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Title:
H I Gas in Higher Density Regions of the Intergalactic Medium
Authors:
Misawa, Toru; Tytler, David; Iye, Masanori; Paschos, Pascal; Norman, Michael; Kirkman, David; O'Meara, John; Suzuki, Nao; Kashikawa, Nobunari
Affiliation:
AA(Department of Astronomy and Astrophysics, Pennsylvania State University, University Park, PA 16802; .), AB(Center for Astrophysics and Space Sciences, MS 0424, University of California at San Diego, 9500 Gilman Drive, La Jolla, CA 92093-0424.; Visiting Astronomer, W. M. Keck Observatory which is a joint facility of the University of California, the California Institute of Technology, and NASA.), AC(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.), AD(Center for Astrophysics and Space Sciences, MS 0424, University of California at San Diego, 9500 Gilman Drive, La Jolla, CA 92093-0424.), AE(Center for Astrophysics and Space Sciences, MS 0424, University of California at San Diego, 9500 Gilman Drive, La Jolla, CA 92093-0424.), AF(Center for Astrophysics and Space Sciences, MS 0424, University of California at San Diego, 9500 Gilman Drive, La Jolla, CA 92093-0424.; Visiting Astronomer, W. M. Keck Observatory which is a joint facility of the University of California, the California Institute of Technology, and NASA.), AG(Center for Astrophysics and Space Sciences, MS 0424, University of California at San Diego, 9500 Gilman Drive, La Jolla, CA 92093-0424.; Visiting Astronomer, W. M. Keck Observatory which is a joint facility of the University of California, the California Institute of Technology, and NASA.), AH(Center for Astrophysics and Space Sciences, MS 0424, University of California at San Diego, 9500 Gilman Drive, La Jolla, CA 92093-0424.; Visiting Astronomer, W. M. Keck Observatory which is a joint facility of the University of California, the California Institute of Technology, and NASA.), AI(National Astronomical Observatory, 2-21-1 Osawa, Mitaka, Tokyo 181-8588, Japan.)
Publication:
The Astronomical Journal, Volume 128, Issue 6, pp. 2954-2961. (AJ Homepage)
Publication Date:
12/2004
Origin:
UCP
AJ Keywords:
Galaxies: ISM, Galaxies: Intergalactic Medium, Galaxies: Quasars: Absorption Lines
DOI:
10.1086/425879
Bibliographic Code:
2004AJ....128.2954M

Abstract

Using H I absorption alone, we attempt to separate H I absorption lines in quasar spectra into two categories: higher density lines (HDLs) and lower density lines (LDLs), 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<logNHI[cm-2]<19). 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 Δv<200 km s-1, whereas lower ones cluster at Δv<100 km s-1. We define HDLs as H I lines with 15<logNHI<19 and all H I lines within 200 km s-1 of a line with logNHI>15 and LDLs as all others with 12<logNHI<15. 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 intergalactic medium gas, whereas the HDLs are likely to be cooler dense gas near to galaxies.

Data presented herein were obtained at the W. M. Keck Observatory, which is operated as a scientific partnership among the California Institute of Technology, the University of California, and the National Aeronautics and Space Administration. The Observatory was made possible by the generous financial support of the W. M. Keck Foundation.

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