Stellar Population and Structural Properties of Dwarf Galaxies and Young Stellar Systems in the M81 Group
Stellar Population and Structural Properties of Dwarf Galaxies and Young Stellar Systems in the M81 Group
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DOI：
10.3847/1538-4357/ab44a7
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发表时间：
2019-09
期刊：
影响因子：
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通讯作者：
S. Okamoto;N. Arimoto;A. Ferguson;M. Irwin;E. Bernard;Y. Utsumi
中科院分区：
文献类型：
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作者：
S. Okamoto;N. Arimoto;A. Ferguson;M. Irwin;E. Bernard;Y. Utsumi
我们使用Subaru望远镜上的Hyper Suprime-Cam来研究M81星系群中心早期型矮星系和年轻恒星系统的结构和光度特性。我们绘制了红巨星分支（RGB）顶端以下6.5平方度范围内的102等恒星的解析图，对应于距离M81 160 × 160 kpc的投影面积。由此产生的恒星目录，使成员星系具有前所未有的灵敏度低表面亮度发射的均匀分析。Sérsic和King轮廓很好地描述了矮星系的径向轮廓，并且没有显示出明显的潮汐破裂特征。这些系统的测量半径大多比现有的文献值大，我们发现IKN（MV，0 =-14.29）的总光度比以前认为的要亮近3等。我们确定了新的矮卫星候选者，d1006+69和d1009+68，我们估计它们的距离为4.3 ± 0.2 Mpc和3.5 ± 0.5 Mpc。MV，0 = −8.91 ± 0.40，[M/H] = −1.83 ± 0.28，d1006+69是目前已知的M81星系群中最暗、最贫金属的矮星之一。在外围潮汐中性氢（H i）碎片中的年轻恒星系统的光度函数意味着在最近的过去连续的星星形成和存在的人口年轻到30百万岁。我们没有发现老RGB星与定义这些物体的年轻MS/切布星重合的证据，支持它们是真正的新恒星系统，由气态潮汐碎片中触发的星星形成的想法。
We use Hyper Suprime-Cam on the Subaru Telescope to investigate the structural and photometric properties of early-type dwarf galaxies and young stellar systems at the center of the M81 Group. We have mapped resolved stars to ∼2 mag below the tip of the red giant branch (RGB) over almost 6.5 square degrees, corresponding to a projected area of 160 × 160 kpc at the distance of M81. The resulting stellar catalog enables a homogeneous analysis of the member galaxies with unprecedented sensitivity to low surface brightness emission. The radial profiles of the dwarf galaxies are well described by Sérsic and King profiles, and show no obvious signatures of tidal disruption. The measured radii for most of these systems are larger than the existing literature values, and we find the total luminosity of IKN (MV,0 = −14.29) to be almost 3 mag brighter than previously thought. We identify new dwarf satellite candidates, d1006+69 and d1009+68, which we estimate to lie at a distance of 4.3 ± 0.2 Mpc and 3.5 ± 0.5 Mpc. With MV,0 = −8.91 ± 0.40 and [M/H] = −1.83 ± 0.28, d1006+69 is one of the faintest and most metal-poor dwarf satellites currently known in the M81 Group. The luminosity functions of young stellar systems in the outlying tidal neutral hydrogen (H i) debris imply continuous star formation in the recent past and the existence of populations as young as 30 Myr old. We find no evidence for old RGB stars coincident with the young MS/cHeB stars that define these objects, supporting the idea that they are genuinely new stellar systems resulting from triggered star formation in gaseous tidal debris.