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arXiv 0905.0001astro-ph.HEastro-ph.CO
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快速暗伽马射线暴的宿主星系:对高遮蔽和甚高红移伽玛暴的观测约束

The Host Galaxies of Swift Dark Gamma-Ray Bursts: Observational Constraints on Highly Obscured and Very High-Redshift GRBs

D. A. Perley, S. B. Cenko, J. S. Bloom, H. -W. Chen, N. R. Butler, D. Kocevski, J. X. Prochaska, M. Brodwin, K. Glazebrook, M. M. Kasliwal, S. R. Kulkarni, S. L… 展开作者

D. A. Perley, S. B. Cenko, J. S. Bloom, H. -W. Chen, N. R. Butler, D. Kocevski, J. X. Prochaska, M. Brodwin, K. Glazebrook, M. M. Kasliwal, S. R. Kulkarni, S. Lopez, E. O. Ofek, M. Pettini, A. M. Soderberg, D. Starr

摘要:

在这项工作中,我们提出了我们的成像活动在凯克天文台的第一个结果,以确定“暗”的伽马射线暴(GRB),事件没有检测到的光学余辉或检测到的光通量显着比预期的微弱,从观察到的X射线余辉。我们发现,在2008年3月由Palomar 60英寸望远镜快速观察到的29个雨燕爆发的统一样本中(其中14个我们归类为黑暗),所有事件都有检测到的光学余辉,可能的光学宿主星系检测,或两者兼而有之。我们的结果限制了来自非常高红移(z > 7)的雨燕伽玛暴的比例,例如最近的伽玛暴090423,在80%的置信度下在0.2- 7%之间。相比之下,相当一部分样品需要大的消光柱(主框架A_V > 1 mag,有几个事件显示A_V > 2-6 mag),确定尘埃消光是暗GRB现象的主要原因。我们推断,一个显着的比例的伽玛暴(和协会,高质量的恒星形成)发生在高度模糊的地区。然而,暗伽马射线暴的宿主星系似乎具有正常的光学颜色,这表明遮蔽尘埃的来源是伽马射线暴祖先附近的本地或在宿主星系内高度不均匀分布。

英文摘要:

In this work we present the first results of our imaging campaign at Keck Observatory to identify the host galaxies of "dark" gamma-ray bursts (GRBs), events with no detected optical afterglow or with detected optical flux significantly fainter than expected from the observed X-ray afterglow. We find that out of a uniform sample of 29 Swift bursts rapidly observed by the Palomar 60-inch telescope through March 2008 (14 of which we classify as dark), all events have either a detected optical afterglow, a probable optical host-galaxy detection, or both. Our results constrain the fraction of Swift GRBs coming from very high redshift (z > 7), such as the recent GRB 090423, to between 0.2-7 percent at 80% confidence. In contrast, a significant fraction of the sample requires large extinction columns (host-frame A_V > 1 mag, with several events showing A_V > 2-6 mag), identifying dust extinction as the dominant cause of the dark GRB phenomenon. We infer that a significant fraction of GRBs (and, by association, of high-mass star formation) occurs in highly obscured regions. However, the host galaxies of dark GRBs seem to have normal optical colors, suggesting that the source of obscuring dust is local to the vicinity of the GRB progenitor or highly unevenly distributed within the host galaxy.

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