用LCDM宇宙学模拟矮星系：模拟围绕Milky Way质量星系的真实卫星群
Reconciling dwarf galaxies with LCDM cosmology: Simulating a realistic population of satellites around a Milky Way-mass galaxy
摘要：
低质量“矮”星系是对冷暗物质（CDM）宇宙结构形成模型的最大挑战。由于这些微弱的星系在银河系（MW）和仙女座（M31）的本星系群（LG）中被观测到，因此了解它们在这样的环境中的形成至关重要。我们目前的第一个结果，从拿铁项目：银河系火灾（反馈在现实环境中）。这个模拟模拟了一个MW质量星系在LCDM宇宙学中z = 0时的形成，包括暗物质、气体和恒星，其分辨率前所未有：重子粒子质量为7070 Msun，气体核/软化适应到1 pc（z = 0时的中值为25 - 60 pc）。Latte的模拟使用GIZMO代码，无网格方法精确的流体动力学和FIRE-2模型的恒星形成和显式反馈内的多相星际介质。这是第一次，Latte自洽地解决了对应于半光半径的矮星系的空间尺度，这些星系形成于MW质量的宿主周围，直到Mstar > 10^5 Msun。Latte的矮星系人口与LG在广泛的性质上一致：（1）恒星质量和恒星速度色散（动力学质量）的分布，包括它们的联合关系;（2）质量-金属丰度关系;（3）各种各样的恒星形成历史，包括它们的质量依赖性。因此，Latte产生了一个真实的Mstar > 10^5 Msun的矮星系群，它不会受到小尺度结构形成的“丢失卫星”或“太大而不能倒”问题的困扰。我们的结论是，重子物理可以调和观测到的矮星系与标准LCDM宇宙学。
英文摘要：
Low-mass "dwarf" galaxies represent the most significant challenges to the cold dark matter (CDM) model of cosmological structure formation. Because these faint galaxies are (best) observed within the Local Group (LG) of the Milky Way (MW) and Andromeda (M31), understanding their formation in such an environment is critical. We present first results from the Latte Project: the Milky Way on FIRE (Feedback in Realistic Environments). This simulation models the formation of a MW-mass galaxy to z = 0 within LCDM cosmology, including dark matter, gas, and stars at unprecedented resolution: baryon particle mass of 7070 Msun with gas kernel/softening that adapts down to 1 pc (with a median of 25 - 60 pc at z = 0). Latte was simulated using the GIZMO code with a mesh-free method for accurate hydrodynamics and the FIRE-2 model for star formation and explicit feedback within a multi-phase interstellar medium. For the first time, Latte self-consistently resolves the spatial scales corresponding to half-light radii of dwarf galaxies that form around a MW-mass host down to Mstar > 10^5 Msun. Latte's population of dwarf galaxies agrees with the LG across a broad range of properties: (1) distributions of stellar masses and stellar velocity dispersions (dynamical masses), including their joint relation; (2) the mass-metallicity relation; and (3) a diverse range of star-formation histories, including their mass dependence. Thus, Latte produces a realistic population of dwarf galaxies at Mstar > 10^5 Msun that does not suffer from the "missing satellites" or "too big to fail" problems of small-scale structure formation. We conclude that baryonic physics can reconcile observed dwarf galaxies with standard LCDM cosmology.
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