论文标题

追踪矮星系的内在形状到四个有效的半径:低质量恒星光环形成的线索

Tracing the Intrinsic Shapes of Dwarf Galaxies out to Four Effective Radii: Clues to Low-Mass Stellar Halo Formation

论文作者

Kado-Fong, Erin, Greene, Jenny E., Huang, Song, Beaton, Rachael, Goulding, Andy D., Komiyama, Yutaka

论文摘要

尽管长期以来在附近的矮星系周围一直观察到光滑,延伸的球形恒星郊区,但尚不清楚矮人是否一般可以托管延长的恒星光环。我们使用来自Hyper Suprime-CAM Subaru战略计划(HSC-SSP)的成像来测量矮星系的形状,以在0.005 <z <0.2 <z <0.2和10^7 <m_star/m_Star/m_sun/m_sun <10^9.6的情况下,以四个有效的半径为四个有效半径。我们发现矮人略有三轴,具有<b/a>> 〜0.75(其中椭圆形的特征是由C <= B <= a约束的三个原理半轴的特征)。在M_STAR> 10^8.5 m_sun上,星系从其中心附近的厚磁盘样生长到四个有效半径下的球体极端。我们还看到,尽管平均而言,蓝色矮人的圆盘比红色矮人较薄,但蓝色和红色矮人都随着半径的函数而生长更多的球体。这种关系对于田间和卫星矮人之间的比较也是如此。这种均匀的球形形状随着半径的函数的统一趋势与低质量星系周围恒星郊区的原位形成机制一致,这与拟议的模型一致,在该模型中,恒星形成反馈在矮人周围产生圆形恒星郊外郊外。

Though smooth, extended spheroidal stellar outskirts have long been observed around nearby dwarf galaxies, it is unclear whether dwarfs generically host an extended stellar halo. We use imaging from the Hyper Suprime-Cam Subaru Strategic Program (HSC-SSP) to measure the shapes of dwarf galaxies out to four effective radii for a sample of dwarfs at 0.005<z<0.2 and 10^7<M_star/M_sun<10^9.6. We find that dwarfs are slightly triaxial, with a <B/A> >~ 0.75 (where the ellipsoid is characterized by three principle semi-axes constrained by C<=B<=A). At M_star>10^8.5 M_sun, the galaxies grow from thick disk-like near their centers towards the spheroidal extreme at four effective radii. We also see that although blue dwarfs are, on average, characterized by thinner discs than red dwarfs, both blue and red dwarfs grow more spheroidal as a function of radius. This relation also holds true for a comparison between field and satellite dwarfs. This uniform trend towards relatively spheroidal shapes as a function of radius is consistent with an in-situ formation mechanism for stellar outskirts around low-mass galaxies, in agreement with proposed models where star formation feedback produces round stellar outskirts around dwarfs.

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