Quiescent ultra-diffuse galaxies in the field originating from backsplash orbits
Quiescent ultra-diffuse galaxies in the field originating from backsplash orbits
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DOI：
10.1038/s41550-021-01458-1
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发表时间：
2021-09
期刊：
影响因子：
14.1
通讯作者：
J. Benavides;L. Sales;M. Abadi;A. Pillepich;D. Nelson;F. Marinacci;M. Cooper;R. Pakmor;P. Torrey;M. Vogelsberger;L. Hernquist
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作者：
J. Benavides;L. Sales;M. Abadi;A. Pillepich;D. Nelson;F. Marinacci;M. Cooper;R. Pakmor;P. Torrey;M. Vogelsberger;L. Hernquist
超漫射星系（udg）是已知的表面亮度最低的星系，具有典型的矮星系的恒星质量，但大小与银河系等大型星系相似。它们扩大尺寸的原因是有争议的，有建议的内部过程，如角动量，反馈，或合并与外部机制，-或两者的组合。从观测上看，我们知道udg是红色的，在群体和星团中是静止的，而它们在野外的对应体是蓝色的，正在形成恒星，，-。这种二分法表明，环境影响是罪魁祸首。然而，最近在野外观察到的孤立的静态udg对这种情况提出了挑战。在这里，我们使用theΛCDM （orΛcold暗物质，whereΛis宇宙常数）宇宙学流体力学模拟来表明，孤立的淬灭udg是作为后挡板星系形成的，它们曾经是另一个星系、星系群或星团晕的卫星，但今天距离它们只有几个Mpc。这些相互作用虽然短暂，但却带走了气体，并潮汐地剥离了暗物质晕的外围，这些暗物质晕现在已经熄灭，似乎是孤立的udg，它们诞生时是恒星形成场udg，占据了矮质量暗物质晕。因此，在细丝和空洞中可能会发现数量不可忽略的静止的udg，与具有类似恒星含量的矮星相比，它们带有过去相互作用的标志，即被剥离的外层光晕缺乏暗物质和气体。
Ultra-diffuse galaxies (UDGs) are the lowest-surface-brightness galaxies known, with typical stellar masses of dwarf galaxies but sizes similar to those of larger galaxies such as the Milky Way. The reason for their extended sizes is debated, with suggested internal processes such as angular momentum, feedback,or mergers versus external mechanisms, , –or a combination of both. Observationally, we know that UDGs are red and quiescent in groups and clusters,whereas their counterparts in the field are blue and star-forming, , –. This dichotomy suggests environmental effects as the main culprits. However, this scenario is challenged by recent observations of isolated quiescent UDGs in the field, –. Here we use theΛCDM (orΛcold dark matter, whereΛis the cosmological constant) cosmological hydrodynamical simulation to show that isolated quenched UDGs are formed as backsplash galaxies that were once satellites of another galactic, group or cluster halo but are today a few Mpc away from them. These interactions, albeit brief, remove the gas and tidally strip the outskirts of the dark matter haloes of the now quenched and seemingly isolated UDGs, which are born as star-forming field UDGs occupying dwarf-mass dark matter haloes. Quiescent UDGs may therefore be found in non-negligible numbers in filaments and voids, bearing the mark of past interactions as stripped outer haloes devoid of dark matter and gas compared to dwarfs with similar stellar content.