EDP Sciences
Free access
Volume 452, Number 2, June III 2006
Page(s) 481 - 485
Section Extragalactic astronomy
DOI http://dx.doi.org/10.1051/0004-6361:20052855

A&A 452, 481-485 (2006)
DOI: 10.1051/0004-6361:20052855

Search for high column density systems with gamma ray bursts

H. Hirashita1, 2, H. Shibai2 and T. T. Takeuchi3

1  SISSA/International School of Advanced Studies, via Beirut 4, 34014 Trieste, Italy
2  Graduate School of Science, Nagoya University, Furo-cho, Chikusa-ku, Nagoya, 464-8602, Japan
    e-mail: [hirashita;shibai]@u.phys.nagoya-u.ac.jp
3  Laboratoire d'Astrophysique de Marseille, Traverse du Siphon BP 8, 13376 Marseille Cedex 12, France
    e-mail: tsutomu.takeuchi@oamp.fr

(Received 10 February 2005 / Accepted 28 February 2006)

We investigate the possibility of searching for metal-poor high column density ($\ga$ $10^{23}~{\rm cm}^{-2}$) clouds at high redshift (z) by using gamma ray burst afterglows. Such clouds could be related to primeval galaxies that may cause a burst of star formation. We show that a large part of hydrogen is in molecular form in such a high column density environment. Therefore, hydrogen molecules (H2) rather than hydrogen atoms should be searched for. Then we show that infrared H2 lines are detectable for metal-poor ($\la$0.01 solar metallicity) high column density ( $\log N_{\rm H}~[{\rm cm}^{-2}]\ga 23.5$) systems at high-z without suffering dust extinction. The optical properties of dust in infrared could also be constrained by observations of high column density systems. Some possible scenarios for producing high column density systems are finally discussed in the context of galaxy evolution.

Key words: galaxies: evolution -- galaxies: ISM -- infrared: ISM -- ISM: dust, extinction -- ISM: lines and bands -- ISM: molecules

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