Evidence for Ultra-diffuse Galaxy Formation through Tidal Heating of Normal Dwarfs
Evidence for Ultra-diffuse Galaxy Formation through Tidal Heating of Normal Dwarfs
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DOI：
10.3847/1538-4357/ac0975
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发表时间：
2021-04
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影响因子：
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通讯作者：
Michael G. Jones;P. Bennet;B. Mutlu-Pakdil;D. Sand;K. Spekkens;D. Crnojević;A. Karunakaran;D. Z
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文献类型：
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作者：
Michael G. Jones;P. Bennet;B. Mutlu-Pakdil;D. Sand;K. Spekkens;D. Crnojević;A. Karunakaran;D. Z
我们利用哈勃太空望远镜 (HST) 成像和 Jansky 甚大阵列的 Hi 映射，追踪了两个在恒星流附近检测到的超漫射星系 (UDG)，以调查它们可能具有潮汐起源的可能性。利用 HST F814W 和 F555W 图像，我们测量 NGC 2708-Dw1 和 NGC 5631-Dw1 的球状星团 (GC) 计数分别为 2−1+1 和 5−2+1 。 NGC 2708-Dw1 在 H i 低于 log (M H i /M ⊙) = 7.3 的 3σ 极限时未被检测到，并且没有明显的 H i 与附近的恒星流相关。有一个 2σ H i 特征与 NGC 5631-Dw1 一致。然而，这种排放与 NGC 5631 发出的大量气体尾部混合，不一定与 UDG 相关。任何 GC 的存在以及 UDG 与其母星系之间缺乏明确的 Hi 连接都强烈不利于潮汐矮星系起源，但不能完全排除它。 GC 计数与正常矮星系的计数一致，最可能的形成机制是这些 UDG 作为正常矮星系诞生，后来被潮汐剥离和加热。我们还在 NGC 2708-Dw1 中发现了一个过亮（MV = −11.1）的 GC 候选者，它可能是一个核星团，随着周围的矮星系失去恒星而转变为超紧凑矮星。
We have followed up two ultra-diffuse galaxies (UDGs), detected adjacent to stellar streams, with Hubble Space Telescope (HST) imaging and H i mapping with the Jansky Very Large Array in order to investigate the possibility that they might have a tidal origin. With the HST F814W and F555W images we measure the globular cluster (GC) counts for NGC 2708-Dw1 and NGC 5631-Dw1 as 2−1+1 and 5−2+1 , respectively. NGC 2708-Dw1 is undetected in H i down to a 3σ limit of log (M H i /M ⊙) = 7.3, and there is no apparent H i associated with the nearby stellar stream. There is a 2σ H i feature coincident with NGC 5631-Dw1. However, this emission is blended with a large gaseous tail emanating from NGC 5631 and is not necessarily associated with the UDG. The presence of any GCs and the lack of clear H i connections between the UDGs and their parent galaxies strongly disfavor a tidal dwarf galaxy origin, but cannot entirely rule it out. The GC counts are consistent with those of normal dwarf galaxies, and the most probable formation mechanism is one where these UDGs were born as normal dwarfs and were later tidally stripped and heated. We also identify an overluminous (M V = −11.1) GC candidate in NGC 2708-Dw1, which may be a nuclear star cluster transitioning to an ultra-compact dwarf as the surrounding dwarf galaxy gets stripped of stars.