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H I gas in higher density regions of the IGM

Published online by Cambridge University Press:  06 October 2005

Toru Misawa ,
David Tytler ,
Masanori Iye ,
Pascal Paschos ,
Michael Norman ,
David Kirkman ,
John O'Meara ,
Nao Suzuki  and
Nobunari Kashikawa
Toru Misawa
Affiliation:
Department of Astronomy and Astrophysics, Pennsylvania State University, University Park, PA 16802, USA
David Tytler
Affiliation:
Center for Astrophysics and Space Sciences, MS 0424, University of California at San Diego, 9500 Gilman Drive, La Jolla, CA 92093-0424, USA W. M. Keck Observatory, a Joint Facility of the University of California, the California Institute of Technology, and NASA, USA
Masanori Iye
Affiliation:
National Astronomical Observatory, 2-21-1 Osawa, Mitaka, Tokyo 181-8588, Japan Department of Astronomical Science, The Graduate University for Advanced Studies, 2-21-1 Osawa, Mitaka, Tokyo 181-8588, Japan
Pascal Paschos
Affiliation:
Center for Astrophysics and Space Sciences, MS 0424, University of California at San Diego, 9500 Gilman Drive, La Jolla, CA 92093-0424, USA
Michael Norman
Affiliation:
Center for Astrophysics and Space Sciences, MS 0424, University of California at San Diego, 9500 Gilman Drive, La Jolla, CA 92093-0424, USA
David Kirkman
Affiliation:
Center for Astrophysics and Space Sciences, MS 0424, University of California at San Diego, 9500 Gilman Drive, La Jolla, CA 92093-0424, USA W. M. Keck Observatory, a Joint Facility of the University of California, the California Institute of Technology, and NASA, USA
John O'Meara
Affiliation:
Center for Astrophysics and Space Sciences, MS 0424, University of California at San Diego, 9500 Gilman Drive, La Jolla, CA 92093-0424, USA W. M. Keck Observatory, a Joint Facility of the University of California, the California Institute of Technology, and NASA, USA
Nao Suzuki
Affiliation:
Center for Astrophysics and Space Sciences, MS 0424, University of California at San Diego, 9500 Gilman Drive, La Jolla, CA 92093-0424, USA W. M. Keck Observatory, a Joint Facility of the University of California, the California Institute of Technology, and NASA, USA
Nobunari Kashikawa
Affiliation:
National Astronomical Observatory, 2-21-1 Osawa, Mitaka, Tokyo 181-8588, Japan
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Abstract

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Using H I absorption alone, we attempt to separate H I absorption lines in quasar spectra into two categories; HDLs (Higher Density Lines) and LDLs (Lower Density Lines), and we discuss the difference in their physical properties. We deblend and fit all H I lines with Voigt profiles, and make an unbiased sample of H I lines covering a wide column density range ($12 < \log N_{HI} < 19$ cm$^{-2}$). To reduce the influence of line blending, we simultaneously fit several Lyman series lines. As a result of a two-point correlation analysis, we found that higher column density H I lines are clustering at $\Delta v < 200$ km s$^{-1}$, while lower ones at $\Delta v < 100$ km s$^{-1}$. We define HDLs as H I lines with $15<\log N_{HI} < 19$ cm$^{-2}$ and all H I lines within $\pm$200 km s$^{-1}$ of a line with $\log N_{HI} > 15$ cm$^{-2}$, and LDLs as others with $12 < \log N_{HI} < 15$ cm$^{-2}$. We found that the HDLs have smaller minimum $b$-values for a given column density than the LDLs. This difference is successfully reproduced by our hydrodynamic simulation. The LDLs seem to be cool or shock-heated diffuse IGM gas, while the HDLs are likely to be cooler dense gas near to galaxies.

Type
Contributed Papers
Information
Proceedings of the International Astronomical Union , Volume 1 , Colloquium C199: Probing Galaxies through Quasar Absorption Lines , March 2005 , pp. 454 - 456
Copyright
© 2005 International Astronomical Union