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Related papers: The thinnest cold HI clouds in the diffuse interst…

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We discuss the thermal evaporation of tiny HI clouds in the interstellar medium. Cold neutral clouds will take ~10^6 - 10^7 yr to evaporate if they are embedded in warm neutral gas and about half as long if embedded in hot gas. Heat flux…

Astrophysics · Physics 2007-05-23 Jonathan D. Slavin

We report on a comparison between 21 cm rotation measure (RM) and the optically-thin atomic hydrogen column density (N_HI) measured towards unresolved extragalactic sources in the Galactic plane of the northern sky. HI column densities…

Astrophysics of Galaxies · Physics 2015-06-16 Tyler Foster , Roland Kothes , Joanne Brown

We present the study of CI/H$_2$ relative abundance in the diffuse cold neutral medium. Using the chemical and thermal balance model we calculated the dependence of CI/H$_2$ on the main parameters of the medium: hydrogen number density,…

Astrophysics of Galaxies · Physics 2024-02-02 Sergei Balashev , Daria Kosenko

The main goal of this analysis is to present a new method to estimate the physical properties of diffuse cloud of atomic hydrogen observed at high Galactic latitude. This method, based on a comparison of the observations with fractional…

Astrophysics · Physics 2009-11-13 Marc-Antoine Miville-Deschenes , Peter G. Martin

We present new high-precision measurements of the opacity of the intergalactic and circumgalactic medium (IGM, CGM) at <z>=2.4. Using Voigt profile fits to the full Lyman alpha and Lyman beta forests in 15 high-resolution high-S/N spectra…

Cosmology and Nongalactic Astrophysics · Physics 2015-06-15 Gwen C. Rudie , Charles C. Steidel , Alice E. Shapley , Max Pettini

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

We report deep, high spectral resolution WSRT HI 21cm observations of four high latitude compact radio sources, that have revealed a new population of tiny, discrete clouds in the diffuse ISM, with peak optical depths tau ~ 0.1-2%, HI…

Astrophysics · Physics 2009-11-11 Robert Braun , Nissim Kanekar

Much of the interstellar medium in disk galaxies is in the form of neutral atomic hydrogen, H I. This gas can be in thermal equilibrium at relatively low temperatures, T < 300 K (the cold neutral medium, or CNM) or at temperatures somewhat…

Astrophysics · Physics 2009-11-07 M. G. Wolfire , C. F. McKee , D. Hollenbach , A. G. G. M. Tielens

We present dust column densities and dust temperatures for $\sim3000$ young high-mass molecular clumps from the Millimetre Astronomy Legacy Team 90 GHz (MALT90) survey, derived from adjusting single temperature dust emission models to the…

Solar and Stellar Astrophysics · Physics 2015-12-24 Andrés E. Guzmán , Patricio Sanhueza , Yanett Contreras , Howard A. Smith , James M. Jackson , Sadia Hoq , Jill M. Rathborne

The smallest polyatomic carbon chain, C$_{3}$, has been identified in interstellar clouds (A$_{v}\sim$1 mag) towards $\zeta$ Ophiuchi, 20 Aquilae, and $\zeta$ Persei by detection of the origin band in its $A^{1}\Pi_{u}-X^{1}\Sigma^{+}_{g}$…

Astrophysics · Physics 2009-11-06 J. P. Maier , N. M. Lakin , G. A. H. Walker , D. A. Bohlender

(Abridged) Using the Arecibo Observatory we have obtained neutral hydrogen (HI) absorption and emission spectral pairs in the direction of 26 background radio continuum sources in the vicinity of the Perseus molecular cloud. Strong…

Astrophysics of Galaxies · Physics 2015-06-22 Snezana Stanimirovic , Claire E. Murray , Min-Young Lee , Carl Heiles , Jesse Miller

We present a study of the cold atomic hydrogen (HI) content of molecular clouds simulated within the SILCC-Zoom project. We produce synthetic observations of HI at 21 cm including HI self-absorption (HISA) and observational effects. We find…

Astrophysics of Galaxies · Physics 2022-03-14 D. Seifried , H. Beuther , S. Walch , J. Syed , J. D. Soler , P. Girichidis , R. Wünsch

We present first results of neutral carbon ([CI], 3P1 - 3P0 at 492 GHz) and carbon monoxide (13CO, J = 1 - 0) mapping in the Vela Molecular Ridge cloud C (VMR-C) and G333 giant molecular cloud complexes with the NANTEN2 and Mopra…

Astrophysics of Galaxies · Physics 2015-06-23 N. Lo , M. R. Cunningham , P. A. Jones , L. Bronfman , P. C. Cortes , R. Simon , V. Lowe , L. Fissel , G. Novak

We interpret observations of intergalactic low ionisation metal absorption systems at redshifts z $\gtrsim$5 in terms of pressure-confined clouds. We find clouds confined by the expected pressure of galactic haloes with masses $11<\log…

Cosmology and Nongalactic Astrophysics · Physics 2021-01-27 Teresita Suarez , Avery Meiksin

The transition from the diffuse warm neutral medium (WNM) to the dense cold neutral medium (CNM) is what set the initial conditions to the formation of molecular clouds. The properties of the turbulent cascade in the WNM, essential to…

Astrophysics of Galaxies · Physics 2021-03-03 Antoine Marchal , Marc-Antoine Miville-Deschênes

We have carried out an extremely long integration-time (9000 s/beam) 21-cm blind survey of 60 square degrees in Centaurus using the Parkes multibeam system. We find that the noise continues to fall as sqrt(t) throughout, enabling us to…

We discuss physical conditions in Galactic neutral hydrogen based on deep, high velocity resolution interferometric HI 21 cm absorption spectroscopy towards 33 compact extra-galactic radio sources. The HI 21 cm optical depth spectra have…

Astrophysics of Galaxies · Physics 2014-07-30 Nirupam Roy , Nissim Kanekar , Jayaram N. Chengalur

An intriguing fact about cosmic gas clouds is that they all appear to have neutral (atomic) hydrogen column densities smaller than 10^{22} cm^{-2}. Observations of damped Ly-alpha (DLA) absorption systems further indicate that the maximum…

Astrophysics · Physics 2009-11-07 Joop Schaye

The high-latitude Galactic H I cloud toward the extragalactic radio source 3C 225 is characterized by very narrow 21 cm emission and absorption indicative of a very low H I spin temperature of about 20 K. Through high-resolution optical…

Astrophysics · Physics 2009-11-11 David M. Meyer , J. T. Lauroesch , Carl Heiles , J. E. G. Peek , Kyle Engelhorn

We present deep HI observations of the compact high-velocity cloud HVC125+41-207 using the 100-m Effelsberg telescope. Our goal was in particular to study the warm neutral medium (WNM) in detail. The Effelsberg data reveal a two phase…

Astrophysics · Physics 2009-11-06 C. Bruens , J. Kerp , A. Pagels