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arXiv 1802.05916astro-ph.GA
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Horizon-AGN模拟中的早型星系自旋演化

Early-type galaxy spin evolution in the Horizon-AGN simulation

Hoseung Choi, Sukyoung K. Yi, Yohan Dubois, Taysun Kimm, Julien. E. G. Devriendt, Christophe Pichon

摘要:

利用Horizon-AGN模拟数据,研究了$z \simeq 1$后合并和环境效应在形成早型星系自旋中的相对作用。我们跟踪了10,037个质量大于10个$^{10} \rm \, M_{\odot}$的色选ETG的自旋演化,这些ETG分为四组:星团中心(3%),星团卫星(33%),集团中心(5%)和场ETG(59%)。我们发现了一个很强的慢转子分数,$f_{\rm SR}$,和大规模ETG的平均自旋的质量依赖性。虽然我们没有发现$f_{\rm SR}$的明显的环境依赖性,但在卫星ETG驱动的自旋参数的平均值中可以看到微弱的趋势,因为它们随着环境变得更密集而逐渐失去自旋。星系合并似乎是总自旋变化的主要原因,在94%的中央ETG与$M_{vir} > 10^{12.5}\rm M_{\odot}$,但只有22%的卫星和外地ETG的晕。我们发现,非合并引起的潮汐扰动更好地与卫星ETG星系自旋下降比合并。考虑到大多数ETG在稠密环境中不处于中心位置,我们得出结论,非合并潮汐扰动效应在局部($z < 1$)宇宙中观察到的ETG自旋演化中发挥了关键作用。

英文摘要:

Using the Horizon-AGN simulation data, we study the relative role of mergers and environmental effects in shaping the spin of early-type galaxies (ETGs) after $z \simeq 1$. We follow the spin evolution of 10,037 color-selected ETGs more massive than 10$^{10} \rm \, M_{\odot}$ that are divided into four groups: cluster centrals (3%), cluster satellites (33%), group centrals (5%), and field ETGs (59%). We find a strong mass dependence of the slow rotator fraction, $f_{\rm SR}$, and the mean spin of massive ETGs. Although we do not find a clear environmental dependence of $f_{\rm SR}$, a weak trend is seen in the mean value of spin parameter driven by the satellite ETGs as they gradually lose their spin as their environment becomes denser. Galaxy mergers appear to be the main cause of total spin changes in 94% of central ETGs of halos with $M_{vir} > 10^{12.5}\rm M_{\odot}$, but only 22% of satellite and field ETGs. We find that non-merger induced tidal perturbations better correlate with the galaxy spin-down in satellite ETGs than mergers. Given that the majority of ETGs are not central in dense environments, we conclude that non-merger tidal perturbation effects played a key role in the spin evolution of ETGs observed in the local ($z < 1$) universe.

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