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arXiv 1912.08511astro-ph.GA
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伽马射线暴宿主星系:比恒星形成率与金属丰度

Gamma-Ray Burst Host Galaxies: Specific Star Formation Rate vs. Metallicity

Gunnlaugur Björnsson

摘要:

观测到的长伽马射线暴(GRB)宿主星系的性质表明,它们通常具有相当低的金属丰度和/或高的比恒星形成率(SFR)。目前还不清楚这些属性中的哪一个是决定星系是否会拥有伽玛射线暴的主导因素。事实上,有迹象表明,至少在本地宇宙中,这两者可能是相关的,金属丰度是决定性的参数。在这里,我们考虑依赖于这两个量的GRB产生模型,并表明与最佳可用数据相比,相应的恒星形成分数与$z\sim 4$的红移似乎难以区分。然而,由特定的SFR确定的GRB托管星系的比例,与观察到的宿主星系的比例比相应的金属丰度确定的比例的张力较小,但这一结论是模型依赖的。在高红移下,星系、恒星质量和恒星形成率函数对于打破伽玛暴产生概率中比率和金属丰度之间的表观简并关系至关重要。

英文摘要:

The observed properties of long gamma-ray burst (GRB) host galaxies show them to often be of a rather low metallicity and/or of high specific star formation rate (SFR). It is not clear which of these properties is a dominant factor in determining if a galaxy will host a GRB or not. In fact there are indications, at least in the local Universe, that the two may be anticorrelated and that the metallicity is the deciding parameter. Here, we consider GRB production models dependent on both quantities and show that when compared to the best available data, the respective star formation fractions appear indistinguishable out to redshift of $z\sim 4$. However, the fraction of galaxies hosting a GRB, as determined by the specific SFR, is less at tension with the observed host galaxy fraction than the corresponding metallicity determined fraction, but this conclusion is model dependent. Well established galaxy stellar mass and star formation rate functions at high redshift are crucial in breaking the apparent degeneracy between the specific rate and metallicity in GRB production probability.

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