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arXiv 2204.09059astro-ph.HE
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在$z\sim0-2$上方短GRB宿主星系的深巡天:对偏移、红移和环境的影响

A deep survey of short GRB host galaxies over $z\sim0-2$: implications for offsets, redshifts, and environments

B. O'Connor, E. Troja, S. Dichiara, P. Beniamini, S. B. Cenko, C. Kouveliotou, J. Becerra Gonzalez, J. Durbak, P. Gatkine, A. Kutyrev, T. Sakamoto, R. Sanchez-Ramirez, S. Veilleux

摘要:

很大一部分(30%)的局部短伽玛射线暴(sGRB)缺乏一个重合的宿主星系。这导致了两种主要的情况:\textit{i}),即祖先系统在其宿主的可见光之外合并,或\textit{ii}),sGRB位于一个微弱而遥远的星系中,没有被后续观测发现。区分这些场景对于限制中子星合并的形成通道,引力波源的速率和环境以及宇宙中重元素的产生具有重要意义。在这项工作中,我们提出了我们的观测活动的结果,针对31 sGRB,缺乏一个假定的宿主星系。我们的研究有效地加倍了充分研究的sGRB宿主星系的样本,现在总共有72个事件,其中$28\%$缺乏一个符合的主机到深极限($r$ \,$\gtrsim$ \,$26$或$F110W$ \,$\gtrsim$ \,$27$ AB MAG),并代表了迄今为止最大的sGRB偏移量的均匀选择目录。我们发现,70%的亚弧秒本地化sGRB发生在10 kpc的主机的核,与一个中位数预计物理偏移量为$5.6$ kpc。使用这个更大的人口,我们发现一个明显的红移演变在他们的位置:爆发在低$z$发生在$2\times$更大的偏移相比,在$z$ \,$>$ \,$0.5$。这种演化可能是由于宿主星系本身的物理演化或对微弱的高$z$星系的偏见。此外,我们在$z$ \,$\gtrsim$ \,$1$发现了一个无宿主sGRB的样本,这表明了一个更大的高$z$人口,限制了红移分布,不利于对数正态延迟时间模型。

英文摘要:

A significant fraction (30\%) of well-localized short gamma-ray bursts (sGRBs) lack a coincident host galaxy. This leads to two main scenarios: \textit{i}) that the progenitor system merged outside of the visible light of its host, or \textit{ii}) that the sGRB resided within a faint and distant galaxy that was not detected by follow-up observations. Discriminating between these scenarios has important implications for constraining the formation channels of neutron star mergers, the rate and environments of gravitational wave sources, and the production of heavy elements in the Universe. In this work, we present the results of our observing campaign targeted at 31 sGRBs that lack a putative host galaxy. Our study effectively doubles the sample of well-studied sGRB host galaxies, now totaling 72 events of which $28\%$ lack a coincident host to deep limits ($r$\,$\gtrsim$\,$26$ or $F110W$\,$\gtrsim$\,$27$ AB mag), and represents the largest homogeneously selected catalog of sGRB offsets to date. We find that 70\% of sub-arcsecond localized sGRBs occur within 10 kpc of their host's nucleus, with a median projected physical offset of $5.6$ kpc. Using this larger population, we discover an apparent redshift evolution in their locations: bursts at low-$z$ occur at $2\times$ larger offsets compared to those at $z$\,$>$\,$0.5$. This evolution could be due to a physical evolution of the host galaxies themselves or a bias against faint high-$z$ galaxies. Furthermore, we discover a sample of hostless sGRBs at $z$\,$\gtrsim$\,$1$ that are indicative of a larger high-$z$ population, constraining the redshift distribution and disfavoring log-normal delay time models.

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