11 pages, 4 figures, accepted for publication in Astronomy and Astrophysics, version with full resolution figures available at http://www.aai.ee/~urmas/ast/NHIE.pdf (40.72 MBytes)
Context. In the HI line profiles in the Leiden-Argentina-Bonn (LAB) all-sky database, we have found a population of very cold HI clouds. So far, the role of these clouds in the interstellar medium (ISM) has remained unclear. Aims. In this paper, we attempt to confirm the existence of the narrow-line HI emission (NHIE) clouds by using the data from the Parkes Galactic all-sky survey (GASS) and try to find their place among other coldest constituents of the ISM. Methods. We repeat the search of NHIE with the GASS data and derive or compile some preliminary estimates for the distribution, temperatures, distances, linear sizes, column and number densities, masses, and the composition of NHIE clouds, and compare these data with corresponding estimates for HI self-absorption (HISA) features, the Planck cold clumps (CC), and infrared dark clouds (IRDC). Results. We demonstrate that from LAB and GASS we can separate comparable NHIE complexes, and the properties of the obtained NHIE clouds are very similar to those of HISA features, but both of these types of clouds are somewhat warmer and more extended and have lower densities than the cores in the Planck CC and IRDC. Conclusions. We conclude that NHIE may be the same type of clouds as HISA, but in different observing conditions, in the same way as the Planck CC and IRDC are most likely similar ISM structures in different observing conditions and probably in slightly different evolutionary stages. Both NHIE and HISA may be an intermediate phase between the diffuse cold neutral medium and star-forming molecular clumps represented by the Planck CC and IRDC.
The Launching of Galactic Winds from a Multiphase ISM
Max Planck Institute for Astrophysics（马普天体物理研究所）；Astronomisches Rechen-Institut, Zentrum für Astronomie, Universität Heidelberg（海德堡大学天文学计算研究所）；Hamburger Sternwarte, Universität Hamburg（汉堡大学天文台）
Influence of galactic arm scale dynamics on the molecular composition of the cold and dense ISM II. Molecular oxygen abundance
分子氧一直是许多观测研究的主题，因为化学模型预测它是氧气的储存库。虽然它已经在星际介质的两个区域被探测到，但它的稀有性对天体化学模型来说是一个挑战。在本文中，我们结合了计算的物理条件与光滑粒子流体动力学（SPH）模拟与我们的全气体颗粒化学模型鹦鹉螺，研究预测的O2丰度在星际物质形成冷芯。因此，我们遵循的气体和冰的化学演化的物质包裹从弥漫的星际条件冷致密的核心。我们的大多数预测的O2丰度低于1 e-8（相对于总质子密度）和预测的柱密度在模拟冷芯是在最大的几个1 e 14 cm-2，在协议的非检测限。这种低的O2丰度可以通过以下事实来解释，即在大部分星际材料中，在O2可以在气相中形成并且免受UV光解离之前，原子氧被耗尽到晶粒表面上（并且被氢化以形成H2O）。我们之所以能得到这个结果，是因为我们考虑了从弥散介质到冷核的物理条件演化的全部历史。
Benzonitrile as a proxy for benzene in the cold ISM: low temperature rate coefficients for CN + C$_6$H$_6$
CN和苯（C $_6$ H $_6$）之间的低温反应是天体化学界的重要兴趣，因为最近发现了苯甲腈，这是利用射电天文学在星际介质（ISM）中发现的第一个芳香分子。苯甲腈被认为是苯的低温替代物，苯是最简单的芳香族分子之一，可能是多环芳烃（PAHs）的前体。为了评估苯甲腈作为苯的替代物的稳健性，需要进行低温动力学测量，以确认在冷密云中发现的低气体温度下反应是否保持快速。在这里，我们研究了C $_6$ H $_6$ + CN反应在15- 295 K的温度范围内，使用完善的CRESU技术（法语缩写代表反应动力学在均匀超音速流）结合脉冲激光光解激光诱导荧光（PLP-LIF）。我们得到的速率系数$k(T)$在（3.6- 5.4）$\times$ 10 $^{-10}$ cm $^3$ s $^{-1}$范围内，在15- 295 K之间没有明显的温度依赖性，证实CN + C $_6$ H $_6$反应在与冷ISM相关的温度下保持快速.
The formation and evolution of stellar clusters is intimately linked to that of their host galaxies. To study this connection, we present the EMP-Pathfinder suite of cosmological zoom-in Milky Way-mass simulations. These simulations contain a sub-grid description for stellar cluster formation and evolution, allowing us to study the simultaneous formation and evolution of stellar clusters alongside their host galaxies across cosmic time. As a key ingredient in these simulations, we include the physics of the multi-phase nature of the interstellar medium (ISM), which enables studies of how the p…
Ranging from a few pc to hundreds of kpc in size, radio jets have, during their evolution, an impact on their gaseous environment on a large range of scales. While their effect on larger scales is well established, it is now becoming clear that they can also strongly affect the interstellar medium (ISM) inside the host galaxy. Particularly important is the initial phase ($<10^6$ yr) of the evolution of the radio jet, when they expand into the inner few kpc of the host galaxy. Here we report on results obtained for a representative group of young radio galaxies using the cold molecular gas as a…
The fate of the interstellar medium in early-type galaxies. IV. The impact of stellar feedback, mergers, and black holes on the cold ISM in simulated galaxies
A Portrait of Cold Gas in Galaxies at 60pc Resolution and a Simple Method to Test Hypotheses That Link Small-Scale ISM Structure to Galaxy-Scale Processes
Modelling the evolution and influence of dust in cosmological simulations that include the cold phase of the interstellar medium
University of Portsmouth（朴茨茅斯大学）；Leiden University（莱顿大学）；University of Vienna（维也纳大学）；University of Hull（赫尔大学）；Lorentz Institute for Theoretical Physics, Leiden University（莱顿大学洛伦兹理论物理研究所）；University of Milano-Bicocca（米兰比可卡大学）；Durham University（杜伦大学）
We present a study of the elemental depletion in the interstellar medium. We combined the results of a Galatic model describing the gas physical conditions during the formation of dense cores with a full-gas-grain chemical model. During the transition between diffuse and dense medium, the reservoirs of elements, initially atomic in the gas, are gradually depleted on dust grains (with a phase of neutralisation for those which are ions). This process becomes efficient when the density is larger than 100~cm$^{-3}$. If the dense material goes back into diffuse conditions, these elements are brough…
Up, Up, and Away? Quantifying ISM Fallback using Ram Pressure Stripping Simulations
Center for Computational Astrophysics, Flatiron Institute（Flatiron Institute 计算天体物理学中心）；Department of Astronomy, Yale University（耶鲁大学天文学系）；Department of Astronomy, Columbia University（哥伦比亚大学天文学系）
We present the results from the study of the resolved distribution of cold molecular gas around eight young (<10^6 yr), peaked-spectrum radio galaxies. This has allowed us to trace the interplay between the radio jets and the surrounding medium. For three of these sources we present new CO(1-0) observations, obtained with NOEMA. In two targets, we also detected CN lines, both in emission and absorption. Combining the new observations with already published data, we discuss the main results obtained. Although we found that a large fraction of the cold molecular gas is distributed in disc-like r…
Thermal Pressure in the Cold Neutral Medium of Nearby Galaxies
动力学和热过程调节多相星际介质（ISM）的结构，并最终确定星系如何通过恒星形成演化。因此，为了约束ISM模型并更好地理解这些过程的相互作用，测量扩散的中性气体的热压力（$P_{\rm th}$）是非常有意义的。结合[C II] 158 $μ$ m，HI和CO数据从31个星系中选择的Herschel KINGFISH样本，我们已经测量了534个主要原子区域的热压，典型的尺寸为$\sim$ 1千秒差距。我们发现在$P_{\rm th}/k\sim10^3-10^5$ K cm $^{-3}$范围内的热压力分布。对于一个子样本的地区的条件相似的扩散，中性气体在银河系平面，我们发现的热压力，遵循对数正态分布的中值为$P_{\rm th}/k\approx3600$ K cm $^{-3}$。这些结果与使用其他观测方法测量的热压力是一致的。我们发现，$P_{\rm th}$增加辐射场强度和恒星形成活动，从气体加热和恒星形成率之间的密切联系所预期的。我们的热压力测量落在该政权的两相ISM与冷，暖中性介质可以存在于压力平衡。最后，我们发现，扩散气体的中平面的热压力是约$\sim30$ %的垂直重量的覆盖ISM，符合流体动力学模拟的结果自我调节恒星形成的星系盘。
The cold interstellar medium (ISM) plays a central role in the galaxy evolution process. It is the reservoir that fuels galaxy growth via star formation, the repository of material formed by these stars, and a sensitive tracer of internal and external processes that affect entire galaxies. Consequently, significant efforts have gone into systematic surveys of the cold ISM of the galaxies in the local Universe. This review discusses the resulting network of scaling relations connecting the atomic and molecular gas masses of galaxies with their other global properties (stellar masses, morphologi…
The precise characteristics of clouds and the nature of dust in the diffuse interstellar medium can only be extracted by inspecting the rare cases of single-cloud sightlines. In our nomenclature such objects are identified by interstellar lines, such as K I, that show at a resolving power of $λ/Δλ\sim 75,000$ one dominating Doppler component that accounts for more than half of the observed column density. We searched for such sightlines using high-resolution spectroscopy towards reddened OB stars for which far-UV extinction curves are known. We compiled a sample of 186 spectra, 100 of which we…
HYPERION. The cold ISM of rapidly growing $z>6$ quasars: diverse gas reservoirs, dust enrichment, and feedback signatures
INAF - Osservatorio Astronomico di Roma（意大利国家天体物理研究所罗马天文台）；IFPU - Institute for Fundamental Physics of the Universe（宇宙基础物理研究所）；INAF, Osservatorio Astronomico di Trieste（意大利国家天体物理研究所的里雅斯特天文台）；INAF – Osservatorio di Astrofisica e Scienza dello Spazio di Bologna（意大利国家天体物理研究所博洛尼亚空间天体物理学与科学观测站）；Scuola Normale Superiore（比萨高等师范学院）
It is expected that as the Sun travels through the interstellar medium (ISM), there will be different filtration of Galactic Cosmic Rays (GCR) that affect Earth. The effect of GCR on Earth's atmosphere and climate is still uncertain. Although the interaction with molecular clouds was previously considered, the terrestrial impact of compact cold clouds was neglected. There is overwhelming geological evidence from 60Fe and 244Pu isotopes that Earth was in direct contact with the ISM 2 million years ago, and the local ISM is home to several nearby cold clouds. Here we show, with a state-of the ar…
Interacting galaxies on FIRE-2: The connection between enhanced star formation and interstellar gas content
我们提出了一套全面的高分辨率（秒差距尺度），理想化的（非宇宙学）星系合并模拟（24轮，恒星质量比~2.5：1），以研究相互作用引起的恒星形成和星际介质（ISM）在各种温度密度制度的演变之间的联系。我们使用GIZMO代码和第二版的“真实环境中的反馈”模型（FIRE-2），该模型捕获了ISM的多阶段结构。我们的模拟旨在代表本地宇宙中的星系合并。在这项工作中，我们专注于“星系对周期”之间的第一次和第二次近心轴通道。我们分裂的ISM分为四个制度：热，温暖，冷，冷密集，热，电离，原子和分子的气体在真实星系中观察到的阶段的动机。我们发现，平均而言，相互作用提高了这对恒星的形成率（约30%，合并套件样本平均值），并提高了它们的冷致密气体含量（约18%）。这伴随着热气体的减少（~11%），冷气体的变化可以忽略不计（~4%的增加），以及热气体的大幅增加（~400%）。密度超过1000 cm ^3的冷密气体（冷超密区）的数量显著增加（约240%），但仅占冷密气体预算的0.15%（平均）。
The Distribution of Thermal Pressures in the Diffuse, Cold Neutral Medium of our Galaxy. II. An Expanded Survey of Interstellar C I Fine-Structure Excitations
我们分析了吸收特征所产生的星际中性碳，出现在紫外光谱中记录的89颗恒星在最高分辨率的阶梯光栅模式的STIS的HST，使我们可以确定碰撞激发的原子的电子基态的精细结构能级的相对布居。从这些信息中，我们得到了在扩散，冷中性介质中的热压力分布。我们发现对数正态压力分布（按质量加权），对数（p/k）平均值等于3.58，均方根色散至少为0.175 dex，这可能是由特征马赫数在1 < M < 4范围内的湍流引起的。然而，分布中的极端尾部高于对数正态函数。总的来说，压力与当地的星光强度和极端的运动学有很好的相关性。大约23%的气体处于低于静态冷中性介质所允许的压力下。几乎所有的气体都伴随着一小部分（~0.05%）具有非常大的压力，log（p/k）> 5.5，这种情况在高速或星光密度增强的区域更普遍。这项调查表明，在寒冷的中性ISM中，热压力的分散主要受恒星形成区驱动的微观湍流控制，还有一些来自宏观事件的额外影响（例如，SN爆炸），这些测量为未来研究湍流对ISM和恒星形成的更广泛影响提供了限制。
Resolving the phase structure of neutral hydrogen (HI) is crucial for understanding the life cycle of the interstellar medium (ISM). However, accurate measurements of HI temperature and density are limited by the availability of background continuum sources for measuring HI absorption. Here we test the use of deep learning for extracting HI properties over large areas without optical depth information. We train a 1D convolutional neural network using synthetic observations of 3D numerical simulations of the ISM to predict the fraction of cold neutral medium (f_CNM) and the correction to the op…
We investigate properties of the interstellar medium (ISM) interacting with shocks around the Galactic supernova remnant IC443, using the results of near-infrared [FeII] and H2 line mapping with the IRSF/SIRIUS. In the present study, we newly performed H2 1-0 S(1) and 2-1 S(1) line mapping with the narrow-band filters tuned for these lines, covering the entire remnant (30'x35'). Combined with an [FeII] line map, our result shows that the H2 line emission is significantly detected in the southern region, while the [FeII] line emission is detected all over the remnant, suggesting that slow and f…
