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Molecular hydrogen clouds are a key component of the interstellar medium because they are the birthplaces for stars. They are embedded in atomic gas that pervades the interstellar space. However, the details of how molecular clouds assemble…

We present the largest Galactic neutral hydrogen HI absorption survey to date, utilizing the Australian SKA Pathfinder Telescope at an unprecedented spatial resolution of 30''. This survey, GASKAP-HI, unbiasedly targets 2,714 continuum…

We present HI observations of the compact high-velocity cloud HVC289+33+251 that was discovered by Putman et al. (2002). Observations with the 100-m Effelsberg telescope demonstrate that this cloud is still unresolved by the 9' beam of the…

Astrophysics · Physics 2011-08-23 C. Bruens , T. Westmeier

In order to investigate the contribution of diffuse components to their total HI emission, we have obtained high precision HI line flux densities with the 100m Green Bank Telescope for a sample of 100 isolated spiral and irregular galaxies…

Astrophysics · Physics 2008-11-26 David E. Hogg , Morton S. Roberts , Martha P. Haynes , Ronald J. Maddalena

We present measurements of the H I spin temperatures (T_s) of the Cold Neutral Medium (CNM) towards radio sources that are closely aligned with stars for which published H_2 ortho-para temperatures (T_{01}) are available from UV…

Astrophysics · Physics 2007-05-23 Nirupam Roy , Jayaram N. Chengalur , Raghunathan Srianand

The G11.11-0.12 Infrared-Dark Cloud has a filamentary appearance, both in absorption against the diffuse 8micron Galactic background, and in emission from cold dust at 850micron. Detailed comparison of the dust properties at these two…

Astrophysics · Physics 2009-11-07 Doug Johnstone , Jason Fiege , R. O. Redman , P. A. Feldman , Sean J. Carey

We present a census of neutral gas in the Milky Way disk and halo down to limiting column densities of $N$(HI)$\sim10^{14}$ cm$^{-2}$ using measurements of HI Lyman-series absorption from the Far Ultraviolet Spectroscopic Explorer (FUSE).…

We develop a new method to constrain the physical conditions in the cool (~10^4 K) circumgalactic medium (CGM) from measurements of ionic column densities, by assuming that the cool CGM spans a large range of gas densities and that small…

Astrophysics of Galaxies · Physics 2016-10-26 Jonathan Stern , Joseph F. Hennawi , J. Xavier Prochaska , Jessica K. Werk

We employ three-band Spitzer-MIPS observations to search for cold dust emission in three neutral hydrogen compact high-velocity clouds (CHVCs) in the vicinity of the Milky Way. Far-infrared emission correlated with HI column density was…

Astrophysics of Galaxies · Physics 2012-03-06 Rik J. Williams , Smita Mathur , Shawn Poindexter , Martin Elvis , Fabrizio Nicastro

We have recently used the Hubble Space Telescope to study a pair of high velocity clouds in the direction of Mrk 509 that have unusual ionization properties. They exhibit strong CIV absorption with little or no low ion absorption or HI 21cm…

Astrophysics · Physics 2007-05-23 Kenneth R. Sembach , Blair D. Savage , Limin Lu , Edward M. Murphy

A model is proposed for determining the distances to falling interstellar clouds in the galactic halo by measuring the cloud velocity and column density and assuming a model for the vertical density distribution of the Galactic interstellar…

Astrophysics · Physics 2009-10-28 Robert A. Benjamin , Laura Danly

We have studied 14 southern infrared dark clouds (IRDCs) using the data taken from the Millimetre Astronomy Legacy Team 90 GHz (MALT90) survey and the GLIMPSE and MIPSGAL mid-infrared survey of the inner Galaxy. The physical and chemical…

Astrophysics of Galaxies · Physics 2015-06-12 Xiao-Lan Liu , Jun-Jie Wang , Jin-Long Xu

We present a multi-wavelength study of the local Leo cold cloud (LLCC), a very nearby, very cold cloud in the interstellar medium. Through stellar absorption studies we find that the LLCC is between 11.3 pc and 24.3 pc away, making it the…

Astrophysics of Galaxies · Physics 2015-05-28 J. E. G. Peek , Carl Heiles , Kathryn M. G. Peek , David M. Meyer , J. T. Lauroesch

We present search results of 22 high latitude (b > 25 deg.) sightlines for OH 18-cm emission using the 305-m radio telescope at the Arecibo Observatory. These sightlines appear in neutral hydrogen emission at intermediate velocities (V_lsr…

Astrophysics of Galaxies · Physics 2023-05-10 Allison Smith , D. Anish Roshi

We carried out synthetic observations of a theoretical model of interstellar carbon in CO, C I and C II including H2 formation. The theoretical model based on numerical simulations of H I gas converging at a velocity of 20 km/s by Inoue &…

Astrophysics of Galaxies · Physics 2018-11-07 Kengo Tachihara , Yasuo Fukui , Takahiro Hayakawa , Tsuyoshi Inoue

We investigate the possible presence of neutral hydrogen (HI) in intergalactic filaments at very low redshift ($z\sim 0.08$), by stacking a set of 274,712 2dFGRS galaxy pairs over 21-cm maps obtained with dedicated observations conducted…

Cosmology and Nongalactic Astrophysics · Physics 2019-08-14 Denis Tramonte , Yin-Zhe Ma , Yi-Chao Li , Lister Staveley-Smith

(Abridged) We have observed CS and C17O lines, and 1.2 mm cont. emission towards a sample of 130 high-mass protostellar candidates with DEC<-30 deg. This is the first step of the southern extension of a project started more than a decade…

Astrophysics · Physics 2009-11-10 F. Fontani , M. T. Beltran , J. Brand , R. Cesaroni , L. Testi , S. Molinari , C. M. Walmsley

Infrared Dark Clouds appear to be the long sought population of cold and dense aggregations with the potential of harbouring the earliest stages of massive star formation. Up to now there has been no systematic study on the temperature…

Astrophysics · Physics 2009-11-11 Thushara Pillai , Friedrich Wyrowski , Sean J. Carey , Karl M. Menten

Far Ultraviolet Spectroscopic Explorer (FUSE) data is used to investigate the molecular hydrogen (H_2) content of intermediate-velocity clouds (IVCs) in the lower halo of the Milky Way. We analyze interstellar absorption towards 56 (mostly…

Astrophysics · Physics 2009-11-07 P. Richter , B. P. Wakker , B. D. Savage , K. R. Sembach

We present a search for infrared dust emission associated with the Leo cloud, a large intergalactic cloud in the M96 group. Mid-infrared and far-infrared images were obtained with IRAC and MIPS on the Spitzer Space Telescope. Our analysis…

Cosmology and Nongalactic Astrophysics · Physics 2015-05-13 C. Bot , G. Helou , W. B. Latter , J. Puget , S. Schneider , Y. Terzian
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