Title: Globular Clusters in NGC 4839 Falling into Coma: Evidence for the Second Infall? Show Chinese title

Title: NGC 4839中的球状星团落入室女座：第二次吸积的证据？

Abstract: NGC 4839 is the brightest galaxy (cD) of the NGC 4839 group at $R\approx 1$ Mpc in the south-west of the Coma cluster, which is known to be falling into Coma. However, it has been controversial whether it is in the first phase of infall or in the second phase of infall after passing the Coma center. We present a wide field study of globular clusters (GCs) in NGC 4839 and its environment based on Hyper Suprime-Cam $gr$ images in the Subaru archive. We compare the GC system of NGC 4839 with that of NGC 4816, which is the brightest member (S0) of the nearby group and lies at a similar distance in the west from the Coma center. Interestingly the spatial distribution of the GCs in NGC 4839 is significantly more compact than that of the GCs in NGC 4816. In addition, the radial number density profile of the GCs in NGC 4839 shows an abrupt drop at $R_{N4839}\approx 80$ kpc, while that of the GCs in NGC 4816 shows a continuous slow decline even in the outer region at $80<R_{N4816}<500$ kpc. The effective radius of the NGC 4839 GC system is about three times smaller than that of the NGC 4816 GC system. This striking difference can be explained if NGC 4839 lost a significant fraction of the GCs in its outskirt when it passed through Coma. This supports strongly the second infall scenario where the NGC 4839 passed the Coma center about 1.6 Gyr ago, and began the second infall after reaching the apocenter in the south-west recently. Show Chinese abstract

Abstract: NGC 4839是位于室女座星系团西南方向距离$R\approx 1$Mpc 处的NGC 4839星系群中最明亮的星系（cD），已知它正在向室女座星系团坠落。 然而，关于它是否处于第一次坠落阶段，或者是在经过室女座星系团中心后的第二次坠落阶段，一直存在争议。 我们基于昴宿星团档案中的Hyper Suprime-Cam $gr$图像，对NGC 4839及其环境中的球状星团（GCs）进行了大范围的研究。 我们将NGC 4839的球状星团系统与NGC 4816的球状星团系统进行了比较，NGC 4816是附近星系群中最明亮的成员（S0），位于距离室女座星系团中心相似距离的西方。 有趣的是，NGC 4839中的球状星团的空间分布明显比NGC 4816中的球状星团更紧凑。 此外，NGC 4839中球状星团的径向数量密度剖面在$R_{N4839}\approx 80$kpc 处出现急剧下降，而NGC 4816中球状星团的径向数量密度剖面即使在外部区域$80<R_{N4816}<500$kpc 处也表现出持续缓慢下降的趋势。 NGC 4839球状星团系统的有效半径大约是NGC 4816球状星团系统的三分之一。 如果NGC 4839在经过室女座星系团时失去了外围部分的球状星团，就可以解释这一显著差异。 这强有力地支持了第二次坠落情景，即NGC 4839大约在16亿年前经过了室女座星系团中心，并最近在西南方向到达远拱点后开始第二次坠落。