line(53µm).We note that the blue-shifted side of this absorption is coincident with the OHΠ3/211/2−9/2line,with a lower level energy of511K;however,the proximity of this spectral feature to the edge of the SW2detector precludes any definitive assignment.The FIR detections of both NH and NH3in Arp220 were reported in Paper I.NH3was also detected via the25GHz inversion transitions by Takano et al.(2005), who derived a NH3column density six times higher than our value.The difference likely arises because of the high FIR continuum opacities in Arp220,which cause the observed FIR absorptions to trace only a fraction of the total gas column.Since there are no such extinction effects at25GHz,the NH3inversion transitions are ex-pected to trace higher NH3column densities.Figure2 shows that,by contrast,the NH3lines are not detected in Mkn231,although the relatively high noise at125µm does not rule out future detection of NH3with Herschel at a level similar to that of Arp220.There are two marginally-detected(2.5σlevel)spec-tral features seen at153.0and152.3µm,in the Mkn231 spectrum(Fig.3).Although close to the expected posi-tion of the main NH feature at153.22µm,the153.0µm feature appears significantly shifted by0.25µm from it, and better coincides with the position of the OH+23−12 line.Also,the152.3µm feature lies at0.1µm from the expected position of the OH+22−11line.In Paper I,we also suggested that OH+could contribute to the spec-trum of Arp220for two reasons:(i)our models were unable to reproduce,using NH and NH3,the observed strong absorption at102µm,which coincides with the expected position of the OH+34−23line;(ii)there was an absorption feature at76.4µm that,if real,could be attributed to the OH+44−33transition.Since OH+has never been detected in the galactic interstellar medium or that of any galaxy,here we only highlight the intrigu-ing possibility of its detection in two ULIRGs.Sensitive, higher-resolution Herschel observations are needed to re-solve this tantalizing speculation.The luminosity of the[C II]2P3/2−2P1/2fine-structure line at158µm is2.5times stronger in Mkn231than in Arp220,but given the higher FIR luminosity of this source(Fig1),the[C II]to FIR luminosity ratios are rather similar,with values of2.5×10−4and2.1×10−4for Mkn231and Arp220,respectively(Luhman et al.2003). These are among the lowest values found in galaxies,il-lustrating the so-called“[C II]deficit”found in ULIRGs. The[C II]line emission from Mkn231is analyzed in§3.4.3.ANALYSIS3.1.Models for the far-infrared continuum Figure4illustrates several ways that the FIR to mil-limeter continuum can befit and interpreted.Wefirst modeled(model A in Fig.4a)the far infrared source in Mkn231as an ensemble of identical dust clouds each of which is heated by its own single central luminosity source.The representative cloud is assumed to be spher-ical,with radius R c,and is divided into concentric shells whose dust temperatures are computed from the balance of heating and cooling(Gonz´a lez-Alfonso&Cernicharo 1999).We used a mixture of silicate and amorphous car-bon grains with optical constants from Preibisch et al. (1993)and Draine(1983).The stellar continuum was taken from Leitherer et al.(1999),but results depend only weakly on this choice because the intrinsic contin-uum is absorbed by the dust and re-emitted at infrared wavelengths.Once the equilibrium temperatures are ob-tained for each shell,the resulting continuum emission from the cloud is computed,and multiplied by N c,the number of clouds in the source required to match the ab-soluteflux densities.This scaled spectrum is shown in Fig.4a.The other three models(B,C,and D,shown in Fig.4b-d)use grey-bodies with uniform dust temper-atures T d to characterize the continuum emission(e.g., Roche&Chandler1993;Armus et al.2007). Assuming that the individual clouds do not overlap along the line of sight,our results do not depend partic-ularly on the radius or luminosity adopted for the model4Gonz´a lez-Alfonso et al. individual cloud because identical results are obtained ifR c is multiplied by a factor ofα,the luminosity byα2,N c byα−2,and the continuum opacity is kept constant(see Paper I).The models are thus characterized by theluminosity of the whole ensemble,the radial opacity ofthe clouds at a given wavelength(which we adopt to be100µm:τ100µm),and the equivalent radius of the source,defined as R eq=N1/2c R c.These parameters are listedin Table2.In model A,the individual clouds are optically thin sothat some degree of cloud overlap would yield a similarfitto the continuum while decreasing the value of R eq.Forinstance,if the clouds are distributed in a spherical vol-ume,R eq=N1/3c R c giving R eq=400pc for clouds withR c=20pc.However,the predicted opacity through themodeled region,N1/3cτ100µm,will be much higher thanthat of an individual cloud,and this physical situationis already described in models B-C where higher opaci-ties along the line of sight and a more compact region ofFIR emission are assumed.In order to avoid this model redundancy,we choose our continuum models such thatan individual“cloud”describes the characteristic contin-uum opacity(τ100µm in Table2)and dust temperaturethrough the whole region(disk),so that the resultingextent of the FIR emission is R eq=N1/2c R c.The observed continuum can be reproduced frommodel A’s cloud ensemble that is optically thin in theFIR.Model A also predicts that the starburst domi-nates the continuum forλ 15µm,while the torus/diskaround the AGN would then dominate the mid-infrared continuum,in qualitative agreement with the models byFarrah et al.(2003).The equivalent radius of the star-burst is slightly larger than the radius of the outer diskobserved by DS98.Becauseτ100µm is low and R eq is high,this model predicts that the FIR radiation density is low,a prediction that is not consistent with our models of theobserved OH line strengths(§3.2).As bothτ100µm and T d are increased in models B andC,the radiation density increases and,therefore,theequivalent size required to reproduce the observed emis-sion becomes smaller.As a consequence,models B and Cpredict increasing compactness of the dust clouds respon-sible for the FIR emission,with R eq=400and200pc respectively.With a single-component model,however,R eq cannot be reduced more than in model C without de-grading the quality of thefit.However,a two-componentmodel as shown in D is able to reproduce the FIR emis-sion,invoking a quite compact(∼100pc)and warm(100K)component(D warm),and a colder and more extendedone that dominates atλ>80µm(D cold).A convenient way to characterize the radiation den-sity in the modeled regions is to compute the radiation temperature at100µm fromT rad(100µm)=hνc2F100µm ,(1)whereΩ=πN c R2c/D2is the solid angle subtended by the modeled source,F100µm is the predictedflux density at100µm,and other symbols have their usual mean-ing.T rad(100µm)is also listed in Table2,together with the gas mass,luminosity,and fraction of the bolometric luminosity for each model.The calculated gas masses assume a gas-to-dust mass ratio of100.In all cases, they are lower than the dynamical masses determined by DS98when R eq is identified with the radial extent of the source(and therefore compatible with the inferred rotation velocities in the disk).Our inferred masses are in models B−D consistent with the mass inferred by PIW07,but are in all cases higher,by at least a factor of two,than the gas masses obtained by DS98.This discrepancy may be explained in at least four possible, different ways:(i)the physical radial extent of the cloud ensemble,which accounts for cloudfilling,is given by R T=f−1/2R eq,where f is the areafilling factor,so that R eq is a lower limit of R T;(ii)our calculated masses de-pend on the mass-absorption coefficient for dust,which we have assumed to beκ1300µm=0.33cm2g−1based on a mixture of silicate and amorphous carbon grains (Preibisch et al.1993;Draine1983),but could be up to a factor∼6higher if the dust is mainly composed of fluffy aggregates(Kruegel&Siebenmorgen1994);(iii) the gas-to-dust mass ratio may depart significantly from the standard value of100;(iv)the masses derived by DS98for Mkn231could be lower limits in the light of the submillimeter CO emission reported by PIW07.A combination of these factors may explain our higher val-ues.The luminosities in Table2account for50-80%of the observed8−1000µm infrared luminosity.Model A implicitly assumes that the calculated luminosity has a starburst origin;the luminosity from model B and from the cold component of model D are also attributable to the starburst in view of the spatial extent of the mod-eled source.Since model C and the warm component of model D are more compact,a combination of AGN and starburst contributions is more plausible.The surface brightness in model C is4×1012L⊙/kpc2,a factor of 2higher than the peak global value found in starburst galaxies by Meurer et al.(1997),suggesting an impor-tant(but uncertain)contribution by the AGN to the observed FIR emission(Soifer et al.2000).Also,the luminosity-to-mass ratio of500L⊙/M⊙coincides with the uppermost limit proposed by Scoville(2004)for a starburst.The very high surface brightness(1.3×1013 L⊙/kpc2)and luminosity-to-mass ratio(∼3300L⊙/M⊙) of the warm component of model D(D warm),as well as its compactness,persuasively indicate that this compo-nent is most probably dominated by the AGN.The most plausible relative contributions by the AGN and the star-burst to D warm are discussed in§4.In summary,different approaches can be used to suc-cessfullyfit the observed FIR continuum emission,with the properties of the clouds that emit that radiation in these approaches spanning a wide range of possible phys-ical scenarios.But ISO/LWS has provided us with spec-troscopic information,and we show next how the ob-served high excitation OH and H2O lines impose impor-tant constraints on these continuum models.3.2.Equivalent widthsWe analyze the OH equivalent widths assuming that the OH molecules form a screen in front of the IR source. The strengths of theΠ3/27/2−5/2and9/2−7/2OH doublets at84and65µm,enable us to conclude that the excited OH covers a substantial fraction of the FIR emis-sion region.Assuming that each line of the84µm dou-High-excitation OH and H2O lines in Mkn2315 blet absorbs all the background84µm continuum overa velocity range of250km s−1along each line of sight,and that there is no significant re-emission in the line,the covering factor is∼50%.This value may be consid-ered a lower limit for the following reasons.The submil-limeter CO line profiles shown by Papadopoulos et al.(2007)have FWHMs of200-250km s−1,and the linesare expected to be broadened by velocity gradients and,in particular,by the disk rotation;therefore,the veloc-ity range of250km s−1assumed above is probably anupper limit.DS98inferred local turbulent velocities ofup to60km s−1at inner radii(100pc)and decreasingas r−0.3.If we adopt an intrinsic Gaussian line profilewith the highest value of the turbulent velocity,∆V=60km s−1,and saturate the84µm line to the degree thatan effective width1of250km s−1is obtained for eachcomponent of the doublet,the derived84µm foregroundopacity at line center is∼50,but the high column den-sity required for this opacity is hard to reconcile withthat inferred from the other observed OH line strengths(§3.3).Finally,some significant re-emission in the84µmOH line is expected because theΠ3/29/2−7/2OH lineat65µm that originates from its upper level is detectedin absorption.We therefore conclude that the observed84µm OH absorption is widespread,and probably cov-ers the bulk of the84µm continuum emission regions.On the other hand,the opacities in the high-lying65µmline should only be moderate;for reference,if we adoptfor each component an upper limit of150km s−1on theeffective velocity interval for the absorption at each sightline,the minimum covering factor for this line is then25%.It is therefore possible that the OH responsible forthe65µm absorption does not entirely coincide with thatproducing the84µm absorption but is only a fraction ofthe latter,consistent with its lower energy level being atnearly300K.Nevertheless,for the sake of simplicity,weassume in this Section that both lines arise in the sameregion–one that,on the basis of the84µm OH strength,covers the total FIR continuum.The derived OH columndensities will be lower limits,and the inferred propertiesof the continuum source will be associated with at least∼50%of the observed FIR emission.The equivalent widths W are then given byW=2× 1−Bν(T ex)Ω6Gonz´a lez-Alfonso et al.N(OH)=3×1017cm−2,yet this column density still overestimates the absorption of the53µm line.Although model B cannot account for the65µm line strength,a region of similar size but lower N(OH)could contribute to the observed absorptions of the119,84and53µm lines.The single-component model that best accounts for the four observed OH lines is model C with R eq=200pc (Fig.5c).The corresponding continuum model(Fig.4c), with T d=74K,alsofits rather well the overall FIR con-tinuum emission.Significantly,our models in§3.3show that the excitation temperatures required to reproduce the observed equivalent widths,40-60K,are those com-puted at the cloud surface if the OH is excited by the in-frared emission from a blackbody at T d=74K.Finally, the dust temperature and gas mass(Table2)in model C are consistent with the gas temperature and H2mass derived by Papadopoulos et al.(2007)from the submil-limeter CO and HCN emission.They found that this warm gas component hosts most of the molecular mass in the galaxy.The H2column density,N(H2)∼1.5×1024 cm−2,indicates high optical depths,as in the galactic Sgr B2molecular cloud,but Mkn231is much warmer. If the column density in Mkn231is concentrated in a face-on disk of thickness H=23pc,as concluded by DS98,the expected density is n(H2)∼2×104cm−3,just the amount needed to account for the CO submillimeter lines(Papadopoulos et al.2007).On the other hand,if this warm and dense component is identified with the inner disk of radius460pc reported by DS98,the area filling factor is f∼0.2.In spite of the general agreement between our model C with other observations,a closer inspection of this model(§3.3)reveals some discrepancies with other OH and H2O lines that suggest that a slightly modified scenario can better explain the overall observed absorption patterns.3.3.Models for OH and H2ORadiative transfer modeling of the observed OH and H2O lines was done using the code described in Gonz´a lez-Alfonso&Cernicharo(1997,1999),which computes the statistical equilibrium populations of a given molecule in spherical symmetry.Line broaden-ing is assumed to be caused by microturbulence.Our code accounts for a non-local treatment of the radia-tive trapping in the molecular lines and of the excita-tion through absorption of photons emitted by dust,as well as for collisional excitation.Both line and contin-uum opacities for photons emitted in both lines and con-tinuum are taken into account.Collisional rates were taken from Offer,van Hemert,&van Dishoeck(1994) and Green,Maluendes,&McLean(1993)for OH and H2O,respectively.As we also found for Arp220(Pa-per I),the overall excitation is dominated by absorption of FIR continuum photons in all models.If shock condi-tions(high density and temperature)were assumed,only the absorption in the lowest-lying lines would be signifi-cantly affected.Once the continuum model isfixed,our results only depend on the molecular column densities and turbulent velocity(see Paper I for a fuller descrip-tion).As mentioned above(§3.2),the observed absorption strengths are not sensitive to the amounts of OH and H2O in the inner regions of the modeled regions,but only to the amounts of OH and H2O that are close to the cloud (or disk)boundary.For this reason,we calculate two val-ues for the derived molecular column densities:N scr(X) denotes the column density for a shell of species X cov-ering the infrared source(i.e.,the screen case),whereas N mix(X)is the inferred column density for models where X and dust are evenly mixed(the mixed case).Evidently N mix will be much higher than N scr,but from our data there are only a few,non-definitive ways to discriminate between the alternatives.The163µm OH and120µm 18OH lines are stronger in the mixed case,but neither of these features is unambiguously detected.Neverthe-less,we do notfind any strong arguments for thinking that OH and H2O are only present on the surface of the disk,and so the N mix values may be considered some-what more reliable.The abundances we derive below are based on this assumption;we revisit the“mixed”case when we discuss models for the[C II]line.Since model C(Fig.4c,Fig.5c,Table2)gives the best single-componentfit to most of the OH equivalent widths,wefirst check if it can account for the observed OH and H2O absorption features.Figure6compares the observed continuum-subtracted spectrum and the mod-eled results(dashed spectrum,mixed case)for the wave-length ranges where the signal-to-noise ratio is adequate. Table3lists the physical parameters obtained for this model.We have assumed a turbulent velocity∆V of40 km s−1(§3.2;DS98).The modelfits satisfactorily the OH119,84,65,and53µm lines,thus demonstrating the approximate validity of the simple method outlined in§3.2.The value of N scr(OH)=1017cm−2is also the same as estimated from the equivalent widths.The H2O column densities are determined by the strengths of the 330→221and331→220lines at66-67µm.Some features of model C,however,are inconsistent with the data.The possible emission in the OH163µm line is not reproduced,and the absorption in the79 and99µm OH lines appears excessive.The model also predicts too much absorption in the322→211(90µm), 220→111(101µm),221→110(108µm),and414→303 (113µm)H2O lines.All these discrepancies suggest that the component that accounts for the absorption of the 65-68µm OH and H2O lines is weaker than postulated in model C at wavelengths longer than80µm.These discrepancies may be resolved by invoking two different components for the FIR continuum emission, as in model D(Fig.4,Table2).The warm-compact component,responsible for the65-68µm OH and H2O lines,will produce weak absorptions in the80-120µm range as a consequence of the relatively weak continuum emission at these wavelengths.The more extended com-ponent will contribute to the observed absorptions in the 53,84,and119µm OH lines.The compactness of the warm component suggests that it is relatively close to the AGN,and thus we have assumed∆V=60km s−1for D warm(Table3);this is the turbulent velocity found by DS98around the rotation curve turnover radius of75pc. For the extended component(D cold),∆V=40km s−1 is assumed.Figure6shows that a betterfit to the over-all spectrum is indeed found with this composite model (grey line),with the lines in the80-120µm range brought down to levels compatible with observations.Also,the model predicts the163µm OH line to be in emission.。
北师大版高中英语选择性必修第二册UNIT6 THE MEDIA Part1 练习含答案
UNIT 6THE MEDIAPart 1TOPIC TALK基础过关练Ⅰ.单词拼写1.(2023浙江1月)A machine can now not only beat you at chess, it can also outperform you in (辩论).2.(2021北京)Your application will be accessed by UNESCO managers and will stay in our database for six months. We do not respond to every (考生).3.(2024安徽芜湖市第十二中学期中)A study in Germany shows that as many as one in three online (购买物) is returned.4.The public-health (运动) has greatly reduced the number of heart disease deaths by 80 per cent over the past three decades.Ⅱ.一词多义1.He is available next week and you can make an appointment with him.词义:2.This new model of the mobile phone is available at selected stores only.词义:Ⅲ.选词填空1.Summer is the perfect time to the new books you meant to read.2.What I still can't is why I always get tired in my life.3., the more customers are promised, the greater the risk of disappointment is.4.(2024安徽合肥一中期中) doubting my inability to perform the trick, I took his direction one step at a time.Ⅳ.单句语法填空1.With no solid evidence, he refused to acknowledge(steal) the lady's purse.2.After consulting my parents, I will put forward this idea to them face to face tomorrow.3.The main theme of the forum is how the youth can drive(推动) change in(politics) and public life.4.She was under house arrest two years ago but remained a powerful representative in last year's(elect).5.Wheelchairs are available(rent) at the information desk.6.It is difficult to say(precise) why maintaining social connections plays a powerful role in keeping the brain young.7.Developing the Yangtze River(economy) Belt is a systematic project which calls for a clear road map and timetable.8.My mum thinks it is a good idea(ride) a bicycle to the countryside.Ⅴ.完成句子1.他们总是告诉我做什么和怎么做。
Chemical Evolution of Late-type Dwarf Galaxies - The windy starburst dwarfs NGC 1569 and NG
a rXiv:as tr o-ph/411635v123Nov24CHEMICAL EVOLUTION OF LATE-TYPE DWARF GALAXIES The windy starburst dwarfs NGC 1569and NGC 1705Donatella Romano,1Monica Tosi,1and Francesca Matteucci 21INAF–Osservatorio Astronomico di Bologna Via Ranzani 1,40127Bologna,Italy [donatella.romano;monica.tosi]@bo.astro.it 2Dipartimento di Astronomia,Universitàdi Trieste Via G.B.Tiepolo 11,34131Trieste,Italy matteucci@ts.astro.it Abstract Thanks to the capabilities of modern telescopes and instrumentation,it is now possible to resolve single stars in external dwarf galaxies,provided they are bright enough.For galactic regions with deep enough photometry,detailed colour-magnitude diagrams are constructed,from which the star formation his-tory and the initial mass function can be inferred by comparison with synthetic diagrams.Both the star formation history and the initial mass function are free parameters of galactic chemical evolution models.In this contribution we show how constraining them through high resolution photometry in principle allows us to better understand the mechanisms of dwarf galaxy formation and evolution.Keywords:Galaxies:evolution,formation,individual:NGC 1569,NGC 17051.IntroductionLow-luminosity galaxies –dwarf galaxies and related systems –are found numerous in the nearby universe.Here we deal with the subclasses of dwarf irregulars (DIGs)and blue compact dwarfs (BCDs).Both have low mass,low metallicity,large gas content and mostly young stellar populations.However,while BCDs are rather compact objects,with centrally concentrated starburst,gas and star distributions,DIGs are dominated by scattered bright H II regions in the optical.The disturbed H I morphologies could be related either to the oc-currence of galactic winds or to episodes of mass accretion and/or ingestion of low-mass companions (e.g.,Kobulnicky &Skillman 1995;Stil &Israel 1998,22002;Cannon et al.2004).In some cases,both mechanisms are competing to determine the physical properties of the galaxy.2.NGC1569and NGC1705Whatever its(unknown)cause,the strong recent star formation activity in NGC1569triggered a galactic outflow whose signature can be observed in different bands(Martin et al.2002).In NGC1705,the H I kinematics is quite regular(Meurer et al.1998).Yet,its spectacular galactic wind(Meurer et al. 1992;Heckman et al.2001)bears witness to the recent rather exceptional star formation activity(Annibali et al.2003).In the following,we will concentrate on these two windy starburst dwarfs.Table1.Observational properties.Distance 2.2±0.6Mpc1 5.1±0.6Mpc6 Gas mass(1.5±0.3)×108M⊙1 1.7×108M a⊙7 Total mass 3.3×108M⊙1 3.4×108M a⊙7 Z0.00420.0048 log(O/H)+128.19–8.373,4,58.21±0.059 log(N/O)−1.39±0.055−1.75±0.06b9Chemical Evolution of Late-type Dwarf Galaxies3 1998;Angeretti et al.2005)and up to∼5Gyr ago for NGC1705(Annibali et al.2003)–there is always evidence that the galaxy was forming stars at that time.The IMF is found to be close to the Salpeter value for both objects.Chemical evolution model resultsTaking advantage of the constraints put on SFH and IMF by the CMD analysis,we construct detailed chemical evolution models for NGC1569and NGC1705aimed at understanding how these galaxies form and evolve.We make the working hypothesis that each galaxy can be described by a one-zone model,a reasonable assumption as long as significant abundance gradients are not observed in these systems.The basic equations we use in order to follow the temporal evolution of sev-eral chemical species in the gas are the same described in Bradamante et al. (1998).The stellar lifetimes are taken into account in detail,i.e.,the instanta-neous recycling approximation is relaxed.Up-to-date stellar nucleosynthesis is included in the model and galactic winds are assumed to originate when the thermal energy of the gas equates its binding energy.The thermal energy of the gas increases due to supernova(SN)explosions and stellar winds;according to Recchi et al.(2001),a higher thermalization efficiency is assigned to Type Ia SNe,because they explode in a warm medium,rarefied by previous Type II SN explosions.The binding energy of the gas depends on the dark matter(DM) amount and distribution;a massive(M dark/M lum=10),diffuse(R eff/R dark =0.1)DM halo is assumed.For late-type dwarfs,mostly metals are expected to be carried away in the outflow,while only a smaller fraction of unprocessed gas is likely to be affected(De Young&Gallagher1990;Mac Low&Ferrara 1999;D’Ercole&Brighenti1999).Fig.1displays some results obtained with different models for NGC1569. The star formation rate,metallicity,oxygen abundance,and carbon(nitrogen) to oxygen abundance ratios in the gas are shown as a function of time for six models differing in the adopted SFH at epochs where no constraints are avail-able from HST photometry,galactic wind efficiency and stellar nucleosynthe-sis.In particular,Models1aN,2aN and2bN assume that only one small burst of star formation preceded the strong last Gyr activity detected with HST.For Models3cN and3cW,the most ancient activity consists of three weak short-lasting bursts,while Model4aN adopts a continuous,low-level star formation in the past.The metal ejection efficiency due to galactic winds is higher for Model2bN than for Models1aN,2aN and4aN,while it is slightly lower for Models3cN and3cW.All the models share the same stellar nucleosynthe-sis prescriptions(van den Hoek&Groenewegen1997yields with constant mass loss parameter along the AGB for low-and intermediate-mass stars,plus Nomoto et al.1997yields for massive stars),but Model3cW(van den Hoek4Figure1.Temporal behaviour of(i)star formation rate,(ii)metallicity,(iii)oxygen abun-dance,(iv)carbon to oxygen,and(v)nitrogen to oxygen abundance ratios in the gas of NGC1569for six different chemical evolution models(see text).Predictions from different models(blue solid curves)are displayed together with the observational values when available (yellow horizontal bands).The star formation rate is actually an input quantity for the models. Notice that measured abundances refer to H II region composition and must then be compared with the end points of the theoretical tracks.&Groenewegen1997yields with metallicity-dependent mass loss parameter along the AGB for low-and intermediate-mass stars,plus Woosley&Weaver 1995yields for massive stars).Detailed discussion of the model results will be presented elsewhere,here we limit ourselves to some basic considerations.Thefirst thing to notice is the high degree of uncertainty which affects model predictions due to uncertaintiesChemical Evolution of Late-type Dwarf Galaxies5 in the stellar nucleosynthesis.By comparing the fourth andfifth columns of Fig.1,it can be seen that the theoretical C/O and N/O may vary by∼0.3–0.4 dex,depending on the assumed stellar yields.In particular,the set with the yields by van den Hoek&Groenewegen(1997;metallicity-dependent mass loss parameter along the AGB)plus Woosley&Weaver(1995)overestimates the nitrogen abundance actually seen in NGC1569.Part of the discrepancy is likely due to the fact that primary nitrogen production from intermediate-mass stars is overestimated by this yield set(see also Chiappini et al.2003).Another important issue is that of the galactic wind efficiency.The most recent,violent star formation activity in NGC1569naturally triggers and sus-tains an outflow on a galactic scale in our model.The more efficient the star for-mation process,the more effective must be the wind in removing the newly pro-duced metals in order to explain the H II region data.For instance,Model2aN (Fig.1,second column),computed by assuming a star formation efficiency higher than Model1aN(Fig.1,first column)during the last Gyr,overproduces the present-day oxygen content and overall metallicity1of the galaxy,unless the efficiency of gas removal from the galaxy is increased(Model2bN,Fig.1, third column).Finally,it is worth stressing that,besides the standard bursting mode of star formation(strong bursts of star formation alternating long quiescent phases) often attributed to DIGs and BCDs by chemical evolution modellers(e.g.Bra-damante et al.1998and references therein),assuming a continuous low-level star formation rate in the past also produces results in good agreement with the observations(Model4aN,Fig.1,last column).Because of the small dif-ferences in the model predictions in the two cases,it is unlikely that future measurements such as abundance determinations for single stars tracing the whole chemical enrichment history of the galaxy will allow us to discriminate between the two opposite scenarios.However,it should be noted that the obser-vational evidence points against long periods of quiescence between successive bursts,at least for the look-back times actually surveyed by the observations.Models for NGC1705are similarly constructed by adopting the SFH and IMF inferred from the observations(Annibali et al.2003).The stellar yields, galactic wind onset conditions and efficiency are the same adopted by success-ful models for NGC1569.While the total and gaseous mass of the system at the present time as well as its current metallicity and oxygen content are easily reproduced,the predicted nitrogen abundance turns out to be always higher than measured from H II regions(cfr.Figs.2a and2b).Interpreting the N/O data.Understanding the origin of nitrogen is one of the major goal of modern astrophysics.Since the pioneering work of Ed-munds&Pagel(1978),a stellar source of primary N has became strongly in demand.Recent abundance data for very metal-poor Galactic halo stars6Figure2a.The temporal evolution of the oxygen abundance in the interstellar medium of NGC1705predicted by the model(red solid line)is compared to the available observations(yellow band;mean value from[O III]λ4363measurements by Lee&Skillman2004).Figure2b.The temporal evolution of the nitrogen to oxygen abundance ratio in the interstellar medium of NGC1705pre-dicted by the model(red solid line)is com-pared to the available observations(at2σ–yellow band;Lee&Skillman2004).(Spite et al.2004;Israelian et al.2004)suggest that an important produc-tion of primary N actually took place in thefirst generation of massive halo stars,while delayed primary N production from intermediate-mass stars likely overwhelms any massive star contribution at later times(e.g.Chiappini et al. 2003).However,current stellar yields probably overestimate the amount of primary nitrogen produced through hot bottom burning in intermediate-mass stars.Clearly,changing the nucleosynthesis prescriptions in such a way that the N/O ratio measured for NGC1705is reproduced,immediately destroys the agreement between model predictions and observations for NGC1569,since a too low N/O ratio is obtained in this case.On the other hand,modifying the intermediate-and high-mass star stellar mass spectrum within the range allowed by HST observations does not offer a viable solution,either.One is left with the possibility that the relative fractions of nitrogen and oxygen lost from the two galaxies are different.Alternatively,in NGC1705we might be seing localized self-pollution due to dying young massive stars born during the last3Myr of star formation activity.Both such hypotheses wait for detailed hydrodynamical computations in order to be verified.Notes1.A smaller effect is seen in the C/O and N/O ratios,since carbon,nitrogen and oxygen are always ejected in the same proportions in the outflow for all the models.AcknowledgmentsDR wish to thank A.Aloisi,H.Lee and E.Skillman for discussions.Chemical Evolution of Late-type Dwarf Galaxies7 ReferencesAnnibali,F.,Greggio,L.,Tosi,M.,Aloisi,A.,and Leitherer,C.2003,AJ,126,2752 Angeretti,L.,Tosi,M.,Greggio,L.,Sabbi,E.,Aloisi,A.,and Leitherer,C.2005,AJ,submitted Bradamante,F.,Matteucci,F.,and D’Ercole,A.1998,A&A,337,338Calzetti,D.,Kinney,A.L.,and Storchi-Bergmann,T.1994,ApJ,429,582Cannon,J.M.,McClure-Griffiths,N.M.,Skillman,E.D.,and Côté,S.2004,ApJ,607,274 Chiappini,C.,Romano,D.,and Matteucci,F.2003,MNRAS,339,63D’Ercole,A.,and Brighenti,F.1999,MNRAS,309,941De Young,D.S.,Gallagher,J.S.,III1990,ApJ,356,L15Edmunds,M.G.,and Pagel,B.E.J.1978,MNRAS,185,77González Delgado,R.M.,Leitherer,C.,Heckman,T.,and Cerviño,M.1997,ApJ,483,705 Greggio,L.,Tosi,M.,Clampin,M.,de Marchi,G.,Leitherer,C.,Nota,A.,and Sirianni,M.1998,ApJ,504,725Heckman,T.M.,Sembach,K.R.,Meurer,G.R.,Strickland,D.K.,Martin,C.L.,Calzetti,D.,and Leitherer,C.2001,ApJ,554,1021Israel,F.P.1988,A&A,194,24Israelian,G.,Ecuvillon,A.,Rebolo,R.,García-López,R.,Bonifacio,P.,and Molaro,P.2004, A&A,421,649Kobulnicky,H.A.,and Skillman,E.D.1995,ApJ,454,L121Kobulnicky,H.A.,and Skillman,E.D.1997,ApJ,489,636Lee,H.,and Skillman,E.D.2004,ApJ,614,698Mac Low,M.-M.,and Ferrara,A.1999,ApJ,513,142Martin,C.L.1997,ApJ,491,561Martin,C.L.,Kobulnicky,H.A.,and Heckman,T.M.2002,ApJ,574,663Meurer,G.R.,Freeman,K.C.,Dopita,M.A.,and Cacciari,C.1992,AJ,103,60Meurer,G.R.,Staveley-Smith,L.,and Killeen,N.E.B.1998,MNRAS,300,705Nomoto,K.,Hashimoto,M.,Tsujimoto,T.,Thielemann,F.-K.,Kishimoto,N.,Kubo,Y.,and Nakasato,N.1997,Nucl.Phys.A,616,79cRecchi,S.,Matteucci,F.,and D’Ercole,A.2001,MNRAS,322,800Spite,M.,Cayrel,R.,Plez,B.,et al.2004,A&A,in press(astro-ph/0409536)Stil,J.M.,and Israel,F.P.1998,A&A,337,64Stil,J.M.,and Israel,F.P.2002,A&A,392,473Storchi-Bergmann,T.,Calzetti,D.,and Kinney,A.L.1994,ApJ,429,572Tosi,M.,Greggio,L.,Marconi,G.,and Focardi,P.1991,AJ,102,951Tosi,M.,Sabbi,E.,Bellazzini,M.,Aloisi,A.,Greggio,L.,Leitherer,C.,and Montegriffo,P.2001,AJ,122,1271van den Hoek,L.B.,and Groenewegen,M.A.T.1997,A&AS,123,305Woosley,S.E.,and Weaver,T.A.1995,ApJS,101,181。
中考英语摄影艺术的表现力提升单选题40题
中考英语摄影艺术的表现力提升单选题40题1.Photography is an art that uses light and ____ to create images.A.colorB.shapeC.sizeD.weight答案：A。
摄影是一门利用光和颜色来创造图像的艺术。
选项B“shape”形状、选项C“size”大小、选项D“weight”重量都与摄影创造图像的主要元素不太相关，而颜色是摄影中非常重要的元素之一。
2.A good photograph often has strong ____.A.contentB.meaningC.contrastD.value答案：C。
一幅好的照片通常有强烈的对比度。
选项A“content”内容、选项B“meaning”意义、选项D“value”价值，虽然对于照片也很重要，但不如对比度更能直接体现照片的视觉效果。
3.The ____ of a photograph can make it more attractive.positionB.backgroundC.subjectD.lightning答案：A。
照片的构图可以使它更具吸引力。
选项B“background”背景、选项C“subject”主题、选项D“lightning”闪电，都不是直接决定照片吸引力的主要因素，而构图是影响照片整体美感的重要方面。
4.In photography, focus is achieved by adjusting the ____.A.lensB.shutterC.flashD.memory card答案：A。
在摄影中，焦点是通过调整镜头来实现的。
选项B“shutter”快门、选项C“flash”闪光灯、选项D“memory card”存储卡都与调整焦点无关。
5.A beautiful landscape photograph often shows the ____ of nature.A.beautyB.powerC.mysteryD.weakness答案：A。
小学上册第二次英语第4单元真题(含答案)
小学上册英语第4单元真题(含答案)英语试题一、综合题(本题有100小题，每小题1分，共100分.每小题不选、错误，均不给分)1.The _______ (小青蛙) croaks loudly at night.2.The __________ (历史的探索) reveals truths.3.What is the opposite of "happy"?A. SadB. AngryC. ExcitedD. Tired答案: A4.The ancient Egyptians are known for their _____ and art.5.We will _______ (玩) soccer tomorrow.6.We visit the ______ (艺术中心) for cultural events.7.I enjoy writing ______ (电影评论) to share my thoughts on what I watch. It’s a way to express my opinions.8.I like to _____ (skateboard) at the park.9. A balloon filled with air is an example of a ______.10.The _____ is made up of stars, planets, and galaxies.11. A ________ (峡谷) is a deep valley between mountains.12.The __________ (历史的视角) can differ among cultures.13. A _____ (tropical) plant grows in warm climates.14.My dad is ________ a car.15. A _____ (植物文化遗产) enriches our connection to nature.16.My favorite color is ___ (red/yellow).17.The ________ grow in the garden.18.What is the name of the famous explorer who discovered Australia?A. James CookB. Abel TasmanC. Ferdinand MagellanD. Christopher Columbus答案: A19.The __________ (历史的影响) shapes perspectives.20.I think it's fun to celebrate __________ because we get to __________.21.I enjoy _____ (reading/watching) movies.22. A _______ can help to test the effects of temperature changes on materials.23.We need to ________ the dishes.24.The ______ (液体) within plant cells is called cytoplasm.25.Sedimentary rocks often contain ______ that can tell us about the environment of the past.26.My brother wants a pet ______ (小狗) to play with.27.My favorite game to play with my friends is ______.28.What is the main purpose of a map?A. To tell timeB. To show directionsC. To cookD. To read答案: B29. A ________ (海峡) connects two larger bodies of water.30.The __________ helps some birds to swim in water.31.The atmosphere is made up of gases including nitrogen and ______.32.I sometimes watch ________ (名词) about toys and learn new ways to play with them. This gives me many ________ (名词) ideas!33.The _____ (quinoa) is a superfood plant.34.In summer, the grass grows __________ (茂盛).35.What is the name of the famous river in Egypt?A. AmazonB. NileC. YangtzeD. Mississippi答案: Banic compounds contain carbon and ______.37.The nurse gives _____ (疫苗) to children.38. A dilute solution contains a ______ concentration of solute.39. A _______ can grow in different climates.40. A ____ has long whiskers and scurries about.41. A frog can change its color based on its ______ (环境).42.I have a ___ (friend/sibling) who loves sports.43.The process of photosynthesis takes place in ______.44.The flowers in the garden bloom in every _______ imaginable.45.The ______ is a small animal that can climb trees.46.The element with the atomic number is ______.47.The __________ (历史的共享) enriches culture.48.I can ______ (管理) my time effectively.49.We will have _____ (fun/work) at the park.50.My brother is a big __________ of basketball. (粉丝)51.The sky is clear and ______ (蓝色) today.52.Ants can carry items many times their ______ (重量).53.The ______ is a layer of rock that lies directly beneath the Earth's surface.54.I love playing ______ (户外游戏) with my friends after school. It’s a great way to relax and have fun.55.My grandma is a wonderful __________ (谈话者) who shares stories.56.The _____ (植物资料) can provide insights into care.57.What do we call the process of animals adapting to their environment?A. EvolutionB. MigrationC. TranspirationD. Hibernation答案:A. Evolution58._____ (weeds) can compete with other plants.59.What is the name of the main character in "The Very Hungry Caterpillar"?A. ButterflyB. CaterpillarC. LadybugD. Ant答案:B60.I have a __________ (形容词) __________ (玩具名) that I take everywhere.61.What do we call the process of taking in oxygen?A. RespirationB. CirculationC. DigestionD. Excretion答案:A. Respiration62.An extinct volcano is one that is unlikely to ______ again.63.I have a collection of ______ (邮票) from my travels around the ______ (世界).64.I like to _____ at the park. (play)65.The capital of Egypt is _____ (92).66. A dog's bark can signal excitement or ________________ (警告).67.In a chemical reaction, products are formed from ________.68.I love to play ________ (户外游戏).69.Which device do we use to see things that are far away?A. MicroscopeB. TelescopeC. BinocularsD. Magnifying glass答案: B70.My uncle lives in . (我叔叔住在。
Unit3Theartofpainting.Reading课件高中英语牛津译林版(2020)选择性
Painting is silent poetry, and poetry is painting that speaks.
--Simonides of Ceos
画是无言的诗， 诗是有声的画。
——凯奥斯岛的西摩尼得斯
Tell different types of paintings
history paintings /
realistic
➢ Focus:
just a brief “impression” every detail in a scene
The Night Watch, 1642, Rembrandt 伦勃朗《夜巡》
The Gleaners, 1857, Millet
the works that came before
➢ Subjects:
everyday subject matter
➢ Techniques:
• •
employ free brushwork use color to show the effect
of light
➢ Styles:
less realistic
• An introduction to the museum
• An introduction to some painters and paintings
• Its influence ude Monet 克劳德·莫奈
Pierre-Auguste Renoir 皮埃尔·奥古斯特·雷诺阿
vivid color
Monet 莫奈 Blue Water Lilies mostly from his garden
小学下册A卷英语第六单元期中试卷
小学下册英语第六单元期中试卷英语试题一、综合题(本题有100小题，每小题1分，共100分.每小题不选、错误，均不给分)1.The _______ (老虎) is a symbol of strength.2.The ________ (watermelon) is juicy.3.What is the capital of the Maldives?A. MaleB. Addu CityC. FuvahmulahD. Laamu AtollA Male4.The invention of the printing press was by ________ (古腾堡).5.The rabbit is ___ (hopping) through the grass.6.My sister loves to __________ (唱歌) in the shower.7.The chemical formula for calcium sulfate is ______.8.My favorite dessert is _______ (我最喜欢的甜点是_______).9. A _______ can be a type of fruit or vegetable.10.The ______ (生态足迹) reflects human impact on nature.11.The first successful flight was achieved by ________ (莱特兄弟).12.Black holes cannot be seen directly because of their ______.13.I enjoy _______ (收集) stickers.14.The __________ can reveal the historical context of geological formations.15.I see a ___ (cloud/rainbow) in the sky.16.What do we call the act of putting something in the correct place?A. OrganizingB. ArrangingC. SortingD. CategorizingA17.What do you call a large structure that holds water?A. ReservoirB. TankC. PoolD. BasinA18.The game starts at _______ (seven) o'clock.19.What is the capital of India?A. DelhiB. MumbaiC. KolkataD. Chennai20.The chemical symbol for potassium is ________.21.The arrangement of atoms in a molecule is known as its _____ structure.22.What do you call a person who makes movies?A. DirectorB. ProducerC. ActorD. CinematographerA23.The puppy is _______ (在吃东西)。
小学下册E卷英语第2单元寒假试卷
小学下册英语第2单元寒假试卷英语试题一、综合题(本题有100小题，每小题1分，共100分.每小题不选、错误，均不给分)1.The ________ (艺术展览) showcase local talents.2.I need to ___ my room. (clean)3.What color do you get when you mix blue and yellow?A. GreenB. PurpleC. OrangeD. Brown4.What do you call a collection of plants grown for display?A. GardenB. NurseryC. GreenhouseD. ArboretumD5.How many players are there in a soccer team?A. 7B. 9C. 11D. 13C6.They are _______ in the classroom.7.The ______ of a cactus helps it survive in dry conditions. (仙人掌的刺帮助它在干燥的环境中生存。
)8.I can _____ my bike without training wheels. (ride)9.What do you call a place where you borrow books?A. LibraryB. MuseumC. ParkD. SchoolA10.What is the name of the famous ship that was used for the first transatlantic voyage?A. MayflowerB. TitanicC. Santa MariaD. EndeavourC11.The kitten is very ________.12. A ______ (青蛙) is an amphibian that lives in water and on land.13.My dog loves to fetch the ______ (球).14.In spring, the rains help the plants to __________. (成长)15.I love watering my _____ (植物) every day.16.__________ (质谱) analyzes the mass of molecules for identification.17.What is the name of the famous Italian dish made with pasta?A. PizzaB. LasagnaC. FettuccineD. RisottoB18.What is the name of the star at the center of our solar system?A. MoonB. SunC. EarthD. MarsB19.What is 4 + 4?A. 6B. 8C. 10D. 12B20.My friend loves __________ (进行科学实验).21.The dog loves to _____ in the garden. (dig)22.What do we call a baby horse?A. FoalB. CalfC. LambD. Kid23.I love to ________ (画画) in my sketchbook.24.I have a _____ (玩具火车) that makes sounds while it moves. 我有一辆会发出声音的玩具火车。
河南省驻马店市2023-2024学年高一下学期7月期末英语试题
河南省驻马店市2023-2024学年高一下学期7月期末英语试题一、阅读理解From the food ingredients, the placing on the plate to the background music and much more, chefs and companies in the UK are planning to change our dining experiences, and the trends in dining out. EntomophagyThis is a proper term for eating insects! Numerous people realize that many of our basic food may disappear in the coming decades and insects can offer people good protein (蛋白质) to replace animal meats, so they believe insects are a good choice. It hasn’t quite happened yet because we all think insects are extremely unpleasant. But, many chefs are already experimenting in the field.A number of top chefs in London are using their cooking creativity to turn something unpleasant into something delicious. Tech at the TableDigital products will probably become a common part of our food and drink experiences in the near future. We’re going to see things like tablets and computer screens that can tell stories around the food we are eating. We’ll be able to change the color of plates digitally, because we know that colors can change the taste of food or make it look better. The Experimental Meal The experimental meal is liked by a growing number of people interested in finding new connections between their senses. They think that food is not just what goes into the mouth, but a whole experience. They’re seeing dining—music, lighting, staff uniforms, temperature changes—as a whole meal. They are trying to put different things together instead of having dinner and then going to the theatre, why not bring the two together? The same goes for cinema and music.1．What is the reason for some people to turn to insects for food?A．The better taste of protein from insects.B．The popularity of some chefs in London.C．The possibility of main food disappearing.D．The performance of some chefs’experiments.2．Why is the color of plates changed digitally?A．To make the food healthy.B．To make the food attractive.C．To make the plate funny.D．To make the plate eco—friendly.3．Why do some people prefer the experimental meal?A．To connect senses in a new way.B．To bring colorful plates together.C．To combine food with digital products.D．To carry out technology experiments.Robin Emmons has grown more than 26, 000 pounds of vegetables to help more than 72, 000 people in Charlotte, North Carolina, who have no way to get fresh healthy food. Access to fresh food is an issue for many communities throughout the United States. According to the Department of Agriculture, nearly 10% of the U. S. population live in low-income areas more than a mile from a supermarket. For residents who lack transportation, buying fresh food is even more difficult.Discovering this problem inspired something inside Emmons, who quit her job to devote herself to a more meaningful thing. She said, “I decided to plant vegetables in my whole backyard, and it just kind of snowballed from there.” Today, Emmons has 200 volunteers helping her tend 9 acres of vegetables on three sites. Since 2008, she says, her nonprofit organization, Sow Much Good, has grown more than 26, 000 pounds of fresh produce for underserved communities in Charlotte.Customers greatly appreciate all that Emmons and her group are doing. She tries to make her produce as affordable as possible. Since Bolin discovered Emmons' produce stand this summer, she has visited it regularly. “I really appreciate all the beautiful and fresh vegetables,” said Bolin, 38. “It's making me and my family healthier.” Keeping it going is a labor of love for Emmons, who spent years doing it for free. Since last week, she has taken a small salary (薪水).Emmons would love to expand her organization across the country, changing food deserts wherever they exist. For now, she's devoted to helping Charlotte residents. “When I see people coming to the farm stand, I feel encouraged,” she said. “I feel like I am giving them a gift—a healthier, longer and better life.”4．Who may need Emmons' help most?A．People fond of planting.B．People lacking fresh food.C．People living in Charlotte.D．People living near supermarkets.5．Why did Emmons leave her job?A．She wanted to help others.B．She was tired of her job.C．She liked planting vegetables.D．She wanted to earn money.6．What is the most important effect of Emmons' deeds?A．People earn a higher income.B．More vegetables are accessible.C．She wins worldwide popularity.D．Her organization makes a profit.7．Which of the following words best describe Emmons?A．Brave and kind.B．Helpful and appreciative.C．Ambitious and devoted.D．Generous and disciplined.When making decisions, most people view cost as an important consideration. While price is undoubtedly important, what about some hidden costs that also come into play? For example, what are the long—term effects of your decision? Have you considered how your decision impacts your relationships? Simply put, hidden costs may be invisible to the naked eye, but they're very visible (可见的) to your wallet. Ignoring these factors can cost you a lot.Consider a scene where a manager cuts costs by asking some workers to leave. While this move reduces salary expenses, how will it impact the morale (士气) and loyalty of the remaining employees? Similarly, imagine somebody spending hours surfing the web, lost in searching for cheaper things. The question is whether the savings equal the spent time. If cost is your only consideration, you'll pay the price. Price Isn't the Only Cost!Furthermore, even if cost is the only factor in your decision—making, all of the “true costs” should be considered. For example, if you're thinking about buying new technology the equipment cost is only part of the price. People will need training, the software may need customization, and you'll probably lose productivity until people get up to speed. Those are real costs too.In addition, even when price is the main consideration, it's important to tell the difference between price and value. For example, when you're investing in a high—quality product from a famous organization, compare maintenance (保养) and repair costs with its competitors, assess the product life span, and hear what existing customers have to say. As the old saying goes, “You get what you pay for.”Always keep in mind that every time you say “yes” to one thing, you're certainly saying “no” to another. So, in decision—making, always consider invisible costs. This ensures you're aiming for the best solution rather than a good one. After all, choices are easy. The tough part is livingwith them.8．What does the underlined phrase “come into play” in paragraph I mean?A．Come into sight.B．Play a part.C．Come into use.D．Play around. 9．What may be the hidden cost of firing workers?A．Reducing salary expenses.B．Cutting costs of the company.C．Doing wonders for the workers' morale.D．Discouraging the remaining workers. 10．How is the passage mainly developed?A．By giving examples.B．By listing figures.C．By using space order.D．By explaining concepts.11．What can we learn from this passage?A．You get what you pay for.B．Price is the main consideration.C．Considering the best solution is easy.D．Be thoughtful when making decisions.As cities balloon with growth, visits to zoos provide an increasingly important opportunity for contact with other species. Though zoos were originally created to help people learn about animals that they had never seen, zoos have a serious role as conservation organizations. Many zoos consider conservation education to be important, and hope to encourage positive attitudes toward animal conservation among their visitors.Traditionally, zoos educate visitors by displaying information. Zoos often attach boring signs to exhibits, describing an animal’s habitat and lifestyle in the wild as well as whether or not the species is endangered. But recently, psychological research has shown that vivid emotional experiences not only attract more attention, they are also better remembered. The scary or funny animal exhibits at the zoo encourage people to pay more attention to information about the animals than they would pay to a written description.The majority of zoo visitors come with family members or on school field trips. Social interactions are thus a key part of the zoo visit. And when people are looking at the animals, there seems to be a tendency to tell what they see to others. In my research at zoos, I found that almost nine out of ten visitors would share their observations of an animal by pointing it out to their companions, or simply by saying “look!”. Social interactions like these are opportunities to create and communicate shared values. Parents who stand in front of an animal exhibit and say “Themommy is looking after her baby.” or even “Look at that!” is giving their children a reason to care about the animal.Zoos can create a culture of conservation. The best exhibits should be the ones that place animals in their natural habitats, where people care for their needs. In this way zoos can help to prevent the disappearance of wild animals from our sight and from our minds.12．What was the original purpose of building the zoo?A．To feed the animals.B．To meet people’s curiosity.C．To bring entertainment to kids.D．To save endangered animals.13．What is the author’s attitude towards the zoo’s traditional way of education?A．Uninterested.B．Positive.C．Negative.D．Unclear. 14．What do people tend to do when appreciating animals?A．They shout to animals.B．They offer their food.C．They take photos of animals.D．They share what they see.15．Which of the following is the best title of the passage?A．The Zoo Attracts People to Visit Animals.B．Communicate with Nature in the Zoo.C．The Zoo Offers Protection to Animals.D．Learn to Care About Animals in the Zoo.Art isn't always an easy and straightforward thing to understand, and it can be hard to appreciate because it has been seen as something that only particularly educated or wealthy people can enjoy. 16 . Anyone can come to appreciate art with a little bit of time and effort.Understand the art and then go a step deeper to understand the artists, their intentions and the historical backgrounds. Artists often create works to comment on major historical events.17 . For example, Pablo Picasso's Guernica (1937) was created in response to the bombings during the Spanish Civil War. It's filled with anti—war symbolism. Picasso said of the artwork, “Painting is not done to decorate apartments. It is an instrument of war against cruelty and darkness.”18 . Art movements grow from popularity of certain ways of creating art. An art school is basically a group of artists, sometimes all in the same region, who all have a similar style or subject matter. Knowing a little bit about these can help you understand why an artist might have made certain choices. For example, painters in the Egyptian school of art had certain rulesthat they had to follow—like the size of any figure they drew was supposed to vary based on the social status of the person they were painting. 19 . Each one symbolized a different aspect of life or death.Check out the life experiences of the artists. Learning a bit about the artists who created a piece can help understand it in a variety of ways. It can help you understand why they made certain artistic decisions. 20 . She had limited mobility after fighting against a serious disease and suffering a bus accident in her early life. Her pain and struggle appears in several of her pieces.A．But our tips will give you a new wayB．Art movements sometimes inspired artistsC．They also couldn't use more than six colorsD．However, this couldn't be further from the truthE．This can give you a window into their unique opinionF．For example, Mexican painter Frida Kahlo had suffered a lotG．Learn about the art movements or schools that influenced the piece二、完形填空It’s the first day of the new term. Graham, my 12-year-old son, was very happy and went to school with great 21 . However, he returned home with an/a 22 face. When asked what had happened, he just 23 his head, saying, “Nothing. I just fell down.” Busy with my work, I 24 his true situation.A few days later, Graham returned with his coat torn and looked sadly at me with 25 eyes. It suddenly 26 me that my son was bullied! Feeling 27 and concerned, I hugged and comforted him. After that, I called Graham’s head teacher, Mrs. Li, reporting what Graham had 28 . Learning about the bullying, which was unexpected, Mrs. Li was 29 and apologized several times for some student’s bad behavior. She promised to handle this bullying seriously and 30 .With time passing by, I noticed that smile began to light up my son’s face. One day, he told me 31 that he got involved in various activities and made some new friends, which was a32 to a worried parent.Graham’s experience has changed all of us. He learns to speak up when something bad happens. I try to listen to him with 33 despite my busy work. And I am always ready to 34 whenever he meets with a hot potato. Although he went through such an unpleasant experience, he’s 35 for the lessons he’s learned.21．A．enthusiasm B．puzzlement C．depression D．determination 22．A．excited B．injured C．round D．bright 23．A．nodded B．shook C．patted D．beat 24．A．understood B．noticed C．ignored D．remembered 25．A．sleepy B．curious C．watery D．sharp 26．A．confused B．attracted C．satisfied D．struck 27．A．guilty B．impressed C．embarrassed D．encouraged 28．A．caused B．heard C．judged D．suffered 29．A．inspired B．shocked C．reserved D．moved 30．A．properly B．slowly C．roughly D．easily 31．A．sensitively B．equally C．constantly D．proudly 32．A．demand B．relief C．doubt D．choice 33．A．judgement B．strategy C．patience D．dream 34．A．back off B．hold back C．give in D．step in 35．A．desired B．regretful C．grateful D．ashamed三、语法填空阅读下面短文，在空白处填入1个适当的单词或括号内单词的正确形式。
CH06 Electronic structure of atoms
orbitals. The orbitals can be described in a shorthand notationusing quantum numbers.6.6REPRESENTATIONS OF ORBITALSWe consider the three-dimensional shapes of orbitals and howthey can be represented by graphs of electron density.6.7MANY-ELECTRON ATOMSWe recognize that the energy levels for an atom with one electronare altered when the atom contains multiple electrons. Eachelectron has a quantum-mechanical property called spin. ThePauli exclusion principle states that no two electrons in an atomcan have the same four quantum numbers (three for the orbitaland one for the spin). Therefore, an orbital can hold a maximum oftwo electrons.6.8ELECTRON CONFIGURATIONSWe learn that knowing orbital energies as well as somefundamental characteristics of electrons described by Hund’s ruleallows us to determine how electrons are distributed in an atom(electron configurations).6.9ELECTRON CONFIGURATIONSAND THE PERIODIC TABLEWe observe that the electron configuration of an atom is related tothe location of the element in the periodic table.207 revolutionary discoveries of the twentieth century—the quantum theory,which explainsmuch of the behavior of electrons in atoms.In this chapter we explore the quantum theory and its importance in chemistry.We begin by looking at the nature of light and how our description of light waschanged by the quantum theory.We will explore some of the tools used in quantummechanics,the “new”physics that had to be developed to describe atoms correctly.Wewill then use the quantum theory to describe the arrangements of electrons in atoms—what we call the electronic structure of atoms.The electronic structure of an atomrefers to the number of electrons in the atom as well as their distribution around thenucleus and their energies.We will see that the quantum description of the electronicstructure of atoms helps us to understand the arrangement of the elements in theperiodic table—why,for example,helium and neon are both unreactive gases,whereassodium and potassium are both soft,reactive metals. ELECTRONIC STRUCTUREOF ATOMSWHAT HAPPENS WHEN SOMEONE switches on a neon light? Electrons in the neon atoms are excited to a higher energy by electricity. An electron can remain in a higher-energy state for only a very short time, and it emits light when it returns to a lower energy. The resulting glow is explained by one of the mostWavelength Wave troughWave peakįFIGURE 6.2Water waves.Thewavelength is the distance between twoadjacent peaks or two adjacent troughs.208CHAPTER 6Electronic Structure of AtomsįFIGURE 6.1Water waves.The movement of a boat through the water forms waves that move away from the boat.6.1|THE WAVE NATURE OF LIGHT Much of our present understanding of the electronic structure of atoms has come from analysis of the light either emitted or absorbed by substances.To understand electronic structure,therefore,we must first learn about light.The light we see with our eyes,visible light,is one type of electromagnetic radiation .Because electromagnetic radia-tion carries energy through space,it is also known as radiant energy .There are many types of electromagnetic radiation in addition to visible light.These different types—radio waves that carry music to our radios,infrared radiation (heat) from a glowing fireplace,X-rays—may seem very different from one another,but they all share certain fundamental characteristics.All types of electromagnetic radiation move through a vacuum at ,the speed of light .All have wavelike characteristics similar to those of waves that move through water.Water waves are the result of energy imparted to the water,perhaps by the dropping of a stone or the movement of a boat on the water surface (ǡFIGURE 6.1).This energy is expressed as the up-and-down movements of the water.A cross section of a water wave (ǡFIGURE 6.2) shows that it is periodic,which means that the pattern of peaks and troughs repeats itself at regular intervals.The dis-tance between two adjacent peaks (or between two adjacent troughs) is called the wavelength .The number of complete wavelengths,or cycles,that pass a given point each second is the frequency of the wave.Just as with water waves,we can assign a frequency and wavelength to electromag-netic waves,as illustrated in ǡFIGURE 6.3.These and all other wave characteristics of electromagnetic radiation are due to the periodic oscillations in the intensities of the electric and magnetic fields associated with the radiation.The speed of water waves can vary depending on how they are created—for exam-ple,the waves produced by a speedboat travel faster than those produced by a rowboat.In contrast,all electromagnetic radiation moves at the same speed,m >s,the speed of light.As a result,the wavelength and frequency of electromagnetic radiation are always related in a straightforward way.If the wavelength is long,fewer cycles of the wave pass a given point per second,and so the frequency is low.Conversely,for a wave to have a high frequency,it must have a short wavelength.This inverse relationship between the frequency and wavelength of electromagnetic radiation is expressed by the equation [6.1]where c is the speed of light,(lambda) is wavelength,and (nu) is frequency.Why do different types of electromagnetic radiation have different properties?Their differences are due to their different wavelengths.ǠFIGURE 6.4shows the vari-ous types of electromagnetic radiation arranged in order of increasing wavelength,a display called the electromagnetic spectrum .Notice that the wavelengths span an enor-mous range.The wavelengths of gamma rays are comparable to the diameters of atomic nuclei,whereas the wavelengths of radio waves can be longer than a football field.Notice also that visible light,which corresponds to wavelengths of about 400 to 750 nm (to ),is an extremely small portion of the electromagnetic spectrum.The unit of length chosen to express wavelength depends on the type of radi-ation,as shown in ĬTABLE 6.1.7*10-7 m 4*10-7 m n l c =ln 3.00*1083.00*108 m >s Wavelength ll(a)(b)G O F I G U R EIf wave (a) has a wavelength of 1.0m and a frequency of cy-cles/s, what are the wavelengthand frequency of wave (b)?3.0*108įFIGURE 6.3Electromagnetic waves.Like water waves, electromagnetic radiationcan be characterized by a wavelength.Notice that the shorter the wavelength, , thehigher the frequency, The wavelength in(b) is half as long as that in (a), and the frequency of the wave in (b) is therefore twiceas great as the frequency in (a).n .l TABLE 6.1•Common Wavelength Units for Electromagnetic RadiationUnit Symbol Length (m)Type of Radiation Angstrom ÅX-rayNanometer nm Ultraviolet,visible Micrometer InfraredMillimeter mm MicrowaveCentimeter cm MicrowaveMeter m 1Television,radio Kilometer km 1000Radio10-210-310-6m m 10-910-10400500600700750 nmVisible regionGamma raysX-rays Ultra-violet V i s i b l e Infrared Microwaves Radio frequency 10Ϫ1110Ϫ910Ϫ510Ϫ310Ϫ110Ϫ7101103102010161012101010810141061041018Wavelength (m)Frequency (s Ϫ1)ǡFIGURE 6.4The electromagneticspectrum.Wavelengths in the spectrum range from very short gamma rays to very long radio waves.G O F I G U R EHow do the wavelength and frequency of an X-ray compare with those of the red light from a neon sign?Frequency is expressed in cycles per second,a unit also called a hertz (Hz).Because it is understood that cycles are involved,the units of frequency are normally given simply as “per second,”which is denoted by or .For example,a frequency of 820kilohertz (kHz),a typical frequency for an AM radio station,could be written as 820kHz,820,000 Hz,,or .820,000>s 820,000 s -1>s s -1Since Rømer’s time,increasingly sophisticated techniques have been used to measure the speed of light.For example,in 1927,A.A.Michelson (1852–1931) set up a rotating mirror at the top of Mount Wilson in California.The mirror bounced light to the top of Mount San Antonio,22 miles away,where another mirror bounced the light back to Mount Wilson.Michelson was able to change the speed of the rotating mirror and measure small displacements in the position of the reflected spot.The value for the speed of light (in air) based on this experiment was .The main source of error was the distance between the mirrors,which was measured within a fifth of an inch in 22 miles.By 1975,the measured value was even more precise,m >s (in vacuum),the error being mostly due to the uncertainty in the length of the meter.In 1983,the meter was redefined based on the distance that light travels in vac-uum in one second.As a result,the value for the speed of light became a fixed,exact quantity,m >s.c =2.99792458*1082.99792458;0.00000004*1082.9980;0.0002*108 m >s THE SPEED OF LIGHTHow do we know that light has a finite speed and doesnot move infinitely fast?During the late 1600s,the Danish astronomerOle Rømer (1644–1710) measured the orbits ofseveral of Jupiter’s moons.These moons movemuch faster than our own—they have orbits of 1–7 days and areeclipsed by Jupiter’s shadow at every revolution.Over many months,Rømer measured discrepancies of up to 10 minutes in the times ofthese orbits.He reasoned that the discrepancies occurred becauseJupiter was farther from Earth at different times of the year.Thus,light from the Sun,which reflected off Jupiter and ultimately to histelescope,had farther to travel at different times of the year,implyingthat light travels at a finite speed.Rømer’s data led to the first esti-mate of the speed of light,.3.5*108 m >s A CLOSER LOOKSAMPLE EXERCISE 6.1Concepts of Wavelength and FrequencyTwo electromagnetic waves are represented in the margin.(a)Which wave has the higher frequency? (b)If one wave represents visible light and the other represents infrared radiation,which wave is which?SOLUTION(a)The lower wave has a longer wavelength (greater distance between peaks).The longer thewavelength,the lower the frequency .Thus,the lower wave has the lower frequency,and the upper wave has the higher frequency.(b)The electromagnetic spectrum (Figure 6.4) indicates that infrared radiation has a longerwavelength than visible light.Thus,the lower wave would be the infrared radiation.PRACTICE EXERCISEIf one of the waves in the margin represents blue light and the other red light,which is which?Answer:The expanded visible-light portion of Figure 6.4tells you that red light has a longer wavelength than blue light.The lower wave has the longer wavelength (lower frequency) and would be the red light.(n =c >l )SECTION 6.1The Wave Nature of Light 209210CHAPTER 6Electronic Structure of AtomsG I V E I T S O M E T H O U G H T Our bodies are penetrated by X-rays but not by visible light. Is this because X-rays travel faster than visible light?6.2|QUANTIZED ENERGY AND PHOTONS Although the wave model of light explains many aspects of its behavior,this model can-not explain several phenomena.Three of these are particularly pertinent to our understanding of how electromagnetic radiation and atoms interact:(1) the emission of light from hot objects (referred to as blackbody radiation because the objects studied ap-pear black before heating),(2) the emission of electrons from metal surfaces on which light shines (the photoelectric effect ),and (3) the emission of light from electronically ex-cited gas atoms (emission spectra ).We examine the first two phenomena here and the third in Section 6.3.Hot Objects and the Quantization of Energy When solids are heated,they emit radiation,as seen in the red glow of an electric stove burner or the bright white light of a tungsten lightbulb.The wavelength distribution of the radiation depends on temperature;a red-hot object,for instance,is cooler than a yellowish or white-hot one (ǡFIGURE 6.5).During the late 1800s,a number of physi-cists studied this phenomenon,trying to understand the relationship between the temperature and the intensity and wavelength of the emitted radiation.The prevailing laws of physics could not account for the observations.In 1900 a German physicist named Max Planck (1858–1947) solved the problem by assuming that energy can be either released or absorbed by atoms only in discrete “chunks”of some minimum size.Planck gave the name quantum (meaning “fixed amount”) to the smallest quantity of energy that can be emitted or absorbed as electro-magnetic radiation.He proposed that the energy,E,of a single quantum equals a constant times the frequency of the radiation:[6.2]E =h n įFIGURE 6.5Color and temperature.The color and intensity of the light emitted bya hot object, such as this pour of moltensteel, depend on the temperature of theobject.G O F I G U R EWhich area in the photographcorresponds to the highesttemperature?SECTION 6.2Quantized Energy and Photons 211The constant h is called Planck’s constant and has a value of joule-second (J-s).According to Planck’s theory,matter can emit and absorb energy only in whole-number multiples of ,such as ,,,and so forth.If the quantity of energy emitted by an atom is ,for example,we say that three quanta of energy have been emitted (quanta being the plural of quantum ).Because the energy can be released only in specific amounts,we say that the allowed energies are quantized —their values are re-stricted to certain quantities.Planck’s revolutionary proposal that energy is quantized was proved correct,and he was awarded the 1918 Nobel Prize in Physics for his work on the quantum theory.If the notion of quantized energies seems strange,it might be helpful to draw an analogy by comparing a ramp and a staircase (įFIGURE 6.6).As you walk up a ramp,your potential energy increases in a uniform,continuous manner.When you climb a staircase,you can step only on individual stairs,not between them,so that your potential energy is restricted to certain values and is therefore quantized.If Planck’s quantum theory is correct,why are its effects not obvious in our daily lives? Why do energy changes seem continuous rather than quantized,or “jagged”? No-tice that Planck’s constant is an extremely small number.Thus,a quantum of energy,,is an extremely small amount.Planck’s rules regarding the gain or loss of energy are always the same,whether we are concerned with objects on the scale of our ordinary ex-perience or with microscopic objects.With everyday objects,however,the gain or loss of a single quantum of energy is so small that it goes completely unnoticed.In contrast,when dealing with matter at the atomic level,the impact of quantized energies is far more significant.G I V E I T S O M E T H O U G H TCalculate the energy (to one significant figure) of one quantum of electromag-netic radiation whose frequency is . Can this radiation produce a burst of energy J? Why or why not?The Photoelectric Effect and PhotonsA few years after Planck presented his quantum theory,scientists began to see its appli-cability to many experimental observations.In 1905,Albert Einstein (1879–1955) used Planck’s theory to explain the photoelectric effect (ǠFIGURE 6.7).Light shining on a clean metal surface causes the surface to emit electrons.A minimum frequency of light,different for different metals,is required for the emission of electrons.For example,light with a frequency of or greater causes cesium metal to emit electrons,but light of lower frequency has no effect.To explain the photoelectric effect,Einstein assumed that the radiant energy strik-ing the metal surface behaves like a stream of tiny energy packets.Each packet,which is like a “particle”of energy,is called a photon .Extending Planck’s quantum theory,4.60*1014 s -1E =5*10-365*10-3 s -1h n 3h n 3h n 2h n h n h n 6.626*10-34Potential energy of person walking up steps increases in stepwise,Potential energy of person walkingup ramp increases in uniform,continuous mannerǡFIGURE 6.6Quantized versus continuous change in energy.Voltage source Positive terminal Radiant energy +–Metal surface Evacuated chamber Radiant energy Metal surface Electrons drawn to positive terminal e –e –e –e –Current indicator įFIGURE 6.7The photoelectric effect.G O F I G U R E Why is it necessary to carry out this experiment in an evacuated212CHAPTER 6Electronic Structure of AtomsEinstein deduced that each photon must have an energy equal to Planck’s constant times the frequency of the light:[6.3]Thus,radiant energy itself is quantized.Under the right conditions,photons striking a metal surface can transfer their en-ergy to electrons in the metal.A certain amount of energy—called the work function —is required for the electrons to overcome the attractive forces holding them in the metal.If the photons striking the metal have less energy than the work function,the electrons do not acquire sufficient energy to escape from the metal,even if the light beam is intense.If the photons have energy greater than the work function of the particular metal,how-ever,electrons are emitted.The intensity (brightness) of the light is related to the number of photons striking the surface per unit time but not to the energy of each photon.Einstein won the Nobel Prize in Physics in 1921 for his explanation of the photoelectric effect.To better understand what a photon is,imagine you have a light source that pro-duces radiation of a single wavelength.Further suppose that you could switch the light on and off faster and faster to provide ever-smaller bursts of energy.Einstein’s photon theory tells us that you would eventually come to the smallest energy burst,given by .This smallest burst consists of a single photon of light.E =h n Energy of photon =E =h n 6.3Energy of a PhotonCalculate the energy of one photon of yellow light that has a wavelength of 589 nm.SOLUTIONAnalyze Our task is to calculate the energy,E,of a photon,given .l =589 nm Plan We can use Equation 6.1 to convert the wavelength to frequency:n =c >l We can then use Equation 6.3 to calculate energy:E =h n Solve The frequency,,is calculated from the given wavelength,as shownin Sample Exercise 6.2:n n =c >l =5.09*1014 s -1The value of Planck’s constant,h,is given both in the text and in the table ofphysical constants on the inside back cover of the text,and so we can easilycalculate E :E =(6.626*10-34 J-s)(5.09*1014s -1)=3.37*10-19 J Comment If one photon of radiant energy supplies ,thenone mole of these photons will supply 3.37*10-19 J =2.03*105 J >mol (6.02*1023 photons >mol)(3.37*10-19 J >photon)PRACTICE EXERCISE(a)A laser emits light that has a frequency of .What is the energy of one photon of this radiation? (b)If the laser emits a pulse containing of this radiation,what is the total energy of that pulse? (c)If the laser emits of energy during a pulse,how many photons are emitted?Answers:(a),(b)0.16 J,(c)4.2*1016 photons3.11*10-19 J 1.3*10-2 J 5.0*1017 photons4.69*1014 s -1The idea that the energy of light depends on its frequency helps us understand the diverse effects of different kinds of electromagnetic radiation.For example,because of the high frequency (short wavelength) of X-rays (Figure 6.4),X-ray photons cause tissue damage and even cancer.Thus,signs are normally posted around X-ray equipment warning us of high-energy radiation.Although Einstein’s theory of light as a stream of photons rather than a wave ex-plains the photoelectric effect and a great many other observations,it also poses a dilemma.Is light a wave,or is it particle-like? The only way to resolve this dilemma is to adopt what might seem to be a bizarre position:We must consider that light possesses both wave-like and particle-like characteristics and,depending on the situation,will behave more like waves or more like particles.We will soon see that this dual nature of light is also a characteristic trait of matter.G I V E I T S O M E T H O U G H TWhich has more energy, a photon of infrared light or a photon of ultraviolet light?įFIGURE 6.8Quantum giants.Niels Bohr (right) with Albert Einstein. Bohr (1885–1962) made major contributions to the quantum theory and was awarded the Nobel Prize in Physics in 1922.SECTION 6.3Line Spectra and the Bohr Model 2136.3|LINE SPECTRA AND THE BOHR MODELThe work of Planck and Einstein paved the way for understanding how electrons are arranged in atoms.In 1913,the Danish physicist Niels Bohr (ǠFIGURE 6.8) offered a theoretical explanation of line spectra,another phenomenon that had puzzled scientists during the nineteenth century.Line SpectraA particular source of radiant energy may emit a single wavelength,as in the light from a laser.Radiation composed of a single wavelength is monochromatic .However,most common radiation sources,including lightbulbs and stars,produce radiation contain-ing many different wavelengths and is polychromatic .A spectrum is produced when radiation from such sources is separated into its component wavelengths,as shown in ǠFIGURE 6.9.merges into indigo,indigo into blue,of colors,containing light of all continuous spectrum .The most familiar example of a continuous spectrum is the rainbow produced when raindrops ormist acts as a prism for sunlight.Not all radiation sources produce acontinuous spectrum.When a high volt-age is applied to tubes that contain differentgases under reduced pressure,the gases emit different colors of light (ǠFIGURE 6.10).The light emitted by neon gas is the familiar red-orange glow of many “neon”lights,whereas sodium vapor emits the yellow light characteristic of some modern streetlights.When light coming from such tubes is passed through a prism,only a few wavelengths are present in the resultant spectra (ĬFIGURE 6.11).Each colored line in such spectra represents light of one wavelength.A spectrum containing radiation of only specific wavelengths is called a line spectrum .When scientists first detected the line spectrum of hydrogen in the mid-1800s,they were fascinated by its simplicity.At that time,only four lines at wavelengths of 410 nm (violet),434 nm (blue),486 nm (blue-green),and 656 nm (red) were observed (Figure 6.11).In 1885,a Swiss schoolteacher named Johann Balmer showed that the wavelengths of these four lines fit an intriguingly simple formula that relates the wavelengths to ter,additional lines were found in the ultraviolet and infrared regions of hydrogen’s line spectrum.Soon Balmer’s equation was extended to a more general one,called the Rydberg equation,which allows us to calculate the wavelengths of all the spectral lines of hydrogen:[6.4]In this formula is the wavelength of a spectral line,is the Rydberg constant ,and and are positive integers,with being largern 2n 2n 1(1.096776*107 m -1)R H l 1l =(R H )a 1n 21-1n 22b įFIGURE 6.9Creating a spectrum.A continuous visible spectrum is produced when a narrow beam of white light is passed through a prism. The white light could be sunlight or light from an incandescent lamp.400450500550600650700 nm įFIGURE 6.11Line spectra of hydrogen and neon.įFIGURE 6.10Atomic emission of hydrogen and neon.Different gases emit light of different characteristic colors whenan electric current is passed through them.Hydrogen (H)Neon (Ne)214CHAPTER 6Electronic Structure of Atomsthan .How could the remarkable simplicity of this equation be explained? It took nearly 30 more years to answer this question.Bohr’s ModelTo explain the line spectrum of hydrogen,Bohr assumed that electrons in hydrogen atoms move in circular orbits around the nucleus,but this assumption posed a problem.According to classical physics,a charged particle (such as an electron) moving in a circu-lar path should continuously lose energy.As an electron loses energy,therefore,it should spiral into the positively charged nucleus.This behavior,however,does not happen—hydrogen atoms are stable.So how can we explain this apparent violation of the laws of physics? Bohr approached this problem in much the same way that Planck had ap-proached the problem of the nature of the radiation emitted by hot objects:He assumed that the prevailing laws of physics were inadequate to describe all aspects of atoms.Fur-thermore,he adopted Planck’s idea that energies are quantized.Bohr based his model on three postulates:1.Only orbits of certain radii,corresponding to certain specific energies,are permitted for the electron in a hydrogen atom.2.An electron in a permitted orbit is in an “allowed”energy state.An electron in an allowed energy state does not radiate energy and,therefore,does not spiral into the nucleus.3.Energy is emitted or absorbed by the electron only as the electron changes from one allowed energy state to another.This energy is emitted or absorbed as a photon that has energy .G I V E I T S O M E T H O U G H TBefore reading further about Bohr’s model, speculate as to how it explains thefact that hydrogen gas emits a line spectrum (Figure 6.11) rather than a continu-ous spectrum.The Energy States of the Hydrogen Atom Starting with his three postulates and using classical equations for motion and for inter-acting electrical charges,Bohr calculated the energies corresponding to the allowed orbits for the electron in the hydrogen atom.Ultimately,the calculated energies fit theformula[6.5]where h,c,and are Planck’s constant,the speed of light,and theRydberg constant,respectively.The integer n,which can have whole-number values of 1,2,3,...,is called the principal quan-tum number .Each orbit corresponds to a different value of n,andthe radius of the orbit gets larger as n increases.Thus,the first al-lowed orbit (the one closest to the nucleus) has ,the next allowed orbit (the one second closest to the nucleus) has ,and so forth.The electron in the hydrogen atom can be in any al-lowed orbit,and Equation 6.5 tells us the energy the electron has in each allowed orbit.Note that the energies of the electron given by Equation 6.5 are negative for all values of n .The lower (more negative) the energy is,the more stable the atom is.The energy is lowest (most negative)for .As n gets larger,the energy becomes less negative andtherefore increases.We can liken the situation to a ladder in which the rungs are num-bered from the bottom.The higher one climbs (the greater the value of n ),the higher the energy.The lowest-energy state (,analogous to the bottom rung) is called the ground state of the atom.When the electron is in a higher-energy state (n = 2 or higher),the atom is said to be in an excited state .ǡFIGURE 6.12shows the energy of the electron in a hydrogen atom for several values of n .n =1n =1n =2n =1q R H E =(-hcR H )a 1n 2b =(-2.18*10-18 J)a 1n 2b E =h n n 1įFIGURE 6.12Energy states in the hydrogen atom.Only states for through and are shown.Energy is released or absorbed when an electron moves from one energy state to another.n =q n =4n =1G O F I G U R E If the transition of an electron fromthe n =3 state to the n =2 stateresults in emission of visible light,is the transition from the n =2state to the n =1 state more likelyto result in the emission of infraredor ultraviolet radiation?SECTION 6.3Line Spectra and the Bohr Model 215What happens to the orbit radius and the energy as n becomes infinitely large? The radius increases as ,so when the electron is completely separated from the nucleus,and the energy of the electron is zero:The state in which the electron is removed from the nucleus is called the reference,or zero-energy,state of the hydrogen atom.In his third postulate,Bohr assumed that the electron can “jump”from one allowed orbit to another by either absorbing or emitting photons whose radiant energy corre-sponds exactly to the energy difference between the two orbits.The electron must absorb energy in order to move to a higher-energy state (higher value of n ).Conversely,radiant energy is emitted when the electron jumps to a lower-energy state (lower value of n ).If the electron jumps from an initial state of energy to a final state of energy ,the change in energy is[6.6]Bohr’s model of the hydrogen atom states,therefore,that only the specific frequencies of light that satisfy Equation 6.6 can be absorbed or emitted by the atom.Substituting the energy expression in Equation 6.5 into Equation 6.6 and recalling that ,we have[6.7]where and are the principal quantum numbers of the initial and final states of the atom,respectively.If is smaller than ,the electron moves closer to the nucleus and is a negative number,indicating that the atom releases energy.For example,if the electron moves from to ,we haveKnowing the energy of the emitted photon,we can calculate either its frequency or its wavelength.For the wavelength,we haveWe have not included the negative sign of the energy in this calculation because wave-length and frequency are always reported as positive quantities.The direction of energy flow is indicated by saying that a photon of wavelength has been emitted .If we solve Equation 6.7 for and replace by its equivalent,from Equation 6.5,we find that Equation 6.7 derived from Bohr’s theory corre-sponds to the Rydberg equation,Equation 6.4,which was obtained using experimental data:Thus,the existence of discrete spectral lines can be attributed to the quantized jumps of electrons between energy levels.G I V E I T S O M E T H O U G H TAs the electron in a hydrogen atom jumps from the orbit to the orbit, does it absorb energy or emit energy?n =7n =31l =-hcR H hc a 1n f 2-1n i 2b =R H a 1n i 2-1n f2b hcR H (-2.18*10-18 J)1>l 1.02*10-7m l =c v =hc ¢E =(6.626*10-34 J-s)(3.00*108 m >s)1.94*10-18 J=1.02*10-7 m ¢E =(-2.18*10-18 J)a 112-132b =(-2.18*10-18 J)a 89b =-1.94*10-18 J n f =1n i =3¢E n i n f n f n i ¢E =h n =hc l =(-2.18*10-18 J)a 1n f 2-1n i 2b n =c >l ¢E =E f -E i =E photon =h n E f E i E =(-2.18*10-18 J)a 1q 2b =0n =q n 2。
The Fascination of Tie Painting
**The Fascination of Tie Painting**In the vast expanse of the artistic domain, Tie Painting emerges as a form that holds an unwavering fascination, like a magnetic force drawing both the artist and the observer into its captivating embrace.A painted tie is not just an accessory to adorn one's neck; it is a microcosm of creativity and expression. It is like a key that unlocks a hidden world of imagination and style. Picture a tie as a narrow canvas, waiting for the artist's brush to etch upon it a tale of artistry and innovation.The process of tie painting is a meticulous and enchanting ritual. The artist's hand moves with a precision and finesse that rivals the craftsmanship of a master watchmaker. The brushstrokes, each one a deliberate act of creation, lay down colors and patterns that form a symphony of visual delight. Just as a poet selects words with care to compose a sonnet, the artist chooses hues and designs to transform the tie into a wearable masterpiece.For instance, a tie painted with images of a stately castle against a backdrop of a setting sun evokes a sense of romance and grandeur. The warm tones of the sky, the imposing structure of the castle, and the soft glow of the evening light all merge to create an atmosphere of timeless beauty. Or consider a tie adorned with abstract patterns that mirror the chaos and order of the universe, inviting the viewer to delve into the depths of its meaning.Tie painting also has the power to bridge the gap between the mundane and the extraordinary. It can take an ordinary piece of fabric and turn it into a statement of individuality and refinement. Much like the works of Rembrandt that have endured through the ages, a painted tie has the potential to become a timeless classic.However, in a world often driven by conformity and mass-produced fashion, the fascination of tie painting can sometimes be overlooked. It is as if this art form is a hidden gem buried beneath the piles of generic and mundane ties. We are so accustomed to the uniformity and predictability of mainstream fashion that we fail to appreciate the unique charm and artistry of a painted tie.We should take a moment to pause and admire the beauty of tie painting. A painted tie is not merely an article of clothing; it is a work of art that reflects the artist's vision and the wearer's personality. It is a rebellion against the ordinary and a celebration of the extraordinary.In conclusion, the fascination of tie painting lies in its ability to transform a simple accessory into a source of inspiration and a symbol of personal style. It is a reminder of the power of art to elevate the mundane to the realm of the sublime.As Michelangelo once said, "I saw the angel in the marble and carved until I set him free." Tie painting is the process of uncovering the hidden beauty within the fabric and setting it free to captivate the world.。
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a r X i v :a s t r o -p h /0503260v 2 22 J u l 2005Astronomy &Astrophysics manuscript no.3046main February 2,2008(DOI:will be inserted by hand later)Metallicity of M dwarfsI.A photometric calibration and the impact on the mass-luminosity relationat the bottom of the main sequence ⋆X.Bonfils 1,2,X.Delfosse 1,S.Udry 2,N.C.Santos 2,3,T.Forveille 1,4,and D.S´e gransan 21Laboratoire d’Astrophysique,Observatoire de Grenoble,BP 53,F-38041Grenoble,C´e dex 9,France2Observatoire de Gen`e ve,51ch.des Maillettes,1290Sauverny,Switzerland 3Centro de Astronomia e Astrofisica da Universidade de Lisboa,Observat´o rio Astr´o nomico de Lisboa,Tapada de Ajuda,1349-018Lisboa,Portugal4Canada-France-Hawaii Telescope Corporation,65-1238Mamalahoa Highway,Kamuela,HI 96743,Hawaii,USAReceived March 14,2005;accepted May 19,2005Abstract.We obtained high resolution ELODIE and CORALIE spectra for both components of 20wide visual binaries com-posed of an F-,G-or K-dwarf primary and an M-dwarf secondary.We analyse the well-understood spectra of the primaries to determine metallicities ([Fe /H])for these 20systems,and hence for their M dwarf components.We pool these metallicities with determinations from the literature to obtain a precise (±0.2dex)photometric calibration of M dwarf metallicities.This calibration represents a breakthrough in a field where discussions have had to remain largely qualitative,and it helps us demon-strate that metallicity explains most of the large dispersion in the empirical V-band mass-luminosity relation.We examine the metallicity of the two known M-dwarf planet-host stars,Gl 876(+0.02dex)and Gl 436(−0.03dex),in the context of prefer-ential planet formation around metal-rich stars.We finally determine the metallicity of the 47brightest single M dwarfs in a volume-limited sample,and compare the metallicity distributions of solar-type and M-dwarf stars in the solar neighbourhood.Key words.Techniques:spectroscopy –stars:abundances –stars:late-type –binaries:visual –planetary systems –stars:individual:Gl 876,Gl 4361.IntroductionThe very low mass M dwarfs are small,cool and faint,but they dominate the Galaxy by number (∼50-70%),and even by to-tal mass (∼70%)(Chabrier 2003).Any realistic model of the Galaxy therefore needs an excellent description of this faint component.Over the last decade,stellar models of very low mass stars have made great strides,but they still have to use some incomplete or approximate input physics (Chabrier &Bara ffe 2000).Descriptions of these stars therefore need a strong empirical basis,or validation.In S´e gransan et al.(2003)and Delfosse et al.(2000,here-after DFS00),we have validated the model predictions for radii and luminosities.The empirical radii match the models very well,and have no dispersion beyond the measurement errors.The infrared mass-luminosity (hereafter M /L)relations also have negligible dispersion,and similarly agree with model predictions.The V-band M /L relation,in contrast,has a large2X.Bonfils et al.:Metallicity of M dwarfsTable1.Observed visual binaries with an M-dwarf secondary.GJ102100:45:45.593−47:33:07.15 5.80G1V CD-48176B00:45:43.5−47:33:0013.5MGl34A00:49:06.291+57:48:54.67 3.44F9V Gl34B00:49:06.5+57:48:557.51K7Gl53.1A01:07:37.872+22:57:17.918.41K4V Gl53.1B01:07:37.7+22:57:1813.60M3Gl81.1A01:57:09.607−10:14:32.75 6.42G5Gl81.1˙B01:57:11.1−10:14:5311.21K7Gl105A02:36:04.894+06:53:12.73 5.79K3V Gl105B02:36:15.3+06:52:1911.68M4Gl107A02:44:11.986+49:13:42.41 4.10F7V Gl107B02:44:11.8+49:13:4310.06M1.5GJ3194A03:04:09.636+61:42:20.99 6.64G4V GJ3195B03:04:43.6+61:44:0812.5M3Gl166A04:15:16.320−07:39:10.33 4.43K1V Gl166C04:15:18.5−07:39:0711.17M4.5Gl21105:41:20.336+53:28:51.81 6.21K1Gl21205:41:30.7+53:29:239.80M0.5Gl231.1A06:17:16.138+05:06:00.40 5.70F9V Gl231.1B06:17:11.0+05:07:0613.42M3.5Gl250A06:52:18.050−05:10:25.37 6.59K3Gl250B06:52:18.1−05:11:2610.09M2Gl297.2A08:10:39.826−13:47:57.15 5.53F7Gl297.2B08:10:34.0−13:48:4811.80M2Gl324A08:52:35.811+28:19:50.95 5.53G8Gl324B08:52:40.8+28:18:5913.14M3.5Gl505A13:16:51.052+17:01:01.86 6.69K2Gl505B13:16:51.7+17:00:569.6M0.5Gl544A14:19:34.864−05:09:04.307.58K1Gl544B14:19:35.0−05:09:0814.1M6NLTT4578918:00:38.894+29:34:18.917.07G2V NLTT4579118:00:45.4+29:33:5713.1MGl768.1A19:51:01.643+10:24:56.62 5.12F8V Gl768.1B19:51:01.1+10:24:4313.1M3.5Gl783.2A20:11:06.074+16:11:16.807.34K1V Gl783.2B20:11:13.4+16:11:0713.94M4Gl797A20:40:45.141+19:56:07.93 6.43G5V Gl797B20:40:44.4+19:53:5911.88M2.5Gl806.1A20:46:12.683+33:58:12.92 2.48K0III Gl806.1B20:46:12.7+33:58:1213.4M3Gl872A22:46:41.581+12:10:22.40 4.20F7V Gl872B22:46:41.6+12:10:2011.7M1Name HDα(2000)δ(2000)ity estimator for very low-mass stars.Sect.5re-examines thedispersion of the V-band M/L relation in the light of the newmetallicities and proposes a more precise mass-metallicity-luminosity relation for very low-mass stars.In Sect.6we applythe metallicity estimator to the two known M-dwarf planet-hoststars.Sect.7lists estimated metallicities for a volume-limitedsample of northern M dwarfs,and compares its metallicity dis-tribution with that of nearby solar-type stars.2.Previous metallicity estimates of M dwarfsThefirst attempt to measure metallicities for M dwarfs wasby Mould(1976,1978)who performed line-by-line analysesof atomic lines in intermediate resolution near-IR spectra ofa few stars,using model atmospheres available then.Joneset al.(1996)used a similar approach,but with the benefit ofatmospheric structures from an early version of the modernPHOENIX code(Allard&Hauschildt,1995).Gizis(1997)matched low resolution optical spectra to synthetic spectrafrom the same Allard&Hauschildt(1995)models,and derivedrelatively crude metallicities that allowed them to classify Mdwarfs into3broad categories(dwarfs,subdwarfs and extremesubdwarfs).Gizis and Reid(1997)validated that metallicityscale with observations of binary stars containing one M-dwarfcomponent and one warmer star.Valenti et al.(1998)performed detailed spectral synthe-sis of a very high resolution spectrum of Gl725B(vB10)toX.Bonfils et al.:Metallicity of M dwarfs3 Table3.Stellar parameters measured on the primaries.[Fe/H]applies for both components.GJ10214391CD-48176B5967±70 4.74±0.14 1.39±0.17−0.08±0.09Gl34A4614Gl34B5895±68 4.43±0.13 1.37±0.22−0.31±0.09Gl53.1A6660Gl53.1B4705±131 4.33±0.260.76±0.25+0.07±0.12Gl81.1A11964Gl81.1B5311±42 3.97±0.080.86±0.05+0.09±0.06Gl105A16160Gl105B4846±65 4.29±0.130.81±0.10−0.19±0.07Gl107A16895Gl107B6328±86 4.43±0.17 1.73±0.31−0.03±0.09GJ3194A18757GJ3195B5681±34 4.49±0.06 1.01±0.07−0.31±0.04Gl166A26965Gl166C5125±56 4.43±0.110.30±0.15−0.33±0.06Gl21137394Gl2125293±109 4.50±0.210.79±0.17+0.04±0.11Gl231.1A43587Gl231.1B5946±32 4.38±0.06 1.15±0.06−0.02±0.04Gl250A50281Gl250B4670±80 4.41±0.160.70±0.19−0.15±0.09Gl297.2A68146Gl297.2B6280±106 4.46±0.21 1.81±0.26−0.09±0.09Gl324A75732Gl324B5283±59 4.36±0.110.87±0.08+0.32±0.07Gl505A115404Gl505B4983±48 4.41±0.090.84±0.07−0.25±0.05Gl544A125455Gl544B5271±189 4.85±0.370.87±0.36−0.20±0.19NLTT45789164595NLTT457915696±41 4.36±0.080.83±0.06−0.07±0.05Gl768.1A187691Gl768.1B6248±93 4.63±0.18 2.36±0.48+0.07±0.12Gl783.2A191785Gl783.2B5094±66 4.31±0.130.30±0.19−0.16±0.08Gl797A197076A Gl797B5889±32 4.59±0.06 1.01±0.06−0.07±0.04Gl806.1A197989Gl806.1B4911±85 2.98±0.17 1.61±0.08−0.05±0.13Gl872A215648Gl872B6156±99 4.09±0.19 4.05±2.01−0.36±0.114X.Bonfils et al.:Metallicity of M dwarfssurements,and we make extensive use of these data in our dis-cussion.3.Observations and analysis3.1.Sample,observation and data reductionWe selected wide physical visual binaries composed of an F-,G-or K-primary component and an M-dwarf secondary,from the Gliese &Jareiss(1991)catalogue of nearby stars,the Poveda et al.(1994)catalogue of wide-binary and multiple sys-tems of nearby stars,and the Gould &Chanam´e (2004)list of physical HIPPARCOS binaries.We further required that the components be separated by at least 5′′and that the secondary be brighter than V =14,to facilitate observations of the faint M dwarf.Fast rotators,double-lined spectroscopic binaries (SB2)and close visual binaries were rejected a priori when known,and otherwise discarded a posteriori .These criteria resulted in a list of 70pairs.We discarded 2systems whose secondaries (GJ 3409B and Gl 771B)were SB2binaries (reported in Table 2).The Gl 549system had to be rejected as the F7V primary is a fast rotator (vsin i ∼50km.s −1).The Gl 695system was also rejected as both components are themselves close visual binaries.Here we analyse 21of those systems (Table 1),of which 20have M-dwarf secondaries (the last one being classified as K7V).Most of the spectra were gathered using the ELODIE spec-trograph (Baranne et al.1996)on the 1.93-m telescope of Observatoire de Haute-Provence (France).ELODIE covers a visible spectral range from 3850to 6800Åwith a resolution of 45000.For GJ 1021,Gl 166A and Gl 250A we reuse spec-tra observed by Santos et al.(2001)with the CORALIE spec-trograph (1.20-m Swiss Telescope,La Silla Observatory ESO,Chile).CORALIE has a slightly wider spectral range than ELODIE,3650to 6900Å,and a slightly higher resolution of 50000.On-line processing is integrated with control software of both spectrographs,and automatically produces optimally extracted,flat-fielded and wavelength calibrated spectra,with algorithms described in Baranne et al.(1996).For all primaries the present observations used the “Object-only”mode of the spectrograph,where its optional reference fiber is not illumi-nated.This mode provides optimal scattered light correction,at the cost of degraded radial velocity precision (∼100m.s −1).The wavelength calibration used a single Thorium-Argon expo-sure obtained at the beginning of each night.For each primary we recorded a sequence of 3spectra,and applied a median filter to remove any unflagged cosmic ray hit.The combined spec-tra have signal-to-noise ratios of approximately 200per pixel (∼300per resolution element),amply su fficient for our spectro-scopic analysis.We also obtained spectra for the secondaries,usually with a much lower signal to noise ratio,from which we planned to derive spectroscopic metallicity diagnostics that can be applied at moderate /low signal to noise ratio data.That goal has proved more di fficult than we expected,and it will be discussed in a future paper if we are successful.parison of T e f f (upper panel)and [Fe /H](lower panel)between our study and Santos et al.(2004,open dia-monds)and Edvardsson et al.(1993,filled diamonds).The er-rorbars represent the individual 1σerrors for our study and for Santos et al.Edvardsson et al.do not list individual error es-timates and we adopt their typical errors of 50K for T e f f and 0.05dex for [Fe /H].The over-plotted lines represent an identity relation,not a fit to the data.3.2.Spectroscopic analysisOur spectroscopic analysis of the primaries follows the pro-cedure described by Santos et al.(2004)for planet host stars.Briefly,we used the Gaussian fitting procedure of the IRAF splot task to the measure equivalent widths (W λ)of 39Fe I and 12Fe II lines.The stellar parameters were then derived using the 2002version of the MOOG code (Sneden 1973),and a grid of Kurucz (1993)ATLAS9model atmospheres.X.Bonfils et al.:Metallicity of M dwarfs5 Fig.2.Left panel:Color-magnitude diagram V−K vs.M K.Thefilled circles correspond to our metallicity determinations and the open circles to those from WW05.The symbol size is proportional to the metallicity.The dashed lines represent isometallicitycontours for the polynomial relation of Eq.1,spaced by0.25dex from−1.50dex(left)to+0.25dex(right).The right-hand axis shows masses from the DFS00K-band Mass-luminosity,which has very low dispersion and allows to interpret thefigure as a Mass-Colour-Metallicity diagram.Gl876and Gl436,the two known M-dwarf planet-host stars,are indicated to illustrate theirsolar metallicity.Right panels:Residuals from the calibration as a function of both M K and V−K photometry.Table3presents the resulting atmospheric parameters(micro-turbulence,effective temperature(T e f f),surface gravity andiron abundance([Fe/H]),which we use as a measurement ofthe overall metallicity([M/H]).The standard errors on T eff,log g,ξt and[Fe/H]were de-rived as described in Santos et al.(2004),following the pre-scriptions of Gonzalez&Vanture(1998).The resulting un-certainties are internal,in the sense that they ignore possiblescale offsets.There is currently some disagreement on e.g.theapropriate temperature scale for solar-type dwarfs,as well aswhich model atmospheres better reproduce the real stellar at-mospheres.The true errors may consequently be larger,but thelisted standard errors are appropriate for comparisons withinour sample.As discussed in Santos et al.(2004,2005),themethod and the grid of ATLAS9atmospheres used gives ex-cellent results,compatible with those derived by other authorsusing other model atmospheres and methods to derive the stel-lar parameters and metallicities.Six of the observed primaries have published stellar param-eters(Santos et al.2004;Edvardsson et al.1993).Comparisonof our determinations of T e f f and[Fe/H]with these litteraturevalues(Fig.1)shows that they agree to within the stated errors.4.A photometric calibration of M-dwarfmetallicitiesFrom this point on,we use a sample(Table4)that combines ourown metallicity measurements with those of WW05.As dis-cussed above,we expect the latter to be reliable,and they reachto lower metallicities for mostly hotter atmospheres.The twodatasets are therefore complementary,but they have enoughoverlap in the(T e f f,[Fe/H])plane to assess possible system-atic differences(Fig.2).Table4contains all WW05stars withknown parallaxes,except LHS1138,listed as a G5dwarf inSIMBAD,and GJ1064D,a clear outlier in our relations andperhaps a photometric binary.We restrict the analysis to starsbrighter than M K=7.5,since the sampling is very sparse forfainter stars.The left panel of Fig.2displays the effect of metallic-ity in the M K vs V−K observational Hertzsprung-Russell di-agram,with symbol sizes proportional to the metallicity of thecorresponding stars.After experimenting with several colour-magnitude diagrams,we found that amongst commonly avail-able photometric bands this combination maximizes the metal-licity sentivity.It is immediately obvious that lower metallicitystars are much bluer at a given absolute M K magnitude,and wefind the metallicity well described by the following polynomialrelation between M K and V−K:[Fe/H]=0.196−1.527M K+0.091M2K+1.886(V−K)−0.142(V−K)2,(1)valid for M K∈[4,7.5],V−K∈[2.5,6]and[Fe/H]∈[−1.5,+0.2]and with an observed dispersion of only0.2dex.Part of this dispersion might be due to a few of the highermass stars having evolved slightly offthe main sequence.Forinstance between8Gyr and10Gyr an0.8M⊙star bright-ens by∼0.3mag in the V band and∼0.2mag in the K band,moving noticeably in the Fig.2diagram.By0.7M⊙stellarevolution effects become small,with a brightening between8Gyr to12Gyr of∼0.1mag in both the V and K bands.The6X.Bonfils et al.:Metallicity of MdwarfsFig.3.V band M /L relation,with masses derived from the K-band M /L relation of DFS00and 2MASS photometry.The filled circles represent our metallicity determinations and the open circles those from WW05.The symbol size is propor-tional to themetallicity,and the dashed contours represent isometallicity for the Eq.1calibration,spaced by 0.25dex from +0.25(left)to -1.5dex (right).The solid lines represents the V-band empirical M /L relation of DFS00.age /metallicity relation might therefore introduce a small sys-tematic bias in our relation,but that would a ffect at most the highest mass fringe of its validity range.The lower panels of Fig.2display the residuals from that relation.The absence of any obvious systematic pattern demon-strates that the calibration remains valid over its stated range.The consistency between the residuals of the WW05measure-ments and ours ensures that any systematic di fference between the two datasets must be small where they overlap,for approx-imately solar metallicities.For significantly subsolar metallic-ities (i.e.well below -0.25dex)we have no independent val-idation of the WW05data.It should be noted however that their approach has maximal uncertainties for high metallicities,where molecular veiling is most severe.The good agreement where di fficulties would be most expected suggests that the low metallicity data points are valid as well.5.The V-band mass-luminosity relationAs demonstrated by DFS00,the infrared J-,H-and K-band M /L relations are very tight and in excellent agreement with model predictions,while the V-band relation has a large in-trinsic scatter.The contrasting dispersions were qualitatively expected from di fferent metallicity sensitivities for the visual and infrared bands (e.g.Chabrier &Bara ffe 2000),but the ex-tent of the e ffect was a surprise to most observers.Metallicity a ffects luminosity through a given photometric filter in two ways.First,higher metallicity decreases the bolometric lumi-Fig.4.Metallicity of M and K dwarfs (filled circles for our measurements,and open circles for WW05data)as a function of the di fference (∆M)between masses calculated from the V-and K-band M /L relations of DFS00.nosity for a given mass,and second,it shifts flux from the visible range to the near-IR through higher line-blanketing by TiO and VO molecular bands.The two mechanisms work to-gether to decrease the luminosity of the more metal-rich stars through visible filters.In the near-IR by contrast,the redward shift of the flux distribution of the metal-rich stars counter-acts their lower bolometric luminosity.The models therefore predict IR absolute magnitudes that are largely insensitive to metallicity,and the tight empirical M /L relations confirm this.DFS00could on the other hand not quantitatively verify their suggestion that metallicity explains the V-band dispersion.The Table 4measurements now allow us to perform this verifica-tion.Since the K-band M /L relation is so tight,we can use the parallaxes and 2MASS photometry to derive accurate masses.Fig.3displays those masses (Mass K )as a function of the M V absolute magnitude,with symbol sizes proportional to the mea-sured metallicity.The figure also shows the DFS00V-band M /L relation,and isometallicity contours obtained by remap-ping Eq.1to the Mass /M V plane.It is immediately obvious that the position relative to the average M /L relation correlates with metallicity,with the smallest symbols far above the M /L relation and the largest ones under that relation.Fig.4provides a more quantitative view,by projecting the Mass /M V /[Fe /H]information along the average V-band M /L relation.This diagram of [Fe /H]as a function of the di fference between masses derived from the V-and K-band M /L relations shows a well-defined linear correlation ([Fe /H ]=−0.149−6.508∆M ,σ([Fe /H ])=0.21).This demonstrates i)that the observed dispersion indeed results primarily from a metallicity e ffect,and ii)that the luminosity shift for a given metallicity is,to first order,constant between 0.8and 0.2M ⊙.X.Bonfils et al.:Metallicity of M dwarfs7 Table4.Apparent magnitudes,parallaxes,masses derived from the M/L relations of DFS00,and metallicities from this study and from WW05.CD-48176B M13.50S7.64±0.0266.92±0.73H0.2120.270−0.08±0.09a GJ3195B M312.50G8.10±0.0343.74±0.84H0.4080.395−0.31±0.04a GJ3825esdM1.514.55±0.03M10.86±0.0136.1±3.2Y0.2550.129−0.93±0.06b GJ687M39.15±0.03M 4.55±0.02220.9±0.9H0.3890.401+0.15±0.09b GJ9192K410.70±0.02M7.76±0.0226.1±2.1H0.7930.691−0.73±0.06b GJ9371sdM0.012.20±0.03M8.67±0.0244.3±2.8H0.4390.299−1.05±0.04bG22-15K5V9.23±0.02M 6.47±0.0241.2±1.3H0.8550.754−0.72±0.07bGl105B M411.67±0.01M 6.57±0.02138.72±1.04H0.2520.248−0.19±0.07aGl107B M1.510.06G 5.87±0.0289.03±0.79H0.5170.528−0.03±0.09aGl166C M4.511.17G 5.9±0.10198.25±0.84H0.2320.236−0.33±0.06aGl191sdM1.08.85±0.03M 5.05±0.02255.1±0.9H0.3880.274−0.99±0.04bGl205M1.57.96±0.01M 4.04±0.26175.7±1.2H0.6000.601+0.21±0.13bGl212M0.59.80±0.01T 5.76±0.0280.13±1.67H0.5720.598+0.04±0.11aGl231.1B M3.513.42G8.28±0.0251.76±0.78H0.2820.309−0.02±0.04aGl250B M210.09G 5.72±0.04114.94±0.86H0.4420.446−0.15±0.09aGl297.2B M211.80±0.01M7.42±0.0244.47±0.77H0.4840.519−0.09±0.09aGl324B M3.513.14G7.67±0.0276.8±0.84H0.2390.273+0.32±0.07aGl380K5 6.60±0.02M 2.96±0.29205.2±0.8H0.7420.759−0.03±0.18bGl411M2V7.49±0.02M 3.25±0.31392.5±0.9H0.4360.410−0.42±0.07bGl412A M0.58.75±0.04M 4.77±0.02206.9±1.2H0.4510.387−0.43±0.05bGl414B M1.59.98±0.04M 5.73±0.0283.8±1.1H0.5440.584+0.02±0.11bGl505B M0.59.60G 5.75±0.0289.07±0.99H0.5540.552−0.25±0.05aGl506.1sdK10.84±0.02M8.17±0.0227.9±2.5H0.7540.573−1.16±0.05bGl526M1.58.46±0.01M 4.42±0.21184.1±1.3H0.5200.431−0.10±0.07bGl53.1B M313.60G8.67±0.0248.2±1.06H0.2800.273+0.07±0.12aGl544B M615.10G9.59±0.0248.12±1.11H0.2150.174−0.20±0.19aGl701M19.37±0.03M 5.31±0.02128.3±1.4H0.5030.480−0.20±0.08bGl768.1B M3.513.10G8.01±0.0351.57±0.77H0.3100.349+0.07±0.12aGl783.2B M413.94G8.88±0.0248.83±0.91H0.2510.243−0.16±0.08aGl797B M2.511.88G7.42±0.0247.65±0.76H0.4600.489−0.07±0.04aGl809M0.58.54±0.04M 4.62±0.02142.0±0.8H0.5840.576−0.13±0.10bGl81.1B K711.21G7.60±0.0329.43±0.91H0.6840.671+0.09±0.06aGl872B M111.70G7.30±0.0261.54±0.77H0.4140.405−0.36±0.11aGl887M0.57.35±0.02M 3.46±0.20303.9±0.9H0.5220.476−0.22±0.09b LHS104esdK713.74±0.02M10.4±0.0219.3±3.0Y0.4710.308−1.33±0.04b LHS12M0.512.26±0.04M8.68±0.0236.1±4.3H0.4860.367−0.89±0.04b LHS170sdK10.68±0.01M7.60±0.0230.2±2.4H0.7530.658−0.97±0.06b LHS173sdK711.11±0.01M7.79±0.0239.2±2.5H0.6150.499−1.19±0.05b LHS174sdM0.512.75±0.01M9.14±0.0222.6±7.4Y0.5540.468−1.11±0.05b LHS1819K410.88±0.02M8.29±0.0317.0±2.6H0.8880.775−0.77±0.09b LHS1841K13.18±0.03M10.39±0.0217.5±3.3Y0.5710.344−1.47±0.06b LHS236sdK713.10±0.01M9.85±0.0218.2±2.9Y0.5700.423−1.32±0.05b LHS2938K710.67±0.02M7.76±0.0219.0±2.0H0.8850.832−0.21±0.11b LHS3084sdK13.43±0.03M9.78±0.0219.1±2.9Y0.5130.416−0.73±0.05b LHS343sdK13.82±0.02M10.66±0.0218.6±3.7Y0.4710.284−1.74±0.03b LHS467esdK712.21±0.03M8.78±0.0226.0±3.6H0.5860.479−1.10±0.05b LHS5337M011.15±0.03M7.47±0.0234.5±3.3H0.6470.624−0.50±0.06b NLTT45791M13.10N8.23±0.0334.57±0.73G0.3980.465−0.07±0.05a8X.Bonfils et al.:Metallicity of M dwarfsWe now have all the elements in hand to examine how the V-band luminosity depends on mass and metallicity,and to compute a mass-metallicity-luminosity relation for very-low-mass stars.Wefind that the V-band luminosity is well described by the following polynomial relation:M V=15.844−16.534Mass+13.891Mass2−7.411Mass3+1.153[Fe/H](2) for Mass∈[0.2M⊙,0.8M⊙]and[Fe/H]∈[−1.5,0.2],and with a dispersion of0.28mag.6.Metallicity of M-dwarf planet-host starsIt is now well established that planet host stars are more metal-richthan the average solar neighbourhood population (Gonzalez1997;Santos et al.2001,2003,2004).Santos et al.established that the planet frequency rises very steeply with stellar metallicity,at least for[Fe/H]>0.While only∼3%of the solar metallicity stars are orbited by a(detected)planet,thisfraction increases to over25%for stars with[Fe/H]above+0.3.One leading explanation for this dramatic dependency is that the probability of planet formation increases non-linearly with the mass of dust in a proto-planetary disk.M dwarfs,with presumably smaller disks and hence smaller disk dust mass at a given metallicity,provide a potentially critical test of that idea. This has up to now been hampered by both small statistic,with only two M-dwarf planet hosts known to date,and the lack of reliable metallicity estimates for those stars.Our calibration re-solves the second of those difficulties,and shows that Gl876 and Gl436,the two known M-dwarf planet-host stars,both have closely solar metallicities(−0.03dex and+0.02dex,re-spectively).Those unremarkable metal abundances do not shed light on whether M dwarf planet hosts are preferentially metal-rich or rger samples will be needed for that,and our calibration will be a useful tool when they become available.7.Metallicity distribution of M dwarfsEquation1allows us to estimate the metallicity of any individ-ual M dwarfs with V-and K-band photometry and a well deter-mined parallax.Here we use it to evaluate the metallicity distri-bution of the Delfosse et al.(2005,in prep)sample of northern M dwarfs within9.25parsecs.This volume-limited sample is believed to be complete,and is therefore representative of the solar neighbourhood.We removed all unresolved binaries as well as the faintest stars which are outside the validity range of the calibration(K∈[4mag,7.5mag]).Table5lists the47re-maining stars with their estimated metallicity.For comparison, we consider a sample of1000non-binary solar-type stars from the CORALIE radial-velocity planet-search programme(Udry et al.2000).This sample of single F,G or K dwarfs is rep-resentative of the solar neighbourhood,and we estimate their metallicity using the Santos et al.(2002)calibration of the area of the cross-correlation function between the stellar spectra and an appropriate template.We display the two distributions and their cumulative functions(Fig.5).The two distribution have similar shapes,but with a∼0.07dex shift of the M-dwarf dis-tribution towards lower metallicities.A Kolmogorov-Smirnov Fig.5.Upper panel:M-dwarf metallicity distribution derived from Eq.1and,over-plotted in dashed line,the metallicity dis-tribution of1000non-variable stars of our CORALIE radial-velocity planet-search programme.Bottom panel:Cumulative distributions of the same samples.test gives an∼8%probability that the two samples are drawn from the same parent distribution.The significance of the off-set is therefore modest,but if real is in the expected direction. Since M-dwarfs have much longer lifetimes than the age of the universe,every M-dwarf that ever formed is still here for us to see,while some of the oldest solar-type stars have evolved to white dwarfs.M dwarfs are thus expected to be slightly older on average,and from the age-metallicity relation there-fore slightly more metal-poor.8.ConclusionsWe have determined the metallicities of20M dwarfs in wide-binary systems that also contain an F,G or K star,under the simple assumption that the two stars have the same composi-tion.Where the parameter spaces overlap,our results are con-sistent with the direct analysis of M-dwarf spectra by Woolf &Wallerstein(2005).This provides a welcome validation of both our assumptions of a common composition and of the WW05analysis of complex M-dwarf spectra.The two datasets cover complementary parameter ranges,and we join them to derive a photometric calibration of very low-mass star metal-licities.The calibration is valid between0.8and0.2M⊙,needs V-and K-band photometry and an accurate parallax,and pro-vides metallicity estimates with∼0.2dex uncertainties.A5% parallax uncertainty results in an additional∼0.2dex metallic-ity uncertainty,making the relation useful only within∼50pc.We use the new metallicities to take a fresh look at the V-band mass-luminosity relation,and demonstrate that its intrin-sic dispersion is indeed due to metallicity.We apply the new calibration to the two known M dwarfs that host planets,Gl876。