Exploring the Host Galaxies of Unusual Astrophysical Transients

大多数天体物理瞬变都是由两种来源之一产生的：一种是物质在致密源上的吸积，释放其引力势；另一种是恒星在生命结束时突然释放能量，与邻近恒星合并或在自身重量的作用下坍缩。在这两种情况下，尤其是在后一种情况下，对瞬变星系的宿主星系及其恒星群的研究可以帮助我们深入了解形成这一事件的起源和环境。核心坍缩伽马射线暴（GRBs）是宇宙中能量最高的爆炸，其中一些达到各向同性能量高达1054尔格s-1。伽马射线暴具有一定的光度范围和不同的光谱和时间分布。附近的几个爆发为研究grb的宿主提供了最好的机会。这些可能与WISE红外巡天探测到的少数GRB宿主在位置上相对应。我们手头有数据，包括VLT/X-Shooter光谱，WHT数据和ATCA无线电观测，探索这些物体，这些将成为这个项目的最初重点。WISE天体的性质将被确定——它们是偶然排列，附近的恒星形成星系，还是更遥远的尘埃星系？研究人员将对潜在的GRB宿主星系进行特征描述，以确定星系的恒星形成速率和化学成分。假设它们产生了伽马射线暴，它们是否具有预期的特性？然后，这项研究将扩展到宿主星系中其他类型的不寻常的天体物理瞬变（可能包括引力波源，或更奇特的瞬变，如frb或tde）。这样的瞬变揭示了直接观察非常具有挑战性的结构和恒星群。因此，它们可能对估计宇宙中被遮蔽的恒星形成的比例至关重要，限制GRB和其他瞬态祖恒星形成的条件，甚至限制恒星相互作用和恒星生命的终结——这是引力波天文学新时代的一个特别突出的点。

Most astrophysical transients arise from one of two sources - the accretion of material onto a compact source, releasing its gravitational potential, or the sudden release of energy when a star reaches the end of its life and merges with its neighbour or collapses under its own weight. In both cases, but particularly the latter, the study of the transient's host galaxy and its stellar populations can lend insights into the progenitor and environment that shape the event. Core collapse gamma-ray bursts (GRBs) are the most energetic explosions in the Universe, with some reaching isotropic energies as high as 1054 ergs s-1. GRBs have a range of luminosities and different spectral and temporal profiles. The handful of nearby bursts offer the best opportunities to study the hosts of GRBs. It is possible that these correspond in position to the small number of GRB hosts detected in the WISE IR survey. We have data in hand, including VLT/X-Shooter spectra, WHT data and ATCA radio observations, exploring these objects, and these will form the initial focus of this project. The nature of the WISE objects will be determined - are they chance alignments, nearby star forming galaxies, or more distant dusty galaxies? Work will be done to characterise potential GRB host galaxies, using to determine the star formation rates and chemical compositions of the galaxies. Do they have the expected properties, given that they produced a GRB?This study will then be extended to the host galaxies of further classes of unusual astrophysical transients (potentially including gravitational wave sources, or more exotic transients such as FRBs or TDEs). Such transients reveal structures and stellar populations that are very challenging to observe directly. Hence they may be critical for estimating the fraction of obscured star formation in the Universe, constraining the conditions under which GRB and other transient progenitors can form, and even placing limits on stellar interactions and the end of stellar life - a particularly salient point in this new era of gravitational wave astronomy.