论文标题
当地宇宙中的早期型矮星系。现场增长的证据
Early-type Dwarf Galaxies in the Local Universe. Evidence of Ex-situ Growth
论文作者
论文摘要
我们报告发现罕见的早期型矮星银河系（DE），SDSS J125651.47+163024.2（以下简称DE1256），具有潮汐功能，可能是由于更小的较小矮星银河而建立的。 DE1256位于处女座集群郊区的几乎孤立的环境中。一项详细的形态检查表明，积聚的恒星种群主要沉积在DE1256的外部，那里的潮汐尾巴最为突出。 DE1256的内部部分完美地模拟了索引n = 0.63和半光radius r $ _ {h} $ = 0.6 kpc的简单sérsic函数，但相反，整个星系的大小为r $ _ {h} $ = 1.2 kpc。假设观察到的两个成分，即内部sérsic和外部潮汐尾部残留物，宿主与推定的矮矮星系之间的质量比为5：1，代表了宿主的恒星群体。我们建议，尽管积聚只占整体恒星人口的20％，但通过增生事件，DE1256的大小增加了两倍。我们的结果首次提供了强有力的观察证据，即DE正在经历两相生长，这是大型星系的常见现象。
We report the discovery of a rare early-type dwarf galaxy (dE), SDSS J125651.47+163024.2 (hereafter dE1256), possessing a tidal feature that was likely built up by accretion of an even smaller dwarf galaxy. dE1256 is located in a nearly isolated environment, at the outskirt of the Virgo cluster. A detailed morphological examination reveals that the accreted stellar population is mainly deposited in the outer part of dE1256, where the tidal tail is most prominent. The inner part of dE1256 is perfectly modeled with a simple Sérsic function of index n = 0.63 and half-light radius R$_{h}$ = 0.6 kpc, but in contrast, the entire galaxy has a size of R$_{h}$ = 1.2 kpc. The mass ratio between the host and the putative accreted dwarf galaxy is calculated to be 5:1, assuming that the observed two components, inner Sérsic, and outer tidal tail residual, represent the host's and accreted galaxy's stellar populations, respectively. We suggest that while the accretion contributes only 20% of the overall stellar population, the size of dE1256 grew by a factor of two via the accretion event. Our results provide, for the first time, strong observational evidence that a dE is undergoing a two-phase growth, a common phenomenon for massive galaxies.
