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arXiv 1401.7813astro-ph.GAastro-ph.CO
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中等红移的紧致静态半导体

Compact Quiescent Galaxies at Intermediate Redshifts

Li-Yen Hsu, Alan Stockton, Hsin-Yi Shih

摘要:

从斯隆数字巡天和英国红外望远镜红外深空巡天共同区域的几次搜索中,我们选择了22个在$z \sim$ 0.4和$z \sim$ 0.9之间的发光星系,它们的颜色和大小与$z>2$的致密静止星系相似。通过探索结构参数和恒星星族,我们发现这些星系中的大多数实际上在$z<2$形成了它们的大部分恒星,并且通常不如$z > 2$中发现的那么紧凑。这些年轻的天体中有几个是盘状的,或者可能是扁长的。这与之前的几项研究一致,这些研究发现,在高红移下的大质量静止星系通常具有盘状形态。如果这些星系被证实是盘状的,它们的形成机制必须能够解释致密性和盘。另一方面,如果这些星系被证实是长扁星系,那么长扁星系在本宇宙中不存在的事实将表明星系形成机制已经在宇宙时间中演化。我们还发现了五个星系形成超过80%的恒星质量在$z>2$。其中三个星系似乎已经被修改为具有类似球体的形态,与大质量星系“由内而外”积聚的场景一致。剩下的星系,SDSS\,J014355.21 +133451.4和SDSS\,J115836.93 +021535.1,具有真正古老的恒星星族和盘状形态。这两个物体将是很好的候选者,几乎未经修改的紧凑的静止星系从高红移,是值得未来的研究。

英文摘要:

From several searches of the area common to the Sloan Digital Sky Survey and the United Kingdom Infrared Telescope Infrared Deep Sky Survey, we have selected 22 luminous galaxies between $z \sim$ 0.4 and $z \sim$ 0.9 that have colors and sizes similar to those of the compact quiescent galaxies at $z>2$. By exploring structural parameters and stellar populations, we found that most of these galaxies actually formed most of their stars at $z<2$ and are generally less compact than those found at $z > 2$. Several of these young objects are disk-like or possibly prolate. This lines up with several previous studies which found that massive quiescent galaxies at high redshifts often have disk-like morphologies. If these galaxies were to be confirmed to be disk-like, their formation mechanism must be able to account for both compactness and disks. On the other hand, if these galaxies were to be confirmed to be prolate, the fact that prolate galaxies do not exist in the local universe would indicate that galaxy formation mechanisms have evolved over cosmic time. We also found five galaxies forming over 80% of their stellar masses at $z>2$. Three of these galaxies appear to have been modified to have spheroid-like morphologies, in agreement with the scenario of "inside-out" buildup of massive galaxies. The remaining galaxies, SDSS\,J014355.21+133451.4 and SDSS\,J115836.93+021535.1, have truly old stellar populations and disk-like morphologies. These two objects would be good candidates for nearly unmodified compact quiescent galaxies from high redshifts that are worth future study.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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