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Register a new userModelling radio luminosity functions of radio-loud AGN by the cosmological evolution of supermassive black holes
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We develop a formalism to model the luminosity functions (LFs) of radio-loud Active Galactic Nuclei (AGN) at GHz frequencies by the cosmological evolution of the supermassive black hole (SMBH). The mass function and Eddington ratio distributions of SMBHs have been taken as starting point for this analysis. Our approach is based on physical and phenomenological relations that allow to statistically calculate the radio luminosity of AGN cores, corrected for beaming effects, by linking it with the SMBH at their center, through the Fundamental Plane of black hole activity. Moreover, radio luminosity from extended jets and lobes is also computed through a power-law relationship that reflects the expected correlation between the inner radio core and the extended jets/lobes. Radio-loud AGN are further divided in two classes, characterized by different accretion modes onto the central BH. If the Eddington ratio is <0.01 they are called low-kinetic (LK-mode) AGN; if >0.01, they are called high-kinetic (HK-mode) AGN, being this critical value roughly corresponding to the transition between radiatively inefficient and efficient accretion flows. The few free parameters used in the present model are determined by fitting two different types of observational data sets: local LFs of radio-loud AGN at 1.4 GHz and differential number counts of extragalactic radio sources at 1.4 and 5 GHz. Our present model fits well almost all published data on LFs of LK-mode AGN and of the total AGN population up to redshifts z<=1.5 and, moreover, in the full range of luminosities currently probed by data. On the other hand, it tends to underestimate some recent measures of the LF of HK-mode AGN at low redshifts, but only at low radio luminosities. The present model is also able to provide a very good fit to almost all data on number counts of radio-loud sources at 1.4 and 5 GHz. (abridged)
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We model the cosmological co-evolution of galaxies and their central supermassive black holes (BHs) within a semi-analytical framework developed on the outputs of the Millennium Simulation (Croton et al., 2006; De Lucia & Blaizot, 2007). In this work, we analyze the model BH scaling relations, fundamental plane and mass function, and compare them with the most recent observational data. Furthermore, we extend the original code developed by Croton et al. (2006) to follow the evolution of the BH mass accretion and its conversion into radiation, and compare the derived AGN bolometric luminosity function with the observed one. We find, for the most part, a very good agreement between predicted and observed BH properties. Moreover, the model is in good agreement with the observed AGN number density in 0<z<5, provided it is assumed that the cold gas fraction accreted by BHs at high redshifts is larger than at low redshifts (Marulli et al., 2008).
We are carrying out a search for all radio loud Active Galactic Nuclei observed with XMM-Newton, including targeted and field sources to perform a multi-wavelength study of these objects. We have cross-correlated the Veron-Cetty & Veron (2010) catalogue with the XMM-Newton Serendipitous Source Catalogue (2XMMi) and found about 4000 matched sources. A literature search provided radio, optical, and X-ray data for 403 sources. Here we summarize the first results of our study.
We present here the first results from the Chandra ERA (Environments of Radio-loud AGN) Large Project, characterizing the cluster environments of a sample of 26 radio-loud AGN at z ~ 0.5 that covers three decades of radio luminosity. This is the first systematic X-ray environmental study at a single epoch, and has allowed us to examine the relationship between radio luminosity and cluster environment without the problems of Malmquist bias. We have found a weak correlation between radio luminosity and host cluster X-ray luminosity, as well as tentative evidence that this correlation is driven by the subpopulation of low-excitation radio galaxies, with high-excitation radio galaxies showing no significant correlation. The considerable scatter in the environments may be indicative of complex relationships not currently included in feedback models.
We present high spatial resolution MIR observations for several nearby radio loud active galactic nuclei (RLAGN), which were obtained using the Gemini North and South telescopes. Of the six observed objects, we detected five in the Si-2 (8.7 microns) and Si-6 (12.3 microns) filters, of which two objects show some evidence of low level extended emission surrounding the unresolved nucleus. In Pictor A, we also obtained an image in Qs (18.3 microns) that has a flux of only half that seen in the Spitzer image, suggesting structure on arcsecond scales. We also used the Si-6 (12.3 microns) flux measurement to investigate correlation between our MIR flux and xray luminosity and compare this to results for AGN in general. This work also forms a basis for future high resolution imaging and spectroscopy of these objects.
We explore radio and spectroscopic properties of a sample of 14 miniature radio galaxies, i.e. early-type core galaxies hosting radio-loud AGN of extremely low radio power, 10^(27-29) erg s^(-1) Hz^(-1) at 1.4 GHz. Miniature radio galaxies smoothly extend the relationships found for the more powerful FRI radio galaxies between emission line, optical and radio nuclear luminosities to lower levels. However, they have a deficit of a factor of ~100 in extended radio emission with respect to that of the classical example of 3CR/FRI. This is not due to their low luminosity, since we found radio galaxies of higher radio core power, similar to those of 3CR/FRI, showing the same behavior, i.e. lacking significant extended radio emission. Such sources form the bulk of the population of radio-loud AGN in the Sloan Digital Sky Survey. At a given level of nuclear emission, one can find radio sources with an extremely wide range, a factor of >~100, of radio power. We argue that the prevalence of sources with luminous extended radio structures in flux limited samples is due to a selection bias, since the inclusion of such objects is highly favored. The most studied catalogues of radio galaxies are thus composed by the minority of radio-loud AGN that meet the physical conditions required to form extended radio sources, while the bulk of the population is virtually unexplored.
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