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arXiv 1310.2255astro-ph.COastro-ph.GA
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暗物质晕对早型星系尺寸和速度弥散演化的影响

The imprint of dark matter haloes on the size and velocity dispersion evolution of early-type galaxies

Lorenzo Posti, Carlo Nipoti, Massimo Stiavelli, Luca Ciotti

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15 pages, 14 figures, 1 table. Matches the Accepted version from MNRAS
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摘要：

早期型星系（ETG）被观察到更紧凑，平均而言，在$z \gtrsim 2$比在$z\simeq 0$，在固定的恒星质量。最近的观测工作表明，这种大小的演变可能反映了类似的主机暗物质晕密度的星系淬火时间的函数的演变。我们通过研究晕中心速度色散（$σ_0$）和半质量半径（$r_{\rm h}$）的分布作为晕质量$M$和红移$z$的函数，在宇宙学$Λ$ -CDM $N$ -体模拟中探索了这一假设。在$0\lesssim z\lesssim 2.5$的范围内，我们发现$σ_0\propto M^{0.31-0.37}$和$r_{\rm h}\propto M^{0.28-0.32}$，接近同源病毒化系统的预期值。在$10^{11} M_\odot \lesssim M\lesssim 5.5 \times 10^{14} M_\odot$范围内的固定$M$处，我们发现$σ_0\propto(1+z)^{0.35}$和$r_{\rm h}\propto(1+z)^{-0.7}$。我们表明，这种演变的晕标度律是由个人的晕增长质量的演变轨道$σ_0\propto M^{0.2}$和$r_{\rm h}\propto M^{0.6}$，符合简单的无耗散合并模型，其中遇到轨道能量占。我们比较了$N$体数据与在$0\lesssim z\lesssim3$观测到的ETG，通过在简单但合理的假设下用恒星成分填充晕：由此产生的星系演化与观测到的ETG一致，直到$z \simeq 2$，但该模型难以再现在$z\gtrsim 2$观测到的快速演化。我们的结论是，相当大一部分的ETG的大小演变可以归因于系统的依赖红移的暗物质晕结构特性。

英文摘要：

Early-type galaxies (ETGs) are observed to be more compact, on average, at $z \gtrsim 2$ than at $z\simeq 0$, at fixed stellar mass. Recent observational works suggest that such size evolution could reflect the similar evolution of the host dark matter halo density as a function of the time of galaxy quenching. We explore this hypothesis by studying the distribution of halo central velocity dispersion ($σ_0$) and half-mass radius ($r_{\rm h}$) as functions of halo mass $M$ and redshift $z$, in a cosmological $Λ$-CDM $N$-body simulation. In the range $0\lesssim z\lesssim 2.5$, we find $σ_0\propto M^{0.31-0.37}$ and $r_{\rm h}\propto M^{0.28-0.32}$, close to the values expected for homologous virialized systems. At fixed $M$ in the range $10^{11} M_\odot \lesssim M\lesssim 5.5 \times 10^{14} M_\odot$ we find $σ_0\propto(1+z)^{0.35}$ and $r_{\rm h}\propto(1+z)^{-0.7}$. We show that such evolution of the halo scaling laws is driven by individual haloes growing in mass following the evolutionary tracks $σ_0\propto M^{0.2}$ and $r_{\rm h}\propto M^{0.6}$, consistent with simple dissipationless merging models in which the encounter orbital energy is accounted for. We compare the $N$-body data with ETGs observed at $0\lesssim z\lesssim3$ by populating the haloes with a stellar component under simple but justified assumptions: the resulting galaxies evolve consistently with the observed ETGs up to $z \simeq 2$, but the model has difficulty reproducing the fast evolution observed at $z\gtrsim 2$. We conclude that a substantial fraction of the size evolution of ETGs can be ascribed to a systematic dependence on redshift of the dark matter haloes structural properties.

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