Spectro-photometric properties of the bulk of the radio-loud AGN population
Spectro-photometric properties of the bulk of the radio-loud AGN population
复制标题
大部分射电强活动星系核群体的分光光度特性
DOI：
10.1051/0004-6361/201014446
复制
发表时间：
2010
影响因子：
6.5
通讯作者：
Italy.
中科院分区：
文献类型：
--
作者：
R. D. Baldi;Alessandro Capetti Sissa;Trieste;I. Torino;Italy.
在以前的论文中，我们表明，通过结合大面积无线电和光学巡天选择的无线电源，有一个强大的赤字无线电发射相对于3CR射电星系匹配线发射光度。我们认为，在高通量限制的样品中，发光的扩展无线电结构的源的流行是由于选择偏差。低射电源形成了大部分的射电响亮AGN人口，但实际上仍然是未开发的。我们在这里分析它们的光度和光谱特性。从它们的发射线来看，大部分样品都是低激发星系（LEG），与3CR天体在相同的线光度水平上相似。LEG的宿主是红色的，质量（10.5 log M*/M 12）的早期型星系（ETG），黑洞质量（7.7 log M BH /M 9），在统计上与低红移的3CR/LEG源的宿主无法区分。没有真正的无线电大声LEG可以找到与黑洞的质量大大小于10 8 M的质量或晚型主机。具有星星形成迹象的星系比例（~5%）与在静止的ETG和3CR/LEG宿主中发现的相似。我们的结论是，无线电发射的赤字不能归因于其主机的属性的差异。我们认为，相反，这可能是由于无线电光度的时间演变。少数（约10%）的样本显示出相当不同的性质;这些与低黑洞质量，螺旋星系或高激发光谱有关。一般来说，这些异常值是塞弗特星系和那些由星星形成提供能量的射电辐射污染的结果。对于具有高激发谱的天体，无论是主天体还是核天体的性质都没有明显的不连续性，因为它们既包括射电静活动星系核，也包括射电响活动星系核。
In a previous paper we showed that the radio sources selected by combining large area radio and optical surveys, have a strong deficit of radio emission with respect to 3CR radio-galaxies matched in line emission luminosity. We argued that the prevalence of sources with luminous extended radio structures in high flux-limited samples is due to a selection bias. Sources with low radio power form the bulk of the radio-loud AGN population but are still virtually unexplored. We here analyze their photometric and spectroscopic properties. From the point of view of their emission lines, the majority of the sample are Low Excitation Galaxies (LEG), similar to the 3CR objects at the same level of line luminosity. The hosts of the LEG are red, massive (10.5 ≲ log M*/M ⊙ ≲ 12) Early-Type Galaxies (ETG) with large black hole masses (7.7 ≲ log M BH /M ⊙ ≲ 9), statistically indistinguishable from the hosts of low redshift 3CR/LEG sources. No genuine radio-loud LEG could be found associated with black holes with a mass substantially smaller than 10 8 M ⊙ or with a late type host. The fraction of galaxies with signs of star formation (~5%) is similar to what is found in both the quiescent ETG and 3CR/LEG hosts. We conclude that the deficit in radio emission cannot be ascribed to differences in the properties of their hosts. We argue that instead this could be due to a temporal evolution of the radio luminosity. A minority (~10%) of the sample show rather different properties; these are associated with low black hole masses, with spiral galaxies, or with a high excitation spectrum. In general these outliers are the result of the contamination from Seyfert galaxies and from those where the radio emission is powered by star formation. For the objects with high excitation spectra there is no clear discontinuity in either the host or nuclear properties because they include radio-quiet as well as radio-loud AGN.