Gas-rich, Field Ultra-diffuse Galaxies Host Few Gobular Clusters
Gas-rich, Field Ultra-diffuse Galaxies Host Few Gobular Clusters
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DOI：
10.3847/2041-8213/acaaab
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发表时间：
2022-11
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影响因子：
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通讯作者：
Michael G. Jones;A. Karunakaran;P. Bennet;D. Sand;K. Spekkens;B. Mutlu-Pakdil;D. Crnojević;S. Janowiecki;L. Leisman;Catherine E. Fielder
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作者：
Michael G. Jones;A. Karunakaran;P. Bennet;D. Sand;K. Spekkens;B. Mutlu-Pakdil;D. Crnojević;S. Janowiecki;L. Leisman;Catherine E. Fielder
我们给出了哈勃太空望远镜成像的14个气体丰富，表面亮度低的星系，距离25-36Mpc，平均有效半径和g带中心表面亮度分别为1.9kpc和24.2mag arcsec−2。其中9个星系符合超扩散星系(UDG)的标准。对比球状星团光度函数的翻转星等更亮的点状来源的检查表明，与密度更高的环境中的那些不同，富含气体的场域UDG拥有非常少的旧球状星团(GC)。大多数目标(九个)的候选选区为零，其余的目标选区各有一到两个候选人。这些发现与恒星质量相近的正常矮小星系的预期大体一致。这排除了富含气体的野外UDG作为富含GC的UDG的潜在祖先的可能性，这些UDG通常在星系团中发现。然而，星系群中的一些可能是直接从磁场中吸积而来的。与最近的其他结果一致，这有力地表明，UDG至少有两条不同的形成途径，而这个亚族只是矮星系群体的极低表面亮度延伸。它们扩散的恒星分布的根本原因尚不清楚，但形成机制似乎只影响恒星(以及潜在的暗物质)的分布，而不会强烈影响中性气体的分布、总恒星质量或GC的数量。
We present Hubble Space Telescope imaging of 14 gas-rich, low-surface-brightness galaxies in the field at distances of 25–36 Mpc, with mean effective radii and g-band central surface brightnesses of 1.9 kpc and 24.2 mag arcsec−2. Nine meet the standard criteria to be considered ultra-diffuse galaxies (UDGs). An inspection of point-like sources brighter than the turnover magnitude of the globular cluster luminosity function and within twice the half-light radii of each galaxy reveals that, unlike those in denser environments, gas-rich, field UDGs host very few old globular clusters (GCs). Most of the targets (nine) have zero candidate GCs, with the remainder having one or two candidates each. These findings are broadly consistent with expectations for normal dwarf galaxies of similar stellar mass. This rules out gas-rich, field UDGs as potential progenitors of the GC-rich UDGs that are typically found in galaxy clusters. However, some in galaxy groups may be directly accreted from the field. In line with other recent results, this strongly suggests that there must be at least two distinct formation pathways for UDGs, and that this subpopulation is simply an extreme low surface brightness extension of the underlying dwarf galaxy population. The root cause of their diffuse stellar distributions remains unclear, but the formation mechanism appears to only impact the distribution of stars (and potentially dark matter), without strongly impacting the distribution of neutral gas, the overall stellar mass, or the number of GCs.