The dependence of gamma-ray burst X-ray column densities on the model for Galactic hydrogen
The dependence of gamma-ray burst X-ray column densities on the model for Galactic hydrogen
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DOI：
10.1051/0004-6361/201628326
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发表时间：
2016-04
期刊：
影响因子：
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通讯作者：
R. Arcodia;S. Campana;R. Salvaterra
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文献类型：
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作者：
R. Arcodia;S. Campana;R. Salvaterra
我们研究了99个明亮的雨燕γ射线爆发的完整样品的X射线吸收。近几年来，人们发现高z伽玛暴的内禀X射线吸收柱密度（NH（z））与红移有很强的相关性，现在认为这种吸收过剩是由于忽略了沿着星系际介质吸收的贡献，即通过沿着视线的干涉天体和弥散的温热星系际介质的吸收。在这项工作中，我们忽略了沿着IGM的吸收，因为我们的目的是研究银河系吸收模型的根本变化对N_H（z）分布的最终影响。因此，我们得出的固有吸收柱密度使用两种不同的银河系吸收模型，莱顿阿根廷波恩HI调查和最近的模型，包括分子氢。我们发现，如果一方面新的银河系模型相当大地影响了单柱密度值，另一方面在整个分布中没有剧烈的变化。很明显，单独的银河柱密度的贡献，无论如何改善，都不足以改变观察到的总趋势，它必须被视为二阶修正。N_H（z）作为红移函数的宇宙学增加仍然存在，为了解释观测到的分布，有必要考虑弥散星系际介质和沿着伽玛暴视线的介入系统的贡献。
We study the X-ray absorption of a complete sample of 99 bright Swift gamma-ray bursts. Over the last few years, a strong correlation between the intrinsic X-ray absorbing column density (N_H(z)) and the redshift was found. This absorption excess in high-z GRBs is now thought to be due to the overlooked contribution of the absorption along the intergalactic medium, by means of both intervening objects and the diffuse warm-hot intergalactic medium along the line of sight. In this work we neglect the absorption along the IGM, because our purpose is to study the eventual effect of a radical change in the Galactic absorption model on the N_H(z) distribution. Therefore, we derive the intrinsic absorbing column densities using two different Galactic absorption models, the Leiden Argentine Bonn HI survey and the more recent model including molecular hydrogen. We find that, if on the one hand the new Galactic model considerably affects the single column density values, on the other hand there is no drastic change in the distribution as a whole. It becomes clear that the contribution of Galactic column densities alone, no matter how improved, is not sufficient to change the observed general trend and it has to be considered as a second-order correction. The cosmological increase of N_H(z) as a function of redshift persists and, in order to explain the observed distribution, it is necessary to include the contribution of both the diffuse intergalactic medium and the intervening systems along the line of sight of the GRBs.