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We update the HI surface density measurements for a subset of 17 THINGS galaxies by dealing with the short-spacing problem of the original VLA HI images. It is the same sample that Bigiel et al. (2010) used to study the relation between HI…

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

We have obtained VLA and optical follow-up observations of the low-velocity H I source HIZSS 3 discovered by Henning et al. (2000) and Rivers (2000) in a survey for nearby galaxies hidden by the disk of the Milky Way. Its radio…

Astrophysics · Physics 2009-11-10 Philip Massey , P. A. Henning , R. C. Kraan-Korteweg

A number of very small isolated HII regions have been discovered at projected distances up to 30 kpc from their nearest galaxy. These HII regions appear as tiny emission line objects in narrow band images obtained by the NOAO Survey for…

About 20 percent of all nearby early-type galaxies ($M_{\star} \gtrsim 6 \times 10^{9}$ M$_{\odot}$) outside the Virgo cluster are surrounded by a disc or ring of low-column-density neutral hydrogen (HI) gas with typical radii of tens of…

Astrophysics of Galaxies · Physics 2016-10-26 Mustafa K. Yıldız , Paolo Serra , Reynier F. Peletier , Tom A. Oosterloo , Pierre-Alain Duc

We suggest that the high--velocity clouds (HVCs) are large clouds, with typical diameters of 25 kpc and containing 5e7 solar masses of neutral gas and 3e8 solar masses of dark matter, falling onto the Local Group; altogether the HVCs…

Astrophysics · Physics 2010-11-23 Leo Blitz , David N. Spergel , Peter J. Teuben , Dap Hartmann , W. Butler Burton

The radial profiles of gas, stars, and far ultraviolet radiation in 20 dwarf Irregular galaxies are converted to stability parameters and scale heights for a test of the importance of two-dimensional (2D) instabilities in promoting star…

Astrophysics of Galaxies · Physics 2015-06-03 Bruce G. Elmegreen , Deidre A. Hunter

Aims: We derive the 3-D HI volume density distribution for the Galactic disk out to R = 60 kpc. Methods: Our analysis is based on parameters for the warp and rotation curve derived previously. The data are taken from the…

Astrophysics · Physics 2015-05-13 P. M. W. Kalberla , L. Dedes

A recent survey of the Galaxy and M31 reveals that more than 90% of dwarf galaxies within 270 kpc of their host galaxy are deficient in HI gas. At such an extreme radius, the coronal halo gas is an order of magnitude too low to remove HI…

Astrophysics of Galaxies · Physics 2015-05-27 Matthew Nichols , Joss Bland-Hawthorn

We use spectroscopic data from HST and FUSE to study the wide range of ionization states of the "highly ionized high-velocity clouds". Studied extensively in OVI absorption, these clouds are usually assumed to be infalling gas in the…

Astrophysics · Physics 2009-11-10 J. A. Collins , J. M. Shull , M. L. Giroux

While massive quiescent galaxies are known to be poor in atomic hydrogen (HI), their true HI content remains poorly constrained due to the limited sensitivity and morphological biases of existing surveys. We present deep HI observations…

Astrophysics of Galaxies · Physics 2025-10-20 Xiao Li , Cheng Li , Cheng Cheng , Houjun Mo , Jing Wang , Amélie Saintonge

Sensitive 21cm HI line observations were performed for 23 dwarf members and possible members of the nearby M81 group of galaxies, including five objects of a clustering of extremely low-surface brightness objects of unknown nature. With the…

Astrophysics · Physics 2007-05-23 W. van Driel , R. C. Kraan-Korteweg , B. Binggeli , W. K. Huchtmeier

We estimate the evaporation timescale for spherical HI clouds consisting of the cold neutral medium surrounded by the warm neutral medium. We focus on clouds smaller than 1pc, which corresponds to tiny HI clouds recently discovered by Braun…

Astrophysics · Physics 2009-11-11 Masahiro Nagashima , Shu-ichiro Inutsuka , Hiroshi Koyama

We compare the gas distribution, kinematics and the current star formation in a sample of 10 very faint (-13.37 < M_B < -9.55) dwarf galaxies. For 5 of these galaxies we present fresh, high sensitivity, GMRT HI 21cm observations. For all…

We derive the molecular properties for a sample of 301 Galactic HII regions including 123 ultra compact (UC), 105 compact, and 73 diffuse nebulae. We analyze all sources within the BU-FCRAO Galactic Ring Survey (GRS) of 13CO emission known…

Multiple SN explosions in disk galaxies efficiently evacuate gas and form cavities with the sizes and shapes of the surrounding envelopes determined by the total amount of injected energy and by the initial gas distribution. Such cavities…

Astrophysics · Physics 2009-11-10 E. I. Vorobyov , Yu. A. Shchekinov

We present empirical HII region oxygen abundances for a sample of low-luminosity starburst galaxies which are in a short lived evolutionary state. All five galaxies are characterized by centrally concentrated star formation, which is…

Astrophysics · Physics 2011-02-11 K. E. Dellenbusch , J. S. Gallagher , P. M. Knezek

We present Australia Telescope Compact Array mosaic HI imaging of the Local Group dwarf irregular galaxy WLM. We find an integrated flux of 149 Jy km/s and a total HI mass of 3.2 x 10^7 solar masses. The major axis of the HI is aligned with…

Astrophysics · Physics 2009-11-10 Dale C. Jackson , Evan D. Skillman , John M. Cannon , Stephanie Cote

We present a method to derive the dynamical mass of face-on galaxy disks using their neutral hydrogen (HI) velocity dispersion. We have applied the method to nearby, gas rich galaxies that have extended HI gas disks and have low…

Astrophysics of Galaxies · Physics 2020-02-05 Mousumi Das , Stacy McGaugh , Roger Ianjamasimanana , James Schombert , K. S. Dwarakanath

Galaxies are thought to grow through accretion; as less massive galaxies are disrupted and merge over time, their debris results in diffuse, clumpy stellar halos enveloping the central galaxy. Here we present a study of the variation in the…

Astrophysics of Galaxies · Physics 2016-10-19 Allison Merritt , Pieter van Dokkum , Roberto Abraham , Jielai Zhang