Related papers: High Redshift HI 21cm Absorption toward Red Quasar…
We have used the Westerbork Synthesis Radio Telescope to detect HI 21cm absorption at $z \sim 0.7645$ in the gravitational lens system towards PMN J0134-0931. The 21cm profile has two broad components, with peak optical depths of $0.047 \pm…
Upon an expansion of all of the searches for redshifted HI 21-cm absorption (0.0021 < z 5.19), we update recent results regarding the detection of 21-cm in the non-local Universe. Specifically, we confirm that photo-ionisation of the gas is…
The Ly-alpha absorption spectrum of the highest redshift quasars indicates that they are surrounded by giant HII regions, a few Mpc in size. The neutral gas around these HII regions should emit 21cm radiation in excess of the Cosmic…
Neutral atomic hydrogen and molecular gas in the host galaxies of radio active galactic nuclei (AGN) can be traced using H I 21-cm and OH-1667 MHz absorption lines to understand the fueling and feedback processes. We present the results of…
Neutral hydrogen traces gravitational potentials. In the nearby universe, 21cm emission-line surveys show that the bulk of the HI resides in well-formed, optically-luminous galaxies. At high redshift, 21cm line absorption against background…
Strong constraints on possible variations in fundamental constants can be derived from HI 21-cm and molecular rotational absorption lines observed towards quasars. With the aim of forming a statistical sample of constraints we have begun a…
Spinning dust grains in front of the bright Galactic synchrotron background can produce a weak absorption signal that could affect measurements of high redshift 21 cm absorption. At frequencies near 80 MHz where the EDGES experiment has…
I report detections of four new HI 21-cm absorbers associated with sources at intermediate redshifts, 0.7 < z < 1.0. The sources are part of a sample of 11 radio-loud galaxies, all at 0.7 < z < 1.0, that were searched for associated HI…
We present a search for associated HI 21 cm absorption in a sample of 29 radio-loud active galactic nuclei (AGNs) at $0.7 < z < 1$, carried out with the upgraded Giant Metrewave Radio Telescope. We detect HI 21 cm absorption against none of…
We present an extragalactic HI 21-cm absorption lines catalog from a blind search at z $\leqslant$ 0.35, using drift-scan data collected in 1325.6 hours by the ongoing Commensal Radio Astronomy FasT Survey (CRAFTS) and FAST All Sky HI…
We present HST spectra for a sample of six QSOs with intermediate redshift (z_a < 1) damped Ly-alpha systems. These observations aim at measuring the HI column density and detect metal lines in order to investigate the metal enrichment of…
We present results from MUSE observations of a 21-cm HI absorption system detected with the Australian Square Kilometre Array Pathfinder radio telescope at redshift $z = 0.4503$ towards the $z = 1.71$ quasar PKS 1610-771. We identify four…
In this paper we investigate the possible reasons why HI 21-cm absorption in damped Lyman-alpha systems (DLAs) has only been detected at low redshift... We suggest that the lack of 21-cm absorption detections at high redshift arises from…
We report the detection of 21-cm absorption from foreground galaxies towards quasars, specifically z_gal = 0.3120 towards SDSS J084957.97+510829.0 (z_qso = 0.584; Pair-I) and z_gal = 0.3714 towards SDSS J144304.53+021419.3 (z_qso = 1.82;…
We study a sample of 17 z>1.5 absorbers selected based on the presence of strong CI absorption lines in SDSS spectra and observed with the ESO-VLT spectrograph X-shooter. We derive metallicities, depletion onto dust, and extinction by dust,…
WSRT observations have provided a first inventory of the incidence of HI 21 cm line absorption associated with AGN at redshifts up to z=1.0. There is a large range in line depths, from tau=0.44 to tau less than 0.001, and a substantial…
We investigate the practice of assigning high spin temperatures to damped Lyman-alpha absorption systems (DLAs) not detected in HI 21-cm absorption. In particular, Kanekar & Chengaulr (2003) have attributed the mix of 21-cm detections and…
We report the detection of redshifted HI~21cm absorption in the $z \sim 2.347$ damped Lyman-$\alpha$ absorber (DLA) towards PKS B0438-436, with the Green Bank Telescope. This is the second-highest redshift at which 21cm absorption has been…
By combining the data from surveys for HI 21-cm absorption at various impact parameters in near-by galaxies, we report an anti-correlation between the 21-cm absorption strength (velocity integrated optical depth) and the impact parameter.…
We describe a search for molecular absorption at millimetre wavelengths associated with dusty molecular tori in active galactic nuclei (AGN). The sample observed consists of 11 flat-spectrum radio sources known to have red optical to…