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首页> 外文期刊>Astronomy and astrophysics >The VLA-COSMOS 3 GHz Large Project: AGN and host-galaxy properties out to z???6
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The VLA-COSMOS 3 GHz Large Project: AGN and host-galaxy properties out to z???6

机译：VLA-COSMOS 3 GHz大型项目：ZGN 6的AGN和主星系属性

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We explore the multiwavelength properties of AGN host galaxies for different classes of radio-selected AGN out to z ? 6 via a multiwavelength analysis of about 7700 radio sources in the COSMOS field. The sources were selected with the Very Large Array (VLA) at 3 GHz (10 cm) within the VLA–COSMOS 3 GHz Large Project, and cross-matched with multiwavelength ancillary data. This is the largest sample of high-redshift ( z ? 6 ) radio sources with exquisite photometric coverage and redshift measurements available. We constructed a sample of moderate-to-high radiative luminosity AGN (HLAGN) via spectral energy distribution decomposition combined with standard X-ray and mid-infrared diagnostics. Within the remainder of the sample we further identified low-to-moderate radiative luminosity AGN (MLAGN) via excess in radio emission relative to the star formation rates in their host galaxies. We show that at each redshift our HLAGN havesystematically higher radiative luminosities than MLAGN and that their AGN power occurs predominantly in radiative form, while MLAGN display a substantial mechanical AGN luminosity component. We found significant differences in the host properties of the two AGN classes, as a function of redshift. At z & 1.5 , MLAGN appear to reside in significantly more massive and less star-forming galaxies compared to HLAGN. At z & 1.5 , we observed a reversal in the behaviour of the stellar mass distributions with the HLAGN populating the higher stellar mass tail. We interpret this finding as a possible hint of the downsizing of galaxies hosting HLAGN, with the most massive galaxies triggering AGN activity earlier than less massive galaxies, and then fading to MLAGN at lower redshifts. Our conclusion is that HLAGN and MLAGN samples trace two distinct galaxy and AGN populations in a wide range of redshifts, possibly resembling the radio AGN types often referred to as radiative- and jet-mode (or high- and low-excitation), respectively, whose properties might depend on the different availability of cold gas supplies.
机译：我们探索了不同类别的无线电选出的AGN到Z？的AGN宿主星系的多波长特性。通过对COSMOS领域中约7700个无线电源的多波长分析，可以看到图6。在VLA–COSMOS 3 GHz大型项目中，使用3 GHz（10 cm）的超大型阵列（VLA）选择了源，并与多波长辅助数据进行交叉匹配。这是最大的高红移（z？6）无线电源样本，具有出色的光度覆盖范围和红移测量功能。我们通过结合标准X射线和中红外诊断的光谱能量分布分解，构造了中到高辐射光度AGN（HLAGN）的样本。在样品的其余部分中，我们通过相对于其宿主星系中恒星形成速率的无线电辐射过量，进一步确定了低度至中度的辐射光度AGN（MLAGN）。我们证明，在每次红移时，我们的HLAGN的系统发光辐射都比MLAGN更高，并且它们的AGN能量主要以辐射形式出现，而MLAGN则显示出相当大的机械AGN发光度分量。我们发现两个AGN类的宿主属性之间存在显着差异，这是redshift的函数。在z ＜ 1.5，与HLAGN相比，MLAGN似乎驻留在质量更大，形成恒星的星系中。在z＆ 1.5，我们观察到恒星质量分布的行为发生了逆转，其中HLAGN填充了较高的恒星质量尾巴。我们认为这一发现可能暗示着容纳HLAGN的星系的缩小，其中最庞大的星系比不那么庞大的星系更早触发AGN活动，然后在较低的红移时衰落到MLAGN。我们的结论是，HLAGN和MLAGN样本在很宽的红移范围内追踪了两个不同的星系和AGN种群，这可能类似于通常被称为辐射和喷射模式（或高和低激发）的无线电AGN类型，其性能可能取决于冷气供应的不同可用性。

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