HerMES：在射电源群中解开活动星系核和恒星形成
HerMES: Disentangling active galactic nuclei and star formation in the radio source population
摘要：
我们将50 μ Jy以上的河外射电源群分为活动星系核（AGN）和恒星形成源。我们的方法的主要方法是适合的红外光谱能量分布（SED），构建使用斯皮策/IRAC和MIPS和赫歇尔/SPIRE测光，在扩展钱德拉深场南380个射电源。从拟合的SEDs，我们确定的相对AGN和恒星形成的红外辐射的贡献。包括其他活动星系核的诊断，如X射线光度，斯皮策/IRAC颜色，无线电光谱指数和恒星形成的总红外通量的比率k-校正的1.4 GHz的通量密度，qIR，我们确定是否在这些来源的无线电发射是由恒星形成或活动星系核。这些射电源中的大多数（60%）在某个波长上显示出活动星系核的特征。在具有活动星系核特征的源中，58%是混合系统，其无线电发射是由恒星形成提供动力的。这意味着在恒星形成过程中选择的射电源有很高的活动星系核分数。低于1.4 GHz的通量密度为1 mJy，以及找到一个强大的贡献源计数从纯恒星形成的来源，我们发现，混合源构成的来源的20- 65%。这一结果表明，混合源有一个显着的贡献，随着源，不主机可检测的活动星系核，所观察到的平坦化的源计数在~ 1 mJy的河外射电源人口。
英文摘要：
We separate the extragalactic radio source population above ~50 uJy into active galactic nuclei (AGN) and star-forming sources. The primary method of our approach is to fit the infrared spectral energy distributions (SEDs), constructed using Spitzer/IRAC and MIPS and Herschel/SPIRE photometry, of 380 radio sources in the Extended Chandra Deep Field-South. From the fitted SEDs, we determine the relative AGN and star-forming contributions to their infrared emission. With the inclusion of other AGN diagnostics such as X-ray luminosity, Spitzer/IRAC colours, radio spectral index and the ratio of star-forming total infrared flux to k-corrected 1.4 GHz flux density, qIR, we determine whether the radio emission in these sources is powered by star formation or by an AGN. The majority of these radio sources (60 per cent) show the signature of an AGN at some wavelength. Of the sources with AGN signatures, 58 per cent are hybrid systems for which the radio emission is being powered by star formation. This implies that radio sources which have likely been selected on their star formation have a high AGN fraction. Below a 1.4 GHz flux density of 1 mJy, along with finding a strong contribution to the source counts from pure star-forming sources, we find that hybrid sources constitute 20-65 per cent of the sources. This result suggests that hybrid sources have a significant contribution, along with sources that do not host a detectable AGN, to the observed flattening of the source counts at ~1mJy for the extragalactic radio source population.
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