On March 20, a paper by Yunnan Observatories’ scientists YUAN Zunli, WANG Jiancheng and their group members was published in The Astrophysical Journal. In this paper they proposed a mixture evolution  scenario to model the radio luminosity function (RLF) of steep-spectrum AGNs (active galactic nuclei) based on a Bayesian method. According to their models, the shape of the RLF is determined by both the density and luminosity evolution. The mixture evolution models also indicate that the density evolution is positive until a redshift of ~1, at which point it becomes negative, while the luminosity evolution is positive to a higher redshift (z>3.5), where it becomes negative. It is exactly because of the joint effect of the density and luminosity evolution that AGNs exhibit luminosity-dependent density evolution properties, namely, the powerful radio AGNs undergo very rapid evolution to a redshift of z~3, while the lower luminosity radio population only experiences much milder positive evolution to z ~1.

AGN is a bright and compact area in the center of an active galaxy. Its radiation covers across almost the entire electromagnetic spectrum, ranging from radio to gamma-ray wavelengths. Since the radiation of radio waveband is less affected by the absorption of dust, the RLF becomes an effective tool to study AGNs’ cosmic evolution. However, due to the incompleteness of radio sample and the limitation of statistical approach, there were some uncertainties to calculate the RLF. The research work completed by YUAN and WANG and their collaborators provides significant evidence for studying the density distribution and accreting process of super-massive black holes.

Information regarding the paper: Zunli Yuan, Jiangcheng Wang, Ming Zhou and Jirong Mao; A Mixture Evolution Scenario of the AGN Radio Luminosity Function, in ApJ 820(1):65.