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arXiv 1503.06799astro-ph.GAastro-ph.CO
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Local Group中卫星矮星系的快速环境淬火

Rapid Environmental Quenching of Satellite Dwarf Galaxies in the Local Group

Andrew R. Wetzel, Erik J. Tollerud, Daniel R. Weisz

摘要:

在本星系群中,几乎所有的矮星系(M_star < 10^9 M_sun)都是银河系(MW)和仙女座星系(M31)的300 kpc(维里半径)以内的卫星星系,它们的恒星形成过程是静止的,几乎没有或没有冷气体。这与相对孤立的矮星系形成强烈对比,矮星系几乎都是活跃的恒星形成和富含气体。这种近乎二分法的现象意味着卫星矮星系在落入MW或M31的晕圈后会迅速转变。我们结合所观察到的静止分数的MW和M31卫星的卫星从探索局部体积模拟(ELVIS)的宇宙学放大模拟套件,以确定典型的时间尺度内的环境过程MW/M31晕去除气体和淬火低质量卫星星系的恒星形成。M_星小于10^8 M_日的卫星的猝灭时间尺度很短,小于2 Gyr,并且在较低的M_星处猝灭更快。如果把MW/M31坠落前卫星被低质量组预处理的时间包括在内,这些卫星猝灭的时间尺度可能要长1 - 2 Gyr。我们比较了以前工作中更大质量卫星星系的猝灭时间尺度,综合了M_star = 10^{3-11} M_sun可观测范围内卫星星系猝灭的性质。随着卫星M_star的增加,卫星猝灭时间尺度迅速增加,在M_star ~ 10^9 M_sun时,猝灭时间尺度在~9.5 Gyr处达到峰值,在M_star更高时,猝灭时间尺度迅速减小到< 5 Gyr at M_star >5 x 10^9 M_sun。总的来说,与麦哲伦云相似,M_star ~ 10^9 M_sun的星系表现出最长的猝灭时标,无论环境或内部机制如何。

英文摘要:

In the Local Group, nearly all of the dwarf galaxies (M_star < 10^9 M_sun) that are satellites within 300 kpc (the virial radius) of the Milky Way (MW) and Andromeda (M31) have quiescent star formation and little-to-no cold gas. This contrasts strongly with comparatively isolated dwarf galaxies, which are almost all actively star-forming and gas-rich. This near dichotomy implies a rapid transformation of satellite dwarf galaxies after falling into the halos of the MW or M31. We combine the observed quiescent fractions for satellites of the MW and M31 with the infall times of satellites from the Exploring the Local Volume in Simulations (ELVIS) suite of cosmological zoom-in simulations to determine the typical timescales over which environmental processes within the MW/M31 halos remove gas and quench star formation in low-mass satellite galaxies. The quenching timescales for satellites with M_star < 10^8 M_sun are short, < 2 Gyr, and quenching is more rapid at lower M_star. These satellite quenching timescales can be 1 - 2 Gyr longer if one includes the time that satellites were environmentally preprocessed by low-mass groups prior to MW/M31 infall. We compare with quenching timescales for more massive satellites from previous works to synthesize the nature of satellite galaxy quenching across the observable range of M_star = 10^{3-11} M_sun. The satellite quenching timescale increases rapidly with satellite M_star, peaking at ~9.5 Gyr for M_star ~ 10^9 M_sun, and the timescale rapidly decreases at higher M_star to < 5 Gyr at M_star > 5 x 10^9 M_sun. Overall, galaxies with M_star ~ 10^9 M_sun, similar to the Magellanic Clouds, exhibit the longest quenching timescales, regardless of environmental or internal mechanisms.

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