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arXiv 2407.05899astro-ph.GA
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作为暗物质本质探针的银河系质量星系的并合恒星晕

The accreted stellar haloes of Milky Way-mass galaxies as a probe of the nature of the dark matter

Victor J. Forouhar Moreno, Azadeh Fattahi, Alis J. Deason, Fergus Henstridge, Alejandro Benítez-Llambay

备注：
Accepted for publication in MNRAS. 14 pages, 8 figures
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AI总结：

本研究利用基于EAGLE模型的宇宙流体动力学模拟，对比冷、温、自相互作用暗物质模型下银河系质量星系的并合恒星晕性质，发现恒星晕相空间结构可作为区分暗物质模型的探针。

摘要：

星系恒星晕主要由宿主星系组装过程中并合的星系遗迹构成，因此其性质反映了卫星星系的质量谱与并合后演化过程。由于暗物质（DM）的本质会对这两方面都产生影响，我们探究了冷暗物质（CDM）、温暗物质（WDM）和自相互作用暗物质（SIDM）模型下并合恒星成分的性质差异。我们利用基于EAGLE（星系演化与环境反馈）星系形成模型的宇宙流体动力学模拟，研究了8个银河系质量暗晕周围的并合恒星族，发现不同模型下的并合恒星质量基本相近。与CDM相比仅存在微小差异的WDM不同，SIDM中并合恒星的分布在$0.05R_{200}$（$10\text{kpc}$）范围内发生了显著变化：中心密度降至$\langle ρ^{\text{SIDM}}_{\text{exsitu}} / ρ^{\text{CDM}}_{\text{exsitu}} \rangle = 0.3$，径向分布更平缓，对数密度斜率分别为$\langle α_{\text{SIDM}} \rangle = -1.4$和$\langle α_{\text{CDM}} \rangle = -1.7$。此外，与CDM中的对应恒星相比，这些恒星的轨道更具切向性，速度各向异性变化量为$\langle Δβ\rangle = - 0.2$。最后，SIDM恒星晕在半径-径向速度空间中拥有数量最多、最显著的超密结构。这是恒星晕前身星并合时标更短与宿主引力势更平缓共同作用的结果，前者导致动力学摩擦和轨道径向化的作用时间更短。综上，我们证明星系恒星晕的相空间结构蕴含关键信息，可用于区分和排除不同的暗物质模型。

英文摘要：

Galactic stellar haloes are largely composed of the remnants of galaxies accreted during the assembly of their host galaxies, and hence their properties reflect the mass spectrum and post-accretion evolution of their satellites. As the nature of dark matter (DM) can affect both, we explore how the properties of the accreted stellar component vary across cold (CDM), warm (WDM) and self-interacting (SIDM) models. We do this by studying accreted stellar populations around eight MW-mass haloes using cosmological hydrodynamical simulations based on the EAGLE galaxy formation model, in which we find that the accreted stellar mass remains similar across models. Contrary to WDM, which only presents minor differences relative to CDM, the distribution of accreted stars in SIDM changes significantly within $0.05R_{200}$ ($10\,\mathrm{kpc}$). The central density reduces to $\langle ρ^{\mathrm{SIDM}}_{\mathrm{exsitu}} / ρ^{\mathrm{CDM}}_{\mathrm{exsitu}} \rangle = 0.3$ and has a shallower radial dependence, with logarithmic density slopes of $\langle α_{\mathrm{SIDM}} \rangle = -1.4$ vs $\langle α_{\mathrm{CDM}} \rangle = -1.7$. Additionally, stars are on more tangential orbits than their CDM counterparts, with a change in the velocity anisotropy of $\langle Δβ\rangle = - 0.2$. Finally, SIDM stellar haloes have the largest number and prominence of overdensities in radius vs radial velocity space. This is due to a combination of shorter stellar halo progenitor merging timescales and shallower host potentials, with the former resulting in less time for dynamical friction and radialisation to operate. In summary, we show that the phase-space structure of galactic stellar haloes encode key information that can be used to distinguish and rule out different DM models.

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