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A search for intervening HI absorption

Published online by Cambridge University Press:  21 March 2013

Sarah N. Reeves ,
Elaine M. Sadler ,
James R. Allison ,
Baerbel S. Koribalksi  and
Stephen J. Curran
Sarah N. Reeves*
Affiliation:
Sydney Institute for Astronomy, School of Physics A28, University of Sydney, NSW 2006, Australia Australia Telescope National Facility, CSIRO Astronomy and Space Science, PO Box 76, Epping, NSW 1710, Australia ARC Centre of Excellence for All-Sky Astrophysics (CAASTRO)
Elaine M. Sadler
Affiliation:
Sydney Institute for Astronomy, School of Physics A28, University of Sydney, NSW 2006, Australia ARC Centre of Excellence for All-Sky Astrophysics (CAASTRO)
James R. Allison
Affiliation:
Sydney Institute for Astronomy, School of Physics A28, University of Sydney, NSW 2006, Australia
Baerbel S. Koribalksi
Affiliation:
Australia Telescope National Facility, CSIRO Astronomy and Space Science, PO Box 76, Epping, NSW 1710, Australia
Stephen J. Curran
Affiliation:
Sydney Institute for Astronomy, School of Physics A28, University of Sydney, NSW 2006, Australia ARC Centre of Excellence for All-Sky Astrophysics (CAASTRO)
*
*email: s.reeves@physics.usyd.edu.au
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Abstract

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HI absorption-line studies provide a unique probe of the gas distribution and kinematics in galaxies well beyond the local universe (z ≳ 0.3). HI absorption-line surveys with next-generation radio telescopes will provide the first large-scale studies of HI in a redshift regime which is poorly understood. However, we currently lack the understanding to infer galaxy properties from absorption-line observations alone. To address this issue, we are conducting a search for intervening HI absorption in a sample of 20 nearby galaxies. Our aim is to investigate how the detection rate varies with distance from the galaxy. We target sight-lines to bright continuum sources, which intercept known gas-rich galaxies, selected from the HIPASS Bright Galaxy Catalogue (Koribalski et al. 2004). In our pilot sample, six galaxies with impact parameters < 20 kpc, we do not detect any absorption lines — although all are detected in 21cm emission. This indicates that an absorption non-detection cannot simply be interpreted as an absence of neutral gas – see Fig. 1. Our detection rate is low compared to previous surveys e.g. Gupta et al. (2010). This is, at least partially, due to the high resolution of the observations reducing the flux of the background source, which will also be an issue in future surveys, such as ASKAP-FLASH.

Keywords

galaxies: evolution — galaxies: ISM — radio lines: galaxies
Type
Contributed Papers
Information
Proceedings of the International Astronomical Union , Volume 8 , Symposium S292: Molecular Gas, Dust, and Star Formation in Galaxies , August 2012 , pp. 162
Copyright
Copyright © International Astronomical Union 2013

References

Allison, J. R.et al. 2012, PASA, 29, 221CrossRefGoogle Scholar
Gupta, N.et al. 2010, MNRAS, 408, 849Google Scholar
Koribalski, B. S.et al. 2004, AJ, 128, 16CrossRefGoogle Scholar
Reeves, S. N.et al. (in prep)Google Scholar