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arXiv 2104.00672astro-ph.GA
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局域宇宙中大质量致密椭圆星系团的球状星团系统:遗迹红块的证据?

Globular Cluster Systems of Massive Compact Elliptical Galaxies in the Local Universe: Evidence for Relic Red Nuggets?

Jisu Kang, Myung Gyoon Lee

摘要:

附近的大质量致密椭圆星系(MCEG)是遗迹星系的强有力的候选者(即在高红移的红块的局部类似物)。预计遗迹星系的球状星团(GC)系统以红色(富含金属)GC为主。NGC 1277在之前的研究中被认为是这样一个星系的独特例子。在这项研究中,我们寻找GC在12个附近的MCEG的距离$\lesssim 100$兆秒差距从哈勃太空望远镜/宽视场相机3 F814 W($I_{814}$)/F160 W($H_{160}$)档案图像。我们发现,大多数这些MCEG主机的GC与$0.0<(I_{814}-H_{160})_0<1.1$的颜色范围丰富的人口。其红色GC的分数范围为$f_{RGC} =0.2$至0.7,平均值为$f_{RGC} =0.48\pm0.14$。我们将MCEG样本分为两组:一组在集群中,另一组在组/字段中。簇MCEG的平均红色GC分数为$0.60\pm0.06$,其比组/场MCEG的值$0.40\pm0.10$大0.2。MCEG星系团的$\sim$值比室女座星系团($f_{RGC} =0.33\pm0.13$)中具有类似恒星质量的巨型早型星系的平均值大0.3。我们的研究结果表明,我们的样本中的大多数MCEG确实是遗迹星系。这进一步意味着MCEG中的大多数红色GC是在大质量星系的早期形成的,并且本地宇宙中的大多数MCEG在大约10 Gyr前成为红块之后很少经历合并。

英文摘要:

Nearby massive compact elliptical galaxies (MCEGs) are strong candidates for relic galaxies (i.e. local analogs of red nuggets at high redshifts). It is expected that the globular cluster (GC) systems of relic galaxies are dominated by red (metal-rich) GCs. NGC 1277 is known as a unique example of such a galaxy in the previous study. In this study, we search for GCs in 12 nearby MCEGs at distances of $\lesssim 100$ Mpc from the Hubble Space Telescope/Wide Field Camera 3 F814W($I_{814}$)/F160W($H_{160}$) archival images. We find that most of these MCEGs host a rich population of GCs with a color range of $0.0<(I_{814}-H_{160})_0<1.1$. The fractions of their red GCs range from $f_{RGC} =0.2$ to 0.7 with a mean of $f_{RGC} =0.48\pm0.14$. We divide the MCEG sample into two groups: one in clusters and the other in groups/fields. The mean red GC fraction of the cluster MCEGs is $0.60\pm0.06$, which is 0.2 larger than the value of the group/field MCEGs, $0.40\pm0.10$. The value for the cluster MCEGs is $\sim$0.3 larger than the mean value of giant early-type galaxies with similar stellar mass in the Virgo cluster ($f_{RGC} =0.33\pm0.13$). Our results show that most of the MCEGs in our sample are indeed relic galaxies. This further implies that a majority of the red GCs in MCEGs are formed early in massive galaxies and that most MCEGs in the local universe have rarely undergone mergers after they became red nuggets about 10 Gyr ago.

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