探测年轻星团中的近红外通量过剩
Probing the near-IR flux excess in young star clusters
摘要：
本文报道了最近对明亮的蓝色致密星系中的年轻星团的研究结果。YSC的年龄分布表明，Haro 11、ESO 185-IG 13和Mrk 930的星暴事件开始于不超过3000万至4000万年前。观察到一个只有3 - 4百万年历史的团簇形成高峰，揭示了一个仍然部分嵌入的独特的团簇样本。相当大一部分的集群（30 - 50%），主要是年轻的10万年，显示出观察到的通量过剩0.8和2.2微米之间。这种所谓的近红外（NIR）过量是不可能重现的，即使是最新的光谱合成模型（包括自洽处理的光电离气体）。我们已经使用这些YSC来探测星团非常早期的演化阶段。在所有三个宿主星系中，分析仅限于光学上最亮的物体，即，只有部分被其出生茧嵌入的系统（因为深度嵌入的集群可能太微弱而无法被检测到）。我们讨论了可能的解释，这种近红外过量的背景下，银河系外的年轻星团和解决大规模恒星形成地区在银河系和附近的麦哲伦星云的红外研究。
英文摘要：
We report the results of a recent study of young star clusters (YSCs) in luminous blue compact galaxies (BCGs). The age distributions of the YSCs suggest that the starburst episode in Haro 11, ESO 185-IG13, and Mrk 930 started not more than 30-40 Myr ago. A peak of cluster formation only 3 - 4 Myr old is observed, unveiling a unique sample of clusters still partially embedded. A considerable fraction of clusters (30 - 50%), mainly younger than 10 Myr, shows an observed flux excess between 0.8 and 2.2 micron. This so-called near-infrared (NIR) excess is impossible to reproduce even with the most recent spectral synthesis models (that include a self-consistent treatment of the photoionized gas). We have used these YSCs to probe the very early evolution phase of star clusters. In all the three host galaxies, the analysis is limited to the optically brightest objects, i.e., systems that are only partially embedded by their natal cocoons (since deeply embedded clusters are probably too faint to be detected). We discuss possible explanations for this NIR excess, in the context of IR studies of both extragalactic young star clusters and resolved massive star forming regions in the Milky Way and in the nearby Magellanic Clouds.
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