Ultra-diffuse Galaxies as Extreme Star-forming Environments. I. Mapping Star Formation in H i-rich UDGs
Ultra-diffuse Galaxies as Extreme Star-forming Environments. I. Mapping Star Formation in H i-rich UDGs
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DOI：
10.3847/1538-4357/ac9964
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发表时间：
2022-09
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影响因子：
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通讯作者：
Erin Kado-Fong;J. Greene;Song Huang;A. Goulding
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作者：
Erin Kado-Fong;J. Greene;Song Huang;A. Goulding
超漫射星系（UDG）既是星系演化的极端产物，也是检验我们对星星形成理解的极端环境。在这项工作中，我们对比的空间分辨星星形成活动的22个H i选定的UDG和35个低质量星系的样本从美国宇航局斯隆阿特拉斯（NSA）目录在120 Mpc。我们采用了一种新的联合光谱能量分布拟合方法来计算星星的形成率和恒星质量表面密度图，利用高空间分辨率的光学成像数据的超级Suprime-Cam斯巴鲁战略计划和银河系演化探测器的紫外线覆盖范围，沿着与H i径向轮廓估计从一个子集的星系，具有空间分辨H i地图。我们发现，UDG有低的星星形成效率作为其原子气体的函数下降到500 pc的规模。我们还发现，我们的UDG样本的恒星质量加权大小是不显着的，当被认为是他们的H i质量的函数时，他们的恒星大小与固定H i质量的NSA矮星相当。这是一个自然的结果，在图片中，UDG正常形成恒星，但效率较低。我们比较我们的结果预测从当代模型的星系形成，特别是发现，我们的意见是很难重现的模型中，UDG经历恒星膨胀，由于有力的星星形成反馈应突发星星形成需要下降到z = 0。
Ultra-diffuse galaxies (UDGs) are both extreme products of galaxy evolution and extreme environments in which to test our understanding of star formation. In this work, we contrast the spatially resolved star formation activity of a sample of 22 H i-selected UDGs and 35 low-mass galaxies from the NASA Sloan Atlas (NSA) catalog within 120 Mpc. We employ a new joint spectral energy distribution fitting method to compute star formation rate and stellar mass surface density maps that leverage the high spatial resolution optical imaging data of the Hyper Suprime-Cam Subaru Strategic Program and the UV coverage of the Galaxy Evolution Explorer, along with H i radial profiles estimated from a subset of galaxies that have spatially resolved H i maps. We find that UDGs have low star formation efficiencies as a function of their atomic gas down to scales of 500 pc. We additionally find that the stellar mass-weighted sizes of our UDG sample are unremarkable when considered as a function of their H i mass—their stellar sizes are comparable to NSA dwarfs at fixed H i mass. This is a natural result in the picture where UDGs are forming stars normally, but at low efficiencies. We compare our results to predictions from contemporary models of galaxy formation, and find in particular that our observations are difficult to reproduce in models where UDGs undergo stellar expansion due to vigorous star formation feedback should bursty star formation be required down to z = 0.