Related papers: Cold gas, the HI 21cm line and evolving galactic p…
We have carried out a sensitive high-latitude (|b| > 15deg.) HI 21cm-line absorption survey towards 102 sources using the GMRT. With a 3-sigma detection limit in optical depth of ~0.01, this is the most sensitive HI absorption survey. We…
The atomic hydrogen (HI) 21cm line measures the gas content within and around galaxies, traces the dark matter potential and probes volumes and objects that other surveys do not. Over the next decade, 21cm line science will exploit new…
Unlike the neutral gas density, which remains largely constant over redshifts of 0 < z < 5, the star formation density exhibits a strong redshift dependence, increasing from the present day before peaking at a redshift of z ~ 2.5. Thus,…
Very sensitive HI 21cm observations have been made in 860 directions at dec >= -43deg in search of weak, Galactic, high-velocity HI emission lines at moderate and high Galactic latitudes. One-third of the observations were made toward…
Galaxies are surrounded by large reservoirs of gas, mostly hydrogen, fed by inflows from the intergalactic medium and by outflows due to galactic winds. Absorption-line measurements along the sightlines to bright and rare background quasars…
We present a 21cm line HI self-absorption (HISA) survey of cold atomic gas within Galactic longitudes 75 to 146 degrees and latitudes -3 to +5 degrees. We identify HISA as spatially and spectrally confined dark HI features and extract it…
We have made HI 21cm-line absorption measurements using the GMRT towards 15 directions in the Galaxy which are known to have high random velocity clouds as seen in the optical absorption lines of CaII and NaI. For the first time, in 6 out…
We discuss the effects of gravitational collapse on the shape of absorption line profiles for low column density (log N(HI) < 14) Lyman Alpha forest clouds and argue by comparison with cosmological simulations that Lyman alpha forest…
The emission of 21-cm radiation from a neutral intergalactic medium (IGM) at high redshift is discussed in connection with the thermal and ionization history of the universe. The physical mechanisms that make such radiation detectable…
This study presents results on detecting neutral atomic hydrogen (HI) 21cm absorption in the spectrum of PKS1413+135 at redshift $z=0.24670041$. The observation was conducted by FAST, with a spectral resolution of 10 Hz, using 10 minutes of…
WSRT observations have been used to investigate the presence of neutral hydrogen in extremely young radio galaxies. These objects were selected from a sample of High-Frequency Peakers (HFPs). We detect 2 of the 6 observed galaxies…
We report the discovery of a new 21-cm HI absorption system using commissioning data from the Boolardy Engineering Test Array of the Australian Square Kilometre Array Pathfinder (ASKAP). Using the 711.5 - 1015.5 MHz band of ASKAP we were…
The results of a CO line survey in central cluster galaxies with cooling flows are presented. Cold molecular gas is detected with the IRAM 30m telescope, through CO(1-0) and CO(2-1) emission lines in 6-10 among 32 galaxies. The…
Recently the EDGES collaboration reported an anomalous absorption signal in the sky-averaged 21-cm spectrum around $z=17$. Such a signal may be understood as an indication for an unexpected cooling of the hydrogen gas during or prior to the…
Detecting HI using redshifted Ly-alpha absorption lines is 1e6 times more sensitive than using the 21cm emission line. We review recent discoveries of HI Ly-alpha absorbers made with the Hubble Space Telescope (HST) which have allowed us a…
A model of Lyman limit QSO absorption systems is investigated where they are produced in gaseous galactic halos with a two-phase structure: a hot phase at the halo virial temperature in approximate pressure equilibrium, and a cold,…
We report statistically significant detection of H I 21-cm emission from intermediate-redshift ($z\approx0.2$-0.6) galaxies. By leveraging multi-sightline galaxy survey data from the Cosmic Ultraviolet Baryon Survey (CUBS) and deep radio…
We present optical spectroscopic and milli-arcsecond scale radio continuum observations of the quasar M1540-1453 ($z_{em}$ = 2.104$\pm$0.002) that shows associated HI 21-cm absorption at $z_{abs}$ = 2.1139. At sub-kpc scales, the powerful…
We present new GHRS observations of Lyman alpha absorption lines associated with a group of galaxies towards the QSO 1545+2101. We have identified eight distinct Lyman alpha absorption features in the spectrum of QSO 1545+2101 at a mean…
The low-redshift Ly-alpha forest of absorption lines provides a probe of large-scale baryonic structures in the intergalactic medium, some of which may be remnants of physical conditions set up during the epoch of galaxy formation. We…