A&A 404, 861-870 (2003)
DOI: 10.1051/0004-6361:20030468

Observations of H I absorbing gas in compact radio sources at cosmological redshifts

R. C. Vermeulen¹, Y. M. Pihlström^{2, 3}, W. Tschager⁴, W. H. de Vries^{5, 6, 7}, J. E. Conway³, P. D. Barthel⁵, S. A. Baum⁶, R. Braun¹, M. N. Bremer^{4, 8}, G. K. Miley⁴, C. P. O'Dea⁶, H. J. A. Röttgering⁴, R. T. Schilizzi^{4, 9}, I. A. G. Snellen¹⁰ and G. B. Taylor<sup>2

1</sup>  Netherlands Foundation for Research in Astronomy (ASTRON), PO Box 2, 7990 AA Dwingeloo, The Netherlands
²  National Radio Astronomy Observatory, PO Box O, Socorro, NM 87801, USA
³  Onsala Space Observatory, 439 92 Onsala, Sweden
⁴  Leiden Observatory, PO Box 9513, 2300RA Leiden, The Netherlands
⁵  Kapteyn Astronomical Institute, PO Box 800, 9700 AV Groningen, The Netherlands
⁶  Space Telescope Science Institute, Baltimore, USA
⁷  Lawrence Livermore National Laboratories, USA
⁸  Astrophysics Department, University of Bristol, Great Britain
⁹  Joint Institute for VLBI in Europe (JIVE), Postbus 2, 7990 AA Dwingeloo, The Netherlands
¹⁰  Institute for Astronomy, University of Edinburgh, Blackford Hill, Edinburgh EH9 3HJ, UK

(Received 17 February 2002 / Accepted 20 March 2003 )

Abstract
We present an overview of the occurrence and properties of atomic gas associated with compact radio sources at redshifts up to z=0.85. Searches for H I 21 cm absorption were made with the Westerbork Synthesis Radio Telescope at UHF-high frequencies (725-1200 MHz). Detections were obtained for 19 of the 57 sources with usable spectra (33%). We have found a large range in line depths, from to . There is a substantial variety of line profiles, including Gaussians of less than 10 km s ^-1, to more typically 150 km s ^-1, as well as irregular and multi-peaked absorption profiles, sometimes spanning several hundred km s ^-1. Assuming uniform coverage of the entire radio source, we obtain column depths of atomic gas between and ( K)( 1/f) cm ^-2. There is evidence for significant gas motions, but in contrast to earlier results at low redshift, there are many sources in which the H I velocity is substantially negative (up to v=-1420 km s ^-1) with respect to the optical redshift, suggesting that in these sources the atomic gas, rather than falling into the centre, may be be flowing out, interacting with the jets, or rotating around the nucleus.

Key words: galaxies: active -- galaxies: evolution -- galaxies: ISM -- radio lines: galaxies

Offprint request: R. C. Vermeulen, rvermeulen@astron.nl

SIMBAD Objects

© ESO 2003

The OpenURL standard is a protocol for transmission of metadata describing the resource that you wish to access. An OpenURL link contains article metadata and directs it to the OpenURL server of your choice. The OpenURL server can provide access to the resource and also offer complementary services (specific search engine, export of references...). The OpenURL link can be generated by different means.

• If your librarian has set up your subscription with an OpenURL resolver, OpenURL links appear automatically on the abstract pages.
• You can define your own OpenURL resolver with your EDPS Account. In this case your choice will be given priority over that of your library.
• You can use an add-on for your browser (Firefox or I.E.) to display OpenURL links on a page (see http://www.openly.com/openurlref/). You should disable this module if you wish to use the OpenURL server that you or your library have defined.