高分辨率宇宙学模拟中星系周介质的环境依赖性
The environmental dependence of the circumgalactic medium in a high-resolution cosmological simulation
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- INAF-IASF Milano（意大利国家天体物理研究所米兰天文台）
- IUCAA（印度大学天体物理研究中心）
- INAF - Osservatorio Astronomico di Trieste（意大利国家天体物理研究所的里雅斯特天文台）
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中文总结 AI 辅助
本研究利用高分辨率宇宙学模拟，首次探究大尺度结构对星系周介质冷暖气相的影响，发现仅当包含卫星星系时才能重现观测到的环境依赖性，强调观测中需区分中央星系与卫星星系。
中文摘要 AI 辅助
观测证据日益表明，星系的星系周介质（CGM）取决于其所嵌入的大尺度结构。当使用类星体视线通过吸收线探测CGM时，研究发现，与孤立星系相比，处于过密环境中的星系的CGM具有更高的天空覆盖率。然而，这种环境依赖性的确切原因仍不清楚。在本工作中，我们旨在首次模拟大尺度结构对CGM的冷和暖（$T\sim10^{4-5}$ K）气体相的影响。我们使用基于EAGLE星系形成模型的高分辨率（$m_{gas}\approx 4.5\times 10^4$ M$_{\odot}$，$m_{dm}\approx 2.4\times 10^5$ M$_{\odot}$）宇宙学模拟。我们选取所有在$z=0$时恒星质量$M_*>10^8$ M$_\odot$的星系，并使用Friends-of-Friends算法将它们分为过密环境中的星系（群星系）和孤立星系。对于这两个样本，我们研究大尺度结构如何影响CGM的物理性质以及冷和暖气体相的测量覆盖比例。当两个群星系和孤立星系样本在恒星质量、暗物质晕质量上匹配，且我们仅使用中央星系时，我们未发现CGM的物理性质和测量的覆盖比例存在显著差异。然而，当包含卫星星系时，我们恢复了覆盖比例差异随环境变化的观测趋势。恢复观测趋势的困难表明在模拟中捕捉多相CGM的复杂性。然而，由于我们关于卫星星系混合的结果不依赖于所采用的子网格物理，本工作表明，在观测研究中需要将中央星系和卫星星系区分开来，以清晰辨别环境对CGM的作用。
英文摘要
There is increasing evidence from observations that the circumgalactic medium (CGM) of galaxies depends on the large-scale structure in which they are embedded. When probing the CGM in absorption using quasar sightlines, studies find an enhanced sky coverage in the CGM of galaxies in overdensities compared to galaxies in isolation. However, the exact reason for this environmental dependence is still unclear. In this work we aim to model for the first time the influence of the large-scale structure on the cool and warm ($T\sim10^{4-5}$ K) gas phases of the CGM. We use a high-resolution ($m_{gas}\approx 4.5\times 10^4$ M$_{\odot}$, $m_{dm}\approx 2.4\times 10^5$ M$_{\odot}$) cosmological simulation based on the EAGLE model of galaxy formation. We select all galaxies at $z=0$ with stellar mass $M_*>10^8$ M$_\odot$ and split them into galaxies in overdensities (group galaxies) and galaxies in isolation using a Friends-of-Friends algorithm. For these two samples, we investigate how the large-scale structure influences the physical properties of the CGM and the measured covering fractions of the cool and warm gas phases. When the two samples of group and isolated galaxies are matched in stellar mass, halo mass, and we use only central galaxies, we do not find any significant difference in the physical properties of the CGM and the measured covering fractions. However, when satellite galaxies are included, we recover the observational trends in the difference of covering fractions with the environment. The difficulty of recovering the observational trends shows the complexity of capturing the multiphase CGM in simulations. However, since our results concerning the admixture of satellites are independent of the employed subgrid physics, this work shows that central galaxies and satellites need to be disentangled in observational studies to clearly discern the role of the environment on the CGM.
