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arXiv 1509.04716astro-ph.SRastro-ph.GA
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岛弧群的扩展结构与潮汐半径

The Arches Cluster: Extended Structure and Tidal Radius

Matthew W. Hosek, Jessica R. Lu, Jay Anderson, Andrea M. Ghez, Mark R. Morris, William I. Clarkson

摘要:

在距离人马座A* 约26 pc的投影距离处,拱门星团提供了在极端银河系中心(GC)环境中恒星形成的洞察力。尽管它的重要性,许多关键属性,如集群的内部结构和轨道历史并不为人所知。本文利用HST WFC 3 IR对拱星团(R > 6.25”)的外围区域进行了天体测量和测光研究。利用自行,我们计算了在120”x 120”视场内,F153 M = 20等(~2.5 M_sun)恒星的成员概率,这个视场比以前对该星团的天体测量研究大144倍。我们构造了半径为75”(8 kpc时约为3 pc)的拱的径向轮廓,这可以很好地用单一的幂律来描述。从这个配置文件中,我们放置一个3-sigma下限为2.8 pc的观测潮汐半径,这是大于预测的潮汐半径(1 - 2.5 pc)。在整个星系团中都观察到了质量分离的证据,并且沿着轨道路径没有明显的潮汐尾结构。在轮廓中没有断裂表明,在大约0.2 - 100万年前,拱门不太可能经历过最接近GC的过程。如果精确,则此约束表明星团位于椭圆轨道上,并且位于与Sgr A* 相交的天空平面的前面。然而,进一步模拟集群的GC潜力需要解释观察到的配置文件更有信心。

英文摘要:

At a projected distance of ~26 pc from Sgr A*, the Arches cluster provides insight to star formation in the extreme Galactic Center (GC) environment. Despite its importance, many key properties such as the cluster's internal structure and orbital history are not well known. We present an astrometric and photometric study of the outer region of the Arches cluster (R > 6.25") using HST WFC3IR. Using proper motions we calculate membership probabilities for stars down to F153M = 20 mag (~2.5 M_sun) over a 120" x 120" field of view, an area 144 times larger than previous astrometric studies of the cluster. We construct the radial profile of the Arches to a radius of 75" (~3 pc at 8 kpc), which can be well described by a single power law. From this profile we place a 3-sigma lower limit of 2.8 pc on the observed tidal radius, which is larger than the predicted tidal radius (1 - 2.5 pc). Evidence of mass segregation is observed throughout the cluster and no tidal tail structures are apparent along the orbital path. The absence of breaks in the profile suggests that the Arches has not likely experienced its closest approach to the GC between ~0.2 - 1 Myr ago. If accurate, this constraint indicates that the cluster is on a prograde orbit and is located front of the sky plane that intersects Sgr A*. However, further simulations of clusters in the GC potential are required to interpret the observed profile with more confidence.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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