M83中星团的动力学质量：光纤馈电多目标光谱测试
Dynamical mass of a star cluster in M83: a test of fibre-fed multi-object spectroscopy
摘要：
目的：我们获得了M83（NGC 5236）中五个年轻大质量星系团的VLT/FLAMES+UVES高分辨率光纤馈送光谱（FFS）。这形成了一个试点研究的基础，测试使用FFS同时测量几个星团的速度色散的可行性，以确定它们的动力学质量;方法：我们采用了两种方法来确定星团的速度色散：互相关的集群光谱与模板光谱和最小化的集群光谱和加宽的模板光谱之间的卡^2值。选择M83中的805星团作为对照，通过与Larsen & Richtler获得的标准中阶梯VLT/UVES光谱的结果进行比较，来测试该方法的可靠性;结果：我们发现，对于一个星团测量的速度分散度与红巨星与红超巨星模板的选择无关，也不依赖于所采用的方法。我们从我们的FFS中测量到星系团805的速度色散为sigma_los = 10.2+/-1.1 km/s。我们的FLAMES+UVES速度色散测量给出M_vir =（6.6+/-1.7 e5 M_sun，与以前的结果一致。这比星团的光度质量大3倍，表明缺乏维里平衡。然而，基于其有效的恒星形成效率，集群是可能的维里化，并可能生存哈勃时间，在没有外部破坏性的力量;结论：我们发现，可靠的速度色散可以确定从FFS。同时观测多个星系团的优点超过了精确的星系背景减除的困难，前提是选择的目标提供足够的信噪比，并且比星系背景亮得多。
英文摘要：
(Abridged) Aims: We obtained VLT/FLAMES+UVES high-resolution, fibre-fed spectroscopy (FFS) of five young massive clusters in M83 (NGC 5236). This forms the basis of a pilot study testing the feasibility of using FFS to measure the velocity dispersions of several clusters simultaneously, in order to determine their dynamical masses; Methods: We adopted two methods for determining the velocity dispersion of the star clusters: cross-correlating the cluster spectrum with the template spectra and minimising a chi^2 value between the cluster spectrum and the broadened template spectra. Cluster 805 in M83 was chosen as a control to test the reliability of the method, through a comparison with the results obtained from a standard echelle VLT/UVES spectrum obtained by Larsen & Richtler; Results: We find no dependence of the velocity dispersions measured for a cluster on the choice of red giant versus red supergiant templates, nor on the method adopted. We measure a velocity dispersion of sigma_los = 10.2+/-1.1 km/s for cluster 805 from our FFS. Our FLAMES+UVES velocity dispersion measurement gives M_vir = (6.6+/-1.7)e5 M_sun, consistent with previous results. This is a factor of ~3 greater than the cluster's photometric mass, indicating a lack of virial equilibrium. However, based on its effective star formation efficiency, the cluster is likely to virialise, and may survive for a Hubble time, in the absence of external disruptive forces; Conclusions: We find that reliable velocity dispersions can be determined from FFS. The advantages of observing several clusters simultaneously outweighs the difficulty of accurate galaxy background subtraction, providing that the targets are chosen to provide sufficient S/N ratios, and are much brighter than the galaxy background.
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