Researches On The Radio Luminosity Function And Evolution Of Radio-loud Active Galactic Nuclei

The radio-loud Active Galactic Nuclei (AGNs) are one of the most intriguingpowerful radio sources. Usually they are classifed as steep-spectrum and fat-spectrum sources. According to the unifed model of AGN, their diference canbe ascribed to the angle of inclination. Both of them can be roughly describedas a picture of "compact core+jet+extended radio lobes". Traditionally, thesteep-spectrum and fat-spectrum sources are studied respectively by radio lumi-nosity functions (RLFs) to obtain the information of their evolution. However,due to the peculiarity of radio radiation and activity, e.g., extension, inclinationdependent, and intermittence, the information obtained by traditional methodsis limited. With the improvement of radio observation accuracy, more and moreradio cores are observed. The existence of radio core is a good indicator of radioactivity. In this thesis, we utilized the public observational data to study the RLFof radio cores. As the radio cores are located at the centers of AGNs, researchon their RLF can helps to explore the relationship between matter accretion andjet more directly.Firstly, a large sample of1063steep-spectrum radio-loud AGNs was estab-lished by consulting literature and database retrieval. Based on the sample, theRLF at408MHz of steep-spectrum radio sources was calculated by the1/Vamethod. The results support a luminosity-dependent density evolution. Most ofthe radio cores in the sample have fux densities at5GHz. Using these data,the core RLF at5GHz was also estimated. The results show that the comovingnumber density of radio cores displays a persistent decline with redshift, imply-ing a negative density evolution. A possible explanation to this result is thatin the earlier epoch of AGNs, the relatively higher accretion rate may adverselyafect the radio emission of jet. The so-called ‘soft’ and ‘hard’ states in X-rayBinaries may also exist in AGNs. The above results were also consistent withprevious researches from diferent point of views. Also, we noticed that the coreRLF is obviously diferent from the total RLF at408MHz band which is mainly contributed by extended lobes, implying that the cores and extended lobes couldnot be co-evolving at radio emission.Becides, the classical1/Vaand P C methods of constructing binned lumi-nosity functions (LFs) are revisited and compared by graphical analysis. Usingboth theoretical analysis and illustration with an example, we show why the twomethods give diferent results for the bins which are crossed by the fux limitcurves L=Llim(z). Based on a combined sample simulated by a Monte Carlomethod, the estimate of two methods are compared with the input model LFs.The two methods give identical and ideal estimate for the high luminosity pointsof each redshift interval. However, for the low luminosity bins of all the redshiftintervals both methods give smaller estimate than the input model. We concludethat once the LF is evolving with redshift, the classical binned methods will un-likely give an ideal estimate over the total luminosity range. Previous researchesnoticed that for objects close to the fux limit1/Vanearly always to be too small.We believe this is due to the arbitrary choosing of redshift and luminosity inter-vals. Because1/Vais more sensitive to how the binning are chosen than P C. Ifthe binning are wisely chosen according to a simple rule of thumb suggested byus, it is hard to say the estimate of P C method is markedly better than the1/Vamethod.