Clocking the formation of today’s largest galaxies: wide field integral spectroscopy of brightest cluster galaxies and their surroundings
Clocking the formation of today’s largest galaxies: wide field integral spectroscopy of brightest cluster galaxies and their surroundings
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DOI：
10.1093/mnras/stz2706
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发表时间：
2019-09
影响因子：
4.8
通讯作者：
L. Edwards;Matthew Salinas;S. Stanley;Priscilla E. Holguin West;Isabella L. Trierweiler;H. Alpert;P. Coelho;Saisneha Koppaka;G. Tremblay;H. Martel;Yuan Li
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文献类型：
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作者：
L. Edwards;Matthew Salinas;S. Stanley;Priscilla E. Holguin West;Isabella L. Trierweiler;H. Alpert;P. Coelho;Saisneha Koppaka;G. Tremblay;H. Martel;Yuan Li
通过测定从星系核心到外围再到团内光区的恒星数量和动力学，研究了局部最亮星系团（BCGs）的形成和演化。收集了23个观测到的BCGs的积分光谱，并确定了高信噪比区域。恒星人口合成代码用于确定每个区域内恒星的年龄，金属丰度，速度和速度色散。ICL光谱最好用比BCG核心更年轻且金属含量更少的人口来建模。样品的平均BCG核心年龄为$\rm 13.3\pm 2.8\，Gyr$和平均金属丰度为$\rm [Fe/H] = 0.30\pm 0.09$，而对于ICL，平均年龄为$\rm 9.2\pm 3.5\，Gyr$和平均金属丰度为$\rm [Fe/H] = 0.18\pm 0.16$。在大多数样本中（17/23），速度色散曲线是上升或平坦的，并且在某些情况下，那些上升值达到宿主星系团的速度色散值。最长的BCGs最接近星团X射线光度的峰值。这一结果与BCG核心和内部区域在很久以前快速形成的想法一致，外部区域和ICL形成的时间较晚，并通过较小的合并继续组装。任何最近在BCGs中形成的星星都是次要的组成部分，并且与星团的冷核状态有关。
The formation and evolution of local brightest cluster galaxies (BCGs) is investigated by determining the stellar populations and dynamics from the galaxy core, through the outskirts and into the intracluster light (ICL). Integral spectroscopy of 23 BCGs observed out to $4\, r_{e}$ is collected and high signal-to-noise regions are identified. Stellar population synthesis codes are used to determine the age, metallicity, velocity, and velocity dispersion of stars within each region. The ICL spectra are best modelled with populations that are younger and less metal-rich than those of the BCG cores. The average BCG core age of the sample is $\rm 13.3\pm 2.8\, Gyr$ and the average metallicity is $\rm [Fe/H] = 0.30\pm 0.09$, whereas for the ICL the average age is $\rm 9.2\pm 3.5\, Gyr$ and the average metallicity is $\rm [Fe/H] = 0.18\pm 0.16$. The velocity dispersion profile is seen to be rising or flat in most of the sample (17/23), and those with rising values reach the value of the host cluster’s velocity dispersion in several cases. The most extended BCGs are closest to the peak of the cluster’s X-ray luminosity. The results are consistent with the idea that the BCG cores and inner regions formed quickly and long ago, with the outer regions and ICL forming more recently, and continuing to assemble through minor merging. Any recent star formation in the BCGs is a minor component, and is associated with the cluster cool core status.