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We derived the dust-to-HI ratio of the intermediate-velocity clouds (IVCs), the high-velocity clouds (HVCs), and the local HI gas, by carrying out a multiple-regression analysis of the 21cm HI emission combined with the sub-mm dust optical…

Astrophysics of Galaxies · Physics 2024-01-24 Takahiro Hayakawa , Yasuo Fukui

We study four lines of sight that probe the transition from diffuse molecular gas to molecular cloud material in Taurus. Measurements of atomic and molecular absorption are used to infer the distribution of species and the physical…

Observational evidence seems to indicate that the depletion of interstellar carbon into dust shows rather wide variations and that carbon undergoes rather rapid recycling in the interstellar medium (ISM). Small hydrocarbon grains are…

In this series of papers we study the structure of the atomic to molecular transition in the giant atomic-molecular complexes that are the repositories of most molecular gas in galaxies, with the ultimate goal of attaining a better…

Astrophysics · Physics 2009-11-13 Mark R. Krumholz , Christopher F. McKee , Jason Tumlinson

The model is constructed of the propagation of gamma-ray burst radiation through a dense molecular cloud. The main processes of the interaction of the radiation with the interstellar gas are taken into account in the simulations: the…

High Energy Astrophysical Phenomena · Physics 2024-05-20 Aleksandr Nesterenok

Studying the atomic-to-molecular transition is essential for understanding the evolution of interstellar medium. The linear edge of Taurus molecular cloud, clearly identified in the $^{13}$CO(1-0) intensity map, serves as an ideal site for…

Astrophysics of Galaxies · Physics 2025-04-03 Ningyu Tang , Feihang Miao , Gan Luo , Di Li , Junzhi Wang , Fujun Du , Donghong Wu , Shu Liu

Far-UV photons (E<13.6 eV) from hot massive stars regulate, or at least influence, the heating, ionization, and chemistry of most of the neutral interstellar medium. Investigating the interaction between FUV radiation and interstellar…

Astrophysics of Galaxies · Physics 2018-09-12 Javier R. Goicoechea , S. Cuadrado , J. Pety , A. Aguado , J. H. Black , E. Bron , J. Cernicharo , E. Chapillon , A. Fuente , M. Gerin , C. Joblin

In the Galactic fountain scenario, supernovae and/or stellar winds propel material into the Galactic halo. As the material cools, it condenses into clouds. By using FLASH three-dimensional magnetohydrodynamic simulations, we model and study…

Astrophysics of Galaxies · Physics 2014-11-20 Kyujin Kwak , Robin L. Shelton , Elizabeth A. Raley

We aim to compare variations in the full-UV dust extinction curve (912-3000 Angstrom), with the HI/H$_2$/total H content along diffuse Milky Way sightlines, to investigate possible connections between ISM conditions and dust properties. We…

Astrophysics of Galaxies · Physics 2023-02-15 Dries Van De Putte , Stefan I. B. Cartledge , Karl D. Gordon , Geoffrey C. Clayton , Julia Roman-Duval

We report the first ensemble results from the FUSE survey of molecular hydrogen in lines of sight with A_V $\gtrsim$ 1 mag. We have developed techniques for fitting computed profiles to the low-J lines of H2, and thus determining column…

We describe a phenomenological model for molecular hydrogen formation suited for applications in galaxy formation simulations, which includes on-equilibrium formation of molecular hydrogen on dust and approximate treatment of both its…

Astrophysics · Physics 2010-12-28 Nickolay Y. Gnedin , Konstantinos Tassis , Andrey V. Kravtsov

We present two sets of grid-based hydrodynamical simulations of high-velocity clouds (HVCs) traveling through the diffuse, hot Galactic halo. These HI clouds have been suggested to provide fuel for ongoing star formation in the Galactic…

Astrophysics of Galaxies · Physics 2011-02-11 Fabian Heitsch , Mary E. Putman

Understanding the molecular gas content in the interstellar medium (ISM) is crucial for studying star formation and galaxy evolution. The CO-to-H$_2$ ($X_{\rm CO}$) and the [CI]-to-H$_2$ ($X_{\rm CI}$) conversion factors are widely used to…

Where dust and gas are uniformly mixed, atomic hydrogen can be traced through the detection of far-infrared (FIR) or UV emission of dust. We considered, for the origin of discrepancies observed between various direct and indirect tracers of…

Astrophysics of Galaxies · Physics 2022-11-30 Jean-Marc Casandjian , Jean Ballet , Isabelle Grenier , Quentin Remy

The majority of hydrogen in the interstellar medium (ISM) is in atomic form. The transition from atoms to molecules and, in particular, the formation of the H$_2$ molecule, is a key step in cosmic structure formation en route to stars.…

Astrophysics of Galaxies · Physics 2018-10-31 Pei Zuo , Di Li , J. E. G. Peek , Qiang Chang , Xia Zhang , Nicholas chapman , Paul F. Goldsmith , Zhi-Yu Zhang

The mass of molecular gas in an interstellar cloud is often measured using line emission from low rotational levels of CO, which are sensitive to the CO mass, and then scaling to the assumed molecular hydrogen H_2 mass. However, a…

Astrophysics of Galaxies · Physics 2015-05-18 Mark G. Wolfire , David Hollenbach , Christopher F. McKee

We present three-dimensional astrochemical simulations and synthetic observations of magnetised, turbulent, self-gravitating molecular clouds. We explore various galactic interstellar medium environments, including cosmic-ray ionization…

Astrophysics of Galaxies · Physics 2021-01-20 Thomas G. Bisbas , Jonathan C. Tan , Kei E. I. Tanaka

The presence of small amounts of atomic hydrogen, detected as absorption dips in the 21 cm line spectrum, is a well-known characteristic of dark clouds. The abundance of hydrogen atoms measured in the densest regions of molecular clouds can…

Astrophysics of Galaxies · Physics 2018-11-21 Marco Padovani , Daniele Galli , Alexei V. Ivlev , Paola Caselli , Andrea Ferrara

We present the first 7.5'x11.5' velocity-resolved map of the [CII]158um line toward the Orion molecular cloud-1 (OMC-1) taken with the Herschel/HIFI instrument. In combination with far-infrared (FIR) photometric images and velocity-resolved…