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arXiv 1202.2357astro-ph.CO
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星系团中的浅暗物质尖点

Shallow Dark Matter Cusps in Galaxy Clusters

Chervin F. P. Laporte, Simon D. M. White, Thorsten Naab, Mateusz Ruszkowski, Volker Springel

摘要:

我们利用Ruszkowski & Springel(2009)的高分辨率无碰撞模拟研究了$z=3$到现在时期$10^{15} \, \rm{M_{\odot}}$星系团中恒星和暗物质组分的演化。在$z=3$的主要祖晕填充与球形模型星系的绝热收缩和不占。我们应用加权方案,使我们能够改变分配给每个模拟粒子的黑暗和恒星材料的相对量,以产生更好地同意与丰度匹配的参数和观测到的凸起尺寸在$z=3$的发光特性。这使得研究初始紧度对质量-尺寸关系演化的影响成为可能。我们发现,对于更紧凑的初始恒星分布的最终Brilliant星团星系的大小增长与质量根据$r\propto M^{2}$,而更广泛的初始分布,$r\propto M$。我们的研究结果表明,在宇宙学的背景下,无碰撞合并可以降低内部暗物质尖点的强度,在固定半径的对数斜率为0.3至0.5的变化。因此,像最近在几个强透镜星系团中发现的那些浅尖点不一定与CDM相冲突,而是可能反映了祖先星系的初始结构,这些结构是在它们的形成过程中在高红移下形成的。

英文摘要:

We study the evolution of the stellar and dark matter components in a galaxy cluster of $10^{15} \, \rm{M_{\odot}}$ from $z=3$ to the present epoch using the high-resolution collisionless simulations of Ruszkowski & Springel (2009). At $z=3$ the dominant progenitor halos were populated with spherical model galaxies with and without accounting for adiabatic contraction. We apply a weighting scheme which allows us to change the relative amount of dark and stellar material assigned to each simulation particle in order to produce luminous properties which agree better with abundance matching arguments and observed bulge sizes at $z=3$. This permits the study of the effect of initial compactness on the evolution of the mass-size relation. We find that for more compact initial stellar distributions the size of the final Brightest Cluster Galaxy grows with mass according to $r\propto M^{2}$, whereas for more extended initial distributions, $r\propto M$. Our results show that collisionless mergers in a cosmological context can reduce the strength of inner dark matter cusps with changes in logarithmic slope of 0.3 to 0.5 at fixed radius. Shallow cusps such as those found recently in several strong lensing clusters thus do not necessarily conflict with CDM, but may rather reflect on the initial structure of the progenitor galaxies, which was shaped at high redshift by their formation process.

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