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首页> 外文期刊>The Astrophysical journal >THE DIFFERENT ENVIRONMENTAL DEPENDENCIES OF STAR FORMATION FOR GIANT AND DWARF GALAXIES
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THE DIFFERENT ENVIRONMENTAL DEPENDENCIES OF STAR FORMATION FOR GIANT AND DWARF GALAXIES

机译：巨型星系和矮星系星系形成的不同环境依赖

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摘要

We examine the origins of the bimodality observed in the global properties of galaxies around a stellar mass of 3 x 10~(10) solar mass by comparing the environmental dependencies of star formation for the giant and dwarf galaxy populations. The Sloan Digital Sky Survey DR4 spectroscopic data set is used to produce a sample of galaxies in the vicinity of the supercluster centered on the cluster A2199 at z = 0.03 that is approx> 90% complete to M_r~* + 3.3. From this we measure global trends with environment for both giant (M_r < -20 mag) and dwarf ( - 19 < M_r < -17.8 mag) subsamples using the luminosity-weighted mean stellar age and Ha emission as independent measures of star formation history. The fraction of giant galaxies classified as old (t > 7 Gyr) or passive (EW [Hα] ≤ 4 A) falls gradually from approx> 80% in the cluster cores to ～40% in field regions beyond 3-4R_(vir), as found in previous studies. In contrast, we find that the dwarf galaxy population shows a sharp transition at ～1R_(vir), from being predominantly old/passive within the cluster, to outside where virtually all galaxies are forming stars and old/passive galaxies are only found as satellites to more massive galaxies. These results imply fundamental differences in the evolution of giant and dwarf galaxies: whereas the star formation histories of giant galaxies are determined primarily by their merger history, star formation in dwarf galaxies is much more resilient to the effects of major mergers. Instead, dwarf galaxies become passive only once they become satellites within a more massive halo either by losing their halo gas reservoir to the host halo or through other environment-related processes such as galaxy harassment and ram pressure stripping.
机译：通过比较巨大星系和矮星系人口的恒星形成对环境的依赖性，我们研究了在3 x 10〜（10）太阳质量的恒星质量周围星系的整体属性中观测到的双峰态的起源。 Sloan Digital Sky Survey DR4光谱数据集用于在以Z = 0.03为中心的团簇A2199上的超级团簇附近生成星系样本，这对M_r〜* + 3.3大约大于90％。据此，我们使用光度加权平均恒星年龄和Ha辐射作为恒星形成历史的独立度量，来测量巨型（M_r <-20 mag）和矮星（-19 7 Gyr）或被动星系（EW [Hα]≤4 A）的巨型星系的比例从簇状核中的大约80％逐渐下降到3-4R_（vir）以上的野外区域的〜40％ ，就像以前的研究一样。相比之下，我们发现矮星系种群在〜1R_（vir）处发生了急剧的转变，从星团内的主要是旧/被动的星团，到实际上所有星系都在形成恒星的外部星团，而旧/被动的星系仅被发现为卫星。到更庞大的星系。这些结果暗示着巨大星系和矮星系演化的根本差异：虽然巨大星系的恒星形成历史主要由它们的合并历史决定，但是矮星系中的恒星形成对大合并的影响更具弹性。相反，只有当矮星系成为更大质量晕圈中的卫星时，它们才会成为被动星系，要么是通过失去其晕圈气藏而失去宿主晕圈，要么是通过其他与环境有关的过程，例如星系骚扰和冲撞压力剥离。

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