On the evolution of young radio-loud AGN
On the evolution of young radio-loud AGN
复制标题
DOI：
10.1046/j.1365-8711.2000.03935.x
复制
发表时间：
2000-02
影响因子：
4.8
通讯作者：
I. Snellen;R. Schilizzi;G. Miley;G. D. Bruyn;M. Bremer;H. Rottgering
中科院分区：
文献类型：
--
作者：
I. Snellen;R. Schilizzi;G. Miley;G. D. Bruyn;M. Bremer;H. Rottgering
本文描述了一个调查的早期演变的河外射电源使用的样品微弱和明亮的千兆赫峰值频谱（GPS）和紧凑的陡谱（CSS）的射电星系。它们的峰值频率，峰值通量密度和角尺寸之间的相关性提供了强有力的证据，同步自吸收是光谱翻转的原因，并表明年轻的射电源以自相似的方式演化。此外，这些数据似乎表明，这些来源在演变过程中是均分的。如果GPS源演化为大尺度射电源，它们的红移依赖的出生函数应该是相同的。因此，由于射电源的寿命被认为比哈勃时间短，所以观测到的GPS和大尺寸源之间的红移分布差异一定是由于它们的光度函数的斜率不同。我们认为，这个斜率是强烈影响的亮度演化的个别来源。提出了GPS源光度随时间增加而大尺度射电源光度随时间减小的光度演化方案。这种演变的情况下，预计在周围介质中的一个冲压压力约束的无线电源与国王配置文件密度。在King剖面的内部，介质的密度是恒定的，射电源的亮度逐渐增加，但当它变得足够大时，周围介质的密度会下降，射电源的亮度也会下降。GPS星系的局部光度函数（LLF）与扩展源的比较是一个很好的测试，这种演变的情况。不幸的是，只有少数的GPS源是已知的在低红移，和LLF只能推导出，假设它们的宇宙数密度演化是类似的陡峭的频谱源。以这种方式推导出的LLF被证明是在良好的协议与拟议的进化方案。然而，不确定性很大，需要更大的、均匀选择的GPS源样本。
This paper describes an investigation of the early evolution of extragalactic radio sources using samples of faint and bright gigahertz peaked spectrum (GPS) and compact steep spectrum (CSS) radio galaxies. Correlations found between their peak frequency, peak flux density and angular size provide strong evidence that synchrotron self-absorption is the cause of the spectral turnovers, and indicate that young radio sources evolve in a self-similar way. In addition, the data seem to suggest that the sources are in equipartition while they evolve. If GPS sources evolve to large size radio sources, their redshift dependent birth-functions should be the same. Therefore, since the lifetimes of radio sources are thought to be short compared to the Hubble time, the observed difference in redshift distribution between GPS and large size sources must be due to a difference in slope of their luminosity functions. We argue that this slope is strongly affected by the luminosity evolution of the individual sources. A scenario for the luminosity evolution is proposed in which GPS sources increase in luminosity and large-scale radio sources decrease in luminosity with time. This evolution scenario is expected for a ram-pressure confined radio source in a surrounding medium with a King profile density. In the inner parts of the King profile, the density of the medium is constant and the radio source builds up its luminosity, but after it grows large enough the density of the surrounding medium declines and the luminosity of the radio source decreases. A comparison of the local luminosity function (LLF) of GPS galaxies with that of extended sources is a good test for this evolution scenario. Unfortunately, only a handful of GPS sources are known at low redshift, and an LLF can only be derived, assuming that their cosmological number density evolution is similar to that of steep spectrum sources. The LLF derived in this way is shown to be in good agreement with the proposed evolution scenario. However, the uncertainties are large, and larger, homogeneously selected samples of GPS sources are needed.