The mass fraction of AGN and the fundamental plane of black hole activity from a large X-ray-selected sample of LINERs

Abstract

A sample of 576 X-ray-selected LINERs was constructed by combining data from the 3XMMDR4 and SDSS-DR7 catalogues. The sample was used to investigate the fraction of galaxies hosting a LINER, finding that the fraction is a strong function of both stellar mass and black hole mass (increasing as fLINER α M1.6±0.2* and fLINER α M0.6±0.1BH, respectively) and that it rises close to unity at the highest black hole masses and lowest X-ray luminosities. After obtaining radio flux densities from the FIRST survey, the sample was also used to investigate the Fundamental Plane of black hole activity - a scale-invariant relationshipbetweenblackhole mass, X-ray luminosity and radio luminosity that is believed to hold across at least nine orders of magnitude of mass. There are key advantages in using only LINERs for the derivation as these are the counterparts of the 'low-hard' X-ray binaries for which the relationship is tightest. The Fundamental Plane was found to be log(LR/erg s-1) = 0.65+0.07-0.07 log(LX 1042 erg s-1) + 0.69+0.10-0.10 log(MBH/108 M⊙) + 38.35+0.10-0.10. The scatter around the plane was 0.73 ± 0.03 dex, too large to suggest that the Fundamental Plane can be used as a tool to estimate black hole mass from the observables of X-ray and radio luminosity. The black hole mass scaling is sensitive to the slope of the mass - velocity dispersion relation and, in order to achieve consistency with X-ray binaries, the analysis favours a steep gradient for this relationship, as found in recent research.