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Register a new userOn the AGN radio luminosity distribution and the black hole fundamental plane
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A. Bonchi
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We have studied the dependence of the AGN nuclear radio (1.4 GHz) luminosity on both the AGN 2-10 keV X-ray and the host-galaxy K-band luminosity. A complete sample of 1268 X-ray selected AGN (both type 1 and type 2) has been used, which is the largest catalogue of AGN belonging to statistically well defined samples where radio, X and K band information exists. At variance with previous studies, radio upper limits have been statistically taken into account using a Bayesian Maximum Likelihood fitting method. It resulted that a good fit is obtained assuming a plane in the 3D L_R-L_X-L_K space, namely logL_R= xi_X logL_X + xi_K logL_K + xi_0, having a ~1 dex wide (1 sigma) spread in radio luminosity. As already shown, no evidence of bimodality in the radio luminosity distribution was found and therefore any definition of radio loudness in AGN is arbitrary. Using scaling relations between the BH mass and the host galaxy K-band luminosity, we have also derived a new estimate of the BH fundamental plane (in the L_5GHz -L_X-M_BH space). Our analysis shows that previous measures of the BH fundamental plane are biased by ~0.8 dex in favor of the most luminous radio sources. Therefore, many AGN studies, where the BH fundamental plane is used to investigate how AGN regulate their radiative and mechanical luminosity as a function of the accretion rate, or many AGN/galaxy co-evolution models, where radio-feedback is computed using the AGN fundamental plane, should revise their conclusions.
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We investigate the 1.4 GHz radio properties of 92 nearby (z<0.05) ultra hard X-ray selected Active Galactic Nuclei (AGN) from the Swift Burst Alert Telescope (BAT) sample. Through the ultra hard X-ray selection we minimise the biases against obscured or Compton-thick AGN as well as confusion with emission derived from star formation that typically affect AGN samples selected from the UV, optical and infrared wavelengths. We find that all the objects in our sample of nearby, ultra-hard X-ray selected AGN are radio quiet; 83% of the objects are classed as high-excitation galaxies (HEGs) and 17% as low-excitation galaxies (LEGs). While these low-z BAT sources follow the radio--far-infrared correlation in a similar fashion to star forming galaxies, our analysis finds that there is still significant AGN contribution in the observed radio emission from these radio quiet AGN. In fact, the majority of our BAT sample occupy the same X-ray--radio fundamental plane as have been observed in other samples, which include radio loud AGN --- evidence that the observed radio emission (albeit weak) is connected to the AGN accretion mechanism, rather than star formation.
We put active galactic nuclei (AGNs) with low-mass black holes on the fundamental plane of black hole accretion---the plane that relates X-ray emission, radio emission, and mass of an accreting black hole---to test whether or not the relation is universal for both stellar-mass and supermassive black holes. We use new Chandra X-ray and Very Large Array radio observations of a sample of black holes with masses less than $10^{6.3} M_{scriptscriptstyle odot}$, which have the best leverage for determining whether supermassive black holes and stellar-mass black holes belong on the same plane. Our results suggest that the two different classes of black holes both belong on the same relation. These results allow us to conclude that the fundamental plane is suitable for use in estimating supermassive black hole masses smaller than $sim 10^7 M_{scriptscriptstyle odot}$, in testing for intermediate-mass black holes, and in estimating masses at high accretion rates.
We perform a detailed study of the location of brightest cluster galaxies (BCGs) on the fundamental plane of black hole (BH) accretion, which is an empirical correlation between a BH X-ray and radio luminosity and mass supported by theoretical models of accretion. The sample comprises 72 BCGs out to $zsim0.3$ and with reliable nuclear X-ray and radio luminosities. These are found to correlate as $L_mathrm{X} propto L_mathrm{R}^{0.75 pm 0.08}$, favoring an advection-dominated accretion flow as the origin of the X-ray emission. BCGs are found to be on average offset from the fundamental plane such that their BH masses seem to be underestimated by the $M_mathrm{BH}-M_mathrm{K}$ relation a factor $sim$10. The offset is not explained by jet synchrotron cooling and is independent of emission process or amount of cluster gas cooling. Those core-dominated BCGs are found to be more significantly offset than those with weak core radio emission. For BCGs to on average follow the fundamental plane, a large fraction ($sim40%$) should have BH masses $> 10^{10}$ M$_{odot}$ and thus host ultramassive BHs. The local BH-galaxy scaling relations would not hold for these extreme objects. The possible explanations for their formation, either via a two-phase process (the BH formed first, the galaxy grows later) or as descendants of high-z seed BHs, challenge the current paradigm of a synchronized galaxy-BH growth.
We have determined the central velocity dispersion and surface brightness profiles for a sample of powerful radio galaxies in the redshift range 0.06<z<0.31, which were selected on the basis of their young radio source. The optical hosts follow the fundamental plane of elliptical galaxies, showing that young radio sources reside in normal ellipticals, as do other types of radio galaxies. As young radio sources are relatively straightforward to select and the contributions of the AGN light to the optical spectra are minimal, these objects can readily be used to study the evolution of the fundamental plane of elliptical galaxies out to z=1, independently of optical selection effects. The black hole masses of the objects in our sample have been determined using the tight empirical relation of M_bh with central velocity dispersion, and for literature samples of classical radio galaxies and optically selected ellipticals. Only the optically selected in-active galaxies are found to exhibit a correlation between M_bh and radio luminosity. In contrast, the radio powers of the AGN in the samples do not correlate with M_bh at all, with objects at a given black hole mass ranging over 7 orders of magnitude in radio power. We have been able to tie in the population of powerful radio sources with its parent population of in-active elliptical galaxies: the local black hole mass function has been determined, which was combined with the fraction of radio-loud black holes as function of M_bh, as determined from the optically selected galaxy sample, to derive the local volume-density of radio galaxies and the distribution of their black hole masses. These are shown to be consistent with the local radio luminosity function and the distribution of black hole masses in the radio selected samples [ABBREVIATED]
We studied the Active Galactic Nuclei (AGN) radio emission from a compilation of hard X-ray selected samples, all observed in the 1.4 GHz band. A total of more than 1600 AGN with 2-10 keV de-absorbed luminosities higher than 10^42 erg/s were used. For a sub-sample of about 50 zlsim 0.1 AGN it was possible to reach a ~80% fraction of radio detections and therefore, for the first time, it was possible to almost completely measure the probability distribution function of the ratio between the radio and the X-ray luminosity Rx=log[L(1.4)/Lx]. The probability distribution function of Rx was functionally fitted as dependent on the X-ray luminosity and redshift, P(Rx|Lx,z). It roughly spans over 6 decades (-7<Rx<-1), and does not show any sign of bi-modality. It resulted that the probability of finding large values of the Rx ratio increases with decreasing X-ray luminosities and (possibly) with increasing redshift. No statistical significant difference was found between the radio properties of the X-ray absorbed and unabsorbed AGN. The measure of the probability distribution function of Rx allowed us to compute the kinetic luminosity function and the kinetic energy density which, at variance with what assumed in many galaxy evolution models, is observed to decrease of about a factor of five at redshift below 0.5. About half of the kinetic energy density results to be produced by the more radio quiet (Rx<-4) AGN. In agreement with previous estimates, the AGN efficiency in converting the accreted mass energy into kinetic power is, on average, ~5x10-3.
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