1<z<2的超密和正常早型星系
Superdense and normal early-type galaxies at 1<z<2
摘要：
我们结合专有和存档的HST观测，收集了62个0.9<z<2的早期类型星系（ETG）的样本，并对其红移和光谱类型进行了光谱确认。整个样本由ACS或NICMOS观测覆盖，部分由Spitzer和AKARI观测覆盖。我们通过拟合它们的HST光分布得到形态参数，通过拟合它们的光谱能量分布得到物理参数。对这些早期类型星的大小-质量和大小-光度关系的研究表明，它们中有很大一部分（约50个）遵循定域关系。这些“正常”的ETG并不比具有可比质量的本地对应物小。剩下的一半样本由紧凑的ETG组成，其尺寸（密度）比当地同行小（高）2.5-3（15-30）倍，最重要的是，比其他正常的ETG在相同的红移和相同的恒星质量。这表明z~2处的正常ETG和超致密ETG来自不同的质量组装历史。
英文摘要：
We combined proprietary and archival HST observations to collect a sample of 62 early-type galaxies (ETGs) at 0.9<z<2 with spectroscopic confirmation of their redshift and spectral type. The whole sample is covered by ACS or NICMOS observations and partially by Spitzer and AKARI observations. We derived morphological parameters by fitting their HST light profiles and physical parameters by fitting their spectral energy distributions. The study of the size-mass and the size-luminosity relations of these early-types shows that a large fraction of them (~50) follows the local relations. These 'normal' ETGs are not smaller than local counterparts with comparable mass. The remaining half of the sample is composed of compact ETGs with sizes (densities) 2.5-3 (15-30) times smaller (higher) than local counterparts and, most importantly, than the other normal ETGs at the same redshift and with the same stellar mass. This suggests that normal and superdense ETGs at z~2 come from different histories of mass assembly.
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