No assembly required: mergers are mostly irrelevant for the growth of low-mass dwarf galaxies
No assembly required: mergers are mostly irrelevant for the growth of low-mass dwarf galaxies
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DOI：
10.1093/mnras/sty1488
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发表时间：
2018-01
影响因子：
4.8
通讯作者：
Alex Fitts;M. Boylan-Kolchin;J. Bullock;D. Weisz;K. El-Badry;Coral Wheeler;C. Faucher-Giguère;E. Quataert;P. Hopkins;D. Keres̆;A. Wetzel;C. Hayward
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作者：
Alex Fitts;M. Boylan-Kolchin;J. Bullock;D. Weisz;K. El-Badry;Coral Wheeler;C. Faucher-Giguère;E. Quataert;P. Hopkins;D. Keres̆;A. Wetzel;C. Hayward
作者：Fitts，A; Boylan-Kolchin，M;布洛克，JS; Weisz，DR; El-Badry，K;惠勒，C; Faucher-Giguere，CA; Quataert，E;霍普金斯，PF; Keres，D; Wetzel，A;海沃德，CC|摘要：© 2018作者。由牛津大学出版社代表皇家天文学会出版。我们研究了孤立矮星系的合并历史，基于一套15个高分辨率宇宙学放大模拟，所有的质量都是Mhalo 1010 M（和M* ~ 105 - 107 M）在z= 0，从现实环境中的反馈项目。这些矮星系在z= 0时的恒星群基本上完全是“原位”形成的：除了两种情况外，90%以上的恒星质量都是在主祖星系中形成的，所有15个星系的恒星质量都有70%是原位形成的。事实上，所有星系的合并都发生在z~ 3之前，这意味着吸积的恒星是古老的。平均而言，我们模拟的矮星在其一生中经历了五次星系合并，典型的合并前星系质量比小于1：10。这种合并的频率一般是可比的，在无耗散模拟时，再加上丰度匹配。其中两个模拟的矮星在z= 0处有一个发光的卫星伴星。这些超微弱的矮星位于或低于目前的可探测性阈值，但对下一代设施来说是有趣的目标。吸积星的贡献很小，这使得无论是用光度测量还是用解析的恒星色星等图（CMD）都很难分辨出绝大多数矮星合并的影响。近场宇宙学的重要意义是，从解析的CMD得到的大质量星系的星星形成历史（SFH）应该跟踪整个宇宙时间内一个主系统中恒星质量的积累，而不是反映合并矮星的许多单个SFH的贡献。
Author(s): Fitts, A; Boylan-Kolchin, M; Bullock, JS; Weisz, DR; El-Badry, K; Wheeler, C; Faucher-Giguere, CA; Quataert, E; Hopkins, PF; Keres, D; Wetzel, A; Hayward, CC | Abstract: © 2018 The Author(s). Published by Oxford University Press on behalf of The Royal Astronomical Society. We investigate the merger histories of isolated dwarf galaxies based on a suite of 15 highresolution cosmological zoom-in simulations, all with masses of Mhalo ≈ 1010M⊙ (and M* ~ 105 - 107M⊙) at z= 0, from the Feedback in Realistic Environments project. The stellar populations of these dwarf galaxies at z= 0 are formed essentially entirely 'in situ': over 90 per cent of the stellar mass is formed in the main progenitor in all but two cases, and all 15 of the galaxies have g 70 per cent of their stellar mass formed in situ. Virtually all galaxy mergers occur prior to z~ 3, meaning that accreted stellar populations are ancient. On average, our simulated dwarfs undergo five galaxy mergers in their lifetimes, with typical pre-merger galaxy mass ratios that are less than 1:10. This merger frequency is generally comparable to what has been found in dissipationless simulations when coupled with abundance matching. Two of the simulated dwarfs have a luminous satellite companion at z= 0. These ultra-faint dwarfs lie at or below current detectability thresholds but are intriguing targets for nextgeneration facilities. The small contribution of accreted stars makes it extremely difficult to discern the effects of mergers in the vast majority of dwarfs either photometrically or using resolved-star colour-magnitude diagrams (CMDs). The important implication for near-field cosmology is that star formation histories (SFHs) of comparably massive galaxies derived from resolved CMDs should trace the build-up of stellar mass in one main system across cosmic time as opposed to reflecting the contributions of many individual SFHs of merged dwarfs.