Monochromatic globular clusters as a critical test of formation models for the dark matter deficient galaxies NGC1052-DF2 and NGC1052-DF4
Pieter van Dokkum, Zili Shen, Aaron J. Romanowsky, Roberto Abraham, Charlie Conroy, Shany Danieli, Dhruba Dutta Chowdhury, Michael A. Keim, J. M. Diederik Kruij… 展开作者
Pieter van Dokkum, Zili Shen, Aaron J. Romanowsky, Roberto Abraham, Charlie Conroy, Shany Danieli, Dhruba Dutta Chowdhury, Michael A. Keim, J. M. Diederik Kruijssen, Joel Leja, Sebastian Trujillo-Gomez
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Published in ApJ Letters. It is difficult to visualize the uniformity of these strange clusters. Our best attempt is Fig. 2, where we compare them to globular clusters in Virgo galaxies
It was recently proposed that the dark matter-deficient ultra-diffuse galaxies DF2 and DF4 in the NGC1052 group could be the products of a "bullet dwarf" collision between two gas-rich progenitor galaxies. In this model DF2 and DF4 formed at the same time in the immediate aftermath of the collision, and a strong prediction is that their globular clusters should have nearly identical stellar populations. Here we test this prediction by measuring accurate F606W-F814W colors from deep HST/ACS imaging. We find that the clusters are extremely homogeneous. The mean color difference between the globular clusters in DF2 and DF4 is $-0.003\pm 0.005$ mag and the observed scatter for the combined sample of 18 clusters with $M_V<-8.6$ in both galaxies is $0.015 \pm 0.002$ mag. After accounting for observational uncertainties and stochastic cluster-to-cluster variation in the number of red giants, the remaining scatter is $0.008^{+0.005}_{-0.006}$ mag. Both the color difference and the scatter are an order of magnitude smaller than in other dwarf galaxies, and we infer that the bullet scenario passes an important test that could have falsified it. No other formation models have predicted this extreme uniformity of the globular clusters in the two galaxies. We find that the galaxies themselves are slightly redder than the clusters, consistent with a previously-measured metallicity difference. Numerical simulations have shown that such differences are expected in the bullet scenario, as the galaxies continued to self-enrich after the formation of the globular clusters.
The emergence of dark matter-deficient ultra-diffuse galaxies driven by scatter in the stellar mass-halo mass relation and feedback from globular clusters
Testing the galaxy collision induced formation scenario for the trail of dark matter deficient galaxies with the susceptibility of globular clusters to the tidal force
A Tip of the Red Giant Branch Distance of $22.1 \pm 1.2$ Mpc to the Dark Matter Deficient Galaxy NGC1052-DF2 from 40 Orbits of Hubble Space Telescope Imaging
Dark Matter Deficient Galaxies And Their Member Star Clusters Form Simultaneously During High-velocity Galaxy Collisions In 1.25 pc Resolution Simulations
Dark matter-deficient twins: FCC 224 and FCC 240 as possible analogues of NGC 1052-DF2 and DF4
Yale University（耶鲁大学）；Swinburne University of Technology（斯威本科技大学）；European Southern Observatory（欧洲南方天文台）；San José State University（圣何塞州立大学）；University of California Santa Cruz（加州大学圣克鲁兹分校）
NGC 6397是最有趣、观测最好、理论研究最多的球状星团之一。现有的观测数据使我们能够研究低金属丰度祖先的理论白矮星冷却序列的可靠性，确定其年龄和未解决的双星的百分比，并评估该星系团的其他重要特征，如初始质量函数的斜率，或具有缺氢大气的白矮星的比例。本文对NGC 6397中的白矮星进行了综合研究。特别是，我们研究了颜色-星等图的形状，以及相应的星等和颜色分布。我们这样做使用最新的蒙特卡罗代码，结合了最新的和可靠的冷却序列和观测偏差的准确建模。我们发现我们的理论模型和观测数据之间有很好的一致性。特别是，我们发现，这种协议是最好的冷却序列，考虑到残余氢燃烧。这一结果具有重要的后果的演化过程中的热脉冲渐近巨星分支阶段的祖星，因为它意味着可观的第三次疏浚在低质量，低金属丰度的祖星预计不会发生。用1.0 Gyr的标准爆发持续时间，我们得到星团的年龄为12.8+0.50-0.75 Gyr。更大的年龄也与观测数据相一致，但需要更长的恒星形成初始爆发持续时间来拟合光度函数。我们的结论是，正确的白矮星opulation的球状星团的建模，结合使用的主序星的数量计数提供了一个独特的工具来模拟的球状星团的属性。
