Related papers: The HI absorption "Zoo"

One of the most important problems in the study of AGN is understanding the detailed geometry, physics, and evolution of the central engines and their environments. The leading models involve an accretion disk and torus around a central…

We present the results of a 21-cm HI survey of 27 local massive gas-rich late-stage mergers and merger remnants with the Robert C. Byrd Green Bank Telescope (GBT). These remnants were selected from the Quasar/ULIRG Evolution Study (QUEST)…

Obscuration of quasars by accreted gas and dust, or dusty intervening galaxies, can cause active galactic nuclei (AGN) to be missed in optically-selected surveys. Radio observations can overcome this dust bias. In particular, radio surveys…

In order to find more examples of the elusive high-redshift molecular absorbers, we have embarked on a systematic discovery program for highly obscured, radio-loud "invisible AGN" using the VLA Faint Images of the Radio Sky at Twenty…

We present results of a blind search for Galactic HI 21-cm absorption lines toward 19130 radio sources, using 390 pointings of MALS, each pointing centered on a source brighter than 200 mJy. We detected 3640 HI absorption features. This…

We report the detection of HI 21-cm absorption in a member of the rare and recently discovered class of compact radio sources, 'Extremely Inverted Spectrum Extragalactic Radio Sources (EISERS)'. EISERS conceivably form a special sub-class…

A high latitude HI 21 cm-line absorption survey toward extragalactic sources was recently completed using the Giant Meterwave Radio Telescope (GMRT). A total of 104 sources with mod(b) > 15 deg. and with a 21 cm flux density greater than 1…

High-redshift radio galaxies (HzRGs) are among the most massive galaxies in the Universe and sites of extreme active galactic nuclei (AGN) feedback processes, powering energetic radio jets. They are typically embedded in giant Ly$\alpha$…

At low radio frequencies (< 100 MHz), classical HII regions may become optically thick (optical depth > 1) and can be observed as discrete absorption regions against the Galactic nonthermal background emission created by Galactic cosmic ray…

We present a summary of recent studies of HI absorption in radio galaxies. The results show how the absorption can be due to a variety of phenomena and how they can help us in understanding more of what is happening in and around AGNs.

We present global VLBI observations of the 21-cm transition of atomic hydrogen seen in absorption against the radio source J0855+5751. The foreground absorber (SDSS~J085519.05+575140.7) is a dwarf galaxy at $z$ = 0.026. As the background…

We present a homogeneous compilation of HI spectral parameters extracted from global 21 cm line spectra for some 9000 galaxies in the local universe (heliocentric velocity -200 < V_Sun < 28,000 km/s) obtained with a variety of large single…

Our work is based on the "Bluedisk" project, a program to map the neutral gas in a sample of 25 HI-rich spirals and a similar number of control galaxies with the Westerbork Synthesis Radio Telescope (WSRT). In this paper we focus on the HI…

VLA observations of large-scale HI and OH absorption in the merging galaxy of NGC6240 are presented with 1 arcsec resolution. HI absorption is found across large areas of the extended radio continuum structure with a strong concentration…

We perform an HI stacking analysis to study the relation between HI content and optical/radio/IR properties of galaxies located in the Lockman Hole area. In the redshift range covered by the observations (up to z = 0.09), we use the SDSS to…

Observations of neutral hydrogen can provide a wealth of information about the kinematics of galaxies. To learn more about the large scale structures and accretion processes, the extended environment of galaxies have to be observed.…

Fast radio bursts (FRBs) emit broad band radio wave radiation that may, in rare cases, encode atomic hydrogen (HI) absorption signals produced as they traverse the interstellar medium of their host galaxies. Combining such signals with high…

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…

Our view of the central regions of AGN has been enriched by the discovery of fast and massive outflows of HI and molecular gas. Here we present a brief summary of results obtained for young (and restarted) radio AGN. We find that HI…

Existing studies of the atomic hydrogen gas content in distant galaxies, through the absorption of the 21-cm line, often infer that the total column density is anti-correlated with the linear extent of the background radio source. We…