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2010MNRAS.408..849G - Mon. Not. R. Astron. Soc., 408, 849-864 (2010/October-3)
GMRT mini-survey to search for 21-cm absorption in quasar-galaxy pairs at z ∼ 0.1.
GUPTA N., SRIANAND R., BOWEN D.V., YORK D.G. and WADADEKAR Y.
Abstract (from CDS):
In the remaining cases, our GMRT spectra provide upper limit on N(Hi) in the range (1017-1018) xTS/cm2. Combining our sample with the z ≤ 0.1 data available in the literature, we find the detectability of 21-cm absorption with integrated optical depth greater than 0.1 km/s to be 50 per cent for the impact parameter less than 20 kpc. Using the surface brightness profiles and a well-established relationship between the optical size and extent of the Hi disc known for nearby galaxies, we conclude that in most of the cases of 21-cm absorption non-detection, the sightlines may not be passing through the Hi gas (1σ column density of a few times 1019/cm2). We also find that in comparison to the absorption systems associated with these QGPs, z < 1 damped Lyman-α absorbers (DLAs) with 21-cm absorption detections have lower Caii equivalent widths despite having higher 21-cm optical depths and smaller impact parameters. This suggests that the current sample of DLAs may be a biased population that avoids sightlines through dusty star-forming galaxies. A systematic survey of QGPs over a wider redshift range using a large sample is needed to confirm these findings and understand the nature of 21-cm absorbers.
Abstract Copyright: © 2010 The Authors. Journal compilation © 2010 RAS
Journal keyword(s): galaxies: evolution - galaxies: ISM - quasars: absorption lines
Nomenclature: Fig. 7 and text: [GSB2010] G1 N=1.
Simbad objects: 46
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