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Various scenarios have been proposed to explain the origin of the Galactic high-velocity clouds, predicting different distances and implying widely varying properties for the Galaxy's gaseous halo. To eliminate the difficulties of studying…

Astrophysics · Physics 2007-05-23 Eric D. Miller , Joel N. Bregman

Aperture synthesis observations of two HI cloud complexes located in the periphery of the Virgo galaxy cluster are presented. These low HI-mass clouds ($M_{HI}<$ 10$^{9}$) are seen projected on the M region of the western Virgo cluster,…

Cosmology and Nongalactic Astrophysics · Physics 2015-05-20 Brian R. Kent

(abridged) We present the HIPASS Bright Galaxy Catalog (BGC) which contains the 1000 HI-brightest galaxies in the southern sky as obtained from the HI Parkes All-Sky Survey (HIPASS). The selection of the brightest sources is based on their…

We present a detailed analysis of the neutral hydrogen kinematics of 12 nearby dwarf irregular galaxies observed as part of the Local Volume HI Survey (LVHIS) conducted at the Australia Telescope Compact Array. For each galaxy we measure…

Cosmology and Nongalactic Astrophysics · Physics 2015-06-04 Emma M. Kirby , Baerbel Koribalski , Helmut Jerjen , Angel Lopez-Sanchez

Arecibo mapping is reported of the neutral hydrogen distribution along selected directions out from the centers of two small High Velocity Clouds (HVC), W486 and W491. Both HVCs have a small inner region where the neutral hydrogen column…

Astrophysics · Physics 2009-11-07 G. L. Hoffman , E. E. Salpeter , M. G. Pocceschi

Compact high-velocity clouds (CHVCs) are the most distant of the HVCs in the Local Group model and would have HI volume densities of order 0.0003/cm^3. Clouds with these volume densities and the observed neutral hydrogen column densities…

Astrophysics · Physics 2009-11-07 Philip R. Maloney , Mary E. Putman

We present a systematic study of the extraplanar gas (EPG) in a sample of 15 nearby late-type galaxies at intermediate inclinations using publicly available, deep interferometric HI data from the HALOGAS survey. For each system we mask the…

We present a catalog of 1964 isolated, compact neutral hydrogen clouds from the Galactic Arecibo L-Band Feed Array Survey Data Release One (GALFA-HI DR1). The clouds were identified by a custom machine-vision algorithm utilizing Difference…

We present a wide (8.5x6.7 degree, 1050x825 kpc), deep (sigma(N_HI)=10^(16.8-17.5) cm^-2) neutral hydrogen (HI) map of the M101 galaxy group. We identify two new HI sources in the group environment, one an extremely low surface brightness…

Cosmology and Nongalactic Astrophysics · Physics 2015-06-11 Chris Mihos , Katie Keating , Kelly Holley-Bockelmann , D. J. Pisano , Namir Kassim

The Arecibo Legacy Fast ALFA survey is in the process of yielding a complete HI dataset of the Virgo Cluster and its environs (Giovanelli et al. 2007, Kent et al., in preparation). Assuming a distance to Virgo of 16.7 Mpc, the minimum…

Astrophysics · Physics 2009-11-13 Brian R. Kent

High Velocity Clouds (HVCs) have recently attracted renewed attention as being long lived, massive dark matter dominated clouds of primordial composition distributed throughout the Local Group. In this picture the HVCs would contain a few…

Astrophysics · Physics 2007-05-23 Martin A. Zwaan

In this paper, we report the peculiar HI morphology of the cluster spiral galaxy NGC 6145, which has a 150 kpc HI filament on one side that is nearly parallel to its major axis. This filament is made up of several HI clouds and the diffuse…

Astrophysics of Galaxies · Physics 2017-08-02 Enci Wang , Jing Wang , Xu Kong , Fulai Guo , Lin Lin , Guobin Mou , Cheng Li , Ting Xiao

A blind survey for HI bright galaxies in the southern Zone of Avoidance, (212 deg < l < 36 deg; |b| < 5 deg), has been made with the 21 cm multibeam receiver on the Parkes 64 m radiotelescope. The survey, sensitive to normal spiral galaxies…

We discovered two small high-velocity compact clouds (HVCCs) in HCN $J=4-3$ and $J=3-2$ maps of the central 20 pc of our Galaxy. Both HVCCs have broad velocity widths ($\Delta V \gtrsim 40$ km s$^{-1}$) and compact sizes ($d\sim 1$ pc), and…

Astrophysics of Galaxies · Physics 2017-07-19 Shunya Takekawa , Tomoharu Oka , Yuhei Iwata , Sekito Tokuyama , Mariko Nomura

We present VLA 21-cm observations of the spiral galaxy ESO 481-G017 to determine the nature of remote star formation traced by an HII region found 43 kpc and ~800 km s^-1 from the galaxy center (in projection). ESO 481-G017 is found to have…

Cosmology and Nongalactic Astrophysics · Physics 2015-05-30 Nitza Santiago-Figueroa , Mary E. Putman , Jessica Werk , Gerhardt R. Meurer , Emma Ryan-Weber

New 21cm HI observations made with the Green Bank Telescope show that the high-velocity cloud known as Smith's Cloud has a striking cometary appearance and many indications of interaction with the Galactic ISM. The velocities of interaction…

Astrophysics · Physics 2009-11-13 Felix J. Lockman , Robert A. Benjamin , A. J. Heroux , Glen I. Langston

We present an analysis of the sky distribution of neutral hydrogen (HI) deficiency and spectral asymmetry for galaxies detected by the HI Parkes All-Sky Survey (HIPASS) as a function of projected environment density. Previous studies of…

Astrophysics of Galaxies · Physics 2020-10-21 T. N. Reynolds , T. Westmeier , L. Staveley-Smith

The HI Parkes All Sky Survey (HIPASS) is a blind extragalactic HI 21-cm emission line survey covering the whole southern sky from declination -90 to +25. The HIPASS catalogue (HICAT), containing 4315 HI-selected galaxies from the region…

Recent observations in the 21cm line with the Green Bank Telescope have changed our view of the neutral interstellar medium (ISM) in several ways. The new data show that in the inner parts of the Milky Way the disk-halo interface is…

Astrophysics · Physics 2015-06-24 Felix J. Lockman