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We present deep HI 21-cm and optical observations of the face-on spiral galaxy M 83 obtained as part of a project to search for high-velocity clouds (HVCs) in nearby galaxies. Anomalous-velocity neutral gas is detected toward M 83, with…

Astrophysics · Physics 2011-02-11 Eric D. Miller , Joel N. Bregman , Bart P. Wakker

The discovery of a previously unknown 21cm HI line source identified as an ultra-compact high velocity cloud in the ALFALFA survey is reported. The HI detection is barely resolved by the Arecibo 305m telescope ~4' beam and has a narrow HI…

The HI mass function (HIMF) for galaxies in the local universe is constructed from the results of the Arecibo HI Strip Survey, a blind extragalactic survey in the 21cm line. The survey consists of two strips covering in total 65 square…

Astrophysics · Physics 2009-10-30 Martin Zwaan , Frank Briggs , David Sprayberry , Ertu Sorar

New 21 cm HI observations have revealed a giant HI cloud in the Galactic plane that has unusual properties. It is quite well defined, about 150 pc in diameter at a distance of 5 kpc, and contains as much as 100,000 Solar Masses of atomic…

Astrophysics · Physics 2009-11-06 Anthony H. Minter , Felix J. Lockman , Glen I. Langston , Jennifer A. Lockman

The presence of HI gas in galaxies is inextricably linked to their morphology and evolution. This paper aims to understand the HI content of the already identified 2210 dwarfs located in the low-to-moderate density environments of the…

A sample of 69 galaxies with radial velocities less than 2500 km/s was selected from the HI Parkes All Sky Survey (HIPASS) to deduce details about star formation in nearby disk galaxies selected with no bias to optical surface brightness…

Astrophysics · Physics 2009-11-11 J. F. Helmboldt , R. A. M. Walterbos , G. D. Bothun , K. O'Neil

Dwarf irregular galaxies are unique laboratories for studying the interaction between stars and the interstellar medium in low mass environments. We present the highest spatial resolution observations to date of the neutral hydrogen content…

Astrophysics · Physics 2009-11-13 Amanda Kepley , Eric Wilcots , Deidre Hunter , Tyler Nordgren

We used the $H\alpha$ images from a large sample of nearby late-type dwarf galaxies to investigate properties of their emission structure. The sample consists of three hundred galaxies of the irregular (Irr), Magellanic irregular (Im), blue…

Astrophysics of Galaxies · Physics 2020-12-16 Karachentsev I. D. , Kaisin S. S

Dwarf irregulars (dIrrs) are among the most common type of galaxy in the Universe. They typically have gas-rich, low surface-brightness, metal-poor, and relatively-thick disks. Here we summarize the current state of our knowledge of the…

Astrophysics of Galaxies · Physics 2024-02-28 Deidre A. Hunter , Bruce G. Elmegreen , Suzanne C. Madden

An extended HI cloud (VIRGOHI 21) with an HI mass of $\sim10^8$ M$_{\odot}$ and no apparent optical counterpart was recently discovered in the Virgo cluster. In order to understand the origin of physical properties of apparently isolated HI…

Astrophysics · Physics 2009-11-11 Kenji Bekki , Baerbel S. Koribalski , Virginia A. Kilborn

We have carefully selected a sample of 60 galaxies that reside in the deepest underdensities of geometrically identified voids within the SDSS. HI imaging of 55 galaxies with the WSRT reveals morphological and kinematic signatures of…

Cosmology and Nongalactic Astrophysics · Physics 2015-06-04 K. Kreckel , E. Platen , M. A. Aragón-Calvo , J. H. van Gorkom , R. van de Weygaert , J. M. van der Hulst , B. Beygu

Five galaxy groups with properties similar to those of the Local Group have been surveyed for HI clouds with the Arecibo Telescope. In total 300 pointings have been observed on grids of approximately 2.5 x 1.5 Mpc centred on the groups. The…

Astrophysics · Physics 2009-11-06 Martin Zwaan

We discuss the morphology and kinematics of the HI of a sample of 30 southern gas-rich early-type galaxies selected from the HI Parkes All-Sky Survey (HIPASS). This is the largest collection of high-resolution HI data of a homogeneously…

Astrophysics · Physics 2009-11-13 T. Oosterloo , R. Morganti , E. M. Sadler , J. M. van der Hulst , P. Serra

Very sensitive 21cm HI measurements have been made at several locations around the Local Group galaxy M31 using the Green Bank Telescope (GBT) at an angular resolution of 9.1', with a 5$\sigma$ detection level of $\rm{N_{HI} = 3.9 \times…

Astrophysics of Galaxies · Physics 2016-01-27 Spencer A. Wolfe , Felix J. Lockman , D. J. Pisano

Growing evidence supports the suggestion that the compact high-velocity clouds of HI (CHVCs) are located throughout the Local Group and continue to fuel galactic evolution. Recent distance estimates to individual objects lie in the range…

Astrophysics · Physics 2009-10-31 Robert Braun , W. Butler Burton

The Galactic Arecibo L-band Feed Array HI (GALFA-HI) survey is mapping the entire Arecibo sky at 21-cm, over a velocity range of -700 to +700 km/s (LSR), at a velocity resolution of 0.18 km/s and a spatial resolution of 3.5 arcmin. The…

We have obtained new HI observations with the 100m Green Bank Telescope (GBT) for a sample of 29 extremely metal-deficient star-forming Blue Compact Dwarf (BCD) galaxies, selected from the Sloan Digital Sky Survey spectral data base to be…

Astrophysics of Galaxies · Physics 2023-05-03 T. X. Thuan , K. M. Goehring , J. E. Hibbard , Y. I. Izotov , L. K. Hunt

{We report the discovery of 20 new dwarf galaxies in the Local Volume identified as optical counterparts to the Five-hundred-meter Aperture Spherical radio Telescope (FAST) All Sky HI Survey (FASHI) sources. The galaxies have a median…

Astrophysics of Galaxies · Physics 2024-05-01 Igor D. Karachentsev , Valentina E. Karachentseva , Serafim S. Kaisin , Chuan-Peng Zhang

Gas velocity dispersions provide important diagnostics of the forces counteracting gravity to prevent collapse of the gas. We use the 21 cm line of neutral atomic hydrogen (HI) to study HI velocity dispersion and HI phases as a function of…

Astrophysics of Galaxies · Physics 2015-08-06 R. Ianjamasimanana , W. J. G. de Blok , Fabian Walter , George H. Heald , Anahi Caldu-Primo , Thomas H. Jarrett

We analyze the radial distribution of HI gas for 23 disk galaxies with unusually high HI content from the Bluedisk sample, along with a similar-sized sample of "normal" galaxies. We propose an empirical model to fit the radial profile of…