Reproducing the CO-to-H$_2$ conversion factor in cosmological simulations of Milky Way-mass galaxies
Laura C. Keating, Alexander J. Richings, Norman Murray, Claude-Andre Faucher-Giguere, Philip F. Hopkins, Andrew Wetzel, Dusan Keres, Samantha Benincasa, Robert … 展开作者
Laura C. Keating, Alexander J. Richings, Norman Murray, Claude-Andre Faucher-Giguere, Philip F. Hopkins, Andrew Wetzel, Dusan Keres, Samantha Benincasa, Robert Feldmann, Sarah Loebman, Matthew E. Orr
We present models of CO(1-0) emission from Milky Way-mass galaxies at redshift zero in the FIRE-2 cosmological zoom-in simulations. We calculate the molecular abundances by post-processing the simulations with an equilibrium chemistry solver while accounting for the effects of local sources, and determine the emergent CO(1-0) emission using a line radiative transfer code. We find that the results depend strongly on the shielding length assumed, which in our models sets the attenuation of the incident UV radiation field. At the resolution of these simulations, commonly used choices for the shielding length, such as the Jeans length, result in CO abundances that are too high at a given H$_2$ abundance. We find that a model with a distribution of shielding lengths, which has a median shielding length of $\sim 3$ pc in cold gas ($T < 300$ K) for both CO and H$_{2}$, is able to reproduce both the observed CO(1-0) luminosity and inferred CO-to-H$_{2}$ conversion factor at a given star formation rate compared with observations. We suggest that this short shielding length can be thought of as a subgrid model which controls the amount of radiation that penetrates giant molecular clouds.
The observed star formation rate of the Milky Way can be explained by applying a metallicity-dependent factor to convert CO luminosity to molecular gas mass and a star formation efficiency per free-fall time that depends on the virial parameter of a molecular cloud. These procedures also predict the trend of star formation rate surface density with Galactocentric radius. The efficiency per free-fall time variation with virial parameter plays the major role in bringing theory into agreement with observations for the total star formation rate, while the metallicity dependence of the CO luminosit…
The Three-mm Ultimate Mopra Milky Way Survey. III. Data Release 6, An Atlas of Physical Conditions, Global Mass Conversion Laws, and 3D Physical Architecture of the Molecular ISM in the Fourth Quadrant
A new catalog of homogenised absorption line indices for Milky Way globular clusters from high-resolution integrated spectroscopy
我们对24个银河系球状星团进行了综合光谱分析。从一个核心半径的光谱观察到每个集群与高波长分辨率~2.0 A的FWHM。结合Puzia et al.（2002）和Schiavon et al.（2005）的两个现有数据集，我们构建了一个包含53个银河系球状星团的Lick光谱指数的大型数据库，这些球状星团具有广泛的金属丰度范围，-2.4 < [Fe/H] < 0.1，以及各种水平分支形态。经验指数到金属丰度的转换关系提供了20舔指数用于推导金属丰度的远程，未解决的恒星系统。
Accurately reproducing the thin cold gas discs observed in nearby spiral galaxies has been a long standing issue in cosmological simulations. Here, we present measurements of the radially resolved HI scale height in 22 non-interacting Milky Way-mass galaxies from the FIREbox cosmological volume. We measure the HI scale heights using five different approaches commonly used in the literature: fitting the vertical volume density distribution with a Gaussian, the distance between maximum and half-maximum of the vertical volume density distribution, a semi-empirical description using the velocity d…
The Milky Way Joins the Extragalactic World: I. PHANGS
The University of Texas at Austin（德克萨斯大学奥斯汀分校）；INAF-IAPS（意大利国家天体物理研究所空间天文与物理学中心）；INAF, Sezione di Lecce（意大利国家天体物理研究所莱切分部）；University of Kentucky（肯塔基大学）；National Astronomical Observatory of Japan（日本国立天文台）；Max Planck Institute for Radio Astronomy（马克斯·普朗克射电天文研究所）；The Ohio State University（俄亥俄州立大学）
To understand how the evolution of grain size distribution in galaxies affects observed dust properties, we apply a post-processing dust evolution model to galaxy merger trees from the IllustrisTNG cosmological hydrodynamical simulation. Our dust model includes stellar dust production, sputtering in hot gas, dust growth by accretion and coagulation in the dense interstellar medium (ISM), and shattering in the diffuse ISM. We decompose the grain size distribution into different dust species depending on the elemental abundances and the dense ISM fraction given by the simulation. In our previous…
CO-dark gas and molecular filaments in Milky Way type galaxies
我们使用移动网格代码AREPO耦合到一个含时的化学网络来研究分子气体在模拟的螺旋星系中的形成和破坏。这使我们能够确定CO排放不跟踪的气体的特性。我们的极高分辨率AREPO模拟使我们能够捕捉光盘的化学演变，而无需求助于参数化的“聚集因子”。我们通过我们模拟的盘星系计算了H2和CO柱密度，并估算了CO发射和CO-H2转换因子。我们发现，在类似的条件下，在当地的星际介质，大约42%的总分子质量应该在CO暗区，在合理的协议与观测估计。这部分是几乎不敏感的CO积分强度阈值用于区分CO亮和CO暗气体，只要这个阈值是小于10 K km/s。CO暗分子气体主要存在于极长（>100 pc）的细丝中，这些细丝被星系切变拉伸在旋臂之间。只有这些细丝的中心在CO中是明亮的，这表明在银河系中观察到的非连续分子云可能只是更大结构的一小部分。CO暗分子气体主要存在于部分分子相中，占总圆盘质量预算的很大一部分。在环境紫外线场较高或表面密度较低的模拟中，暗气体比例较高，这意味着具有这些条件的外部星系可能具有更大比例的暗气体。
There are many well-known correlations between dark matter and baryons that exist on galactic scales. These correlations can essentially be encompassed by a simple scaling relation between observed and baryonic accelerations, historically known as the Mass Discrepancy Acceleration Relation (MDAR). The existence of such a relation has prompted many theories that attempt to explain the correlations by invoking additional fundamental forces on baryons. The standard lore has been that a theory that reduces to the MDAR on galaxy scales but behaves like cold dark matter (CDM) on larger scales provid…
MEGATRON: Reproducing the Diversity of High-Redshift Galaxy Spectra with Cosmological Radiation Hydrodynamics Simulations
University of Chicago（芝加哥大学）；Kavli Institute for Cosmological Physics, University of Chicago（芝加哥大学卡弗里宇宙物理学研究所）；University of Bath（巴斯大学）；Sorbonne Université（索邦大学）；Institut d’Astrophysique de Paris（巴黎天体物理研究所）；CNRS（法国国家科学研究中心）；Lund University（隆德大学）；Universite Claude Bernard Lyon 1（里昂第一大学）；CRAL UMR5574（天体物理与行星学研究中心）；ENS de Lyon（里昂高等师范学校）；University of Oxford（牛津大学）；Kavli Institute for Cosmology, University of Cambridge（剑桥大学卡弗里宇宙学研究所）；Cavendish Laboratory, University of Cambridge（剑桥大学卡文迪许实验室）；Yonsei University（延世大学）
Being one of the most abundant atomic/molecular species observed in dense molecular gas, atomic carbon ($\mathrm{C}^0$) is a potential good tracer of molecular gas mass in many chemical/physical environments, though the $\mathrm{C^0}$ abundance variation outside the Galactic disk region is yet to be fully known. This paper presents a wide-field 500 GHz [CI] map of the Galactic central molecular zone (CMZ) obtained with the ASTE 10-m telescope. Principal component analysis and non-LTE multi-transition analysis have shown that the [CI] emission predominantly originates from the low-excitation ga…
We describe the public release of the Cluster Monte Carlo Code (CMC) a parallel, star-by-star $N$-body code for modeling dense star clusters. CMC treats collisional stellar dynamics using Hénon's method, where the cumulative effect of many two-body encounters is statistically reproduced as a single effective encounter between nearest-neighbor particles on a relaxation timescale. The star-by-star approach allows for the inclusion of additional physics, including strong gravitational three- and four-body encounters, two-body tidal and gravitational-wave captures, mass loss in arbitrary galactic …
