Related papers: Ultra-Compact High Velocity Clouds as Minihalos an…

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…

A small survey of the UV-absorbing gas in 12 low-$z$ galaxy groups has been conducted using the Cosmic Origins Spectrograph (COS) on-board the Hubble Space Telescope (HST). Targets were selected from a large, homogeneously-selected sample…

The gas content of the complete compilation of Local Group dwarf galaxies (119 within 2 Mpc) is presented using HI survey data. Within the virial radius of the Milky Way (224 kpc here), 53 of 55 dwarf galaxies are devoid of gas to limits of…

The recent discovery of thousands of ultra diffuse galaxies (UDGs) in nearby galaxy clusters has opened a new window into the process of galaxy formation and evolution. Several scenarios have been proposed to explain the formation history…

We present a pilot survey of 21 lines of sight towards UCHII regions in the H2CO 1-1 (6cm) and 2-2 (2cm) transitions, using the H2CO centimeter lines as a molecular gas densitometer. Using Arecibo and Green Bank beam-matched observations,…

A head-tail high-velocity cloud (HVC) is a neutral hydrogen halo cloud that appears to be interacting with the diffuse halo medium as evident by its compressed head trailed by a relatively diffuse tail. This paper presents a sample of 116…

Aims: we studied the global distribution and kinematics of the extra-planar neutral gas in the Milky Way. Methods: we built 3D models for a series of Galactic HI layers, projected them for an inside view, and compared them with the…

We have conducted an HI 21 cm emission-line survey of six loose groups of galaxies chosen to be analogs to the Local Group. The survey was conducted using the Parkes Multibeam instrument and the Australia Telescope Compact Array (ATCA) over…

We have conducted an HI 21 cm emission-line survey using the Parkes 20cm multibeam instrument and the Australia Telescope Compact Array (ATCA) of six loose groups of galaxies chosen to be analogs to the Local Group. The goal of this survey…

We report on the detection of low-column density neutral hydrogen clumps in the halo of the Milky Way. Using high-resolution (FWHM~7 km/s) optical spectra obtained with the VLT/UVES spectrograph we detect narrow interstellar absorption by…

We present results from ground-based optical imaging of a low-mass dwarf galaxy discovered by the ALFALFA 21-cm HI survey. Broadband (BVR) data obtained with the WIYN 3.5-m telescope at Kitt Peak National Observatory (KPNO) are used to…

The Arecibo HI Strip Survey probed the halos of ~300 cataloged galaxies and the environments of ~14 groups with sensitivity to neutral hydrogen masses > 10^7 M_sun. The survey detected no objects with properties resembling the High Velocity…

We have detected over 400 HI clouds in the lower halo of the Galaxy within the pilot region of the Galactic All-Sky Survey (GASS), a region of the fourth quadrant that spans 18 degrees in longitude, 40 degrees in latitude and is centered on…

We evaluate recent and upcoming low-redshift neutral hydrogen (HI) surveys as a cosmological probe of small scale structure with a goal of determining the survey criteria necessary to test ultra-light axion (ULA) dark matter models.…

Current explanation of the overabundance of dark matter subhalos in the Local Group (LG) indicates that there maybe a limit on mass of a halo, which can host a galaxy. This idea can be tested using voids in the distribution of galaxies: at…

We present the results of the spectroscopic and photometric follow-up of two field galaxies that were selected as possible stellar counterparts of local high velocity clouds. Our analysis shows that the two systems are distant (D>20 Mpc)…

VIRGOHI21 is an HI source detected in the Virgo Cluster survey of Davies et al. (2004) which has a neutral hydrogen mass of 10^8 M_solar and a velocity width of Delta V_20 = 220 km/s. From the Tully-Fisher relation, a galaxy with this…

The VLA Galactic Plane Survey (VGPS) of the first Galactic quadrant was searched for HI emission with velocities well above the maximum velocity allowed by Galactic rotation. A sample of 17 small fast-moving clouds was identified. The…

We present Keck/DEIMOS spectroscopy of the first complete sample of ultra-diffuse galaxies (UDGs) in the Virgo cluster. We select all UDGs in Virgo that contain at least 10 globular cluster (GC) candidates and are more than $2.5\sigma$…

We present results from our Parkes Multibeam HI survey of 3 loose groups of galaxies that are analogous to the Local Group. This is a survey of groups containing only spiral galaxies with mean separations of a few hundred kpc, and total…