论文标题
旧矮星系中的星爆核
Starbursting Nuclei in Old Dwarf Galaxies
论文作者
论文摘要
早期型矮星系的核（DES）通常比星系主体年轻，而且这种年龄的差异一直是一个难题。为了探索DES中年轻核的起源，我们研究了具有与Des'核相似但迄今为止蓝色的DES样品。我们发现（1）紧凑的星形斑点的典型恒星质量为宿主星系恒星质量的百分之一； （2）一些斑点位于星系中心的略微位置； （3）从公开可用的斯隆数字天空调查纤维光谱中测得的H $α$同等宽度显示它们的形成年龄很少。 （4）它们的发射线金属度为12 \，+\，log（o/h）与太阳值一样高，而基础星系具有典型的des恒星种群，即log（z/z $ _ {\ sun} $ _ {\ sun} $）\，$ \ sim $ \，$ \，$ - 0.8 $。基于结果，我们认为，中央恒星形成的斑点可以提供DES中核形成的肉眼观点，并讨论旧DES中幼小核的可能形成机制。我们特别建议这些不中心的紧凑型恒星形成区域可以作为\ cite {guillard16}的“湿迁移”场景中提出的核的种子。
Nuclei of early-type dwarf galaxies (dEs) are usually younger than the galaxy main body, and such discrepancy in age has been a puzzle. To explore the origin of young nuclei in dEs, we study a sample of dEs having compact star-forming blobs that are visually similar to dEs' nuclei but by far bluer. We find that (1) the compact star-forming blobs have a typical stellar mass of one percent of the host galaxy stellar mass; (2) some of the blobs are positioned slightly off from the center of the galaxies; (3) the H$α$ equivalent width measured from the publicly available Sloan Digital Sky Survey fiber spectroscopy shows their formation ages being an order of few Mega-year; and (4) their emission line metallicities, 12\,+\,log(O/H), are as high as the solar value, while the underlying galaxies have the typical stellar populations of dEs, i.e., log(Z/Z$_{\sun}$)\,$\sim$\,$-0.8$. Based on the results, we argue that the central star-forming blobs can provide a caught-in-the-act view of nuclei formation in dEs, and discussing possible formation mechanisms of young nuclei in old dEs. We particularly propose that these off-centered compact star-forming regions may act as seeds of nuclei as proposed in the `wet migration' scenario of \cite{Guillard16}.
