蓝色E/S0星系从z~1的演化：合并残余还是盘重建星系？
Evolution of blue E/S0 galaxies from z~1: merger remnants or disk rebuilding galaxies?
摘要：
研究色质量空间中星系双峰分布的异常值，例如位于蓝色云中的形态早期型星系，可以帮助更好地理解导致星系在该空间迁移的物理机制。在本文中，我们研究了210 M*/Msol>10^10蓝色E/S 0 s在z~1.4和z~0.2之间的性质在COSMOS场中的演化，并证实了来自zCOSMOS 10 k释放的光谱红移。我们首先观察到，阈值质量，在以前的研究中定义为在z=0的质量以下，蓝色早型星系的人口开始相对于被动E/S 0丰富，从log（M*/Msol）~10.1在z~0.3到log（M*/Msol）~10.9在z~1。第二，在蓝色E/S 0星系的性质中似乎存在一个翻转质量。log（M*/Msol）~10.8以上的蓝色E/S 0类似于可能在~3 Gyr时间尺度内迁移到红色序列的合并残留。在这个质量以下，它们似乎更接近正常的晚型星系，就好像它们是轻微合并的结果，这些合并触发了中心恒星的形成，并建立了一个中心凸起部分，或者从周围的气体中（重新）建立了一个圆盘，这表明它们正在向后移动或留在蓝色云中。与阈值质量相比，该转换质量似乎没有从z~1显著地演变，因此似乎与蓝色E/S 0的相对丰度无关。
英文摘要：
Studying outliers from the bimodal distribution of galaxies in the color-mass space, such as morphological early-type galaxies residing in the blue cloud, can help to better understand the physical mechanisms that lead galaxy migrations in this space. In this paper we study the evolution of the properties of 210 M*/Msol>10^10 blue E/S0s between z~1.4 and z~0.2 in the COSMOS field with confirmed spectroscopic redshifts from the zCOSMOS 10k release. We first observe that the threshold mass, defined at z=0 in previous studies as the mass below which the population of blue early-type galaxies starts to be abundant relative to passive E/S0s, evolves from log(M*/Msol)~10.1 at z~0.3 to log(M*/Msol)~10.9 at z~1. Second, there seems to be a turn-over mass in the nature of blue E/S0 galaxies. Above log(M*/Msol)~10.8 blue E/S0 resemble to merger remnants probably migrating to the red-sequence in a time-scale of ~3 Gyr. Below this mass, they seem to be closer to normal late-type galaxies as if they were the result of minor mergers which triggered the central star-formation and built a central bulge component or were (re)building a disk from the surrounding gas, suggesting that they are moving back or staying in the blue-cloud. This turn-over mass does not seem to evolve significantly from z~1 in contrast with the threshold mass and therefore does not seem to be linked with the relative abundance of blue E/S0s.
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