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{We study in some details the statistical properties of the turbulent 2-phase interstellar atomic gas.{We present high resolution bidimensional numerical simulations of the interstellar atomic hydrogen which describe it over 3 to 4 orders…

Astrophysics · Physics 2015-06-24 P. Hennebelle , E. Audit

We present a comprehensive study of MHD waves and instabilities in a weakly ionised system, e.g., an interstellar molecular cloud. We determine all the critical wavelengths of perturbations across which the sustainable wave modes can change…

Solar and Stellar Astrophysics · Physics 2011-04-01 Telemachos Ch. Mouschovias , Glenn E. Ciolek , S. A. Morton

We have presented the non-equilibrium (time-dependent) cooling rate and ionization state calculations for a gas behind shock waves with $v \sim 50-150$ km s$^{-1}$ ($T_s \sim 0.5 - 6\times 10^5$ K). Such shock waves do not lead to the…

Cosmology and Nongalactic Astrophysics · Physics 2015-05-30 Evgenii O. Vasiliev

To understand the formation of a magnetically dominated molecular cloud out of an atomic cloud, we follow the dynamical evolution of the cloud with a time-dependent axisymmetric magnetohydrodynamic code. A thermally stable warm atomic cloud…

Astrophysics · Physics 2009-11-13 S. Van Loo , S. A. E. G. Falle , T. W. Hartquist , T. J. T. Moore

I describe the scenario of molecular cloud (MC) evolution that has emerged over the past decade or so. MCs can start out as cold atomic clouds formed by compressive motions in the warm neutral medium (WNM) of galaxies. Such motions can be…

Astrophysics of Galaxies · Physics 2010-09-22 Enrique Vazquez-Semadeni

The diffuse interstellar medium is dynamic, and its chemistry and evolution is determined by shock fronts as well as photodissociation. Shocks are implied by the supersonic motions and velocity dispersion often statistically called…

Astrophysics of Galaxies · Physics 2021-03-17 William T. Reach , Carl Heiles

The structure and dynamics of diffuse gas in the Milky Way and other disk galaxies may be strongly influenced by thermal and magnetorotational instabilities (TI and MRI) on scales of about 1-100 pc. We initiate a study of these processes,…

Astrophysics · Physics 2009-11-10 Robert A. Piontek , Eve C. Ostriker

Linear analysis of the stability of diffuse clouds in the cold neutral medium with uniform magnetic field is performed. We consider that gas in equilibrium state is heated by cosmic rays, X-rays and electronic photoeffect on the surface of…

Solar and Stellar Astrophysics · Physics 2019-05-22 Alexander E. Dudorov , Constantine E. Stepanov , Sergey O. Fomin , Sergey A. Khaibrakhmanov

{It has recently been proposed that giant molecular complexes form at the sites where streams of diffuse warm atomic gas collide at transonic velocities.} {We study the global statistics of molecular clouds formed by large scale colliding…

Astrophysics · Physics 2009-11-13 P. Hennebelle , R. Banerjee , E. Vazquez-Semadeni , R. Klessen , E. Audit

We perform linear analysis of thermal instability in a contracting large cloud filled with warm HI gas and investigate the effect of metallicity and radiation flux. When the cloud reaches critical density n_f, the cloud fragments into cool,…

Astrophysics · Physics 2009-10-31 Motomichi Tashiro , Ryoichi Nishi

I discuss the role of self-gravity and radiative heating and cooling in shaping the nature of the turbulence in the interstellar medium (ISM) of our galaxy. The heating and cooling cause it to be highly compressible, and, in some regimes of…

Astrophysics of Galaxies · Physics 2012-02-22 Enrique Vazquez-Semadeni

We investigate the atomic-to-molecular gas transition in the molecular formation cloud HLCG 92-35. Using the ROHSA algorithm to decompose GALFA-H I data, we find the Lukewarm Neutral Medium (LNM) to be the dominant mass component,…

Astrophysics of Galaxies · Physics 2026-03-17 Yamato Matsuzuki , Hiroaki Yamamoto , Kengo Tachihara

The radiative cooling of optically thin gaseous regions and the formation of a two-phase medium and of cold gas clouds with a clumpy substructure is investigated. In optically thin clouds, the growth rate of small isobaric density…

Astrophysics · Physics 2009-10-31 A. Burkert , D. N. C. Lin

Molecular clouds, which harbor the birthplaces of stars, form out of the atomic phase of the interstellar medium (ISM). We aim to characterize the atomic and molecular phases of the ISM and set their physical properties into the context of…

Thermal instability in the circum-galactic medium (CGM) can be responsible for the existence of cold clouds (e.g., high-velocity clouds) embedded in a hot diffuse medium (e.g., X-ray emitting gas). While many previous studies have analyzed…

Astrophysics of Galaxies · Physics 2025-12-24 Izumi Seno , Shu-ichiro Inutsuka , Jiro Shimoda

Thermal instability (TI) is a trigger mechanism, which can explain formation of condensations through some regions of the interstellar clouds. Our goal here is to investigate some conditions for occurrence of TI and formation of…

Astrophysics of Galaxies · Physics 2019-08-14 Mohsen Nejad-Asghar

Using the adaptive mesh refinement code MG, we perform 3D hydrodynamic simulations of a supernova-cloud interaction in the "large cloud regime". The cloud is initially atomic and evolving due to the thermal instability (TI) and gravity. We…

Astrophysics of Galaxies · Physics 2022-05-16 M. M. Kupilas , J. M. Pittard , C. J. Wareing , S. A. E. G. Falle

The hydrodynamic state of the interstellar medium (ISM) heated and randomly stirred by supernovae (SNe) is investigated. We use a three-dimensional non-ideal hydrodynamic ISM model in a domain extending 0.5 x 0.5 kpc horizontally and 2 kpc…

Astrophysics of Galaxies · Physics 2013-12-04 Frederick Gent , Maarit J. Mantere , Anvar Shukurov , Andrew Fletcher , Graeme R. Sarson

This paper describes 3D simulations of the formation of collapsing cold clumps via thermal instability inside a larger cloud complex. The initial condition was a diffuse atomic, stationary, thermally unstable, 200pc diameter spherical cloud…

Astrophysics of Galaxies · Physics 2019-03-20 C. J. Wareing , S. A. E. G. Falle , J. M. Pittard

We perform global linear stability analysis and idealized numerical simulations in global thermal balance to understand the condensation of cold gas from hot/virial atmospheres (coronae), in particular the intracluster medium (ICM). We pay…

Astrophysics of Galaxies · Physics 2016-02-15 Prakriti Pal Choudhury , Prateek Sharma