2SLAQ亮红星系巡天中的射电星系：II。射电强和射电静LRG的恒星星族
Radio galaxies in the 2SLAQ Luminous Red Galaxy survey: II. The stellar populations of radio-loud and radio-quiet LRGs
摘要：
本文分析了2dF-SDSS亮红星系和类星体（2SLAQ）红移巡天的375个射电星系的光谱。我们研究了这些星系的恒星星族和发射线性质的演化。通过构建复合光谱，并与来自同一调查的无线电安静源的匹配样本进行比较，我们还研究了活跃核的存在对星系的影响。由红移和射电亮度分类的复合光谱都需要两个分量来描述它们，我们将其解释为老年群体和年轻群体。我们没有发现射电星系中年轻群体的年龄随红移的演化，也没有发现它们与射电宁静比较样本的不同。类似地，与射电源没有相关性，除了最强大的射电源（P（1.4）> 10^26 W/Hz）比功率较小的源具有更年轻的恒星和更强的发射线。这表明，我们已经找到了无线电功率的阈值，在那里强发射线“打开”，无线电功率约为10^26 W/Hz。除了非常强大的射电星系外，目前活跃的射电活动星系核的存在似乎与观测到的z~0.5的发光红色星系的恒星星族的任何变化都不相关。
英文摘要：
We present an analysis of the optical spectra of a volume-limited sample of 375 radio galaxies at redshift 0.4<z<0.7 from the 2dF-SDSS Luminous Red Galaxy and QSO (2SLAQ) redshift survey. We investigate the evolution of the stellar populations and emission-line properties of these galaxies. By constructing composite spectra and comparing with a matched sample of radio-quiet sources from the same survey, we also investigate the effect on the galaxy of the presence of an active nucleus. The composite spectra, binned by redshift and radio luminosity, all require two components to describe them, which we interpret as an old and a younger population. We found no evolution with redshift of the age of the younger population in radio galaxies, nor were they different from the radio-quiet comparison sample. Similarly, there is no correlation with radio power, with the exception that the most powerful radio sources (P(1.4) > 10^26 W/Hz) have younger stars and stronger emission lines than the less powerful sources. This suggests that we have located the threshold in radio power where strong emission lines "switch on", at radio powers of around 10^26 W/Hz. Except for the very powerful radio galaxies, the presence of a currently-active radio AGN does not appear to be correlated with any change in the observed stellar population of a luminous red galaxy at z~0.5.
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