在空间和时间中分辨的星系演化：来自CALIFA巡天的由内而外的生长观点
The evolution of galaxies resolved in space and time: an inside-out growth view from the CALIFA survey
摘要：
星系的生长是理解宇宙及其组成的结构和演化的关键问题之一。星系团可以通过吸积晕或星系际气体云，或者通过与较小或类似质量的星系合并来增加恒星质量。可用的气体转化为恒星形成的速率，这控制了宇宙中金属的生成。迄今为止，对于本星系群以外的任何给定星系，还没有获得它们的恒星质量组装的空间分辨历史。在这里，我们展示了大质量星系如何从内到外增长它们的恒星质量。我们报告的结果，从分析的第一个105星系的最大的三维光谱调查星系在本地宇宙（CALIFA）。我们应用化石记录的恒星星族光谱合成方法，恢复了每个星系的空间和时间分辨的恒星形成历史。我们表明，第一次，缩小的信号是空间保存，与内部和外部区域增长更快的更大质量的星系。此外，我们还发现，5-7 Gyr前发生的球状体成分、核心和内部星系的相对增长率在临界恒星质量约10^10 Msun时显示出最大值。我们还发现，质量小于~10^10 Msun的星系表现出由外向内生长的过渡，从而与低质量星系生长的解析研究结果相联系。
英文摘要：
The growth of galaxies is one of the key problems in understanding the structure and evolution of the universe and its constituents. Galaxies can grow their stellar mass by accretion of halo or intergalactic gas clouds, or by merging with smaller or similar mass galaxies. The gas available translates into a rate of star formation, which controls the generation of metals in the universe. The spatially resolved history of their stellar mass assembly has not been obtained so far for any given galaxy beyond the Local Group. Here we demonstrate how massive galaxies grow their stellar mass inside-out. We report the results from the analysis of the first 105 galaxies of the largest to date three-dimensional spectroscopic survey of galaxies in the local universe (CALIFA). We apply the fossil record method of stellar population spectral synthesis to recover the spatially and time resolved star formation history of each galaxy. We show, for the first time, that the signal of downsizing is spatially preserved, with both inner and outer regions growing faster for more massive galaxies. Further, we show that the relative growth rate of the spheroidal component, nucleus and inner galaxy, that happened 5-7 Gyr ago, shows a maximum at a critical stellar mass ~10^10 Msun. We also find that galaxies less massive than ~10^10 Msun show a transition to outside-in growth, thus connecting with results from resolved studies of the growth of low mass galaxies.
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