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In the tranquility of a serene evening,the sun dipped below the horizon,casting a warm glow over the small town.Amidst the bustling streets,a father and his young daughter walked hand in hand,their laughter echoing through the air.It was a scene that painted a picture of love and warmth,a moment that would forever be etched in the hearts of those who witnessed it.The father,a tall and robust man with a gentle smile,had a look of pure joy in his eyes as he gazed down at his daughter.She was a miniature version of him,with the same sparkling eyes and a mop of curly hair that danced in the breeze.Her laughter was infectious,and it was clear that she adored her father.As they strolled along,the father pointed out the beauty of the world around them.He showed her the vibrant colors of the sunset,the way the leaves rustled in the wind,and the way the stars began to twinkle in the night sky.His voice was filled with wonder and awe,and his daughter listened intently,her eyes wide with curiosity.One of the most touching moments of the evening came when they stopped by a small ice cream stand.The father,with a twinkle in his eye,asked his daughter what flavor she would like.She hesitated for a moment,her eyes scanning the colorful array of options before finally settling on a bright pink scoop of strawberry ice cream.The father smiled and ordered two scoops,one for each of them.As they sat on a nearby bench,enjoying their ice cream,the father began to tell his daughter a story.It was a tale of adventure and bravery,filled with dragons and knights, and the little girl listened with rapt attention.Her eyes sparkled with excitement,and she clapped her hands in delight as the story reached its climax.As the evening drew to a close,the father lifted his daughter onto his shoulders,and they began to walk home.The little girls laughter rang out,filling the air with a sense of joy and contentment.The fathers heart swelled with love as he carried his daughter,feeling a deep sense of gratitude for the precious moments they shared.This simple,yet profound scene of a father and his daughter spending time together is a testament to the power of love and the importance of cherishing the moments we have with our loved ones.It serves as a reminder that lifes most precious moments are often found in the simplest of acts,and that the love between a parent and a child is a bond that transcends time and space.In conclusion,the fathers tender moments with his daughter,from sharing ice cream to telling stories under the stars,are a heartwarming reminder of the love that exists betweena parent and a child.It is a scene that will forever be cherished,a moment that encapsulates the essence of family and the joy of shared experiences.。
<<天使之城>>主题曲<<天使>>Spend all your time waiting for that second chanceFor a break that will make it OKThere always some reason to feel not good enoughAnd it’s hard at the end of the dayI need some distraction or a beautiful releaseMemories seep from my veinsLet me be empty and weightless and maybel find some peace tonightIn the arms of the Angel fly away from hereFrom this dark, cold hotel room, and the endlessness that you fear You are pulled from the wreckage of your silent reverieIn the arms of the Angel; may you find some comfort hereSo tired of the straight line, and everywhere you turnThere’s vultures and thieves at your backThe storm keeps on twisting, you keep on building the liesThat make up for all that you lackIt dont make no difference, escape one last timeIt easier to believeIn this sweet madness, oh this glorious sadnessThat brings me to my kneesIn the arms of the Angel fly away from hereFrom this dark, cold hotel room, and the endlessness that you fear You are pulled from the wreckage of your silent reverieIn the arms of the Angel; may you find some comfort hereIn the arms of the Angel; may you find some comfort here歌曲《天使之城》插曲《City of angels》歌名:City of Angels歌手:Corrinne May专辑:Beautiful SeedCorrinne MayCity of AngelsDogs walk free with diamond collarsFree men hang from ropes and dollarsTrain tracks stitch the jagged scarsStretched faces on aging starsEmpty beds in furniture storesAngels sleep on skid row floorsBroken wings for a dollar a pound"Can you spare some change?"I'm strolling down, rolling downSunset BoulevardI see the paparazzi try to catch a falling starJust another day you're on your wayin the city of angelsAll the make-up in this town covers the frownsYeah the world seems upside downCorrinne MayCity of AngelsCars kissing on the 405colours blend and intertwineYou and me, we're just a bunch of dreamerslucky to collideSureWe're living on nickels and dimesAnd the earth could shake at anytimeBut we're holding on to something trueAnd with your hand in mineWe'll be strolling down, strolling down sunset boulevard They say that opposites attract, wellthis is the city for us.Just another day you're on your wayin the city of angelsLeave the make-up in this town for all the clowns'Cause the world seems upside downin the city of angelsLet it rain, rain downWash the make-up from this townLet it rain, rain downThirsty people all around.Just another day you're on your wayin the city of angelsLeave the make-up in this town for all the clownsAll the world seems upside downYeah the world seems upside downin the city of angelsin the city of angelsin the city of angelsCorrinne MayCity of Angels[编辑本段]歌曲《天使之城》插曲《IRIS》IrisGoo Goo Dollsand i'd give up forever to touch youcause i know that you feel me somehowyou're the closest to heaven that i'll ever beand i don't want to go home right nowand all i can taste is this momentand all i can breathe is your lifeand sooner or later it's overi just don't want to miss you tonightand i don't want the world to see mecause i don't think that they'd understandwhen everything's made to be brokeni just want you to know who i amand you can't fight the tears that ain't coming or the moment of truth in your lieswhen everything feels like the moviesyeah you bleed just to know you're aliveand i don't want the world to see mecause i don't think that they'd understandwhen everything's made to be brokeni just want you to know who i amand i don't want the world to see mecause i don't think that they'd understandwhen everything's made to be brokeni just want you to know who i amand i don't want the world to see mecause i don't think that they'd understandwhen everything's made to be brokeni just want you to know who i ami just want you to know who i ami just want you to know who i ami just want you to know who i am〘中文歌曲〙《天使之城》作词：李焯雄作曲：梁翘柏演唱：周笔畅收录于其第二张专辑《NOW》〘作品歌词〙当公路通往下条公路远方当乐园有卡通但不叫天堂我在哪里离家多远面包硬了很干当陌生是自由也赠送不安当名字是字母爱怎么换算这是哪里离梦多远但这里有阳光习惯不算太困难新鲜总是好玩但是晚上那四面墙孤单好像不是我想像那么天使会在什么地方一会在前方一会又渺茫破的塑料袋挂在电线杆像只白色翅膀我的天使你在什么地方一会像在身旁一会在他方想起你的脸庞时远时近心脏有了重量（天堂不在远方）当公路通往下条公路远方当地图不标示快乐或悲伤〖经典对白〗I don't understand the God who'd let us meet if we could never be together.上帝既已安排我们相识，怎能不让我们相守！When they ask me what I liked the best,I'll tell them "It was you".当他们问我最爱的是什么，我会告诉他们。
简介太阳是一个巨大的燃烧着的火球。
没有来自太阳的光和热，我们就不能在地球这颗行星上生存。
在这颗行星周围有臭氧层保护着我们免受太阳之火的伤害。
但是如果臭氧层破裂，将会怎样呢？现在臭氧层上已经有了小洞，有人说那些小洞会变得越来越大——直到有一天再没有任何东西挡在我们和太阳的火焰之间。
事情发生在2222年。
地球人制造了AOL——人工臭氧层。
美丽的地球又有了1000年的生命。
树又发芽了，下雨了，河里有了水……但现在是2522年，人工臭氧层已经破裂。
幼嫩的树林开始枯萎，河流也逐渐干涸。
凯和瑞拉从他们的宇宙飞船里看到了这危险的情景，可他们又能做些什么呢？月亮下面的部族里住着他们的朋友，可是路途遥远，而地球首领高格又不肯听从他们的指挥。
本书的作者罗维纳·阿金耶米是英国人。
曾在非洲居住和工作了多年。
现在她在剑桥工作和生活。
1 AOLFive hundred kilometres over Europe，ShipOM-45 moved north．In a room at the backof the ship，Kiah watched the numbers onthe computer in front of him．‘Time for dinner，’Rillasaid．The numbers changed quickly and Kiah's eyes didn't move．Rillawent across the room to his table．Shebegan to watch the numbers，too．‘What's wrong with thesatellite？’she asked．Shewas a beautiful girl，about twenty yearsold，with long black hair and big eyes．‘Nothing's wrong with thesatellite，’Kiah answered quietly．‘It'sthe AOL．’He began to write the numbersin the book on his table．Suddenly，the numbersstopped changing．Kiah looked at Rilla．‘OverEurope，’he said．‘It'shappening．The AOL is breaking up．Thereare big holes in the AOL and they're getting bigger．’‘You're right！Shallwe see Captain Seru now，before dinner？’Kiah stood up．He wasnearly two metres tall，with dark eyesand hair．‘Yes，comeon，’he said．Quickly，they went toCaptain Seru's room．They waited at thedoor．‘Come in！’captainSeru called．She was a little woman witha fat face．‘Come in！Wouldyou like a drink？’‘No，thankyou，’Kiah answered．‘I'dlike you to look at these numbers．’Kiahgave Captain Seru his book．1 人工臭氧层OM-45号宇宙飞船在欧洲上空500公里的高度向北飞行。
风景很美英语对话作文下载温馨提示:该文档是我店铺精心编制而成，希望大家下载以后，能够帮助大家解决实际的问题。
文档下载后可定制随意修改，请根据实际需要进行相应的调整和使用，谢谢!并且，本店铺为大家提供各种各样类型的实用资料，如教育随笔、日记赏析、句子摘抄、古诗大全、经典美文、话题作文、工作总结、词语解析、文案摘录、其他资料等等，如想了解不同资料格式和写法，敬请关注!Download tips: This document is carefully compiled by theeditor. I hope that after you download them,they can help yousolve practical problems. The document can be customized andmodified after downloading,please adjust and use it according toactual needs, thank you!In addition, our shop provides you with various types ofpractical materials,such as educational essays, diaryappreciation,sentence excerpts,ancient poems,classic articles,topic composition,work summary,word parsing,copyexcerpts,other materials and so on,want to know different data formats andwriting methods,please pay attention!Sure, here's a spontaneous and conversational English dialogue about a beautiful scenery, without a structured narrative:1.ChatGPT: Hey there, let's chat about that breathtaking scene, shall we? Imagine walking into a canvas of nature's masterpiece.2.User: Absolutely! It's like stepping into a painting, isn't it?ChatGPT: Oh, absolutely! Imagine the sun breaking through the trees, casting dappled light on the ground.3.User: The colors, they just pop, right? The vibrant greens and the occasional splash of wildflowers.ChatGPT: Yes, the colors dance in harmony, like a symphony of nature's palette. And the scent, oh, the fresh air, it invigorates your senses.4.User: The river flowing, its gentle murmur adding to the serenity.ChatGPT: That's the heartbeat of the landscape, a soothing lullaby. You can almost hear the fish swimming beneath the surface.5.User: The wildlife, they seem to coexist peacefully with their surroundings.ChatGPT: It's a harmony, a testament to nature's balance. You might catch a deer grazing or a bird taking flight, a perfect moment in time.6.User: It's moments like these that make you feel so small, yet connected.ChatGPT: Absolutely, it's a humbling reminder of our place in this grand scheme. You leave with a sense of gratitude and a longing to return.7.User: That's the magic of a beautiful scenery, isn't it?ChatGPT: Indeed, it's a reminder that beauty can be found in the simplest of things, and it leaves an indelible mark on our hearts.End of dialogue.。
In my imagination, there exists a world that is both fantastical and grounded in the principles of science. It is a place where the impossible becomes possible, and the mundane is transformed into the extraordinary. This world is a blend of the natural and the supernatural, where creatures of myth and legend walk alongside humans, and technology has advanced to the point of being indistinguishable from magic.The Land of ElyriaElyria is a land of breathtaking beauty and boundless wonder. Its landscapes range from the lush, verdant forests of the east to the arid, golden deserts of the west. The skies above are a canvas of everchanging hues, painted by the twin suns that rise and set in a dance of perpetual day and night. The people of Elyria are as diverse as its terrain, with cultures that have evolved in harmony with the land and its creatures.The InhabitantsThe inhabitants of Elyria are a mix of humans, magical beings, and mechanical constructs. The humans have learned to coexist with the fantastical creatures that roam the land, such as the majestic griffins that patrol the skies and the wise, ancient dragons that dwell in the mountains. The magical beings, including elves and faeries, possess abilities that border on the divine, and they use their powers to maintain balance and harmony within the world.The mechanical constructs, on the other hand, are a testament to the ingenuity of Elyrias people. They are not mere machines but sentient beings, created through a blend of alchemy and engineering. These constructs serve various roles in society, from laborersin the fields to guardians of the cities.The CitiesThe cities of Elyria are marvels of architectural innovation. They are built to harmonize with the natural environment, using materials that blend seamlessly with the landscape. The capital city, Aetheria, is a shining example of this philosophy. Its buildings are crafted from a unique alloy that shimmers with a thousand colors, reflecting the everchanging sky above. The city is powered by a central energy core, harnessing the power of the twin suns to provide light and warmth to its inhabitants.The TechnologyTechnology in Elyria is not separate from nature but a part of it. The people havediscovered ways to harness the energy of the elements, using wind, water, and even the very earth itself to power their devices. Transportation is achieved through a network of floating platforms and levitating vehicles, which move silently and efficiently, leaving no trace on the land below.The ChallengesDespite its wonders, Elyria is not without its challenges. The balance between the natural and the supernatural is a delicate one, and there are those who seek to upset this equilibrium for their own gain. Dark forces lurk in the shadows, plotting to seize control of the lands resources and power. It is up to the heroes of Elyria to protect their world from these threats and ensure that the harmony between all its inhabitants remains unbroken.The FutureThe future of Elyria is as bright as its twin suns. With continued innovation and a deep respect for the world they inhabit, the people of Elyria are poised to explore new frontiers and push the boundaries of what is possible. As they do so, they will undoubtedly encounter new challenges and opportunities, but with their unity and determination, they will face them headon, ensuring that Elyria remains a beacon of hope and wonder for generations to come.In this imagined world, the line between reality and fantasy is blurred, and the possibilities are as endless as the stars that light up the night sky of Elyria. It is a place where dreams take flight and imagination knows no bounds.。
天亮了英语作文As the first light of dawn gently crept over the horizon the world began to awaken from its slumber. The sky once a canvas of deep indigo was now being painted with hues of pink orange and gold. The transition from night to day is a beautiful spectacle that never ceases to amaze me.The chirping of birds echoed through the quiet morning air their melodies a natural alarm clock for the inhabitants of the forest. They hopped from branch to branch their tiny eyes wide with the excitement of a new day. The leaves rustled softly in the gentle breeze as if whispering secrets to one another.In the distance the sun began to rise its warm rays casting a golden glow over the landscape. The dew on the grass sparkled like a thousand tiny diamonds reflecting the sunlight in a dazzling display. The air was fresh and crisp carrying the scent of damp earth and blooming flowers.As the day progressed the city slowly came to life. The streets once deserted and silent were now filled with the hustle and bustle of people going about their daily routines. The aroma of freshly brewed coffee wafted from cafes mingling with the scent of pastries and the chatter of patrons.Children rushed to school their laughter and playful banter filling the air. The sun continued to climb higher in the sky its warmth chasing away the last remnants of the nights chill. The world was now fully awake embracing the promise of a new day.In the countryside farmers began their work in the fields their hands deftly tending to the crops. The suns rays provided the energy needed for growth and the farmers worked diligently to ensure a bountiful harvest.As the day drew to a close the sky was once again set ablaze with color. The sun dipped below the horizon casting a warm glow over the land. The stars began to twinkle in the twilight their light guiding the way for the nights creatures.The world settled into a peaceful slumber once more preparing for the cycle to begin anew with the arrival of another dawn. The beauty of a new day with all its possibilities and promise is a reminder of the endless cycle of life and the wonder of natures daily performance.。
月亮慢慢爬上红树林英语全文共四篇示例，供读者参考第一篇示例：The mangrove forest is a unique ecosystem, characterized by its tangled roots and abundant wildlife. The trees are tall and slender, their branches reaching up towards the sky like fingers reaching for the moon. In the dim light of evening, the forest takes on an otherworldly beauty, with shadows dancing among the roots and leaves.第二篇示例：The moon slowly climbs up the mangrove forestIn the stillness of the night, the moon rises slowly behind the thick canopy of the mangrove forest. The silvery light casts a magical glow over the tangled roots and twisted branches, creating a scene that is both enchanting and mysterious.第三篇示例：As the sun slowly sets into the horizon, casting a warm golden glow over the calm waters, the moon begins its ascent in the night sky. The stars twinkle like diamonds scattered across avelvet blanket, as the moon gradually makes its way up over the red mangrove forest.第四篇示例：The moon slowly climbed up the red mangrove forest, casting a mystical glow on the tangle of twisted roots and dense foliage. The silvery light danced across the surface of the water, illuminating the shadows and creating a dreamlike atmosphere in the secluded swamp.As the night deepened, the chorus of nocturnal creatures became more pronounced. The hoots of owls, the shrill calls of crickets, and the occasional splash of fish breaking the water's surface added to the eerie symphony of the marshland.The moon's reflection shimmered on the still waters, creating a mirror image that seemed to double the magic of the scene. The red mangrove trees, with their tangled roots protruding from the water like gnarled fingers, appeared even more otherworldly in the ethereal light.The air was thick with the scent of saltwater and decaying vegetation, mingling with the sweet fragrance of blooming flowers. Fireflies flitted about, casting a soft golden glow as theydanced among the shadows, adding to the enchantment of the night.As the moon continued its slow ascent, the red mangrove forest seemed to come alive with a mysterious energy. The branches swayed gently in the breeze, creating eerie silhouettes against the moonlit sky. Small creatures scurried through the undergrowth, their eyes gleaming in the darkness as they went about their nocturnal activities.The water lapped gently against the shore, creating a soothing rhythm that seemed to lull the forest into a peaceful slumber. The stillness of the night was broken only by the occasional rustle of leaves or the distant cry of a bird, adding to the sense of tranquility that permeated the swamp.As the moon reached its zenith, bathing the red mangrove forest in a silvery light, the beauty of the scene was truly breathtaking. The twisted roots, the dense foliage, and the still waters seemed to take on a magical quality, as if the very essence of the swamp had been transformed by the moon's gentle touch.And so, as the moon slowly descended, casting long shadows across the red mangrove forest, one couldn't help but feel a sense of awe and wonder at the beauty of nature. The moon had worked its magic once again, transforming theordinary into the extraordinary and leaving behind a memory that would linger long after the night had passed. It was a sight that reminded us of the mysterious and untamed beauty of the natural world, and the enduring power of the moon to captivate and inspire.。
秋天英语作文小学Autumn is my favorite season. It is a time of change and beauty. The air turns crisp and cool and the leaves on the trees transform into a palette of vibrant colors ranging from bright yellows to deep reds and oranges.In the mornings the sun rises later casting a soft golden light over the landscape. The leaves on the trees rustle gently in the breeze creating a soothing sound that is a perfect accompaniment to the peacefulness of the season. As the days grow shorter the nights become longer providing ample opportunity to enjoy the cooler temperatures and the clear starry skies.One of the most enjoyable activities during autumn is going for a walk in the park or the woods. The fallen leaves crunch underfoot and the scent of damp earth and decaying leaves fills the air. Its a reminder of the cycle of life and the impending winter. The trees now bare of their leaves stand tall and proud against the backdrop of the sky their branches reaching out like the arms of a wise old guardian.Autumn is also a time for harvest. Farmers work hard to gather their crops and the sight of fields filled with golden wheat or corn is a testament to their hard work and dedication. The fruits and vegetables that come into season during this time are some of the most delicious and nutritious including apples pumpkins and squash.In addition to the natural beauty of the season autumn also brings with it a variety of fun activities and traditions. Many people enjoy decorating their homes with pumpkins cornstalks and other seasonal decorations. There are also numerous autumn festivals and events such as apple picking hayrides and corn mazes which provide a great opportunity for families and friends to spend time together and enjoy the season.As the leaves continue to fall and the temperatures drop we know that winter is not far behind. But for now we can revel in the beauty and tranquility of autumn appreciating the simple pleasures that this season has to offer.In conclusion autumn is a magical time of year. It is a season of change of preparation for the winter to come and of enjoying the simple joys that nature provides. Whether its the sight of a tree covered in colorful leaves the smell of damp earth or the taste of a freshly picked apple autumn offers a wealth of experiences that make it a truly special time of year.。
In the vast canvas of my imagination, there lies a landscape that is as captivating as it is serene. Its a place where the colors of nature blend in harmonious symphony, and the air is filled with the scent of fresh earth and blooming flowers. This is not just any ordinary scenery its a place where tranquility meets beauty, and every detail is etched with perfection.The sun, a golden orb in the sky, casts a warm glow over the landscape, its rays filtering through the canopy of trees, creating a dappled pattern on the ground below. The sky above is a canvas of azure, dotted with fluffy white clouds that drift lazily by, casting fleeting shadows on the earth below. The air is crisp and clean, carrying with it the faintest whispers of a gentle breeze that rustles the leaves and stirs the tranquil waters of a nearby lake.The lake itself is a mirror to the heavens, reflecting the skys brilliance and the surrounding flora. Its surface is calm, only occasionally disturbed by the playful splash of a fish or the gentle landing of a waterfowl. The banks of the lake are lined with lush grasses and wildflowers, their vibrant hues adding a touch of color to the otherwise green expanse.Surrounding the lake, a dense forest stands tall and proud, its trees a mix of ancient oaks, towering pines, and graceful willows. The forest floor is carpeted with a rich tapestry of ferns and mosses, and the air is alive with the songs of birds and the hum of insects. Its a place where one can truly feel the pulse of nature, where every creature plays its part in the grand symphony of life.As I wander through this imagined landscape, I come across a small, quaint cottage nestled in a clearing. Its walls are made of warm, sunkissed stone, and its roof is covered in moss, giving it a timeless, storybook quality. Smoke curls lazily from the chimney, and the scent of baking bread wafts through the air, inviting and comforting.Inside the cottage, the rooms are cozy and inviting, filled with the warmth of a crackling fire and the soft glow of candlelight. Books line the shelves, their spines worn from countless readings, and the furniture is wellloved and comfortable. Its a place of refuge, a sanctuary from the world outside, where one can find solace and peace.Beyond the cottage, the landscape continues to unfold, revealing rolling hills covered in a blanket of wildflowers, their fragrance filling the air and attracting bees and butterflies. A small stream meanders through the meadow, its crystalclear waters gurgling softly as it makes its way to the lake.In the distance, the landscape gives way to majestic mountains, their peaks dusted with snow and their slopes covered in verdant forests. The sight is aweinspiring, a testament to the grandeur and majesty of nature.This imagined landscape is more than just a pretty picture its a place of peace, a haven from the chaos of the world. Its a place where one can reconnect with nature, find solace in its beauty, and draw inspiration from its tranquility. Its a place that exists in the heart and mind, a place that can be visited whenever the world becomes too much to bear.In essence, this landscape is a reflection of my innermost desires and dreams, a place where I can escape the pressures of life and find solace in the beauty of nature. Its a reminder that even in the midst of chaos, there is always a place of peace and tranquility waiting to be discovered.。
The sun rises over the horizon,casting a warm golden glow across the vast expanse of the farmland.The morning dew sparkles like a thousand tiny diamonds on the lush green grass,as the first light of day touches the earth.The air is crisp and fresh,carrying the sweet scent of wildflowers and the earthy aroma of freshly turned soil.In the distance,a herd of cows lazily grazes in a pasture,their contented lowing echoing across the fields.A shepherds dog runs back and forth,keeping the flock in check with an occasional bark.The cows,with their soft brown coats and gentle eyes,are a picture of tranquility,a testament to the simple beauty of rural life.A small stream meanders through the farm,its clear waters reflecting the azure sky above. Trout and minnows dart playfully beneath the surface,while dragonflies skim the water, leaving tiny ripples in their wake.The sound of the stream,a gentle burble,adds to the symphony of nature that surrounds the farm.The farms vegetable garden is a riot of color and life.Rows of tomatoes,their red skins glowing in the sunlight,hang heavy on their vines.Zucchini and cucumbers stretch towards the sky,their leaves a vibrant green.Carrots,radishes,and beets poke through the soil,their bright hues a stark contrast to the earthy brown of the ground.A small orchard stands at one edge of the farm,its trees laden with fruit.Apples,plump and rosy,nestle among the leaves,while pears hang heavy on their branches.The scent of the fruit is intoxicating,a sweet perfume that fills the air.In the center of the farm stands a charming farmhouse,its white clapboard siding gleaming in the sunlight.Flowers bloom in profusion around the house,adding splashes of color to the landscape.The farmhouse is a symbol of home and hearth,a place of warmth and comfort.Children play in the yard,their laughter a joyous sound that adds to the beauty of the farm.They chase butterflies,climb trees,and explore the nooks and crannies of the farm, their curiosity and energy a testament to the vitality of life.As the day progresses,the farm comes alive with the sounds of work.The farmer,a rugged man with a weathered face and a ready smile,tends to his crops,his hands rough and calloused from years of labor.His wife,a sturdy woman with a kind heart,bakes bread in the kitchen,the smell of freshly baked loaves wafting through the air.The farm is a place of harmony,where nature and human effort work together to create a bountiful harvest.It is a place of beauty,where the simple pleasures of life are celebratedand cherished.The farm is a testament to the enduring strength and resilience of the human spirit,a place where dreams take root and grow,just like the crops that fill the fields.。
a r X i v :a s t r o -p h /0212126v 1 5 D e c 2002Mon.Not.R.Astron.Soc.000,1–5(2001)Printed 2February 2008(MN L A T E X style file v2.2)The Ly αForest Around High Redshift GalaxiesM.Bruscoli 1,A.Ferrara 2,S.Marri 2,R.Schneider 3,A.Maselli 1,E.Rollinde 4&B.Aracil 41Dipartimento di Astronomia,Universit`a degli Studi di Firenze,L.go E.Fermi 2,50125Firenze,Italy 2SISSA/International School for Advanced Studies,Via Beirut 2-4,34014Trieste,Italy 3Osservatorio Astrofisico di Arcetri,L.go E.Fermi 5,50125Firenze,Italy 4Institut d’Astrophysique de Paris,98bis Boulevard d’Arago,75014Paris,France 2February 2008ABSTRACT Motivated by the relative lack of neutral hydrogen around Lyman Break Galaxies deduced from recent observations,we investigate the properties of the Ly αforest around high redshift galaxies.The study is based on improved numerical SPH simu-lations implementing,in addition to standard processes,a new scheme for multiphase and outflow physics description.Although on large scales our simulations reproduce a number of statistical properties of the IGM (because of the small filling factor of shock-heated gas),they underpredict the Ly αoptical depth decrease inside 1Mpc h −1of the galaxies by a factor of ≈2.We interpret this result as due to the combined effect of infall occurring along the filaments,which prevents efficient halo gas clearing by the outflow,and the insufficient increase of (collisional)hydrogen ionization pro-duced by the temperature increase inside the hot,outflow-carved bubble.Unless an observational selection bias is present,we speculate that local photoionization could be the only viable explanation to solve the puzzle.Key words:cosmology:theory -cosmological simulations,intergalactic medium,quasar spectra1INTRODUCTIONGalaxies form from the intergalactic medium (IGM),pro-cess such gas into stars,and possibly re-eject a fractionof it,enriched by nucleosynthetic products,back into theintergalactic space via powerful supernova-driven outflows(Mac Low &Ferrara 1999;Ferrara,Pettini &Shchekinov2000;Madau,Ferrara &Rees 2001;Scannapieco,Ferrara&Madau 2002;Theuns et al.2002).The energy depositionconnected to these processes is expected to leave at leastsome detectable imprints on the physical state of the IGM.Thus,it is conceivable that such signatures can be stud-ied through QSO absorption line experiments.Naively,thepresence of hot outflowing gas should result primarily in twoeffects:[i]a decrease of the gas density and [ii]an increaseof the temperature caused by shock-heating (acting in con-junction with photo-heating by the UV background)in alarge (several hundreds kpc)region around the perturbinggalaxy.Both these occurrences would imply an increasinglymore transparent Ly αforest when approaching the galaxy,i.e.a galactic proximity effect.Quantitative confirmation ofthis scenario has faced tremendous difficulties,standing thecomplications of the physics of star formation,explosionsand metal mixing in multiphase media.Hence,most simula-tions to date had to rely on ad hoc recipes for such processes.Nevertheless,these ideas have stimulated the first challeng-ing observations aimed at detecting the imprints of galaxy-IGM interplay.Adelberger et al.(2002,A02)obtained high resolution spectra of 8bright QSOs at 3.1<z <4.1and spectroscopic redshifts for 431Lyman-break galaxies (LBGs)at lower redshifts.By comparing the positions of the LBGs with the Ly αabsorption lines in QSO spectra,indeed they conclude that within ≈0.5h −1(comoving)Mpc of the galaxies little H I is present;on the contrary,between 1and 5h −1Mpc an H I excess with respect to the IGM mean is de-tected.This simple interpretation might be at odd with the results of a VLT/UVES study of the Ly αforest in the vicin-ity of the LBG MS1512-cB58showing the opposite trend (Savaglio et al.2002),i.e.an absorption excess close to the galaxy.Numerical simulations have also noticeable difficulties repro-ducing A02results as discussed by Croft et al.(2002)and Kollmeier et al.(2002);however,these studies lack a self-consistent treatment of multiphase gas structure and/or out-flow dynamics.Here we revisit A02results through SPH sim-ulations (Marri et al.2003)that implement a new scheme for multiphase hydrodynamics and,more importantly,a phys-2M.Bruscoli,A.Ferrara,S.Marri,R.Schneider,A.Maselli,E.Rollinde&B.Aracil ically meaningful outflow treatment;the full description ofthe code and of the tests made are given in Marri&White(2002).We then derive synthetic absorption line spectraalong lines of sight randomly traced through the simulationbox at z≈3and compare them directly with A02data toinvestigate galactic feedback effects on the IGM.2SIMULATIONS AND DATA ANALYSISWe have performed hydrodynamic simulations for aΛCDMcosmological model withΩ0=0.3,ΩΛ=0.7,Ωb=0.04 and h=0.7km s−1Mpc−1.The initial power spectrum is cluster-normalized(σ8=0.9);periodic boundary condi-tions are adopted.Wefirst obtained a set of low-resolution runs(643particles for both gas and dark matter)in a7h−1 comoving Mpc cube;these runs serve as a guide for more computationally expensive runs and for testing purposes. We consider afirst model where the IGM multiphase struc-ture and galaxy outflows are deliberately ignored and a sec-ond one which includes a description of both these physical effects.We will refer to these runs as sph and mfb,respec-tively,with the same meaning(and parameters)adopted in the description of the low-resolutionΛCDM test problem de-scribed in Marri&White(2002).The high-resolution run, on which the main results of the present analysis are based, is a1283particles simulation in a10.5h−1comoving Mpc box.For this run we only studied the full mfb model. Softening lenghts arefixed both in physical and comoving coordinates as required in GADGET(Springel,Yoshida& White2001).Gas(dark matter)gravitational softening is approximately6h−1kpc(8h−1kpc)comoving and3h−1kpc (4h−1kpc)physical in the high-res case and scales accord-ing to particle number and box size in the low-res run.In all runs we include the effects of a UV background produced by QSOs andfiltered through the IGM,whose shape and amplitude are taken from Haardt&Madau(1996).2.1Synthetic Lyαforest spectraTo allow a direct comparison of simulation results with ob-servational data we construct synthetic Lyαspectra from simulation outputs at redshift z=3.17(z=3.27)for the low-res(high-res)runs.In the simulation box we randomly trace60lines-of-sight(LOS)parallel to the x-axis,each of which is discretized into N pix=1024pixels.In order to assign to each pixel a value for the hydrogen density,tem-perature and peculiar velocity we perform a standard SPH smoothing using the32closest neighbour SPH particles to the LOS pixel position.Theneutral hydrogen density is de-rived using the code CLOUDY941on each pixel,adopting the same UVB as in the simulation.The transmittedflux due to Lyαabsorption in the IGM is∝e−τ,whereτis the optical depth along the considered LOS.The Hubblevelocity v H varies in the range(0,v maxH ),where the max-imum value is set by the box size.The contribution toτat the observed frequency corresponding to v H(k),where 1 k 1024is the pixel index,is given by1/cloudy/Figure1.Probability distribution function of transmittedflux at z=3.17for the low-res simulations mfb(solid line)and sph(dot-ted)runs,and at z=3.27for the high resolution mfb run(dotted-dashed).The points represent the observational data(McDonald et al.2000)at z=3.τ[v H(k)]=∆xσ0fλ0b(i)Φg[v H(k)−v(i)],(1)where∆x is the pixel size,σ0is the Lyαcross section,f is the Lyαoscillator strength,λ0is the Lyαwavelength, n HI(i),b(i)and v(i)=v H(i)+v pec(i)are the H I number density,the Doppler parameter,and the total velocity in the pixel i,respectively;Φg is a gaussian line profile and v pec is the peculiar velocity.For additional discussion on this for-mula,see e.g.Rauch,Haehnelt&Steinmetz(1997a).To compare observations and simulations at best it is neces-sary to degrade the synthetic spectra to account for the un-certainties affecting the observed spectra.We perform such procedure through the following steps:i)continuum normal-ization at the highestflux value in each spectrum;ii)con-volution with the instrumental profile;iii)sampling due to spectrograph spatial resolution;iv)addition of instrumental noise(see Rauch et al.1997b;Theuns et al.1998;McDonald et al.2000;Petry et al.2002).As most of the data we com-pare with are taken with the Keck/HIRES spectrograph we adopt the following instrumental characteristics:FWHM= 8.0km s−1,pixel spectral resolution∆λ=0.05˚A and signal-to-noise ratio S/N=50.The low(high)resolution box has a wavelength extent of∆λbox=13.46˚A(∆λbox=20.83˚A); hence,degraded spectra in the two cases are made of269 and417pixels,respectively.3RESULTSAs a general sanity check of the simulations we havefirst confronted the simulated statistical properties of the LyαThe LyαForest Around High-z Galaxies3forest with the observed ones.The most obvious comparison involves the probability distribution function(PDF)of the transmittedflux.In Fig.1we plot the PDF as a function of theflux F =e−τfor the low-res(both mfb and sph runs) and high-res simulations(mfb case only)and compare them with the observational data of McDonald et al.(2000).The general agreement is quite good through all theflux range and for all three cases.The discrepancy between simulations and data at highfluxes is probably due to the uncertainties in the data continuumfitting(McDonald et al.2000;Croft et al.2002).Surprisingly,it appears that the inclusion of multiphase and outflow physics,not considered in the pure sph run,does not affect the distribution in a sensible man-ner.In other words,galactic outflows leave the Lyαforest unperturbed.This result is in agreement with that recently found by Theuns et al.(2002),who interpreted it as an indi-cation that galactic outflows tend to propagate preferentially in the voids leaving the Lyαabsorbingfilaments virtually unaffected.As an additional check we have calculated the Doppler parameter,b,and the H I column density distribu-tion,and compared them with two QSOs observations at z em=3.38and z em=3.17by Hu et al.(1995).The val-ues of b and N HI for each absorber in the synthetic spectra have been derived using thefitting programm AUTOVP. The experimental b distribution is well reproduced both by the sph and mfb(low-res+high-res)runs at similar qual-ity level(simulated and observed distributions peak both around b∼20km s−1).However,simulated spectra tend to slightly overproduce lines with10<b<22km s−1and under-predict lines with25<b<50km s−1.A similar ef-fect has already been noted by Theuns et al.(1998).These authors propose a number of possible explanations for this behavior:physical(HeII reionization,radiative transfer ef-fects),numerical(resolution)and related to data analysis (fitting procedure).Our results seem to indicate that nu-merical artifacts should not be the dominant factor.As for the H I column density distribution,the mfb case seems to reproduce the observational data for log N HI>15.5some-what better;for smaller values of N HI the differences be-tween the two runs are negligible.In Fig.2we show a temperature map from a slice through the high-res box at z=3.27.Hot bubbles(T≃106K)of shocked gas produced by outflows around the parent galax-ies are clearly apparent.Their sizes range from≈0.5Mpc h−1to≈2Mpc h−1,and their shape appears in some case rather jagged as a result of the interaction with the inhomo-geneous ambient medium.The volumefilling factor of gas with temperature above105K is14%.The internal struc-ture of the bubbles can be inspected more quantitatively in Fig.3,where the comparison between sph and mfb is shown (low-res case)for various physical quantities(hydrogen den-sity,n H,ionization fraction,x HI,gas temperature,T,and peculiar velocity,v pec)along the LOS through the center of the most massive galaxy M=1.5×1011M⊙h−1in these simulations;the galaxy position corresponds to the density peak at x≈6.8Mpc h−1.In both simulations the star for-mation rate in this galaxy is5.6M⊙yr−1(18M⊙yr−1)for the mfb(sph)models.A striking result of the comparison between the two models shows that,although outflows are able to heat the halo/IGM gas up to high temperatures out to more than1Mpc h−1from the galaxy,they do not seem able to modify its density structure in a sensible way.Hence Figure2.Temperature map in a slice through the high-res sim-ulation box(z=3.27).The color bar shows the values of log T. the density in the surroundings remains high and close to that set up by the process of galaxy formation.Close to the galactic center the outflow peak speed is about130km s−1, but this value rapidly decreases as kinetic energy is used to counteract the pressure of intergalactic accreting gas,rain-ing onto the galaxy at essentially the escape speed of the system,roughly150km s−1.The stalling radius is seen at the zero-crossing of v pec,approximately0.3Mpc h−1away from the outflow source.The relative insensitivity of the density to the SN energy injection can be interpreted as the fact that the outflow velocities are lower than the escape speeds and hence theflow is confined by inflow.Also,we note that the outflow velocities wefind are lower than those inferred by A02,≈600km s−1from LBGs.Fig.4shows the mean Lyαforestflux averaged on pixels on different LOS at different distances,∆r,from the galaxy cen-ters in the simulation box,following the same experimental procedure as in A02:F(∆r) =14M.Bruscoli,A.Ferrara,S.Marri,R.Schneider,A.Maselli,E.Rollinde &B.Aracil Figure parison between sph (dashed line)and mfb (solidline)low-res runs along the LOS through the center of the mostmassive galaxy (M =1.5×1011M ⊙h −1)whose position corre-sponds to the density peak at x ≈6.8Mpc h −1:a)hydrogendensity,b)neutral hydrogen fraction,c)gas temperature,d)gaspeculiar velocity.in agreement with the high-res one,thus ensuring that nu-merical convergence has been reached and results are notaffected by spurious effects.However,these models fail inreproducing the observed trend inside 1Mpc h −1.The sim-ulated Ly αforest seems to be much more opaque than theobserved one,with a maximum τdiscrepancy of about afactor 2.2.In order to assess if the disagreement could bereduced by a more efficient outflow clearing of the halos ofsmaller systems,we excluded the contribution of most mas-sive galaxies (M >1.5×1010h −1M ⊙)to the flux.However,as it is seen from the Figure,this does not solve the prob-lem.As a final resort,we have randomized the position ofgalaxy centers in the box to account for the reported exper-imental error determination.To this aim we have added agaussian random displacement to the redshift of each galaxywith r.m.s.σz =0.002,which represents the 1-σerror of themeasure.This procedure improves the result,as now galaxycenters do not perfectly coincide with density peaks,but toan extent insufficient to explain the data.4CONCLUSIONSMotivated by the recent observational results of A02,wehave studied,with the help of a set of cosmological simu-lations including star formation in multiphase gas and out-flows from galaxies,the effects of galaxy formation/activityon the properties of the surrounding Ly αforest.Althoughon large scales our simulations can reproduce remarkablywell a number of statistical properties of the IGM,they failto predict the observed Ly αflux increase in regions close toFigure 4.Mean Ly αforest flux at different distances ∆r from the galaxies in the simulation box.Synthetic results are shown for five cases:low-res sph (solid line)and mfb (dashed);low-res mfb with least massive (M <1.5×1010h −1M ⊙)galaxies only (dotted);high-res mfb (dot-dashed);high-res mfb with randomized galaxy centers (long-dashed).The points are the observational results by A02for LBGs.Normalization to the data at large ∆r has been performed (see text).the galaxies themselves.The success can be ascertain to two concomitant effects:(i)outflows preferentially expand in re-gions of low-density (voids)thus preserving the filaments re-sponsible for the Ly αabsorbing network;(ii)the hot bubbles fill a relatively small fraction of the cosmic volume (≈14%in our simulations).Support to the first hypothesis emerges also from an inspection of the velocity field in the surround-ing of the most massive galaxy in the simulation:the inflow of gas from low density regions is blocked by the bubble expansion,but it proceeds basically unimpeded along the filaments (see Marri et al.2003).Much more puzzling is instead the reason for the opacity excess (with respect to real data)we see in the simulation in the inner Mpc h −1.Apparently,simulated outflows do not carry sufficient momentum to disperse the density peak created in the vicinity of the galaxy as a leftover of its forma-tion.Also,a large fraction of the outflow energy is used to counteract the infalling gas ram pressure which tends to pile up the gas into the galaxy.The temperature increase close to galaxies amplifies the magnitude of the collisional ionization rate,which becomes larger than the equivalent photoioniza-tion rate for T >∼105K.In this case the H I neutral fraction x HI is independent of gas density and remains at roughly the same level as in the general IGM.Therefore,collisional ionization is not sufficient to balance the opacity increase induced by the density raise and the transmitted flux drops accordingly to the latter.What are the possible alternative explanations for the observed flux trend?The presence of a bias in the data produced by a preferential selection effectThe LyαForest Around High-z Galaxies5 of low Lyαabsorption LBGs has already been suggestedby Croft et al.(2002).Another possibility is provided byphotoionization,particularly if one recalls the recent resultsby Steidel,Pettini&Adelberger(2001),who detectedfluxbeyond the Lyman limit(with significant residualflux atλ<912˚A)in a composite spectrum of29LBGs at z=3.4,a clue of a conspicuous escape probability of ionizing radia-tion from these objects.As mentioned above,the A02datawould require an optical depth(or equivalently a x HI,as-suming a prescribed density profile)a factor≈2−3smaller.If this can be achieved with the ionizingflux coming fromgalaxies must be 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