Journal Article

H <span class="smallCaps">i</span> absorption towards nearby compact radio sources

Yogesh Chandola, S. K. Sirothia and D. J. Saikia

in Monthly Notices of the Royal Astronomical Society

Published on behalf of The Royal Astronomical Society

Volume 418, issue 3, pages 1787-1795
Published in print December 2011 | ISSN: 0035-8711
Published online December 2011 | e-ISSN: 1365-2966 | DOI:
H i absorption towards nearby compact radio sources

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We present the results of H i absorption measurements towards a sample of nearby compact steep-spectrum (CSS) and gigahertz-peaked spectrum (GPS) radio sources, the Compact Radio sources at Low Redshift (CORALZ) sample, using the Giant Metrewave Radio Telescope (GMRT). We observed a sample of 18 sources and find seven new detections. These sources are of lower luminosity than earlier studies of CSS and GPS objects, and we investigate any dependence of H i absorption features on radio luminosity. Within the uncertainties, the detection rates and column densities are similar to the more luminous objects, with the GPS objects exhibiting a higher detection rate than for the CSS objects. The relative velocity of the blueshifted absorption features, which may be due to jet–cloud interactions, are within ∼−250 km s−1 and do not appear to extend to values over 1000 km s−1 seen for the more luminous objects. This could be due to the weaker jets in these objects, but requires confirmation from observations of a larger sample of sources. There appears to be no evidence of any dependence of H i column density on either luminosity or redshift, but these new detections are consistent with the inverse relation between H i column density and projected linear size.

Keywords: galaxies: active; galaxies: evolution; galaxies: jets; galaxies: nuclei; radio lines: galaxies

Journal Article.  5584 words.  Illustrated.

Subjects: Astronomy and Astrophysics

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