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arXiv 2001.07367astro-ph.GAastro-ph.CO
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低质量星系群的运动学动荡

Kinematic unrest of low mass galaxy groups

G. Gozaliasl, A. Finoguenov, H. G. Khosroshahi, C. Laigle, C. C. Kirkpatrick, K. Kiiveri, J. Devriendt, Y. Dubois, J. Ahoranta

备注：
9 pages, 5 figures
发表信息：
A&A 635, A36 (2020)
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摘要：

为了更好地了解星系群的形成，我们研究了宇宙演化巡天（COSMOS）中大量光谱证实的X射线星系群的运动学，其中星系群成员的采样率高达$z=1$。我们比较了我们的结果与{ \sc Horizon-AGN}的宇宙流体动力学模拟的预测。利用相空间动力学方法分析了晕质量为$M_{\mathrm{200c}}\sim 10^{12.6}-10^{14.50}M_\odot$的星系群的动力学性质，结果表明，低质量星系群（$M_{\mathrm{200c}}<2 \times 10^{13} M_\odot$）中最亮的星系群（BGG）比高质量星系群具有更大的相对于群速度色散的自行. BGG固有速度与该组速度离散度之比的离散度$σ_{\mathrm{BGG}}/σ_{group}$，对于低质量组平均为$1.48 \pm 0.13$，对于高质量组平均为$1.01 \pm 0.09$。对{ \sc Horizon-AGN}模拟的比较分析表明，随着星系群质量的减小，BGG特有速度的传播也有类似的增加，尽管BGG特有速度分布的振幅、形状和模式只有在高质量星系群中才能保持一致。拥有一个具有大的奇特速度的BGG的群更有可能从$L_x-σ_{v}$关系中偏移;这可能是因为BGG的奇特运动受到新成员吸积的影响。

英文摘要：

In an effort to better understand the formation of galaxy groups, we examine the kinematics of a large sample of spectroscopically confirmed X-ray galaxy groups in the Cosmic Evolution Survey (COSMOS) with a high sampling of galaxy group members up to $z=1$. We compare our results with predictions from the cosmological hydrodynamical simulation of {\sc Horizon-AGN}. Using a phase-space analysis of dynamics of groups with halo masses of $M_{\mathrm{200c}}\sim 10^{12.6}-10^{14.50}M_\odot$, we show that the brightest group galaxies (BGG) in low mass galaxy groups ($M_{\mathrm{200c}}<2 \times 10^{13} M_\odot$) have larger proper motions relative to the group velocity dispersion than high mass groups. The dispersion in the ratio of the BGG proper velocity to the velocity dispersion of the group, $σ_{\mathrm{BGG}}/σ_{group}$, is on average $1.48 \pm 0.13$ for low mass groups and $1.01 \pm 0.09$ for high mass groups. A comparative analysis of the {\sc Horizon-AGN} simulation reveals a similar increase in the spread of peculiar velocities of BGGs with decreasing group mass, though consistency in the amplitude, shape, and mode of the BGG peculiar velocity distribution is only achieved for high mass groups. The groups hosting a BGG with a large peculiar velocity are more likely to be offset from the $L_x-σ_{v}$ relation; this is probably because the peculiar motion of the BGG is influenced by the accretion of new members.

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