Dynamical Evidence for a Massive, Young Globular Cluster in NGC 1569
Dynamical Evidence for a Massive, Young Globular Cluster in NGC 1569
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DOI：
10.1086/310181
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发表时间：
1996-05
期刊：
影响因子：
--
通讯作者：
L. C. Ho;A. Filippenko
中科院分区：
文献类型：
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作者：
L. C. Ho;A. Filippenko
最近用哈勃太空望远镜（HST）进行的高分辨率观测表明，在各种星暴系统中都常见具有非凡亮度和致密性的星团。人们猜测这些星团代表了当今年轻球状星团的类似物。使用 Keck 10 m 望远镜上的 HIRES 中阶梯光栅摄谱仪，我们获得了附近矮星系 NGC 1569 中的一个“超级星团”（星团“A”）的高色散光谱。该星团的大小可从已发表的 HST 图像中得知。视线速度色散 (σ* = 15.7 ± 1.5 km s-1) 是通过对其可见波长处的积分光谱进行互相关分析来测量的。如果星团受到引力束缚并且速度是各向同性的，则应用维里定理意味着该星团的总恒星质量为 (3.3 ± 0.5) × 105 M☉。该天体在10-15 Gyr老化后的质量、质量密度和可能的质光比与银河球状星团的典型值完全一致。我们的结果强烈表明，至少一些通过 HST 发现的发光、致密、年轻的星团确实会演变成银河系中所见类型的正常球状星团。
Recent high-resolution observations with the Hubble Space Telescope (HST) reveal that star clusters of extraordinary luminosity and compactness are commonly found in a variety of starburst systems. There has been much speculation that these clusters represent present-day analogs of young globular clusters. Using the HIRES echelle spectrograph on the Keck 10 m telescope, we obtained high-dispersion optical spectra of one of the “super star clusters” (cluster “A”) in the nearby dwarf galaxy NGC 1569. The size of the cluster is known from published HST images. The line-of-sight velocity dispersion (σ* = 15.7 ± 1.5 km s-1) has been measured from a cross-correlation analysis of its integrated spectrum at visual wavelengths. If the cluster is gravitationally bound and the velocities are isotropic, application of the virial theorem implies that the cluster has a total stellar mass of (3.3 ± 0.5) × 105 M☉. This object's mass, mass density, and probable mass-to-light ratio after aging 10-15 Gyr are fully consistent with the typical values of Galactic globular clusters. Our result strongly suggests that at least some of the luminous, compact, young star clusters being discovered with HST will indeed evolve into normal globular clusters of the type seen in the Milky Way.