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Stellar Model Chromospheres and Spectroscopic Diagnostics 恒星模型色球和光谱诊断
IF 33.3 1区 物理与天体物理 Q1 Earth and Planetary Sciences Pub Date : 2017-08-18 DOI: 10.1146/ANNUREV-ASTRO-091916-055327
J. Linsky
The discovery of exoplanets and the desire to understand their atmospheric chemical composition and habitability provides a new rationale for understanding the radiation from X-rays to radio wavelengths emitted by their host stars. Semiempirical models of stellar atmospheres that include accurate treatment of radiative transfer of all important atoms, ions, and molecules provide the essential basis for understanding a star's emitted radiation that is our main data source for characterizing a star and the radiation environment of its exoplanets. In Solar-type and cooler stars, the ultraviolet and extreme ultraviolet radiation formed in their chromospheres and transition regions drive the photochemistry in exoplanet atmospheres. In this review, I describe and critique the development of semiempirical static and time-dependent models of the chromospheres and transition regions of the Sun and cooler stars as well as the spectroscopic diagnostics upon which these models are based. The related topics of stellar...
系外行星的发现以及了解其大气化学成分和可居住性的愿望为理解其宿主恒星发出的从x射线到无线电波长的辐射提供了新的理论依据。恒星大气的半经验模型,包括对所有重要原子、离子和分子的辐射转移的精确处理,为理解恒星发射的辐射提供了必要的基础,这是我们描述恒星及其系外行星辐射环境的主要数据源。在类太阳和温度较低的恒星中,在色球和过渡区形成的紫外线和极紫外线辐射驱动了系外行星大气中的光化学反应。在这篇综述中,我描述和批评了半经验静态和时间依赖模型的发展,这些模型是基于太阳和较冷恒星的色球和过渡区域,以及这些模型所依据的光谱诊断。恒星的相关主题…
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引用次数: 63
How to Characterize Habitable Worlds and Signs of Life 如何描述宜居世界和生命迹象
IF 33.3 1区 物理与天体物理 Q1 Earth and Planetary Sciences Pub Date : 2017-08-18 DOI: 10.1146/annurev-astro-082214-122238
L. Kaltenegger
The detection of exoplanets orbiting other stars has revolutionized our view of the cosmos. First results suggest that it is teeming with a fascinating diversity of rocky planets, including those in the habitable zone. Even our closest star, Proxima Centauri, harbors a small planet in its habitable zone, Proxima b. With the next generation of telescopes, we will be able to peer into the atmospheres of rocky planets and get a glimpse into other worlds. Using our own planet and its wide range of biota as a Rosetta stone, we explore how we could detect habitability and signs of life on exoplanets over interstellar distances. Current telescopes are not yet powerful enough to characterize habitable exoplanets, but the next generation of telescopes that is already being built will have the capabilities to characterize close-by habitable worlds. The discussion on what makes a planet a habitat and how to detect signs of life is lively. This review will show the latest results, the challenges of how to identify an...
对围绕其他恒星运行的系外行星的探测彻底改变了我们对宇宙的看法。第一个结果表明,它充满了迷人的岩石行星多样性,包括那些位于宜居带的行星。即使是我们最近的恒星半人马座比邻星,在其宜居带中也有一颗小行星比邻星b。通过下一代望远镜,我们将能够窥视岩石行星的大气层,并一瞥其他世界。利用我们自己的行星及其广泛的生物群作为罗塞塔石碑,我们探索如何在星际距离内探测系外行星的宜居性和生命迹象。目前的望远镜还不足以描述宜居系外行星的特征,但已经在建造的下一代望远镜将有能力描述附近宜居世界的特征。关于是什么使地球成为栖息地以及如何发现生命迹象的讨论很活跃。这篇综述将展示最新的结果,如何识别一个。。。
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引用次数: 152
Small-Scale Challenges to the ΛCDM Paradigm ∧CDM范式的小规模挑战
IF 33.3 1区 物理与天体物理 Q1 Earth and Planetary Sciences Pub Date : 2017-07-13 DOI: 10.1146/annurev-astro-091916-055313
J. Bullock, M. Boylan-Kolchin
The dark energy plus cold dark matter (ΛCDM) cosmological model has been a demonstrably successful framework for predicting and explaining the large-scale structure of the Universe and its evolution with time. Yet on length scales smaller than ∼1 Mpc and mass scales smaller than ∼1011M⊙, the theory faces a number of challenges. For example, the observed cores of many dark matter–dominated galaxies are both less dense and less cuspy than naively predicted in ΛCDM. The number of small galaxies and dwarf satellites in the Local Group is also far below the predicted count of low-mass dark matter halos and subhalos within similar volumes. These issues underlie the most well-documented problems with ΛCDM: cusp/core, missing satellites, and too-big-to-fail. The key question is whether a better understanding of baryon physics, dark matter physics, or both is required to meet these challenges. Other anomalies, including the observed planar and orbital configurations of Local Group satellites and the tight baryonic...
暗能量加冷暗物质(ΛCDM)宇宙学模型已经被证明是一个成功的框架,用于预测和解释宇宙的大尺度结构及其随时间的演化。然而,在小于~ 1 Mpc的长度尺度和小于~ 1011M⊙的质量尺度上,该理论面临着许多挑战。例如,观测到的许多以暗物质为主的星系的核心比ΛCDM中天真地预测的密度更小,也更少。本星系群中的小星系和矮卫星的数量也远远低于类似体积内的低质量暗物质晕和亚晕的预测数量。这些问题构成了ΛCDM最充分记录的问题:尖端/核心、缺失卫星和大到不能倒。关键的问题是,是否需要更好地理解重子物理学、暗物质物理学,或者两者都需要来应对这些挑战。其他异常,包括观测到的本群卫星的平面和轨道构型以及紧密重子…
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引用次数: 823
High-Mass Star and Massive Cluster Formation in the Milky Way 银河系中大质量恒星和大质量星团的形成
IF 33.3 1区 物理与天体物理 Q1 Earth and Planetary Sciences Pub Date : 2017-05-31 DOI: 10.1146/annurev-astro-091916-055235
F. Motte, S. Bontemps, F. Louvet
This review examines the state-of-the-art knowledge of high-mass star and massive cluster formation, gained from ambitious observational surveys, which acknowledges the multiscale characteristics of these processes. After a brief overview of theoretical models and main open issues, we present observational searches for the evolutionary phases of high-mass star formation, first among high-luminosity sources and more recently among young massive protostars and the elusive high-mass prestellar cores. We then introduce the most likely evolutionary scenario for high-mass star formation, which emphasizes the link of high-mass star formation to massive cloud and cluster formation. Finally, we introduce the first attempts to search for variations of the star-formation activity and cluster formation in molecular cloud complexes in the most extreme star-forming sites and across the Milky Way. The combination of Galactic plane surveys and high–angular resolution images with submillimeter facilities such as Atacama Large Millimeter Array (ALMA) are prerequisites to make significant progress in the forthcoming decade.
这篇综述研究了高质量恒星和大质量星团形成的最新知识,这些知识来自雄心勃勃的观测调查,它承认这些过程的多尺度特征。在简要概述了理论模型和主要悬而未决的问题之后,我们提出了对高质量恒星形成演化阶段的观测搜索,首先是在高亮度源中,最近是在年轻的大质量原恒星和难以捉摸的高质量恒星前核心中。然后,我们介绍了大质量恒星形成的最可能的进化场景,强调了大质量恒星形成与大质量云团和星团形成的联系。最后,我们介绍了在最极端的恒星形成地点和整个银河系的分子云复合体中寻找恒星形成活动和星团形成变化的首次尝试。银河平面测量和高角度分辨率图像与亚毫米设备(如阿塔卡马大型毫米波阵列(ALMA))的结合是在未来十年取得重大进展的先决条件。
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引用次数: 190
Ultraluminous X-Ray Sources 超亮X射线源
IF 33.3 1区 物理与天体物理 Q1 Earth and Planetary Sciences Pub Date : 2017-03-31 DOI: 10.1146/annurev-astro-091916-055259
P. Kaaret, H. Feng, T. Roberts
We review observations of ultraluminous X-ray sources (ULXs). X-ray spectroscopic and timing studies of ULXs suggest a new accretion state distinct from those seen in Galactic stellar-mass black hole binaries. The detection of coherent pulsations indicates the presence of neutron-star accretors in three ULXs and therefore apparently super-Eddington luminosities. Optical and X-ray line profiles of ULXs and the properties of associated radio and optical nebulae suggest that ULXs produce powerful outflows, also indicative of super-Eddington accretion. We discuss models of super-Eddington accretion and their relationship to the observed behaviors of ULXs. We review the evidence for intermediate-mass black holes (IMBHs) in ULXs. We consider the implications of ULXs for super-Eddington accretion in active galactic nuclei, heating of the early Universe, and the origin of the black hole binary recently detected via gravitational waves.
我们回顾了超发光X射线源(ULX)的观测结果。ULX的X射线光谱和时间研究表明,存在一种不同于银河系恒星质量黑洞双星的新吸积状态。相干脉动的探测表明,三个ULX中存在中子星吸积体,因此显然存在超爱丁顿光度。ULX的光学和X射线线轮廓以及相关的射电和光学星云的性质表明,ULX会产生强大的外流,这也表明超级爱丁顿吸积。我们讨论了超级爱丁顿吸积的模型及其与ULX观测行为的关系。我们回顾了ULX中存在中等质量黑洞的证据。我们考虑了ULX对活动星系核中超级爱丁顿吸积、早期宇宙加热以及最近通过引力波探测到的黑洞双星起源的影响。
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引用次数: 264
Stellar Dynamics and Stellar Phenomena Near a Massive Black Hole 大质量黑洞附近的恒星动力学和恒星现象
IF 33.3 1区 物理与天体物理 Q1 Earth and Planetary Sciences Pub Date : 2017-01-17 DOI: 10.1146/annurev-astro-091916-055306
T. Alexander
Most galactic nuclei harbor a massive black hole (MBH), whose birth and evolution are closely linked to those of its host galaxy. The unique conditions near the MBH—high velocity and density in the steep potential of a massive singular relativistic object—lead to unusual modes of stellar birth, evolution, dynamics, and death. A complex network of dynamical mechanisms, operating on multiple timescales, deflects stars to orbits that intercept the MBH. Such close encounters lead to energetic interactions with observable signatures and consequences for the evolution of the MBH and its stellar environment. Galactic nuclei are astrophysical laboratories that test and challenge our understanding of MBH formation, strong gravity, stellar dynamics, and stellar physics. I review from a theoretical perspective the wide range of stellar phenomena that occur near MBHs, focusing on the role of stellar dynamics near an isolated MBH in a relaxed stellar cusp.
大多数星系核都有一个巨大的黑洞(MBH),它的诞生和演化与它的宿主星系密切相关。mbh附近的独特条件——在一个巨大的奇异相对论天体的陡峭势能下的高速度和高密度——导致了恒星诞生、演化、动力学和死亡的不寻常模式。一个复杂的动力机制网络,在多个时间尺度上运行,使恒星偏转到拦截MBH的轨道上。如此近距离的接触导致了具有可观测特征的能量相互作用,并对MBH及其恒星环境的演化产生了影响。星系核是天体物理实验室,用来测试和挑战我们对MBH形成、强引力、恒星动力学和恒星物理的理解。我从理论角度回顾了发生在MBH附近的各种恒星现象,重点是在松弛的恒星尖端中孤立MBH附近的恒星动力学的作用。
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引用次数: 97
Theoretical Challenges in Galaxy Formation 星系形成的理论挑战
IF 33.3 1区 物理与天体物理 Q1 Earth and Planetary Sciences Pub Date : 2016-12-20 DOI: 10.1146/annurev-astro-081913-040019
T. Naab, J. Ostriker
Numerical simulations have become a major tool for understanding galaxy formation and evolution. Over the decades the field has made significant progress. It is now possible to simulate the formation of individual galaxies and galaxy populations from well-defined initial conditions with realistic abundances and global properties. An essential component of the calculation is to correctly estimate the inflow to and outflow from forming galaxies because observations indicating low formation efficiency and strong circumgalactic presence of gas are persuasive. Energetic “feedback” from massive stars and accreting supermassive black holes—generally unresolved in cosmological simulations—plays a major role in driving galactic outflows, which have been shown to regulate many aspects of galaxy evolution. A surprisingly large variety of plausible subresolution models succeeds in this exercise. They capture the essential characteristics of the problem, i.e., outflows regulating galactic gas flows, but their predicti...
数值模拟已经成为了解星系形成和演化的主要工具。几十年来,这一领域取得了重大进展。现在有可能从具有实际丰度和全局特性的定义良好的初始条件中模拟单个星系和星系群的形成。计算的一个重要组成部分是正确估计形成星系的流入和流出,因为表明低形成效率和强星系周围气体存在的观测是有说服力的。来自大质量恒星和超大质量黑洞的能量“反馈”——通常在宇宙学模拟中未得到解决——在驱动星系外流中起着重要作用,这已被证明可以调节星系演化的许多方面。令人惊讶的是,各种各样的似是而非的亚分辨率模型在这一实践中取得了成功。他们抓住了问题的基本特征,即,流出调节星系气体流动,但他们的预测……
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引用次数: 317
A Fortunate Half-Century 幸运的半个世纪
IF 33.3 1区 物理与天体物理 Q1 Earth and Planetary Sciences Pub Date : 2016-09-19 DOI: 10.1146/ANNUREV-ASTRO-081915-023259
J. Ostriker
The author has had the happy opportunity to work and study in the field of theoretical astrophysics during a half-century of unparalleled observational discovery. Quasars, pulsars, large-scale cosmic structure, galaxy evolution, and many other phenomena were discovered using revolutionary new observational techniques. In the same period of time, analytical tools ranging from new disciplines like plasma physics to enormously enhanced computational facilities became available, giving theoreticians the machinery to make some sense of this new world. At the start of the era the extragalactic world was largely framed as a quasi-homogeneous Universe of static galaxies formed by unknown and in fact unexamined processes. By the end of the period there was widespread acceptance of a self-consistent, evolving cosmological model amenable to calculation and comprehension. The author was fortunate indeed to have had the chance to collaborate with many wonderfully talented colleagues during this exciting time, attempti...
在半个世纪无与伦比的观测发现中,作者有幸在理论天体物理学领域工作和学习。类星体、脉冲星、大尺度宇宙结构、星系演化和许多其他现象都是使用革命性的新观测技术发现的。在同一时期,从等离子体物理学等新学科到大大增强的计算设备,各种分析工具都变得可用,给理论家们提供了理解这个新世界的机器。在这个时代的开始,银河系外的世界在很大程度上被框定为一个准均匀的宇宙,由未知的、实际上未经检验的过程形成的静态星系。到这一时期结束时,人们普遍接受了一种自洽的、不断发展的、易于计算和理解的宇宙模型。在这个激动人心的时刻,作者确实很幸运有机会与许多才华横溢的同事合作。
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引用次数: 2
Six Decades of Spiral Density Wave Theory 六十年的螺旋密度波理论
IF 33.3 1区 物理与天体物理 Q1 Earth and Planetary Sciences Pub Date : 2016-09-19 DOI: 10.1146/ANNUREV-ASTRO-081915-023426
F. Shu
The theory of spiral density waves had its origin approximately six decades ago in an attempt to reconcile the winding dilemma of material spiral arms in flattened disk galaxies. We begin with the earliest calculations of linear and nonlinear spiral density waves in disk galaxies, in which the hypothesis of quasi-stationary spiral structure (QSSS) plays a central role. The earliest success was the prediction of the nonlinear compression of the interstellar medium and its embedded magnetic field; the earliest failure, seemingly, was not detecting color gradients associated with the migration of OB stars whose formation is triggered downstream from the spiral shock front. We give the reasons for this apparent failure with an update on the current status of the problem of OB star formation, including its relationship to the feathering substructure of galactic spiral arms. Infrared images can show two-armed, grand design spirals, even when the optical and UV images show flocculent structures. We suggest how t...
螺旋密度波理论起源于大约60年前,当时试图解决扁平盘状星系中物质旋臂的缠绕困境。我们首先从盘状星系中线性和非线性螺旋密度波的最早计算开始,其中准平稳螺旋结构(QSSS)假设起着核心作用。最早的成功是预测了星际介质的非线性压缩及其嵌入的磁场;最早的失败似乎是没有探测到与OB星迁移相关的颜色梯度,OB星的形成是在螺旋激波锋的下游触发的。我们给出了这一明显失败的原因,并更新了OB恒星形成问题的当前状态,包括它与银河系旋臂羽状亚结构的关系。红外图像可以显示双臂,大设计螺旋,甚至当光学和紫外图像显示絮状结构。我们建议如何……
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引用次数: 73
Astrophysics with Extraterrestrial Materials 外星物质的天体物理学
IF 33.3 1区 物理与天体物理 Q1 Earth and Planetary Sciences Pub Date : 2016-09-19 DOI: 10.1146/ANNUREV-ASTRO-082214-122505
L. Nittler, F. Ciesla
Extraterrestrial materials, including meteorites, interplanetary dust, and spacecraft-returned asteroidal and cometary samples, provide a record of the starting materials and early evolution of the Solar System. We review how laboratory analyses of these materials provide unique information, complementary to astronomical observations, about a wide variety of stellar, interstellar and protoplanetary processes. Presolar stardust grains retain the isotopic compositions of their stellar sources, mainly asymptotic giant branch stars and Type II supernovae. They serve as direct probes of nucleosynthetic and dust formation processes in stars, galactic chemical evolution, and interstellar dust processing. Extinct radioactivities suggest that the Sun's birth environment was decoupled from average galactic nucleosynthesis for some tens to hundreds of Myr but was enriched in short-lived isotopes from massive stellar winds or explosions shortly before or during formation of the Solar System. Radiometric dating of met...
地外物质,包括陨石、行星际尘埃和航天器返回的小行星和彗星样本,提供了太阳系起始物质和早期演化的记录。我们回顾了这些材料的实验室分析如何提供独特的信息,补充天文观测,关于各种各样的恒星,星际和原行星过程。太阳系前星尘颗粒保留了其恒星源的同位素组成,主要是渐近巨型分支星和II型超新星。它们是恒星核合成和尘埃形成过程、星系化学演化和星际尘埃处理的直接探测器。已灭绝的放射性物质表明,太阳的诞生环境与银河系核合成的平均水平分离了几十到几百迈尔,但在太阳系形成前不久或形成期间,大量的恒星风或爆炸丰富了短寿命同位素。放射性定年法测定…
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引用次数: 113
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Annual Review of Astronomy and Astrophysics
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