Metal absorption from galaxies in the process of formation
光谱分形状英文名
光谱分形状英文名Fractal SpectraThe captivating world of fractals has long been a source of fascination for scientists, mathematicians, and artists alike. One particularly intriguing aspect of this intricate geometric realm is the exploration of fractal spectra. These remarkable patterns, rooted in the fundamental principles of light and energy, have the power to unveil the hidden complexities of our natural world.Fractals, by their very nature, are self-similar structures that exhibit patterns at every scale, from the microscopic to the cosmic. When applied to the study of light and electromagnetic radiation, these fractal structures reveal a depth of understanding that transcends the boundaries of traditional scientific inquiry. The fractal spectra, a manifestation of this interplay between light and geometry, offer a unique window into the underlying rhythms and harmonies that govern the universe.At the core of fractal spectra lies the concept of self-similarity, where patterns repeat across different scales. This principle is exemplified in the renowned Mandelbrot set, a striking fractal shape that hascaptured the imagination of countless individuals. When this fractal is subjected to spectral analysis, the resulting patterns often exhibit a remarkable level of complexity and beauty, mirroring the intricate structure of the original form.One of the key aspects of fractal spectra is their ability to reveal the hidden harmonies within the electromagnetic spectrum. By decomposing light into its constituent wavelengths, the fractal patterns that emerge often display intricate and mesmerizing designs. These patterns can be seen in the vibrant hues of a rainbow, the shimmering iridescence of butterfly wings, and the shimmering patterns of light on the surface of a pond.Delving deeper into the realm of fractal spectra, we begin to uncover the profound connections between the microscopic and the macroscopic. The self-similar patterns observed in the spectra of individual atoms and molecules are echoed in the larger-scale structures of galaxies and cosmic phenomena. This realization has led to groundbreaking discoveries in fields such as quantum physics, astrophysics, and materials science, as researchers strive to unravel the underlying principles that govern the behavior of light and energy.The exploration of fractal spectra has also had a profound impact on our understanding of the natural world. By studying the fractalpatterns in the absorption and emission spectra of various materials, scientists have been able to gain insights into the molecular and atomic structures of these substances. This knowledge has enabled advancements in fields ranging from chemistry and materials science to biology and medical research.Furthermore, the fractal nature of light has inspired a wealth of artistic expression and technological innovation. Visual artists have long been captivated by the mesmerizing patterns of fractal spectra, incorporating them into mesmerizing works of art that blur the boundaries between science and aesthetics. Similarly, the principles of fractal optics have revolutionized the design of optical devices, from high-resolution imaging systems to advanced communication technologies.In conclusion, the exploration of fractal spectra represents a profound and ongoing journey of scientific discovery, artistic expression, and technological advancement. By delving into the intricate patterns and harmonies that govern the behavior of light and energy, we unlock a deeper understanding of the fundamental principles that shape our universe. The study of fractal spectra promises to continue yielding transformative insights, as we strive to unravel the mysteries of the natural world and push the boundaries of human knowledge and creativity.。
高三英语材料科学单选题60题
高三英语材料科学单选题60题1.Metal is a common material in engineering. Which of the following is not a metal?A.ironB.aluminumC.glassD.copper答案：C。
本题考查材料科学中金属的概念。
铁（iron）、铝（aluminum）和铜（（copper）都是常见的金属。
而玻璃（（glass）是一种非金属材料，主要由硅酸盐等组成。
2.Which material is often used for insulation?A.steelB.plasticC.goldD.silver答案：B。
在材料科学中，塑料（（plastic）常被用作绝缘材料。
钢（steel）、金（（gold）和银（（silver）都是导电性能较好的金属材料，不适合用于绝缘。
3.In the field of materials science, which one is a composite material?A.woodB.paperC.concreteD.water答案：C。
混凝土（（concrete）是一种复合材料，由水泥、骨料和水等组成。
木头（（wood）是天然材料。
纸（（paper）主要由纤维素等组成，不是复合材料。
水（water）是一种化合物，不是复合材料。
4.Which material is known for its high hardness?A.rubberB.leatherC.diamondD.cloth答案：C。
在材料科学中，钻石（（diamond）以其高硬度而闻名。
橡胶（rubber）、皮革（leather）和布（cloth）的硬度都较低。
5.Which of the following materials is ductile?A.brickB.glassC.copperD.stone答案：C。
在材料科学中，铜（（copper）是一种具有延展性（（ductile）的金属材料。
小学下册第11次英语第三单元测验卷
小学下册英语第三单元测验卷英语试题一、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 chemical formula for ethanol is __________.2.What do we call the act of sharing information?A. CommunicatingB. DisseminatingC. BroadcastingD. All of the AboveD3.What is the opposite of "happy"?A. JoyfulB. SadC. ExcitedD. AngryB4.What is the name of the popular video-sharing platform?A. VimeoB. YouTubeC. TwitchD. DailymotionB5.My favorite dish is ______ (米饭).6.The _____ (小猪) oinks happily in the mud.7. A solution is made of a solvent and a _______.8.The pizza is ______ (cut) into slices.9.My ________ (玩具) encourages exploration.10.What is the capital of Sudan?A. KhartoumB. OmdurmanC. Port SudanD. NyalaA11.The country known for its windmills is ________ (荷兰).12.The ancient Greeks were known for their ________ philosophy.13.What is the color of the sky on a clear day?A. GreenB. YellowC. BlueD. RedC Blue14.What do we call a person who studies music?A. MusicologistB. ComposerC. PerformerD. All of the above15.The classroom is _____ and tidy. (clean)16.What do we call the process of water soaking into the ground?A. InfiltrationB. PercolationC. AbsorptionD. SaturationA17.I enjoy _______ (参加)体育活动。
2022-2023年银行招聘之银行招聘职业能力测验提升训练试卷B卷附答案
2022-2023年银行招聘之银行招聘职业能力测验提升训练试卷B卷附答案单选题（共60题）1、Questions 95-98 refer to the following advertisement.A.For 10 daysB.For 12 daysC.For 15 daysD.For 18 days【答案】 A2、消费者权益保护法中，消费者是指为( )需要而购买、使用经营者所提供的商品或接A.转卖B.生活消费C.生产D.储存【答案】 B3、5，10，26，50，122，（）A.148B.158C.170D.178【答案】 C4、不正当竞争行为会扰乱社会经济秩序。
下列行为中，不属于不正当竞争行为的是（）。
A.某经营者扩大产品功能，误导消费者B.某超市以低于成本价的价格出售即将到期的牛奶C.某经营者使用某知名品牌的商品D.某经营者冒用认证标志.伪造产地【答案】 B5、书架上共有书168本，分别放在4层。
第一层本数的2倍是第二层本数的一半．第一层比第三层少2本，比第四层多2本，则第一层有多少本书?（）A.30B.24C.34D.26【答案】 B6、国家主席习近平于2013年10月4日在马来西亚国家皇宫会见马来西亚最高元首哈利姆。
马来西亚已成为中国在东盟第( )大贸易伙伴，两国合作日益紧密，共同利益日益扩大。
A.一B.二C.三D.四【答案】 A7、商业银行风险转移是一种（）。
A.事中控制B.事后控制C.业务控制D.事前控制【答案】 D8、有形资产是指那些具有实物形态的资产；而无形资产是指企业拥有或者控制的没有实物形态的可辨认非货币性资产。
A.巨力索具股份有限公司发明了一种十二股绳索套及其制作方法，并取得了发明专利权B.加多宝拥有王泽邦祖传的独家配方的凉茶，并在多年精心耕耘过程中形成了完整的工艺体系C.即使可l：I可乐公司倒闭，这个商标的价值也能让它重新发展起来D.泸州老窖集团拥有中国规模最大的现代化生产基地、包装生产基地、基酒储存基地等【答案】 D9、看来，不只是贵族有偏见，平民也自有平民的偏见，这种偏见就是看不见每个人都应该享有人之为人的尊严和独自为人的权利。
2004年10月英语(二)试题与答案--解析
2004 年下半年英语〔二〕试题及答案2004 年下半年高等教育自学考试全国统一命题考试英语二第一局部选择题〔共50 分〕I. Vocabulary and Structure (10 point, 1 point for each item)从以下各句四个选项中选出一个最正确答案，并在答题卡上将相应的字母涂黑．1. It offers us a fuller sense of being intensely alive from to moment. A. time B. moment C. period D. instant2. It maybe worth remembering that John Major didn ’ t himself go to Oxford, most of his ministers did. A. after B. since C. while D. if 3. The effects of rapid travel the body are far more disturbing than we realize. A. on B. in C. for D. to 4. Herpowers of persuasion were no avail. A. for B. by C. with D. to 5. There is little likelihood that a panel of five wants togo through the of all shaking hands with you. A. process B. prospect C. precedent D. presence 6. It is the right to change employers which employment from slavery. A. distinguishes B. derives C. releases D. relieves 7. It is touchingto see how a cat or dog itself to a family and wants to share in all its goings and comings. A. sacrifices B. opposes C.exposes D. attaches 8. A healthy self-esteem is a resource for coping when difficulties . A. rise B. raise C. arise D.arouse 9. The challenge is not one of expansion , the rapid growth in enrollment over the last 40 years has come to anend. A. As a result B. By all means C. In contrast D. On the contrary 10. Management often works hard to set up asituation work is done in series. A. that B. where C. which D. whatII. Cloze Test (10 points, 1 point for each item)以下短文中有十个空格，每个空格有四个选项．根据上下文要求选出最正确答案，并在答题卡上将相应的字母涂黑．Maybe you know that the letter “ V 〞 stands for Victory in western countries. But do you know the 11 of the sign?During World War II, Europe was occupied by the Germans. A lot of people 12 to Britain. Among them was one Belgian( 比利时人 ) 13 Victor Dalveli. He loved his country very much. And every day, he used shortwave radio to broadcast tothe Belgian people, calling 14 them to resist the German occupies. On the last day of 1940, he asked hiscountrymen to write the 15“ V〞wherever they could to show their determinationtowinthe final victory. In a few days,it appeared everywhere. 16 , it spread to the other occupied countries in Europe. Because it was simple and 17 it soonbecame very popular. When friends met, they stretched out 18 middle and index fingers to greet each other. At that time,in certain restaurants, knives and forks were placed in such a way 19 form a“ V〞. And in some clock spurposely stopped 20 11:05 to show the sign of “ V〞11.. A. meaning B. shape C. history D. definition 12. A. had escaped B. escaped C. have escaped D. escape 13. A. naming B. being named C. named D. to name 14. A. up B. out C.on D. off 15. A. letter B. alphabet C. expression D. word 16. A. Latter B. Later C. Late D. Lately 17. A. meaningful B.energetic C. magnifice nt D. interesting 18. A. his B. their C. one ’ s D. everybody ’ s 19. A. in order to B. so D. as to 20. A. on B. in C. by D. atIII. Reading Comprehension (30 points, 2 points for each item) 从以下每篇短文的问题后所给的四个选择项中选出一个最正确答案，并在答题卡上将相应的字母涂黑．Passage OneQuestions 21 to 25 are based on the following passage.In reading the world ’ s great literature on human excellence and personal success, I’ve found that to launch ourselvesinto a life of true success we need to satisfy one basic condition: pursue our vision with stubborn ( 顽强的 ) consistency.The biggest difference between people who succeed and those who don ’ t is not usually talent but persistence. On myway to work one morning, I met Rudy Ruettiger, who is now a motivational speaker. He has grown up in Joliet, listening tostories about Notre Dame and dreaming of one day playing football there. Friends told him he wasngood enough student to be admitted. So he gave up his dream and went to work in a power plant. Then a friend waskilled in an accident at work. Shocked, Rudy suddenly realized that life is too short not to pursue your dreams. In 1972, atthe age of 23, he enrolled at Holy Cross Junior College in South Bend, Ind. He got good enough grades to transfer toNotre Dame, where he finally ma de the football team as a member of the“ scout team〞, the players who help thprepare for games. Rudy was living his dream, almost. But he wasn ’ t allowed to suit up for the games themse next year, after Rudy requested it, the coach told Rudy he could put on his uniform for the season ’ s final game. A there he sat, on the Notre Dame bench during the game. A student started shouting, “We want Rudy! 〞 Soon others joined in. Finally, at the age of 27, with 27 seconds left to play, Rudy Ruettiger was sent onto the field-and made the final tackle ( 阻截 ). So his team won the game. When I met Rudy 17 year later, it was in the parking lot outside NotreDame stadium ( 体育场 ), where a camera crew was filming scenes for Rudy, a motion picture about his life. His storyillustrates that there is no limit to where your dreams can take you. 21. The writer believes that the key to achievingsuccess is . A . developing one ’talents B. seizing opportunities C. having wide vision D. sticking to one ’goals 22. According to the passage, Rudy once gave up his dream of playing football for Notre Dame because . A. his friend waskilled there B. his foot was injured in an accident C. he lacked confidence in himself D. he failed in the entrance examination 23. Rudy quit his job in the power plant because . A. his friend encouraged him to B. his outlook on lifechanged C. he was disappointed in his future D. he was shocked by his friend’ s death 24. Rudy was tran Dame . A. as a good student B. as a good player C. with the help of a coach D. with the help of a friend 25. A cameracrew was making a movie about Rudy’ s life because . A. Rudy was the oldest player at Notre Dame B. Rudy succeeded in realizing his dream C. Rudy was the best speaker at Notre Dame D. Rudy succeeded in developing his abilityPassage TwoQuestions 26 to 30 are based on the following passage.NASA, the U.S. space agency, believes there’ s a good chance that we’ re not alone in the universe. Last fall, began a new project called the High Resolution Microwave Survey (HRMS). Its aim: to find evidence of life in one ofthe billions of galaxies in the universe. The search for intelligent life on other planets isn’ t years ago. That ’whens scientists built a huge transmitt er to send radio waves into space. Scientists thought smartbeings on other planets might pick up the signals. Scientists also have sent a message about humans and our solarsystem to a nearby constellation (星座 ). But because the constellation is 25,000 light years away, a return messagewouldn ’ t reach Earth for 50,000 years! So don ’ t wait up for an answer. So far, no extraterrestrial ( 地球外的 ) beingsthat we know of have returned our“ calls.〞 But according to Dr. Jill Tarter, an HRMS scientist, we haven’ t exactlyhad our ears wide open. “ Now, how ever,〞 says Dr. Tarter,“ we’ ve built the tools we need to listen well.Dr. Tarter switched on the largest radio receiver in the world. It’ s an enormous metal bowl stretching 1,0valley in Puerto Rico. Meanwhile,another NASA scientist turned on a huge radio receiver in California Mojave’sDesert. NASA hopes these big dishes-and others around the world-will pick up radio signals from new world. Dr. FrankDrake has been searching for life in outer space for years. He explains the HRMS project this way: To listen to your radio,you move the tuner on the dial until the channels come in loud and clear: Now imagine radio receivers that scanour galaxy “ listening 〞 to 14 million channels every second. That ’ s what NASA ’ s radio receivers in Pu California are doing. But that ’ s not all. Powerful computers hooked to the receivers examine every signal carefully. Thecomputers try to match the signals to ones that scientists already recognize, such as human-made signals. If they can ’t,Drake and Tarter check on them. “ It could prove there is radio technology elsewhere in the universe, 〞 says Dr. Tarter.“ And that would mean we ’ re not alone.〞26、 NASA scientists started a new project in order to _______. A、 discover life in other galaxies B、 send humanbeings into space C、 find evidence of a new galaxy D 、 confirm the number of galaxies27、According to Dr.Jill Tarter ,the reason why we haven ’t received any return any return messages from outer space isthat_______. A 、 our ears are not sharp enough to hear them B、 our equipment hasn’t been good enough C、 it takesmillions of yuars for them to reach us D 、 it takes quite a long time to send them28、 Dr.Jill Tarter compares the large receiver to _______. A 、 the human ear B、 the universe C、 a metal bowl D 、a huge dish29、 According to Dr.Frank Drake ,NASA’ s radio receivers in Puerto Rico and California are _______. A 、 trying tocheck on every channel carefully B 、 moving the tuner on the dial for clear channels C、 scanning the universe forpossible signals D 、 picking up radio signals from new world30、The best title of this passage is ________. A 、 Signals from the Space B 、 The Invention of New Radio ReceiversC、 The Intelligent Life in Outer SpaceD、NASA Listens for Space NeighborsPassage ThreeQuestions 31 to 35 are based on the following passage.Even a careful motorist( 开汽车的人 ) may commit a motoring offence (XX ).In this case, he will appear in apolice court .This is a court ruled by a judge without a jury (陪审团 ).A judge has powers to pass sentence for relativelyminor offences only ;serious charges are dealt with by a judge and a jury. In certain cases, a motoring offender maychoose to go before a judge and a jury ,instead of appearing before just a judge .A court is also used for the conduct ofpreliminary investigations to dedermine whether or not a motoring offender shall appear for trial in a higher court.When his case comes up in court ,the motorist hears his name called by the clerk of the court, and comes forward toidentify himself.The judge then calls for the policeman who charged the offender and asks him to give evidence. He isexpected to ive an account of what happened when the offence was committed and to mention any special circumstances.For example the offence may have been partly due to the foolishness of another motorist.It would beunwise for the motoring offender to exaggerate this.It will not help his case to try to blame someone else for his ownmistake. If you are guilty ,it is of course wise to admit it and say you’ re sorry for committing the offence and taking up the court ’imes t.Judges are not heartless and a motorist may be lucky enough to hear one say：“ You’ ve got goodreasons ,but you have broken the law and I ’ll have to impose a fine .Pay five pounds.Next case. 〞 Some short-temperedpeople forget that both policemen and judges have a public duty to perform,and aren rude to them. This does not pay! Ajudge will not let off an offender merely because he is respectful,but a polite law-breaker may certainly hope that thejudge will extend him what tolerance the law permits.31、Even a careful motorist may be asked to go to a police court for______. A、an injury B、a motoring offence32、The underlined word “ one 〞(paragraph 5) refers to _____. A 、a jury member B 、a police officer C 、a motoristD 、a judge33、A motoring offender is usually charged by ______. A、a judge B、a jury C、a policeman D、another motorist34、 It is foolish for a motoring offender to _______. A、overstate another motorist’ s mistake B、mentionsomeone else’ s foolishness C 、 argue that he is not guilty D、choose to go before a jury35、 If a man knows that he is guilty, he should ______. A、be polite to the policeman and the judge B、try hisbest to appear before just a judge C 、save the court’s time and pay the fine D、admit the wrong and say sorry to thecourt第二局部非选择题〔共50 分〕Ⅳ.Word Spelling(10 points,1point for two items)36. 乐意地，容易地ad. r_______ 37. 日常工作，常规n. r______ 38. 多数，大半n. m_______ 39.永恒的，不断的a. c______ 40. 偏袒的，局部的 a. p_______ 41. 漆工，画家 n. p______ 42. 跳跃，飞跃 v. l______ 43. 易管理的 a. m_______ 44.缩短，减少vi. S______ 45. 软毛，毛皮n. f_______ 46. 意图，打算n. I_______ 47. 情形，身份 n. s________ 48. 软管，地铁n. t________ 49.口头的，口的a. o_______ 50. 牺牲品，受害者n. v_______ 51.鉴赏，感谢vt. a_______ 52. 目标，球门n. g______ 53. 装置，方法n. d_______ 54. 分配，委派vt. a______ 55. 娱乐，消遣n. a______Ⅴ.Word Form56.Should doctors be allowed_________(take) the lives of others? 57. Two of _________(big) earthquakes that wereever recorded tood place in China and Alaska. 58. Electronic amplifiers also made possible a fantastic in volume ,themusic ______(become) as loud and penetrating as the human ear could stand. 59. Every decision has constraints_______(base ) on policies, procedures ,laws, precedents ,and the like. 60. The more seriously this issought ,________(likely ) positive attitudes towards leisure as well academic work will be encouraged. 61. Attempts tobreak up this old system _______(make ) in every presidential election in the past one hundred years. 62.These mineplanets ,together with the sun ,make up what _______(call) our solar system. 63. Nations are classified as “ aged 〞when they have 7% or more of their people aged 65 or above ,and by about 1970 every one of the advancedcountries______(become) like this. 64. ----------- 〔 watch 〕 over by guards with guns, the convicts raised their legs in unison and made their way to the edge of the highway. 65.Either of these factors could account for some individuals------------(be) able to do well using inefficient methods.Ⅵ将以下各句译成英语66.我不知道他是否能够提供有力的证据。
2024年小学四年级下册第二次英语第3单元综合卷
2024年小学四年级下册英语第3单元综合卷考试时间：80分钟（总分:140）A卷考试人：_________题号一二三四五总分得分一、综合题(共计100题)1、填空题：The _______ (The Berlin Wall) fell in 1989, signaling the end of the Cold War.2、填空题：A gecko can climb ______ (墙).3、填空题：I like to __________ (动词) my __________ (玩具名) with colorful stickers.4、 Mountains run through _____ (南美洲). 填空题：The Ande5、听力题：Light-years measure the ______ that light travels in one year.6、填空题：The _____ (自然环境) is important for biodiversity.7、听力题：The chemical symbol for silver is _______.8、听力题：The chemical symbol for mercury is _______.9、What do we call the process by which organisms adapt to their environment?a. Evolutionb. Mutationc. Adaptationd. Natural selection答案:a10、What do you call the middle of a story?A. BeginningB. ClimaxC. EndingD. Rising action11、听力题：We went to the ________ yesterday.12、听力题：I ride my ________ (bike) to school.13、听力题：I want to go to the ________.14、听力题：I like to ride my ___ (scooter).15、填空题：We have a ______ (特别的) program at school.16、听力题：The __________ is famous for its cherry blossoms.17、听力题：In a chemical reaction, the rate can be influenced by factors such as concentration, temperature, and _____.18、听力题：The __________ is known for its ancient temples.19、填空题：A ________ (种植策略) is key for success.20、填空题：The food is _______ (热乎乎的).21、填空题：I enjoy _______ (和家人一起)在公园散步。
一些关于宇宙的简单的知识英语作文
一些关于宇宙的简单的知识英语作文Here's an essay about some simple knowledge about the universe, written in English and aimed at elementary school students, with around 2000 words.The Fascinating UniverseHave you ever looked up at the night sky and wondered about all those twinkling stars? The universe is a vast and mysterious place, filled with amazing objects and mind-boggling facts. Let me share some simple but fascinating knowledge about the cosmos we live in.Our UniverseFirst, let's talk about our universe. The universe is everything that exists – all the planets, stars, galaxies, and even the empty space between them. It's incredibly big, and scientists estimate that it's about 13.8 billion years old! Can you imagine how old that is? It's older than anyone or anything on Earth.The Earth and the Solar SystemThe Earth, our home planet, is just a tiny speck in the universe. It's part of our solar system, which consists of the Sun and everything that orbits around it. The Sun is a star, a huge ballof hot gas that provides us with light and heat. Without the Sun, life on Earth wouldn't exist.Apart from the Earth, our solar system has seven other planets: Mercury, Venus, Mars, Jupiter, Saturn, Uranus, and Neptune. Each planet is unique and has its own interesting features. For example, Jupiter is the largest planet, while Mercury is the smallest. Saturn is famous for its beautiful rings, which are made of billions of tiny chunks of ice and rock.Stars and GalaxiesBeyond our solar system, there are countless stars in the universe. Stars are massive, glowing balls of hot gas, just like our Sun, but much bigger and further away. The stars we see in the night sky are actually suns in other solar systems, millions or even billions of miles away.Stars are often grouped together in galaxies, which are huge collections of stars, gas, and dust held together by gravity. Our galaxy, the Milky Way, is a spiral-shaped galaxy containing over 100 billion stars! It's just one of the billions of galaxies in the universe.Fascinating FactsHere are some more fascinating facts about the universe:The universe is constantly expanding, meaning that galaxies are moving away from each other all the time.Black holes are regions in space where the pull of gravity is so strong that nothing, not even light, can escape them.Shooting stars are not really stars at all. They are tiny pieces of rock or dust burning up as they enter Earth's atmosphere.The largest known star is called VY Canis Majoris, and it's so big that if it were placed at the center of our solar system, it would extend past the orbit of Saturn!It takes light from the nearest galaxy, the Andromeda Galaxy, over 2.5 million years to reach us.Exploring the UniverseIsn't the universe amazing? Scientists use powerful telescopes and spacecraft to study and explore the cosmos. They are constantly making new discoveries and learning more about the mysteries of the universe.Who knows what incredible things we might find out in the future? Perhaps one day, humans will even travel to other planets or galaxies. For now, we can enjoy gazing up at the night sky and marveling at the beauty and vastness of the universe we call home.。
Metals in Star-Forming Galaxies at High Redshift
a rXiv:as tr o-ph/56285v113J un25From Lithium to Uranium:Elemental Tracers of Early Cosmic Evo-lution Proceedings IAU Symposium No.228,2005V.Hill,P.Fran¸c ois &F.Primas,eds.c 2005International Astronomical Union DOI:00.0000/X000000000000000X Metals in Star-Forming Galaxies at High Redshift Claus Leitherer Space Telescope Science Institute,3700San Martin Dr.,Baltimore,MD 21218,USA email:leitherer@ Abstract.The chemical composition of high-redshift galaxies is an important property that gives clues to their past history and future evolution.Measuring abundances in distant galaxies with current techniques is often a challenge,and the canonical metallicity indicators can often not be applied.I discuss currently available metallicity indicators based on stellar and interstellar absorption and emission lines,and assess their limitations and systematic uncertainties.Recent studies suggest that star-forming galaxies at redshift around 3have heavy-element abundances already close to solar,in agreement with predictions from cosmological models.Keywords.galaxies:abundances,galaxies:high-redshift,galaxies:starburst,ultraviolet:galax-ies2Claus Leithererparison between the observed spectrum of MS1512–cB58(solid)and two syn-thetic models with1/4Z⊙(lower;dashed)and Z⊙(upper;dotted).The models have continuous star formation,age100Myr,and Salpeter IMF between1and100M⊙.The stellar lines are weaker in the metal-poor model(from Leitherer et al.2001).3.Techniques—Restframe Optical versus UVAbundance determinations typically fall into two categories,either relying on indica-tors in the restframe optical,or on those in the restframe UV.The restframe optical wavelength region has traditionally been used to determine galaxy abundances from nebular emission lines.At a redshift of z=3,the restframe optical is observed in the near-infrared(IR)H and K bands.Spectroscopic observations of LBGs in the near-IR have become technically feasible(e.g.,Pettini et al.2001)but abundance analyses are still challenging.Only the strongest lines such as,e.g.,Hα,Hβ,[N II]λ6584,or[O III]λ5007are detectable at sufficient S/N.Even when good-quality spectra are available,the atmospheric windows usually restrict the wavelengths to a narrow range,which precludes commonly used techniques such as the classical R23strong-line method(McGaugh1991). The need for alternative variants of the classical strong-line method led Pettini&Pagel (2004)to readdress the usefulness of the N2and O3N2ratios.The former is defined as the ratio[N II]λ6584over Hαand was recently discussed by Denicol´o et al.(2002);the latter includes the oxygen line for the ratio([O III]λ5007/Hβ)/([N II]λ6584/Hα)and was originally introduced by Alloin et al.(1979).After calibrating the two abundance indicators with a local H II region sample,Pettini&Pagelfind that O3N2and N2predict O/H to within0.25dex and0.4dex at the2σconfidence level,respectively.The observed frame optical wavelength region corresponds to the restframe UV of LBGs.The UV contains few nebular emission lines in star-forming galaxies(Leitherer 1997)and has rarely been used for chemical composition studies in local galaxies of this type.Fig.1compares the UV spectrum of the LBG MS1512–cB58with theoretical spectra(Leitherer et al.2001).Three groups of lines can be distinguished:(i)Interstellar absorption lines,most of which are strong and heavily saturated.Only in very few cases can unsaturated absorption lines in LBGs be used for an abundance analysis.(ii)Broad stellar-wind lines with emission and blueshifted absorption.These lines are the telltales of massive OB stars whose stellar winds are metallicity dependent.(iii)Weak photospheric absorption lines which can only be seen in high-quality spectra.Abundance studies from stellar lines in restframe UV spectra must rely either on suitable template stars or on extensive non-LTE radiation-hydrodynamic models which are only beginning to become available(Rix et al.2004).Metals in High-z Galaxies3 4.The Chemical Composition of LBGsAn initial,rough estimate of the heavy-element abundances can be obtained from the equivalent widths of the strong UV absorption lines.Heckman et al.(1998)pointed out the close correlation of the Si IVλ1400and C IVλ1550equivalent widths with O/H in a sample of local star-forming galaxies.This correlation seems surprising,as these stellar-wind lines are deeply saturated.The reason for the metallicity dependence is the behavior of stellar winds in different chemical environments.At lower abundance,the winds are weaker and have lower velocity,and the lines become weaker and narrower.As a result,the equivalent widths are smaller at lower O/H.If the same correlation holds at high redshift,the observed equivalent widths in LBGs suggest[O/H]≃–0.5(Leitherer 1999).A similar,somewhat weaker correlation exists between O/H and the equivalent widths of the strongest interstellar lines.This is even more unexpected because the equivalent widths of saturated lines have essentially no dependence on the column density N ion:W∝b[ln(N ion/b)]0.5.Therefore the correlation must be caused by the b factor, and therefore by velocity.More metal-rich galaxies are thought to host more powerful starbursts with correspondingly larger mechanical energy release by stellar winds and supernovae.The energy input leads to increased macroscopic turbulence and higher gas velocities at higher O/H(Heckman et al.1998).If the same applies to star-forming galaxies in the high-redshift universe,their measured equivalent widths again indicate an oxygen abundance of about1/3the solar value.Pettini et al.(2001)determined oxygen abundances infive LBGs from emission lines in restframe optical spectra.The redshift range of the sample dictated the use of the R23 method.The galaxies turned out to be rather metal-rich,with O/H somewhat below the solar value.This is roughly in agreement with restframe UV results,and an order of magnitude above the metallicities found in damped Lyman-αabsorbers(DLA)which are found at the same redshift.Because of the double-valued nature of the R23method, the possibility exists but is deemed less likely that the sample has oxygen abundances of only1/10the solar value.The lensed LBG MS1512–cB58and its bright restframe UV spectrum can be studied at sufficiently high S/N and resolution to detect and resolve faint,unsaturated interstellar absorption lines.Pettini et al.(2002)measured numerous transitions from H to Zn cov-ering several ionization stages.Abundances of several key elements could be derived.The α-elements O,Mg,Si,P,and S all have abundances of about40%solar,indicating that the interstellar medium is highly enriched in the chemical elements produced by type II supernovae.In contrast,N and the Fe-peak elements Mn,Fe,and Ni are all less abundant than expected by factors of several.In standard chemical evolution models,most of the nitrogen is produced by intermediate-mass stars,whereas type Ia supernovae contribute most of the Fe-peak elements.Since the evolutionary time scales of intermediate-and low-mass stars are significantly longer than those of massive stars producing theα-elements, the release of N and the Fe-group elements into the interstellar medium is delayed by ∼109yr.MS1512–cB58may be an example of a star-forming galaxy in its early stage of chemical enrichment,consistent with its cosmological age of only about15%of the age of the universe.Mehlert et al.(2002)provided similar arguments to explain variation of the C IVλ1550line relative to Si IVλ1400in a small sample of LBGs.C IV appears to decrease in strength relative to Si IV from lower to higher redshift,which may reflect the time delay of the carbon release by intermediate-mass stars.The interstellar lines in LBGs have blueshifts with velocities of up to several hun-dred km s−1indicating large-scale outflows.The associated galactic mass-loss rates of ∼102M⊙yr−1are comparable to the rates of star formation.The newly formed heavy4Claus LeithererFigure2.Left pair of panels:comparison of the observed spectrum of MS1512–cB58(thick) with fully synthetic spectra(thin)forfive different metallicities,from twice solar to1/20solar. First panel:region around1425˚A;second:region of the Fe III blend near1978˚A.Each pair of panels is labeled with the metallicity of the synthetic spectrum shown.Right pair of panels: same as left pair,but for Q1307–BM1163(from Rix et al.2004).elements are removed from their birth sites by stellar winds and supernovae and are trans-ported into the halo and possibly into the intergalactic medium(Pettini et al.2002). Detailed studies of weak interstellar lines such as that done for MS1512–cB58remain a technical challenge,even for high-throughput spectrographs at the largest telescopes. Furthermore,the results for Fe-peak elements carry some uncertainty because of the a priori unknown depletion corrections.Abundance analyses using stellar lines are not affected by depletion uncertainties.However,the existence of non-standard element ratios precludes the use of locally observed template spectra for spectral synthesis.Therefore our group(F.Bresolin,R.Kudritzki,C.Leitherer,M.Pettini,S.Rix)has embarked on a project to model the spectra of hot stars and link them with a spectral synthesis code to predict the emergent UV spectrum of a composite stellar population as a function of metallicity.We generated a grid of hydrodynamic non-LTE atmospheres with the WM-basic code(Pauldrach et al.2001)and calculated the corresponding UV line spectra.The resulting library was incorporated into the Starburst99code(Leitherer et al.1999)which then allowed us to compute a suite of model spectra for appropriate stellar population parameters.As afirst application,we used several faint stellar blends around1425˚A and 1978˚A as a metallicity indicator(Rix et al.2004).The1425˚A feature is a blend of Si III, C III,and Fe V,and the1978˚A absorption is mainly Fe III.The synthesized spectra for five metallicities are compared to the observed restframe UV spectra of MS1512–cB58 and Q1307–BM1163in Fig.2.The model having40%solar metal abundance provides the bestfit to the data,in agreement with the results from other methods.A variety of independent techniques lead to consistent results for the chemical com-position of LBGs.While each method by itself is subject to non-negligible uncertainties,Metals in High-z Galaxies5Figure3.Metallicity-luminosity relationship.Data for local spiral and irregular galaxies are from Garnett(2002).The z=2objects are overluminous for their(O/H)abundances,derived using the N2calibration of Pettini&Pagel(2004)but lie closer to the relationship for the local galaxies than z=3LBGs(from Shapley et al.2004).the overall agreement of the results gives confidence in the derived abundances.LBGs at z≃3have heavy-element abundances of about1/3the solar value.5.Cosmological PerspectiveStar-forming galaxies at z≃3,at an epoch when the universe’s age was only15% the present value,display a high level of chemical enrichment.What does their chemical composition tell us about their relation to other galaxies at lower redshift and to other structures found at z=3?Galaxies at somewhat lower redshift have only recently become accessible for detailed study due to the combined challenges of instrumentation and the galactic spectral prop-erties.Shapley et al.(2004)obtained K-band spectroscopy of seven UV-selected star-forming galaxies at redshifts between2and2.5.The N2method calibrated by Pettini &Pagel(2004)was used as an abundance diagnostic.When compared to the original higher-z LBGs,the z≃2sample is more metal-rich.This can be seen in Fig.3,where O/H of the z=2galaxies is compared with that of LBGs at z≃3and of local star-forming galaxies over a range of blue luminosities.The latter were analyzed with the R23method.The z=2sample has almost solar chemical composition but is still less metal-rich than local late-type galaxies with comparable luminosities.As a caveat,the comparison rests on the assumption that the N2and R23calibrations have no significant offset.The difference between the average redshift of the LBG sample and of the z=2 galaxies translates into a mean age difference of about1Gyr.Both the chemical proper-ties and the masses of the z=2galaxies and LBGs are consistent with standard passive evolution models.Kewley&Kobulnicky(2005)followed the metallicity evolution of star-forming galaxies with comparable luminosities from z=0to3.5.O/H was determined from restframe optical emission lines using the strong-line method in four homogeneous galaxy samples. The samples were taken from the CfA2survey,from the GOODSfield,from Shapley et al.(2004),and from the LBG sample,covering z≈0,0.7,2.1−2.5,and2.5−3.5, respectively.The average oxygen abundance in the local universe,as defined by the CfA2 sample is about solar.O/H decreases with redshift to approximately1/3solar at z=3.6Claus LeithererIt is instructive to compare the heavy-element abundances of LBGs to those of DLAs and to the Lyman-forest at the same redshift(Pettini2004).DLA systems have metallic-ities of about1/15Z⊙and are thought to be the cross sections of the outer regions and halos of(proto)-galaxies seen along the sightlines of quasars.Although the properties of LBGs and DLAs do not immediately support a close relation between the two classes of objects,at least some link seems likely.If so,the observed outflows in LBGs may provide the metal enrichment of the halos.The Lyman-forest is predicted by cold dark matter models to result from structure formation in the presence of an ionizing background. The Lyman-forest had long been thought to be truly primordial,but metal enrichment of1/100–1/1000Z⊙has recently been detected(Aguirre et al.2004).This relatively high metal abundance early in the evolution of the universe could have been produced by afirst generation of Population III stars.Such stars can account for the amount of metals,and at the same time could have provided copious ionizing photons,as metal and photon production are closely correlated.Alternatively,star-forming galaxies at high redshift could be the production sites of the metals seen in the intergalactic medium if superwinds are capable of removing the newly formed metals from galactic disks. AcknowledgementsI would like to thank Max Pettini for a careful reading of the manuscript and for providing invaluable comments.ReferencesAguirre,A.,Schaye,J.,Kim,T.,Theuns,T.,Rauch,M.,&Sargent,W.2004,ApJ,602,38 Alloin,D.,Collin-Souffrin,S.,Joly,M.,&Vigroux L.1979,A&A,78,200Denicol´o,G.,Terlevich,R.,&Terlevich,E.2002,MNRAS,330,69Garnett,D.R.2002,ApJ,581,1019Giavalisco,M.2002,ARAA,40,579Heckman,T.M.,Robert,C.,Leitherer,C.,Garnett,D.,&van de Rydt,F.1998,ApJ,503,646 Kewley,L.,&Kobulnicky,H.A.2005,in R.de Grijs&R.M.Gonz´a lez Delgado(eds.),Star-bursts:From30Doradus to Lyman Break Galaxies,(Dordrecht:Springer),p.307 Kulkarni,V.P.,Fall,S.M.,Lauroesch,J.T.,York,D.G.,Welty,D.E.,Khare,P.,&Truran, J.W.2005,ApJ,618,68Leitherer,C.1997,in:W.H.Waller,M.N.Fanelli,J.E.Hollis,&A.C.Danks(eds.),The Ultraviolet Universe at Low and High Redshift:,(Woodbury:AIP),p.119Leitherer,C.1999,in:J.Walsh&M.Rosa(eds.),Chemical Evolution from Zero to High Redshift, (Berlin:Springer),p.204Leitherer,C.,Le˜a o,J.R.S.,Heckman,T.M.,Lennon,D.J.,Pettini,M.,&Robert,C.2001, ApJ,550,724Leitherer,C.,et al.1999,ApJS,123,3McGaugh,S.1991,ApJ,380,140Mehlert,D.,et al.2002,A&A,393,809Pauldrach,A.W.A.,Hoffmann,T.L.,&Lennon,M.2001,A&A,375,161Pettini,M.2004,in:C.Esteban,R.J.Garc´ıa L´o pez,A.Herrero,&F.S´a nchez(eds.),Cosmo-chemistry,XIII Canary Islands Winter School,(Cambridge:CUP),p.257Pettini,M.,Rix,S.A.,Steidel,C.C.,Adelberger,K.L.,Hunt,M.P.,&Shapley,A.E.2002, ApJ,569,742Pettini,M.,Shapley,A.E.,Steidel,C.C.,Cuby,J.,Dickinson,M.,Moorwood,A.F.M., Adelberger,K.L.,&Giavalisco,M.2001,ApJ,554,981Rix,S.A.,Pettini,M.,Leitherer,C.,Bresolin,F.,Kudritzki,R.,&Steidel,C.C.2004,ApJ, 615,98Shapley,A.E.,Erb,D.K.,Pettini,M.,Steidel,C.C.,&Adelberger,K.L.2004,ApJ,612,108 Steidel,C.C.,Adelberger,K.L.,Giavalisco,M.,Dickinson,M.&Pettini,M.1999,ApJ,519,1。
Metal Abundances of KISS Galaxies III. Nebular Abundances for Fourteen Galaxies and the Lum
a r X i v :a s t r o -p h /0408342v 1 18 A u g 2004Accepted ApJ Submission:8/2/04Metal Abundances of KISS Galaxies III.Nebular Abundances for Fourteen Galaxies and the Luminosity-Metallicity Relationship for H II Galaxies Janice C.Lee Steward Observatory,University of Arizona,Tucson,AZ 85712jlee@ John J.Salzer Astronomy Department,Wesleyan University,Middletown,CT 06459slaz@ and Jason Melbourne UCO/Lick Observatory,UC Santa Cruz,Santa Cruz,CA 95064jmel@ ABSTRACTWe report results from the third in a series of nebular abundance studiesof emission-line galaxies from the KPNO International Spectroscopic Survey (KISS).Galaxies with coarse metallicity estimates of 12+log(O/H)less than8.2dex were selected for observation.Spectra of 14galaxies,which cover the full optical region from [OII]λλ3727,3729to beyond [SII]λλ6717,6731,are pre-sented,and abundance ratios of N,O,Ne,S,and Ar are computed.The auroral[OIII]λ4363line is detected in all 14galaxies.Oxygen abundances determined through the direct electron temperature (T e )method confirm that the sample is metal-poor with 7.61≤12+log(O/H)≤8.32.By using these abundances in conjunction with other T e -based measurements from the literature,we demon-strate that H II galaxies and more quiescent dwarf irregular galaxies follow similar metallicity-luminosity (L-Z)relationships.The primary difference is a zero-pointshift between the correlations such that H II galaxies are brighter by an averageof0.8B magnitudes at a given metallicity.This offset can be used as evidenceto argue that low-luminosity H II galaxies typically undergo factor of two lumi-nosity enhancements,and starbursts that elevate the luminosities of their hostgalaxies by2to3magnitudes are not as common.We also demonstrate thatthe inclusion of interacting galaxies can increase the scatter in the L-Z relationand may force the observed correlation towards lower metallicities and/or largerluminosities.This must be taken into account when attempting to infer metalabundance evolution by comparing local L-Z relations with ones based on higherredshift samples since the fraction of interacting galaxies should increase withlook-back time.Subject headings:galaxies:abundances-galaxies:starburst-galaxies:dwarf-galaxies:evolution-H II regions1.IntroductionOne of the broad goals of the KPNO International Spectroscopic Survey(KISS,Salzer et al.2000)is to provide a large,statistically complete sample of emission-line galaxies (ELGs)that can be used to study the chemical enrichment and star-formation properties of active galaxies in the local universe(z 0.095).As part of this endeavor,we have been engaged in a long-term effort to obtain optical long-slit spectroscopy for KISS ELG candidates identified via line-emission in the initial low-dispersion objective-prism survey. The emission lines in the spectra from these follow-up observations supply accurate redshifts, allow for the determination of the type of activity occurring in the galaxies(Baldwin,Phillips &Terlevich1981,Veilleux&Osterbrock1987)and depending on the quality of the data,can also provide a measurement of the heavy element abundance(e.g.Searle&Sargent1972, Izotov,Thuan&Lipovetsky1994)and the star formation rate(Kennicutt1998).Metal abundance,in particular,provides insight into the evolutionary status of galaxies because the presence of elements heavier than hydrogen and helium indicates that chemical processing has occurred via star formation and the subsequent expulsion of metals into the interstellar medium.By combining abundance measurements with additional quantities such as luminosity and gas mass,a wealth of analyses may be undertaken.For example,models of chemical evolution which can constrain the presence of inflows and outflows may be tested (e.g.Kennicutt&Skillman2001).Correlations of the metallicity with other properties such as dynamical mass(e.g.Lequeuex et al.1979),rotational velocity(e.g.Garnett2002),and B luminosity(e.g.Skillman,Kennicutt&Hodge1989)may be studied.The application ofthe last of these analyses to large datasets has recently begun(e.g.2dF,Lamareille et al. 2004;SDSS,Tremonti et al.2004),and includes the work presented in this series of papers describing our follow-up abundance studies of KISS star-forming ELGs.In these papers, we have thus far:(1)empirically derived coarse abundance estimates for519galaxies and used these results to determine the form of the B-band metallicity-luminosity relationship over approximately seven magnitudes(Melbourne&Salzer2002;hereafter Paper I),and(2) begun to publish the follow-up spectra and present nebular abundance calculations for high signal-to-noise data which include detection of the temperature sensitive[O III]λ4363line (Melbourne et al.2004;hereafter Paper II).In this paper,we present abundance quality spectrophotometry for an additional14 galaxies collected over two seasons at the6.5m MMT1on Mount Hopkins.The galaxies chosen for these observations are ones which are identified as metal-poor(12+log(O/H) 8.2)using the empirical strong-lined estimator developed in Paper I.Our MMT targets previously had“quick-look”follow-up spectra available(most of which were taken with spectrographs with little or no sensitivity in the blue),which allowed for the calculation of these coarse estimates based on the[O III]λ5007/Hβand[N II]λ6583/Hαline ratios,but not for the more accurate T e-based nebular abundances which require the[O III]λ4363line. Therefore,one of the objectives of the MMT observations was to secure robust detections of[O III]λ4363for additional targets in order to enlarge the sample of12galaxies presented in Paper bining the data presented here and in Paper II,there are23unique KISS ELGs for which T e-based metallicities can be computed.These results are used in the next paper in the KISS abundance series(Salzer et al.2004,hereafter Paper IV)to improve the calibration of our empirical strong-lined oxygen abundance estimator,to update the KISS ELG L-Z relation in the B-band with a larger sample of763galaxies,and to further determine it in the near-infrared J,H and K-bands.In the analysis given here,our sample of23KISS galaxies with directly determined neb-ular abundances is used in conjunction with other data from the literature to re-evaluate the B-band luminosity-metallicity relationship for low-luminosity H II galaxies,and to compare this relation with the one followed by the population of more quiescent dwarf irregular(dIrr) galaxies.While a tight correlation of increasing oxygen abundance with increasing luminos-ity has already been carefully quantified by exclusively using T e-determined abundances and accurate photometry for the dIrrs(e.g.Skillman et al.1989,Richer&McCall1995,H.Lee et al.2003),a similar treatment for H II galaxies is not available.In fact,previous investiga-tions of the L-Z relation in the low-luminosity regime have typically excluded galaxies thatare strongly star-forming since these objects are thought to obscure any relationship that might be found.An implicit assumption here is that the underlying relationship is between mass and metallicity(e.g.Lequeux et al.1979,Tremonti et al.2004),and that the large contribution of light from starbursting regions causes the observed B luminosity to be a poor indicator of stellar mass.Papers which do investigate the L-Z relationship for H II galaxies have primarily examined it using either small samples,empirically estimated abundances, and/or estimated luminosities(e.g.Hunter&Hoffman1999,Salzer et al.1989,Kobul-nicky&Zaritsky1999).In general,these studies alsofind a trend of increasing metallicity with increasing luminosity for the H II galaxies,albeit with considerably larger scatter,and sometimes with major deviations when compared to the L-Z relationship for dIrrs.Here,we attempt to provide a more robust analysis for this ing only directly determined abundances,wefind that H II galaxies and more quiescent dIrrs follow similar relationships. We quantify and discuss some possible physical interpretations of the differences that exist.2.Spectroscopy2.1.Properties of the Observed SampleGeneral properties of the galaxies that were observed at the MMT are compiled in Table1.The objects selected for observation are ones with12+log(O/H) 8.2dex,as determined via the empirical strong-lined estimator developed in Paper I.Nevertheless,the observed sample still spans a wide range in luminosity,from-12.46to-19.40in M B.We also preferentially chose targets with lower apparent brightnesses to take advantage of the MMT’s large light collecting area.The median m B of the observed sample is18.40.The locations of the targets in the log([O III]λ5007/Hβ)versus log([N II]λ6583/Hα) plane are shown in Figure1.This classical diagnostic diagram(Baldwin,Phillips&Ter-levich1981)is used to empirically distinguish between ELGs in which photoionization is primarily due to non-thermal,power-law continua(i.e.ones which contain AGN),and those where the emission is mainly powered by hot OB stars.In thisfigure,the points repre-sent all KISS ELGs with good quality spectra2which have been classified as star-forming.Galaxies with nebular abundances based on spectra taken at Lick Observatory(Paper II)are additionally marked with open diamonds while the ones presented here are circled.Three galaxies observed at Lick(KISSR85,KISSR666and KISSB23)were re-observed with the MMT in order to check dubious[O III]λ4363detections as discussed in detail in Paper II.The two strong-line ratios plotted in Figure1also form the basis of the empirical abun-dance determination method described in Paper I.For star-forming systems,the distribution of points in this plot form a well-defined locus:low-metallicity systems occupy the upper left and the metal abundance smoothly increases as one moves along the locus toward the lower right corner of the diagram.As would be expected,all of the MMT targets lie within the low-metallicity,high-excitation region of the plot;they generally have high[O III]λ5007/Hβratios but low[N II]λ6583/Hαratios.The one galaxy which lies considerably offthe locus, and has been observed both at Lick and the MMT,is KISSB23.As discussed in Paper II, the emission in this object is powered by a lower excitation source,most likely because its starburst is past its peak,as indicated by a relatively low value of[OIII]λ5007/[OII]λ3727 calculated from its spectrum.2.2.ObservationsThe data presented in this paper were obtained with the Blue Channel Spectrograph on the6.5m MMT on the nights of May10,2002and April3,2003.Conditions were photometric on both nights.In May2002,we used a500line mm−1grating blazed at5410˚A infirst order along with a3600˚A UV blockingfilter to prevent overlap from second order light in the red.With the3072×102415µpixel CCD detector(CCD22)installed on the spectrograph at that time,this set-up provided coverage between3650˚A and7200˚A,a pixel scale of0.′′6(when binned by2in the spatial direction),and a spectral resolution of5˚A FWHM for a1.′′5×180′′slit.At the end of February2003,the detector was replaced with a smaller2688×51215µpixel chip(CCD35),resulting in a loss of approximately400˚A in spectral coverage when the above set-up is used.Therefore,in April2003we chose to use a lower dispersion300line mm−1grating instead to ensure that wavelengths between and including[O II]λλ3726,29and[S II]λλ6717,31were adequately sampled by the detector for the range of redshifts spanned by our targets(∆cz∼24,000km s−1).The300line mm−1grating,blazed at4800˚A and used infirst order,provided coverage between3600˚A and8400˚A,and a spectral resolution of9˚A FWHM for a1.′′5×180′′slit.The spatial scale did not change since the pixel sizes on the old and new detectors were the same.Exposure times for each galaxy ranged from10to15minutes(see Table1).Our objective was to obtain good signal-to-noise(SNR∼20)in the weak[O III]λ4363line sothat it could be used to estimate the nebular electron temperature which is necessary for an accurate determination of the metal abundance.Since the sensitivity of the slit-viewing camera allowed for direct viewing of the majority our targets,we were able to confirm that the pointing of the telescope was accurate enough to allow for slit positioning based on the target’s coordinates(as listed in Table1),and were also able to make small adjustments to the pointing by eye when necessary.Spectrophotometric standards from Massey et al.(1988)were observed every few hours to allow forflux calibration.The spectrograph slit was aligned with the parallactic angle to minimize the effects of differential atmospheric refraction for all standard star and galaxy observations.Bias,HeNeAr lamp,quartz lamp and twilightflat-field exposures were taken following routine procedures.2.3.Data ReductionThe data were reduced following standard methods,using Image Reduction and Analysis Facility3(IRAF)software.The bias level was determined for each frame using an overscan region,while a mean bias image constructed from20zero-second exposures was used to correct for any two-dimensional structure introduced by the read-out electronics.The dark-count level was measured using a series of exposures taken with the shutter closed,and was found to be negligible.Flat-fielding was carried out by combining a series of several quartz-lamp spectra that was normalized and corrected for any wavelength-dependent response. Spectra of the twilight sky were used to account for the illumination variation along the slit. These variations were found to be very small(under1%).Once the standard CCD reductions were completed,the spectra were extracted to a one-dimensional format using the APALL routine.The extraction apertures were set on a case-by-case basis,and depended on the two-dimensional profile of the source along the slit. In most cases,the emission regions of our targets were unresolved spatially,and the extraction region was chosen to include most of the lineflux present(8-11pixels or4.′′8-6.′′6wide).The sky background was subtracted in the same step,typically using object-free regions20-30 pixels wide on either side of the target spectrum.The He-Ne-Ar lamp spectra were used to establish the wavelength scale,and spectra of several spectrophotometric standard stars from Massey et al.(1988)were used to establish theflux scale.The standard stars were also used to create a template telluric absorption spectrum that was scaled and used tocorrect the spectra of our ELGs.This step is important,since at the typical redshifts of our target galaxies lines like[S II]λλ6717,6731,[N II]λλ6548,6583,and/or Hαcan fall within the atmospheric B-band(6860-6890˚A)and have theirfluxes significantly underestimated.In cases where more than one spectral image was obtained for a given galaxy,the individual spectra were processed fully and then combined prior to measurement.All linefluxes were measured using the SPLOT routine.An accurate estimate of the internal reddening along the line-of-sight to each emission region is measured using the Balmer line ratios.We use a routine that simultaneously solves for the underlying Balmer absorption and for the exponential reddening coefficient c Hβ.The three lowest-order Balmer line ratios are used for this process.The values for c Hβand the equivalent width of the underlying Balmer absorption lines(assumed to be the same for all four lines)that give consistent results for all three ratios are determined.For the majority of the galaxies observed wefind an underlying absorption equivalent width of3–4˚A.The derived estimates of c Hβfor each galaxy are shown in Table2.This value of c Hβis then used to correct all measured line ratios for reddening,following the standard prescription(e.g., Osterbrock(1989):I(λ)exp[c Hβf(λ)](1)F(Hβ)where f(λ)is derived from studies of absorption in the Milky Way(using values taken from Rayo et al.1982).2.4.Spectral DataSpectra of the14galaxies observed at the MMT are presented in Figure2.As would be expected for the high-equivalent width,star-forming ELGs found in KISS,the galaxies in this sample exhibit H II region-like spectra which have strong emission-lines superimposed on a faint,blue continuum.The full intensity range is plotted for each galaxy in the top panel to illustrate the ratios of the strong emission-lines,while an expanded version is presented in the bottom panel to more clearly show the quality of the weakest lines.Reddening corrected flux ratios with respect to Hβfor lines with equivalent widths above1˚A are reported in Table2.3.Metal AbundancesWe calculate metal abundances from the MMT spectra,following the same techniques described in Paper II.The method is summarized below and our results are presented inTable3.3.1.Electron Density and TemperaturesCalculations of the electron density and electron temperature are performed by using the IRAF NEBULAR package ZONES routine(Shaw et al.1995).We assume a two zone ionization model for the nebular emission regions studied.In the higher ionization zone oxy-gen is doubly ionized,whereas in the low ionization zone oxygen is singly ionized.Hydrogen is assumed to be ionized throughout both regions.We use the sulfur line ratio,[S II]λ6716/λ6731(Izotov et al.1994)to determine the electron density,which in all measurable cases is roughly100e−cm−3.In some cases the observed line ratio results in an unphysically small value of the electron density.This is usually caused by the sulfur lines falling within the atmospheric B-band.In these cases,we assign the galaxy the typical nebular density of100e−cm−3.The sulfur lines are the only adequate electron density indicator available in the spectra,therefore we assume that both zones have the density indicated by the sulfur lines.We calculate the temperature in the higher ionization zone using the traditional oxygen line ratio[O III](λ4959+λ5007)/λ4363(Aller1984,Osterbrock1989).We then estimate the temperature in the low ionization zone,using the relationship derived by Pagel et al. (1992)based on the models of Stasinska(1990),t e([OII])=2((t e([OIII])−1+0.8)−1,(2) where t’s are temperatures measured in units of104K.The measured electron densities and temperatures are given in Table3.3.2.Ionic and Total AbundancesThe ionic abundances are calculated with the IRAF NEBULAR package ABUND(Shaw et al.1995)routine.The input data include the electron density and temperature for the two ionization zones,as well as the de-reddened line ratios with respect to Hβ.When there is adequate S/N in the required emission-lines,we calculate ionic abundance ratios with respect to H+for the following ions:O+,O++,N+,S+,S++,Ne++,and Ar++.We use the ionization correction factors given by Izotov et al.(1994),ICF(N)=NO+,(3)ICF(Ne)=NeO++,(4)ICF(S)=SAr++=[0.15+x(2.39−2.64x)]−1,(6) x=O+4When metallicities relative to the solar value are discussed,the older value of the solar oxygen abundance of8.92(Lambert1978)is assumed rather than the more recent determination of8.69(Allende-Prieto, Lambert&Apslund2001)to facilitate comparison with previous work.The errors in the oxygen abundances range from0.03to0.09dex,with an average value of parison of these T e-based abundances with those computed using our strong-line estimator are presented in Paper IV.We now turn to examining the behavior of metal abundances relative to oxygen.Abun-dance ratios have been well studied both theoretically and observationally since they provide important insights into stellar nucleosynthesis and chemical evolution in general(see review given by Pagel1997and references therein).Specifically,it is expected that theα-process elements,such as O,Ne,S,and Ar should not vary with respect to one another since they are all primary elements created in the same population of massive stars,and should be produced infixed proportions over a given population and promptly returned to the ISM through Type II supernovae.The prediction of constantα-element ratios has been borne out by previous observations(e.g.Izotov&Thuan 1999,Paper II),and is re-confirmed by the new abundance measurements presented here.In Figure3,we plot log(Ne/O),log(S/O)and log(Ar/O)as a function of12+log(O/H),where the KISS ELGs observed at the MMT are indicated by open circles and those observed at Lick(Paper II)are indicated by open diamonds.We also plot the sample of blue compact dwarfs(BCDs)presented in Izotov&Thuan(1999)for comparison(smallfilled squares). The insets in the lower left corners of each panel shows the average errors for the Izotov and Thuan(1999)data.Our average errors are larger than those for the Izotov and Thuan (1999)dataset because of the relative faintness of our targets and the lower S/N of our spectral data.The KISS data show no significant trends of these quantities with the oxygen abundance.Unlike Ne/O,S/O and Ar/O,N/O has been shown to systematically increase with oxygen abundance for higher metallicity galaxies(e.g.Vila-Costas&Edmunds1993).The interpretation of this trend and its scatter in the context of understanding the dominant population of stars responsible for the build-up of N in the ISM is not straightforward and continues to be debated.The complexity which makes the origins of N enhancement more difficult to understand is the additional mechanism of secondary N production via the CNO cycle which is expected to mainly occur in intermediate mass stars.The reader is referred to Henry et al.(2000)for a review of the theories of N enhancement.We simply note here that constant values of N/O favor models in which N is created as result of primary CNO processing,whereas increasing values of N/O with oxygen abundance instead indicate a contribution from secondary processing where C and O from a previous generation of stars have been incorporated.N/O as a function of12+log(O/H)is also shown in Figure3.Because the scatter at a given O/H is large for the KISS galaxies,it is difficult to discern any significant trends.However,at12+log(O/H) 8.0the lower envelope defined by the KISS ELGs does appear to be rising linearly and follows the same relationship as the Izotov&Thuan(1999)sample. This may indicate secondary N production in the higher metallicity KISS ELGs.The absence of a correlation at lower metallicities is consistent with the conclusion that N is the mainly the product of primary processes in these galaxies.In Table4,average abundance ratios for the KISS ELGs observed at the MMT are compared with the values computed for the Lick dataset(Paper II)as well as those given in Izotov&Thuan(1999)for their sample of BCDs.Total averages for the combined Lick/MMT sample,where the MMT abundances supersede the Lick abundances for the three re-observed galaxies(KISSR85,KISSR666,KISSB23),are also tabulated.The results from the different datasets are in good agreement.4.The L-Z Relationship4.1.H II Galaxies vs.Dwarf IrregularsTo investigate the relationship between luminosity and metallicity for the population of H II galaxies,we use the abundance results presented here and in Paper II,along with additional data from the literature.As noted in the introduction,the L-Z relation for more quiescent dwarf irregular galaxies has already been carefully quantified by exclusively using T e-determined abundances and accurate photometry(e.g.Skillman et al.1989,Richer& McCall1995,H.Lee et al.2003).However a similar treatment for H II galaxies,so named because their light is dominated by star-formation occurring in compact regions(Melnick et al.1985),is not available.In fact,previous investigations of the L-Z relation in the low-luminosity regime have typically excluded galaxies that are strongly star-forming since these objects are thought to obscure any relationship that might exist.An implicit assumption here is that the fundamental relationship is between mass and metallicity(e.g.Lequeux et al.1979,Tremonti et al.2004),and that the overwhelming contribution of light from starbursting regions causes the observed B luminosity to be a poor indicator of stellar mass.From previously published work,we select H II galaxies with abundances from Kob-ulnicky&Skillman(1996)and Izotov&Thuan(1999)that have B photometry in either Salzer et al.(1989)or Gil de Paz et al.(2003).In the analysis that follows,we only use abundances that have been determined directly using the T e method.Magnitudes are cor-rected for Galactic extinction and we adopt an H o of75km s−1Mpc−1.All of these data are compiled in Table5.Note that the absolute magnitudes given in Table5for the KISS ELGs supersede those computed using the objective-prism redshifts that are published inthe original survey papers(Salzer et al.2001,Salzer et al.2002,Gronwall et al.2004). Redshifts based on long-slit spectral data are a great deal more accurate(σ=15-30km s−1)than those estimated from the coarse objective-prism spectra(σ∼850km s−1).A conservative value for the typical uncertainty in the KISS absolute magnitudes would then be0.3mag.This mainly reflects the error in the recessional velocity-based distance,since the photometric uncertainties are small,ranging from0.03mags for the brighter objects in the sample,to∼0.1for galaxies with B∼20(Salzer et al.2001).The positions of the H II galaxies in the L-Z plane are shown in Figure4asfilled symbols,where the triangles are KISS ELGs(N=23)and the circles represent the galaxies from the literature(N=31).Both samples occupy the same areas of parameter space,and show the familiar trend of increasing oxygen abundance with increasing luminosity.Tofit the data we compute the bisector of an initial ordinary least-squaresfit where M B and Z are taken as the independent and dependent variables respectively,and a secondfit where the variables are interchanged.The results of thefits(given in Table6)show that the KISS and literature H II galaxy samples,whether combined or considered separately,define the same L-Z relationship to within the errors.Thefit to the composite H II galaxy sample is shown in Figure4by the solid line.In Figure4,we also overplot nearby“normal”field dwarf irregulars(i.e.those that are not undergoing a massive,concentrated,burst of star-formation at the present epoch)from H.Lee et al.(2003)as open circles.This most recent determination of the L-Z relation for dwarf irregulars is essentially an update of the work published by Richer&McCall (1995),where H.Lee et al.(2003)follow their protocol of only including galaxies with T e based oxygen abundances and distances determined using stellar indicators,andfind that the addition of new data does not significantly change the earlier result.Both the Richer &McCall(1995)and H.Lee et al.(2003)results are also consistent with the relationship found by Skillman,Kennicutt&Hodge(1989).Figure4demonstrates that the populations of H II galaxies and more quiescent dIrrs define very similar luminosity-metallicity relationships,albeit with a small shift such that H II galaxies tend towards larger luminosities at a given oxygen parison of the formalfit for the dIrrs computed in H.Lee et al.(2003)(given in Table6and shown in Figure4as a dotted line)and ourfit for the total H II galaxy sample confirms that a subtle zero-point shift is detectable.It would appear as though the difference is not significant because of the∼0.5dex formal error on the zero-point.However,this is due to the covariance of the slope and the zero-point–a small error in the slope results in a large error in the intercept due to the large lever arm of the points relative to the y-axis.If we instead perform a constrained least-squaresfit with the slopefixed at-0.153,which is thevalue reported by both Skillman et al.(1989)and H.Lee et al.(2003)for the dIrrs,the resulting zero-point for the total H II galaxy sample is5.46±0.03,and the error in the zero-point for the H.Lee et al.(2003)dIrrs becomes±0.04.These statistics suggest that there is a luminosity shift of0.8B magnitudes between the correlations followed by the two populations which is significant at the3to4σlevel.4.2.Physical Interpretation of Shifts in the L-Z PlaneHow can this difference in the correlations be physically understood?It seems reason-able to attribute the zero-point offset to a systematic luminosity shift in the populations, particularly if the fundamental correlation is between stellar mass and metallicity(Tremonti et al.2004).Since H II galaxies have B luminosities that are less representative of the total stellar mass because of the large contribution of light from the starbursting regions,we can possibly expect these galaxies to show a shift to higher luminosities when compared with other galaxies that are not forming stars as vigorously.As discussed above,we see such a shift in Figure4.However,we can go one step further and interpret the offset as indicative of the amount of the average luminosity enhancement in the H II galaxy population.That is,the results of our analysis suggest a scenario where the typical H II galaxy is in a state of moderate brightening in which the starburst component is contributing about0.8magnitude of additional light in the B-band.This conclusion is consistent with independent studies that have used surface brightness decompositions to separate star-forming components from the underlying“host”in low-luminosity H II galaxies andfind that the star-formation regions elevate the host luminosity by an average of0.75B magnitudes(Salzer&Norton1998, Papaderos et al.1996and references therein).A systematic deviation of H II galaxies from the established dIrr relation has also been previously noted in passing by authors who investigate the L-Z relation over a larger lumi-nosity range for galaxies at higher redshift and use local H II galaxies from the literature and the present day L-Z relationship for comparison(e.g.Kobulnicky&Zaritsky1999,Contini et al.2002).These studies also attribute this deviation to the brightening caused by the typical starburst in an H II galaxy,but they show much larger average offsets of2to3 magnitudes.These results can be reconciled with our smaller quoted offset by noting that the low-luminosity ends of their L-Z relationships are defined with the data from Richer &McCall(1995).Using the more recently updated version of these data in H.Lee et al. (2003),as is done here,yields an approximate1magnitude shift towards higher luminosities, which reduces the apparent offsets between the two populations in those papers to1to2 magnitudes.This is more consistent with our results.Therefore if Figure4is robust,and。
2024上海静安区高三英语二模
静安区2023学年第二学期期中教学质量调研高三英语试卷(完卷时间：120分钟满分：140分)2024年4月考生注意：1. 试卷满分140分，完卷时间120分钟。
2. 本调研设试卷和答题纸两部分，全卷共12页。
所有答题必须涂(选择题)或写(非选择题)在答题纸上，做在试卷上一律不得分。
第I 卷(共100分)I. Listening ComprehensionSection ADirections: In Section A, you will hear ten short conversations between two speakers. At the end of each conversation,a question will be asked about what was said. The conversations and the questions will be spoken only once. After you hear a conversation and the question about it,read the four possible answers on your paper,and decide which one is the best answer to the question you have heard.1. A. At a grocery store. B. At a florist's stand.C. At a bank counter.D. At an electronic shop.2. A. Sign up for a fitness class. B. Shop for fitness equipment.C. Have a fitness test.D. Watch a fitness video.3. A. Pay the ticket right away. B. Challenge the ticket.C. Ignore the ticket.D. Apologize to the parking officer.4. A. She is available on Saturday. B. She will cancel her dentist appointment.C. She can not cover the man's shift.D. She forgot about the shift.5. A. The woman had better give him an extension on the deadline.B. The woman had better draft the proposal by herself.C. The woman had better approve the proposal.D. The woman had better give insights on the budget section.6. A. She doesn't like animals from the shelter.B. She prefers buying pets from breeders.C. She thinks adopting a pet is a bad idea.D. She supports the idea of adopting a pet.7. A. Either of them is an experienced chef.B. Both of them have experienced failures in the kitchen.C. Neither of them are fond of cooking.D. Both of them are concerned about the new recipe.8. A. Bungee jumping is safeB. Bungee jumping is thrilling.C. Bungee jumping might have risks.D. Bungee jumping is sure to be regrettable.9. A. The man should borrow the book several days later.B. The woman urgently needs the book back.C. The man does not need to return the book quickly.D. The woman is unwilling to lend the man the book.10. A. The woman's parents will not appreciate a surprise party.B. The woman should prioritize her parents' preferences for the party.C The man dislikes the idea of a surprise party.D. The woman should plan a party based on her own preferences.Section BDirections: In Section B,you will hear two short passages and one longer conversation. After each passage or conversation,you will be asked several questions. The passages and the conversation will be read twice,but the questions will be spoken only once. When you hear a question,read the four possible answers on your paper and decide which one would be the best answer to the question you have heard.Questions 11 through I3 are based on the following speech.11. A. A pupil in need of help. B. A person promising to donate money.C. A member from a charity.D. A teacher in the Semira Region.12. A. 10%. B. 35%. C. 50%. D. 65%.13. A. To train teachers for the disabled. B. To help a pupil with special needs.C. To pay for a walking holiday.D. To organize a charity club for the disabled.Questions 14 through 16 are based on the following passage.14. A. To distract other students from doing well.B. To impress his friends with the shining ring.C. To improve his chances in the exam.D. To honor his grandfather by wearing a ring.15. A. By having enough time for breaks.B. By breaking down learning into portions.C. By informing teachers of the study habits.D. By wearing lucky objects.16. A. Start revision ahead of time.B. Reward oneself during revision.C. Consider different learning styles.D. Stay up late for the exam.Questions 17 through 20 are based on the following conversation.17. A. To inquire about travel recommendations.B. To discuss cultural festivals in Southeast Asia.C. To plan a solo travel adventure to Thailand.D To learn about Mr. Patel's travel experiences.18. A. Europe and Africa. B. Thailand and VietnamC. South America and Australia.D. Japan and China.19. A. Solely cultural exploration.B. Primarily outdoor adventures.C. A mix of cultural and outdoor experiences.D. Luxurious and private accommodations.20. A. It is ideal for meeting fellow travelers.B. It offers exclusive travel experiences.C. It is a more comfortable and secure stay.D. It offers authentic cultural immersion.II. Grammar and VocabularySection ADirections:After reading the passage below,fill in the blanks to make the passages coherent and grammatically correct.For the blanks with a given word,fill in each blank with the proper form of the given word;for the other blanks,use one word that best fits each blank.Beethov-hen's first symphonyOn a grey Friday morning at a Hawke's Bay farm,members of New Zealand's symphony orchestra dressed in black to perform their latest composition in front of a large crowd.The music contained many marks of traditional classical music,but as it began,the instruments started to make loud,rough sounds more commonly __21__(hear)in chicken coops than in an auditorium.However,no feathers were angered by this departure from tradition, ___22__the audience that gathered to listen to the concert last week was,in fact,a couple of thousand chickens.The piece of music-Chook Symphony No. 1-__23__(create)specifically for the birds out of an unlikely partnership between the orchestra and an organic free-range chicken farm which wanted a piece of chicken-friendly music to enrich its flocks' lives.“We've been playing classical music for the chickens for some years now because ___24 ___ is well researched that the music can calm the chickens down,”says Ben Bostock,one of the two brothers who__25(own)the Bostock Brothers farm. Research has shown animals can respond positively to classical music,and chickens are particularly responsive to baroque(巴洛克格),according to some studies.The composer,Hamish Oliver,__26__used the baroque tradition as a starting point and drew inspiration from composers such as Corelli,Bach,and Schnitke,wanted the piece to be playful by including sounds from a chicken's world. “The trumpet imitates the c hicken …the woodwind instruments are the cluckiest,especially if you take the reeds off. ”The early stages of composition were spent _______(test)out which instruments and sounds the chickens responded to best.“They didn't like any big banging. ”Bostock said,adding that when the birds respond positively to themusic,they tend__28__(wander)farther among the trees. Bostock now hopes chicken farmers around the world will use the piece of music to calm their own birds.For Oliver,having input from the farmers about __ 29__the chickens were responding to particular sounds and instruments was a highlight of the project.The symphony has searched exhaustively __30__any other examples of orchestras making music specifically for chickens and believes this to be a world-first,says Peter Biggs,the orchestra's chief executive.Section BDirections :Complete the following passage by using the words in the box. Each word can only be used once. Note thatA new way to reduce poachingResearchers are working on a pilot program backed by Russia's Rosatom Corp to inject rhino horns(犀牛角)with radioactive material,a strategy that could discourage consumption and make it easier to detect illegal trade.Poachers(偷猎者)killed 394 rhinos in South Africa for their horns last year,government data shows,with public and private game __31__lacking the resources needed to monitor vast tracts of land and protect the animals that live there.While the toll was a third lower than in 2019 and the sixth __32_drop,illegal hunting remains the biggest threat to about 20,000 of the animals in the country —the world's biggest population.Thousands of__33__sensors along international borders could be used to detect a small quantity of radioactive material____34___into the horns,according to James Larkin,a professor at the University of Witswatersrand in Johannesburg,who has a background in radiation protection and nuclear security. “A whole new_35_of people could be able to detect the illegal movement of rhino horn,"he said. Some alternate methods of discouraging poaching,including poisoning, dyeing and removing the horns,have raised a variety of opinions as to their virtue and efficacy.Known as The Rhisotope Project,the new anti-poaching __36__started earlier this month with the injection of an amino acid(氨基酸)into two rhinos' horns in order to detect whether the compound will move into the animals' bodies. Also,__37__studies using computer modeling and a replica rhino head will be done to determine a safe dose of radioactive material. Rhino horn is used in traditional medicine,as it is believed to cure disease such as cancer,__38__as a show of wealth and given as gifts."If we make it radioactive, these people will be hesitant to buy it,"Larkin said. "We're pushing on the whole supply chain. "Besides Russia's state-owned nuclear company,the University of Witwatcrsrand. scientists and private rhino owners are involved in the project. If the method is ___39__feasible,it could also be used to curb illegal trade in elephant ivory.“Once we have developed the whole project and got to the poi nt where we completed the proof of concept,then we will be making this whole idea ____40_to whoever wants to use it. " Larkin said.III. Reading ComprehensionSection ADirections: For each blank in the following passages there are four words or phrases marked A, B. C and D. Fill in each blank with the word or phrase that best fits the context.City air is in a sorry state. It is dirty and hot. Outdoor pollution kills 4. 2m people a year, according to the World Health Organization. Concrete and tarmac meanwhile,absorb the sun's rays rather than reflecting them back into space,and also ___41 ___plants which would otherwise cool things down by evaporative transpiration(蒸腾作用). The never-ceasing__42_of buildings and roads thus tums urban areas into heat islands,discomforting residents and worsening dangerous heatwaves.A possible answer to the twin problems of pollution and heat is trees. Their leaves may destroy at least some chemical pollutants and they certainly __43__tiny particles floating in the air. which are then washed to the ground by rain. Besides transpiration,they provide __44___.To cool an area effectively, trees must be planted in quantity. Two years ago, researchers at the University of Wisconsin found that American cities need 40%tree___45___to cut urban heat back meaningfully. Unfortunately,not all cities —and especially not those now springing up in the world's poor and middle-income countries —are __46___with parks, private gardens or a sufficient number of street trees. And the problem is likely to get worse. At the moment,55%of people live in cities. By 2050 that share is expected to reach 68%.One group of botanists believe they have at least a partial ___47___to this lack of urban vegetation. It is to plant miniature simulacra(模拟物)of natural forests, ecologically engineered for rapid growth. Over the course of a career that began in the 1950s,their leader,Miyawaki Akira, a plant ecologist at Yokohama National University in Japan. has developed a way to do this starting with even the most___ 48___deserted areas. And the Miyawaki method is finding increasing___ 49___around the world.Dr Miyawaki's insight was to deconstruct and rebuild the process of ecological succession, by which ___50___land develops naturally into mature forest. Usually,the first arrival is grass, followed by small trees and,finally. larger ones.The Miyawaki method___51 ___some of the early phases and jumps directly to planting the kinds of species found in a mature wood.Dr Miyawaki has__52__the planting of more than 1,500 of these miniature forests,first in Japan,then in other parts of the world. Wherever they are planting,though,gardeners are not restricted to__53 __nature's recipe book to the letter. Miyawaki forests can be customized to local requirements. A popular choice__54__ is to include more fruit trees than a natural forest might support,thus creating an orchard that requires no maintenance.If your goal is to better your __55__surroundings,rather than to save the planet from global warming,then Dr Miyawaki might well be your man.41. A. thrive B. nourish C. displace D. raise42. A. assessment B. maintenance C. spread D. replacement43. A. release B. trap C. reflect D. dissolve44. A. attraction B. shadow C. interaction D. shade45. A. consumption B. coverage C. interval D. conservation46. A. blessed B. lined C. piled D. fascinated47. A. treatment B. obstacle C,warning D. solution48. A. unnoticed B. unpromising C. untested D. unfading49. A. criticism B. favor C. sponsor D. anxiety50. A. bare B. graceful C. faint D. mysterious51. A highlights B. skips C. improves D. pushes52. A. accessed B. spotted C. supervised D. ranked53. A. disturbing B. balancing C. following D. reducing54. A. for example B. in essence C. on the other hand D. after all55. A. suburban B. leisure C. scenic D. immediateSection BDirections: Read the following three passages. Each passage is followed by several questions or unfinished statements. For each of them there are four choices marked A,B,C and D. Choose the one that fits best according to the information given in the passage you have read.(A)From Marie Tussaud's Chamber of Horrors to Disneyland's Haunted Mansion(鬼屋)to horror-themed escape rooms,haunted house attractions have terrified and delighted audiences around the world for more than 200 years.These attractions turn out to be good places to study fear. They help scientists understand the body's response to fright and how we perceive some situations as enjoyably thrilling and others as truly terrible. One surprising finding;having friends close at hand in a haunted house might make you more jumpy,not less so.Psychologist and study co-author Sarah Tashjian,who is now at the University of Melbourne, and her team conducted their research with 156 adults,who each wore a wireless wrist sensor during their visit. The sensor measured skin responses linked to the body's reactions to stress and other situations. When the sensor picked up,for example,greater skin conductance —that is,the degree to which the skin can transmit an electric current —that was a sign that the body was more aroused and ready for fight or flight. In addition to this measure,people reported their expected fear (on a scale of 1 to 10)before entering the haunted house and their experienced fear (on the same scale)after completing the haunt.The scientists found that people who reported greater fear also showed heightened skin responses. Being with friends,Tashjian and her colleagues further found,increased physiological arousal during the experience,which was linked to stronger feelings of fright. In fact,the fear response was actually weaker when people went through the house in the presence of strangers.Other investigators have used haunted houses to understand how fear and enjoyment can coexist. In a 2020 study led by Marc Malmdorf Andersen,a member of the Recreational Fear Lab at Aarhus University in Denmark,scientists joined forces with Dystopia Haunted House. The Danish atraction includes such terrifying experiences as being chased by "Mr. Piggy",a large, chain-saw-wielding man wearing a bloody butcher's apron and pig mask. People between the ages of 12 and 57 were video recorded at peak moments during the attraction,wore heart-rate monitors throughout and reported on their experience. People's fright was tied to large-scale heart-rate fluctuations;their enjoyment was linked to small-scale ones. The results suggest that fear and enjoyment can happen together when physiological arousal is balanced "just right".56. Studing haunted house attractions helps scientists to learn about _____.A. the psychological effects of fear on individualsB. the history of horror-themed entertainmentC. the body's response to material rewardsD. the impact of technology on people's enjoyment57. How did Sarah Tashjian and her team conduct their research on haunted house experiences? A. By surveying participants.B. By analyzing historical records.C. By employing wireless wrist sensors.D. By using virtual reality simulations.58. What did Tashjian and her colleagues discover in their study?A. Being with fiends elevated level of physiological arousal.B. The fear reaction was stronger in the company of strangers.C. Psychological effect was unrelated to intensified feelings of fright.D. Those reporting lightened fear showed increased skin responses.59,It can be concluded from the 2020 study led by Marc Malmdorf Andersen that ____.A. fear and enjoyment can not happen at the same timeB. large-scale heart-rate fluctuations were linked to enjoymentC. the age of the participants was not related to the study's findingsD. fear and enjoyment can coexist under certain conditions(B)Is an electric vehicle right for you?Many people will ask themselvesthat question for the first time this year.Prices are falling,battery range is risingand mainstream brands are adding new EVs at a breakneck pace.Here are three things anybody seriously considering buying an EV should know:1. The price to install a 240v chargerAnybody who owns an electric vehicle needs a 240-volt charger at home. With one,you can recharge overnight,so you start every day with the equivalent of a full tank.Just a few years ago,home 240v EV chargers cost $2,500-$3,000,including installation,but prices have declined as competition grows with the number of EVs on the road.2. The time it takes to chargeAbout 80%of miles driven in EVs are powered by electricity charged at home,but you'll need to charge elsewhere occasionally. That's when charging time becomes a big deal,but how long it takes depends on a couple of factors.First,voltage from the charger. Getting 250 miles of range in seven hours from a 240v charger is fine when you're charging overnight at home,but it's a deal breaker if you're going 300 miles for a weekend getaway. In that case,you'll want to look for a 400v DC fast charger. They're not as common as 240v public chargers yet,but they're becoming more widespread.There's another factor:the on-board charger. It regulates how fast the battery can accept electricity. A vehicle with a higher-capacity on-board charger accepts electricity faster.3. Where to chargeGood route-planning apps will help you find chargers on a road trip.“Most people have no idea how many public charging stations are within,say,a 10-or 15- mile radius(半径)because they're small,people don't look for them or even don't know what to look for,and they're rarely signposted,"said journalist John Voelcker,who has studied EVs and charging exhaustively.4. On the horizonIf an EV doesn't meet your needs now, watch this space. They're coming closer,but large numbers of gasoline vehicles will remain in production for years. Beyond that,companies will keep making spare parts for oil-burners for decades.60. Which of the following statements is TRUE according to the passage?A. The price of installing a home EV charger has remained stable in the past few years.B. It's quite easy to identify the public charging stations with the help of striking signposts.C. Popular brands are introducing new EVs at an incredibly fast rate.D. An electric vehicle can't provide the same amount of energy as a completely filled fuel tank.61. The underlined phrase "watch this space" in the last paragraph probably means" _______ ”.A. give up the plan to purchase an EVB. make space for an EVC. find an alternative to EVD. keep an eye out for future developments62. This passage is mainly intended to _______ .A illustrate the factors charging time depends onB. offer advice on purchasing an electric vehicleC. look forward to the future of electric vehiclesL explain the reason for the falling prices of electric vehicles(C)Flinging brightly coloured objects around a screen at high speed is not what computers' central processing units were designed for. So manufacturers of arcade machines invented the graphics-processing unit (GPU),a set of circuits to handle video games' visuals in parallel to the work done by the central processor. The GPU's ability to speed up complex tasks has since found wider uses:video editing, cryptocurency mining and most recently,the training of artificial intelligence.AI is now disrupting the industry that helped bring it into being. Every part of entertainment stands to be affected by generative AI,which digests inputs of text,image,audio or video to create new outputs of the same. But the games business will change the most,argues Andreessen Horowitz,a venture-capital(VC)firm. Games interactivity requires them to be stuffed with laboriously designed content:consider the 30 square miles of landscape or 60 hours of music in “Red Dead Redemption 2”a recent cowboy adventure. Enlisting Al assistants to chum it out could drastically shrink timescales and budgets.AI represents an "explosion of opportunity"and could drastically change the landscape of game development. Making a game is already easier than it was:nearly 13,000 titles were published last year on Steam,a games platform,almostdouble the number in 2017. Gaming may soon resemble the music and video industries in which most new content on Spotify or YouTube is user-generated. One games executive predicts that small firms will be the quickest to work out what new genres are made possible by Al. Last month Raja Koduri,an executive at Intel,left the chip maker to found an Al-gaming startup.Don't count the big studios out,though. If they can release half a dozen high-quality titles a year instead of a couple,it might chip away at the hit-driven nature of their business,says Josh Chapman of Konvoy,a gaming focused VC firm. A world of more choices also favors those with big marketing budgets. And the giants may have better answers to the mounting copyright questions around Al. If generative models have to be trained on data to which the developer has the rights,those with big back-catalogues will be better placed than startups. Trent Kaniuga,an artist who has worked on games like "Fortnite",said last month that several clients had updated their contracts to ban Al-generated ant.If the lawyers don't intervene,unions might. Studios diplomatically refer to Al assistants as “co-pilots”,not replacements for humans.63. The original purpose behind the invention of the graphics-processing unit (GPU)was to______A. speedup complex tasks in video editing and cryptocurency miningB. assist in the developing and training of artificial intelligenceC. disrupt the industry and create new outputs using generative AID. offload game visual tasks from the central processor64. How might the rise of AI-gaming startups affect the development of the gaming industry?A. It contributes to the growth of user-generated content.B. It facilitates blockbuster dependency on big studios.C. It decreases collaboration between different stakeholders in the industry.D. It may help to consolidate the gaming market under major corporations.65. What can be inferred about the role of artificial intelligence in gaming?A. AI favors the businesses with small marketing budgets.B. AI is expected to simplify game development processes.C. AI allows startups to gain an edge over big firms with authorized data.D. AI assistants may serve as human substitutes for studios.66. What is this passage mainly about?A. The evolution of graphics-processing units (GPUs).B. The impact of generative AI on the gaming industry.C. The societal significance of graphics-processing units(GPUs).D. The challenges generative AI presents to gaming studios.Section CDirections: Read the following passage. Fill in each blank with a proper sentence given in the box. Each sentence can beTime to end Santa's 'naughty list'?Many of us have magical memories of Santa secretly bringing gifts and joy to our childhood homes —but is there a darker side to the beloved Christmas tradition?I was —and I'm happy to admit it —a loyal believer of Santa. I absolutely loved the magic of Christmas,especially Santa Claus,and my parents went above and beyond to encourage it. However,as I begin to construct my own Santa Claus myth for my daughter,I can't help but feel guilty. Could it undermine her trust in me?_____67______Backin1978,a study published in the American Journal of Orthopsychiatry(矫正精神医学)found that 85%of four-year-olds said they believed in Santa. In 2011,research published in the Journal of Cognition and Development found that 83%of 5-year-olds claimed to be true believers.I guess it's not all that surprising. _____68 _____He features in every Christmas TV show and movie. Each year the North American Aerospace Defence Command (NORAD)allows you to track Santa's journey on Christmas Eve. To reassure children during the pandemic in 2020,the World Health Organization issued a statement declaring that Santa was “immune”from Covid 19. And it's precisely this effort on behalf of parents,and society in general,to create such seemingly overwhelming evidence for the existence of Santa Claus that David Kyle Johnson,a professor of philosophy at King's College in Pennsylvania,describes as 'The Santa Lie' in his book The Myths That Stole Christmas. He highlights how we don't simply ask children to imagine Santa,but rather to actually believe in him. _____69 _____The 'Santa lie' can reduce trust between a parent and a child. _____70 _____It is the creation of false evidence and convincing kids that bad evidence is in fact good evidence that discourages the kind of critical thinking we should be encouraging in children in this era. “The ‘Santa lie' is part of a parenting practice that encourages people to believe what they want to believe,simply because of the psychological reward,”says Johnson. “That's really bad for society in general. ”IV. Summary WritingDirections: Read the following passage. Summarize the main idea and the main point(s)of the passage in no more than 60 words. Use your own words as far as possible.Exploring the Appeal of VintageToday,the term“vintage”applies to almost everything. Vintage is more recent than an antique (古董)which is defined as 100 years old or more. It basically means reviving something old- fashioned or filled with memories. For an object to be considered vintage,it must be unique and genuine enough to retain at least some of its original charm.We buy vintage because it creates a sense of personal connection for us:it speaks to our childhood memories and that feels good. We also buy vintage because we're rebels. Vintage is a protest against modern mainstream culture. In an age of technology,buying vintage is a refuge from our fast-paced,high-tech world. We want our children to make the most of their creativity and know how to entertain themselves without electronic gadgets. Ironically,early video games are now considered vintage.Of all the vintage objects,vintage toys are forever attractive for both adults and children. Although some toys have emotional value,others have high market value and are expensive to collect. Vintage toys that were made in small quantities often bring a higher value than those that were mass produced. That means,if you own one of the 2,000 “Peanuts”royal blue beanie baby elephants that were manufactured with a darker blue coat than originally intended,you might have something valuable on your hands. In fact,due to a manufacturer error,this is the most collectible beanie baby around —and worth about f3,000.If you're motivated and feeling lucky,you can find deals on vintage toys by browsing charity shops,secondhand stores,community centers,flea markets and garage sales. You never know what kind of treasures are hiding at the bottom of a mixed box in someone's basement,garage or attic.第Ⅱ卷(共40分)V. TranslationDirections: Translate the following sentences into English. using the words given in the brackets.72. 他在升旗仪式上的演讲得到了高声喝彩。
TheHubble一只望远镜的革命英语美文
TheHubble一只望远镜的革命英语美文The Hubble一只望远镜的革命英语美文The Hubble 一只望远镜的革命When most people think of space, what come to mind are names like John Glenn and Neil Armstrong. When scientists think about space, the name that comes to mind is Hubble, a space telescope we sent on a twenty-year Journey to explore the origins of the universe. It"s already being called the most scientifically significant space project we ever embarked on. Taking pictures of the universe that literally let you and me and everyone else look back in time and see what the universe looked like13 billion years ago.很多人想到太空时,首先在脑海中出现的名字不是约翰·格林就是尼尔·阿姆斯特朗。
而当科学家想到太空时,他们脑海中出现的是哈勃太空望远镜。
二十年来哈勃望远镜一直在为我们探索宇宙的起源之谜,它被称为是人类所进行的最具科学意义的太空项目。
从它拍摄的宇审照片上,我们每人都能回顾到宇宙在130亿年前的模样。
The images are like nothing ever seen before, as much art as science, visions of a universe more violent and fantastic than anyone had dared to imagine. Everything from razor-sharp views of the planets in our own solar system, to the vast stellar nurseries where stars and planets are born. Some show us the explosive outbursts of dying suns, others the swirling masses of stars that make up the galaxies. But Hubble isn"t just giving us extraordinary pictures, it"s helping astronomers unlock the secrets of the universe.照片所展示的图像是我们前所未见的：科学犹如艺术，宇宙图像比任何人敢的还要热烈，奇异。
万物和谐共存的英语作文
万物和谐共存的英语作文In the vast expanse of our universe, the concept of harmonyis not just a philosophical ideal but a fundamental necessity for the survival and prosperity of all life forms. The English essay that follows delves into the essence of harmonious coexistence and its significance in our world.From the microscopic organisms in the soil to the sprawling galaxies in the cosmos, everything is interconnected in a delicate web of existence. The principle of harmonious coexistence is the cornerstone of a balanced ecosystem and a peaceful society. It is the recognition that all entities, regardless of their size or complexity, have a role to playin the grand scheme of life.The Natural WorldIn nature, harmony is maintained through a series of checks and balances. The predator-prey relationship, for instance, ensures that no single species becomes too dominant, thus preserving biodiversity. Trees and plants engage in a symbiotic relationship with the soil and the atmosphere, exchanging nutrients and oxygen in a cycle that sustains life on Earth.Human InteractionThe same principle applies to human societies. Harmony is achieved when individuals respect the rights and dignity of others, fostering a sense of community and cooperation. Cultural diversity is a testament to the richness that can emerge from the harmonious coexistence of differenttraditions and beliefs.Challenges to HarmonyHowever, the harmony of existence is constantly threatened by human activities such as deforestation, pollution, and the overexploitation of resources. These actions disrupt the balance of ecosystems and can lead to the extinction of species and the degradation of the environment.The Path to HarmonyTo achieve harmony, we must adopt sustainable practices that minimize our impact on the environment. This includes conserving energy, reducing waste, and supporting policies that protect natural habitats. Education plays a crucial role in raising awareness about the importance of ecological balance and the need for responsible stewardship of our planet.The Role of TechnologyAdvancements in technology can also contribute to harmonious coexistence. Innovations in renewable energy, for example, can help us reduce our reliance on fossil fuels, therebydecreasing pollution and the risk of climate change.Similarly, technological solutions can aid in the restoration of damaged ecosystems and the monitoring of wildlife populations.ConclusionIn conclusion, the harmonious coexistence of all things isnot merely a romantic notion but a practical imperative forthe continued existence of life on Earth. It requires a concerted effort from all segments of society to respect the interconnectedness of all living beings and to act in waysthat preserve the delicate balance of our planet's ecosystems. By doing so, we can ensure a future where humans and nature thrive together in a symphony of shared existence.。
小学上册J卷英语第5单元寒假试卷
小学上册英语第5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.What do we call a large body of water?A. RiverB. LakeC. OceanD. Pond2.The chemical name for water is __________.3.What is the name of the fairy tale character who had long hair?A. RapunzelB. ArielC. BelleD. JasmineA Rapunzel4.My family enjoys __________ during the holidays, especially __________.5.What do we call the process of making a plan?A. OrganizingB. PlanningC. StrategizingD. Coordinating6.The ______ is essential for many ecosystems.7.What do you call a place where you can borrow books?A. SchoolB. LibraryC. ParkD. StoreB8.What do you call the process of water falling from the sky?A. EvaporationB. CondensationC. PrecipitationD. Transpiration9.The Milky Way is just one of many galaxies in the _______.10.My toy ________ can dance.11.The chemical formula for aluminum sulfate is __________.12. A __________ is crucial for the development of civilizations.13.I built a _____ (模型) of a spaceship.14.The __________ can reveal patterns in sedimentation and erosion.15.I like to watch cartoons about my toy ____. (玩具名称)16.The capital of Iran is __________.17. A ______ (蜥蜴) can warm itself in the sun.18.The __________ (历史的启示) can guide future actions.19.The ______ is a common houseplant that needs a lot of sunlight. (这是一种常见的室内植物，需要很多阳光。
小学上册第九次英语第4单元测验试卷
小学上册英语第4单元测验试卷英语试题一、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.My favorite fruit is _______.2.I enjoy having sleepovers with my _________ (玩具朋友).3.I have a _____ of markers. (set)4.What do you call a large area of sand?A. DesertB. BeachC. DuneD. OasisA5.What is the capital of the Philippines?A. ManilaB. CebuC. DavaoD. IloiloA6.What is the capital of Italy?A. VeniceB. RomeC. FlorenceD. MilanB7.The Milky Way is just one of many galaxies in the _______.8.What do you call the process of photosynthesis?A. Production of foodB. Growth of plantsC. Absorption of sunlightD. All of the aboveD9.My friend’s sister, ______ (我朋友的妹妹), loves to dance.10.The __________ can indicate the presence of valuable minerals.11.What do we call the area of land that is lower than the surrounding land?A. HillB. ValleyC. MountainD. PlateauB Valley12.I saw a _______ (小鸟) perched on a tree.13.My aunt teaches ____ (science) at the middle school.14.The _______ (青蛙) has long legs.15. A ____(green finance) supports environmentally-friendly projects.16.What is the main source of energy for the Earth?A. The MoonB. The SunC. StarsD. Wind17.What do we call the large container used for storing liquids?A. TankB. BottleC. JugD. BarrelA18.In a battery, chemical energy is converted into ________ energy.19.The chemical symbol for neptunium is __________.20.What do we call the study of the interactions between organisms and their environment?A. EcologyB. BiologyC. ZoologyD. Botany21.What is the name of the famous American author known for "The Kite Runner"?A. Khaled HosseiniB. Mohsin HamidC. Salman RushdieD. Jhumpa LahiriA22.How do bees communicate?A. DancingB. SingingC. BuzzingD. WhistlingA23.What is the name of the holiday celebrated on October 31st?A. ThanksgivingB. ChristmasC. HalloweenD. New YearC24.I wear ___ (glasses).25.What do we call a person who studies the ocean?A. OceanographerB. Marine BiologistC. GeologistD. All of the above26.He is ________ a letter.27.The __________ is a famous area known for its scenic routes.28.The ________ (花园) is filled with colorful blooms.29.I like to _______ (与朋友一起)去看电影.30.What do you call an animal that can live both in water and on land?A. FishB. AmphibianC. ReptileD. MammalB31.Which fruit is yellow and curved?A. AppleB. BananaC. OrangeD. PearB32.The smallest particle of an element is called a(n) _______.33.The Earth's interior is composed mainly of ______ materials.34.The capital of Belgium is _______.35.The first successful spacecraft to land on the moon was ______ (阿波罗11号).36.The capital of Iran is __________.37.I enjoy making ________ (名词) for my toys to play with in their own world.38.What do we call a sweet drink made from cocoa?A. Hot ChocolateB. MilkshakeC. SmoothieD. Milk39. A ________ is a large area of land that has a lot of vegetation.40.I enjoy going to the ______ (市场) to buy fresh fruits and vegetables. It’s important to eat healthy.41.What do you call a tool used to measure length?A. ScaleB. RulerC. StopwatchD. CompassB42.__________ are substances that can increase the rate of a reaction.43.The man has a funny ________.44.The _______ (French and Indian War) was fought between Britain and France in North America.45.What is the capital of Jamaica?A. KingstonB. Montego BayC. NegrilD. Ocho RiosA46.We play ______ (游戏) during recess.47.The clouds are ______ (fluffy) and white.48.ts can _____ (存活) in extreme conditions. Some pla49.What is the largest ocean on Earth?A. AtlanticB. IndianC. ArcticD. Pacific50.What do you call a group of wolves?A. PackB. FlockC. SchoolD. PrideA51.I enjoy planting _______ in my garden (我喜欢在我的花园里种_______).52. A _____ (植物教育资源) can enhance community knowledge.53.In my dream, I can fly like a ______ (鸟). It would be amazing to see the world from above.54.The ______ can be found in almost every habitat.55.The ________ was a significant event in the history of civil rights.56.What do we call a person who studies the effects of climate change on species?A. EcologistB. BiologistC. ConservationistD. Environmental ScientistA57.The ______ (香味) of fresh herbs can enhance cooking.58.When I help others, I feel ______ (满足). It’s important to be kind and ______ (乐于助人).59.What is the capital of Malaysia?A. Kuala LumpurB. YangonC. BangkokD. HanoiA60.Which shape has no corners?A. SquareB. TriangleC. CircleD. Rectangle61.My dad is a great __________ (支持者) in my education.62.The __________ is known for its beautiful landscapes.63.Which vegetable is orange and looks like a stick?A. CarrotB. CucumberC. PotatoD. LettuceA64.What is the primary source of energy for the Earth?A. The MoonB. The SunC. StarsD. Geothermal Energy65.I like to ride my ______ (scooter).66.The doctor, ______ (医生), gives advice on staying healthy.67.What do you call a traditional Japanese dish made of rice?A. PizzaB. SushiC. PastaD. TacosB68.What do we call a person who studies insects?A. EntomologistB. BiologistC. ZoologistD. Ecologist69.What is the term for a young sheep?A. CalfB. FoalC. LambD. KidC70.What is the capital of Saint Vincent and the Grenadines?A. KingstownB. GeorgetownC. Arnos ValeD. CalliaquaA71.What do you call a book that tells real-life events?A. FictionB. NonfictionC. BiographyD. FantasyB72.I love to eat ______ in the summer.73.The __________ of a fish can help it steer while swimming.74.The __________ was a significant event in the history of civil rights in America. (华盛顿大游行)75.She is a nurse, ______ (她是一名护士), who works long hours.76.The Great Barrier Reef is found off the coast of __________.77.What do we call a person who studies philosophy?A. PhilosopherB. TheologianC. LogicianD. All of the above78.Penguins are birds that cannot ______.79.The ________ was a famous historical figure known for his peace efforts.80.Which planet is known as the Red Planet?A. VenusB. MarsC. MercuryD. JupiterB81.I found a _______ (小虫) crawling on the ground.82.The _____ (蜗牛) hides in its shell when scared.83. A sloth spends most of its time ________________ (睡觉).84.The _______ (猫) likes to scratch furniture.85.How many colors are in the flag of the USA?A. TwoB. ThreeC. FourD. Five86.I love to draw ________ (风景) in my notebook.87. (Revolutionary) War was fought for American independence. The ____88.My favorite season is __________ because I love __________.89.Which animal is known for its long neck?A. ElephantB. GiraffeC. RhinoD. Hippo90.I like to eat ______ for dinner.91.The center of the Earth is very ______.92.What do you call the person who teaches students?A. DoctorB. TeacherC. LawyerD. Chef93.The ______ of a tree is often wider than its trunk. (树的冠层通常比树干更宽。
小学下册第3次英语第四单元自测题[含答案]
![小学下册第3次英语第四单元自测题[含答案]](https://img.taocdn.com/s3/m/393a7547492fb4daa58da0116c175f0e7cd11994.png)
小学下册英语第四单元自测题[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. A green _______ can be very refreshing.2.The __________ is a large forest in Germany. (黑森林)3.bay) is a body of water partially surrounded by land. The ____4. A _______ is a reaction that releases heat.5.My cousin is very __________. (幽默)6. A _______ is formed when two or more atoms bond together.7.I enjoy visiting the ______ (市集) to find unique handmade items.8.What is the name of the story about a girl who befriends seven dwarfs?A. CinderellaB. Snow WhiteC. RapunzelD. Aladdin答案:B9. A ____ is a small insect that can be found in gardens.10.I enjoy spending time at the ________ (图书馆), where I can find many interesting ________ (书籍).11.What instrument is played with keys?A. GuitarB. DrumsC. PianoD. Flute答案:C12. A ______ is a type of model used in science.13.The _____ (植物观赏) attracts many visitors.14.The chemical formula for brassylic acid is ______.15.I enjoy playing with my ________ when it rains.16.During break time, I enjoy playing ______ (捉迷藏) with my classmates. It’s always a good laugh.17.I can imagine different worlds with my ________ (玩具名称).18.The __________ (历史的深刻反思) influences decisions.19.What do we call a place where you can see many different kinds of animals?A. ZooB. AquariumC. MuseumD. Park答案:A20.The process of separating mixtures is called ______.21.My mom reads me . (我妈妈给我读。
小学上册P卷英语第5单元测验试卷(有答案)
小学上册英语第5单元测验试卷(有答案)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 ________ (bus) is late today.2.What do we call the place where we watch movies?A. TheaterB. MuseumC. LibraryD. Park答案:A3.How many legs does a cat have?A. 4B. 3C. 2D. 54.What is the name of the famous Egyptian queen?A. CleopatraB. NefertitiC. HatshepsutD. Tutankhamun5.The density of an object is its mass divided by its ______.6.The puppy is very ________ (活泼).7.What do you call a story that is made up?A. FactB. FictionC. TruthD. Reality8.The __________ (历史的价值观) shape societal norms.9.My sister is a ______. She enjoys reading books.10.What is the term for a young seal?A. PupB. CalfC. KitD. Cub答案:A11.The simplest form of matter is called an _______. (元素)12.My uncle enjoys hiking in the ____ (mountains).13.I like ________ (collecting) stickers.14.The chemical formula for iron(III) oxide is __________.15.The chemical formula for ethyl alcohol is _______.16.I saw a ________ jumping in the river.17.My brother loves to eat __________. (零食)18.The fish are _______ (swimming) in the pond.19.I have a special place for my __________ (玩具名).20.The capital of Cambodia is __________.21.Insects have ______ legs.22.What is the capital of Russia?A. MoscowB. St. PetersburgC. KievD. Minsk答案:A23.The ________ has long arms and loves bananas.24.The ________ (文化价值观) shape societies.25.I think every day is an opportunity to __________.26.What is 10 - 2?A. 7B. 8C. 9D. 1027.What is the name of the famous mouse created by Walt Disney?A. Mickey MouseB. Jerry MouseC. Stuart LittleD. Speedy Gonzales答案:A28. A __________ is a reaction that produces gas bubbles.29.What is the primary color of the ocean?A. GreenB. BlueC. RedD. Yellow30.What is the name of the famous rock band from Liverpool?A. The Rolling StonesB. The BeatlesC. Led ZeppelinD. Pink Floyd答案:B31.The __________ (淘金热) brought many people to California in the 1840s.32. A _______ is a reaction that produces sound energy.33.The teacher is _____ (kind/mean) to us.34.My family has a picnic at the ________.35.I enjoy going to the ______ with my friends.36.What is 3 x 4?A. 10B. 11C. 12D. 1337.The chemical symbol for antimony is ______.38.What do you call the part of the plant that absorbs water?A. LeafB. StemC. RootD. Flower答案:C39.My mom takes care of the ____.40.Sedimentary rocks are made from particles that have ______ together over time.41.Reptiles lay ______.42.What is the primary color of a fire truck?A. BlueB. YellowC. RedD. Green答案:C43.Mount Kilimanjaro is found in _____ (14).44.I love taking ______ (照片) of beautiful landscapes. It helps me capture special moments.45.The __________ (国际合作) is needed for global issues.46.The kitten is ___. (curious)47.Which season comes after winter?A. FallB. SummerC. SpringD. Rainy答案:C48.My ___ (小狗) loves to dig in the sand.49.The first newspaper was published in _______. (德国)50.My ________ (表姐) loves animals and wants to be a vet.51. A ______ (鸟) can sing sweet melodies in the morning.52.The __________ sky is perfect for stargazing. (清澈的)53.What is the opposite of hot?A. WarmB. ColdC. CoolD. Freezing54. A _______ is a chemical that can absorb hydrogen ions.55.What shape has four equal sides?A. TriangleB. RectangleC. SquareD. Circle答案:C56.The chemical formula for calcium hydroxide is _____.57.I can ______ my bike without training wheels. (ride)58.My cousin is a talented ____ (pianist).59. A ____(coast) is where the land meets the ocean.60.We see a _____ (car/bird) in the tree.61.What is the largest organ in the body?A. BrainB. LiverC. SkinD. Heart62.Which animal is famous for its black and white stripes?A. LionB. TigerC. ZebraD. Leopard答案:C63.The flowers are ___ (swaying) in the breeze.64.The symbol for magnesium oxide is _____.65.What is the name of the famous fairy tale character who had long hair?A. RapunzelB. CinderellaC. Snow WhiteD. Belle答案:A66. A ______ (生态平衡) is vital for sustaining life.67. A solution that contains dissolved ions is called a _______.68.The ________ (audience) claps after the show.69.The capital of Malaysia is _______.70.The first man-made satellite was named _____.71.It is ___ outside today. (sunny)72.The _____ (生态思维) promotes balance in nature.73.The _____ (grapevine) produces delicious fruit.74.My ________ (外公) loves to fish at the lake.75.My brother is really into _______ (名词). 他每天都 _______ (动词).76.The _____ (植物园) displays various species of plants from around the world.77.What is the name of the famous American landmark that is a national park in South Dakota?A. YellowstoneB. Mount RushmoreC. YosemiteD. Grand Canyon答案:B78.The ____ lives in trees and loves to eat fruits.79.We play _______ during recess.80.Which insect makes honey?A. AntB. ButterflyC. BeeD. Fly答案:C81.The chemical properties of metals include conductivity and ______.82.I have _____ (many) toys at home.83. A _____ (植物保育计划) can restore habitats for wildlife.84.The process of sedimentation allows particles to ______ out of a solution.85.What is the opposite of rich?A. PoorB. WealthyC. AffluentD. Abundant答案:A86. A __________ is formed by the accumulation of sand or gravel.87.What do we call a story that is made up or fictional?A. Non-fictionB. FableC. FantasyD. Myth答案:C88.Which is the largest ocean on Earth?A. AtlanticB. IndianC. ArcticD. Pacific答案:D89.The fish swims in the ______ (水) all day long.90.I want to _______ a story.91.I like to _______ my friends at school.92.The _______ can provide a sense of achievement.93.The _______ (The Scientific Method) transformed science and experimentation.94.The city of Helsinki is the capital of _______.95.What instrument is used to measure temperature?A. RulerB. ThermometerC. ScaleD. Clock答案:B96.I think staying organized helps me manage my __________.97.I love to grow _____ (蔬菜) at home.98.The tarantula is a large _______ (蜘蛛).99.What is the term for a baby chicken?A. PigletB. CalfC. ChickD. Lamb答案:C100.What color is an orange?A. BlueB. OrangeC. GreenD. Purple答案:B。
九江2024年01版小学5年级下册第14次英语第5单元测验卷[有答案]
![九江2024年01版小学5年级下册第14次英语第5单元测验卷[有答案]](https://img.taocdn.com/s3/m/366c51750a4e767f5acfa1c7aa00b52acfc79cd4.png)
5. 填空题： I saw a _______ (小鹿) in my yard.
6. 填空题： The ancient Egyptians built their temples to honor _____.
22. 填空题： My __________ (玩具名) always brings me __________ (名词).
23. 听力题： The _____ (music/dance) is fun.
24. 选择题： Which bird is known for its colorful feathers and ability to mimic sounds? A. Crow B. Parrot C. Sparrow D. Eagle 答案:B
11. 填空题： Iceland is known for its beautiful ________ (冰岛以其美丽的________) and geysers.
12. 选择题： What do you call a young horse? A. Foal B. Colt C. Filly D. All of the above 答案:D
42. 听力题： The bread is ___. (fresh)
43. 听力题： To grow a plant, you need _______ and sunlight.
44. 听力题： The cake is ________ and sweet.
45. 选择题： How many days are there in a week? A. 5 B. 6 C. 7 D. 8
On the Origin of the Clustered QSO Metal Absorption Lines
Xiangdong Shi Department of Physics, Queen’s University, Kingston, Ontario, Canada, K7L 3N6
arXiv:astro-ph/95010tro.queensu.ca
WWW: http: //astro.queensu.ca/ shi/
Abstract
Observations show that there is significant clustering of QSO metal absorption lines within the range of velocity dispersion between 200km/sec and 600 km/sec. With a reasonable supernova rate, it is shown that high velocity gases driven by SNe and/or strong stellar winds could explain the clustered absorptions, provided that QSO metal-line absorbers are galactic halos or dwarf galaxies. Rich clusters of galaxies, on the other hand, cannot yield the observed clustering of QSO metal absorption lines. Subject Headings : Galaxies: Quasars: absorption lines—Stars: supernovae
- 1、下载文档前请自行甄别文档内容的完整性，平台不提供额外的编辑、内容补充、找答案等附加服务。
- 2、"仅部分预览"的文档,不可在线预览部分如存在完整性等问题,可反馈申请退款(可完整预览的文档不适用该条件!)。
- 3、如文档侵犯您的权益，请联系客服反馈,我们会尽快为您处理(人工客服工作时间：9:00-18:30)。
a rXiv:as tr o-ph/96809v11Aug1996Metal absorption from galaxies in the process of formation Martin G.Haehnelt Max-Planck-Institut f¨u r Astrophysik,Karl-Schwarzschild-Straße 1,85740Garching,Germany Abstract.In a hierarchical cosmogony present-day galaxies build up by continuous merging of smaller structures.At a redshift of three the matter content of a typical present-day galaxy is split into about ten individual protogalactic clumps.Numeri-cal simulations show that these protogalactic clumps have a typical distance of about 100kpc,are embedded in a sheet-like structure and are often aligned along filaments.Artificial QSO spectra were generated from hydrodynamical simulations of such re-gions of ongoing galaxy formation.The metal and hydrogen absorption features in the artificial spectra closely resemble observed systems over a wide range in HI column density.Detailed predictions of the column density as a function of impact parameter to protogalactic clumps are presented for HI,CII,CIV,SiIV,NV and OVI.The expected correlations between column densities of different species and their role in understand-ing the physical properties of the gas from which galaxies form are discussed.The model is able to explain both high-ionization multi-component heavy-element absorbers and damped Lyman alpha systems as groups of small protogalactic clumps.1Introduction While at low redshift metal absorption systems have been convincingly demon-strated to arise in the haloes of rather normal galaxies (Boisse &Bergeron 1991,Steidel 1995),much less is known about the nature of metal absorption system at redshifts z >∼2(Sargent,Boksenberg &Steidel 1988;Petitjean &Bergeron 1994;Aragon-Salamanca et al.1994).Recently,it was shown that the prominent com-plex CIV absorption features observed at high redshift can be well reproduced by the absorping properties of regions in which galaxies form by hierarchical merging (Haehnelt,Steinmetz &Rauch 1996).Here we present further resultsconcerning the metal absorption properties of such regions.2Numerical SimulationsThe simulations were performed using GRAPESPH (Steinmetz 1996).The cos-mological background model is a Ω=1,H 0=50km s −1Mpc −1cold dark mat-ter (CDM)cosmogony with a normalization of σ8=0.63.The baryon fraction is Ωb =0.05.The gas particle masses is 5×106M ⊙.The high resolution region of the simulation box is about 5.5comoving Mpc across and contains three galaxies with circular velocities between 100and 200km s −1at redshift zero.For the UV2Martin G.HaehneltFig.1.The left panel shows the HI column density(log N(HI))distribution of the inner700kpc(proper length)of the simulation box projected along one of the axis at z=3.07.In the right panel the column densities of a set of ions is plotted as a function of the impact parameter to a typical protogalactic clump in the simulation.A homogeneous metallicity of0.01solar is assumed.background a power-law spectrum with spectral indexα=−1.5,a normaliza-tion of J21(z=3)=0.3and a redshift dependence as given by Vedel,Hellsten &Sommer–Larsen(1994)was assumed.The photoionization code CLOUDY (Ferland1993)was used to calculate the ionization state of the gas(see the contribution by Steinmetz in this volume for a more detailed description of the simulation).3The gas distributionThere are about20collapsed protogalactic clumps(PGC’s)aligned in afilamen-tary matrix which itself is embedded in a sheet-like structure(Figure1a).Figure 2a shows the observed column density distribution of HI and a set of other ionic species observable in absorption systems of intermediate HI column density at high redshift.The crosses show the observed HI distribution(f(N)N)obtained by Petitjean et al.(1993).Apart from the high column density end the shape of the observed and simulated HI distribution correspond rather well.There self-shielding becomes important which is not taken into account in the simulation. The normalization was freely adjusted as the simulation box is too small to be a fair sample of the universe.In Figure2b the typical column density(mean log N)is shown as function of absorption-weighted overdensityδ=|ρ−¯ρ|/¯ρ.There is a tight correlation between column density and density confirming the visualMetal absorption from galaxies in the process of formation3Fig.2.The left panel shows the fraction of the projected simulation box which has column density N(per ln N).In the right panel the mean log N is plotted against the absorption weighted mean overdensity along the line-of-sight.A homogeneous metal-licity of0.01solar is assumed.impression from Figure1a that higher column densities probe the centre of the collapsed PGC’s.Low column densities arise from the more diffuse gas in sheets andfilaments between the collpased objects.Figure1b and2b show that the spatial distribution of different ionic species differs.Species like CII and SiIV are only strong in the dense inner regions of the PGC’s and the column density falls offrather rapidly on scales of10kpc or less.Higher ionization species probe the gas further away from the PGC’s.The high CIV column density extends to scales of typically30kpc.A closer inspection of the simulation shows that CIV is a good tracer of thefilamentary matrix connecting the PGC’s.NV and OVI probe even lower densities.Especially OVI is a good tracer of the diffuse intergalactic medium in the sheets between the PGC’s.4Column density ratios of different ionic speciesIn Figure3we show a selection of column density ratios as function of HI and CIV column density assuming a homogeneous metallicity of0.01solar.These ratios can be used as diagnostic of the UV radiationfield and the metallicity of the gas.As consequence of the tight density-column density correlation the ratio of the species[CII/HI]and[SiIV/HI]drops rather fast towards lower HI column density.[CIV/HI]has a pronounced peak arround log N(HI)∼14to15while [OVI/HI]rises rapidly towards small column densities.Recently,there have been measurements of CII,SiIV,CIV and NV column densities down to log N(HI)= 14.5by Soingaila&Cowie(1996).Even so the number of detected lines are small the measured[SiIV/CIV]seems to be larger than those shown in Figure3b by a factor of3at the relevant CIV column density while[NV/CIV]is smaller by about the same factor.A preliminary analysis suggests that this indicates4Martin G.HaehneltFig.3.A set of column density ratios is shown as function of HI and CIV column density.A homogeneous metallicity of0.01solar is assumed.an ionizing spectrum softer than the assumed power law at high energies(see Rauch,Haehnelt&Steinmetz1996for a further discussion).OVI has not yet been searched for at small HI column densities.If OVI should turn out to be weak below log N(HI)=14.5this would strongly argue for a metallicity gradient towards low-density regions.ReferencesAragon-Salamanca A.,Ellis R.S.,Schwartzenberg J.-M.,Bergeron J.A.,1994,ApJ, 421,27Bergeron J.,Boiss´e P.,1991,A&A,243,344Ferland G.J.,1993,University of Kentucky Department of Physics and Astronomy Internal ReportHaehnelt M.G.,Steinmetz M.,Rauch M.1996,ApJ,465,L95Petitjean P.,Webb J.K.,Rauch M.,Carswell R.F.,Lanzetta K.,1993,MNRAS,262, 499Petitjean P.,Bergeron J.A.,1994,A&A,283,759Rauch M.,Haehnelt M.G.,Steinmetz M.,1996,submittedSargent W.L.W.,Boksenberg A.,Steidel C.C.,1988,ApJS,68,539Songaila A.,Cowie L.L.,1996,Astronomical Journal,in pressSteidel C.C.,1995,in QSO Absorption Lines,Proc.ESO Workshop,ed.G.Meylan (Heidelberg:Springer),p.139.Steinmetz M.,1996,MNRAS,278,1005Vedel H.,Hellsten U.,Sommer–Larsen J.,1994,MNRAS,271,743。