On the X-ray, optical emission line and black hole mass properties of local Seyfert galaxies

Abstract

We investigate the relation between X-ray nuclear emission, optical emission line luminosities and black hole masses for a sample of 47 Seyfert galaxies. The sample, which has been selected from the Palomar optical spectroscopic survey of nearby galaxies (Ho et al. 1997a, ApJS, 112, 315), covers a wide range of nuclear powers, from L 2−10 keV ∼ 10 43 erg/s down to very low luminosities (L 2−10 keV ∼ 10 38 erg/s). Best available data from Chandra, XMM-Newton and, in a few cases, ASCA observations have been considered. Thanks to the good spatial resolution available from these observations and a proper modeling of the various spectral components, it has been possible to obtain accurate nuclear X-ray luminosities not contaminated by off-nuclear sources and/or diffuse emission. X-ray luminosities have then been corrected taking into account the likely candidate Compton thick sources, which are a high fraction (>30%) among type 2 Seyferts in our sample. The main result of this study is that we confirm strong linear correlations between 2-10 keV, [OIII]λ5007, H α luminosities which show the same slope as quasars and luminous Seyfert galaxies, independent of the level of nuclear activity displayed. Moreover, despite the wide range of Eddington ratios (L/L Edd ) tested here (six orders of magnitude, from 0.1 down to ∼10 −7 ), no correlation is found between the X-ray or optical emission line luminosities and the black hole mass. Our results suggest that Seyfert nuclei in our sample are consistent with being a scaled-down version of more luminous AGN.

Measuring the level of nuclear activity in Seyfert galaxies and the unification scheme

“…In Paper I we report that in our sample of 20 Seyferts, 7/10 type 2 Seyferts are Compton-thick and 13 Seyferts (10 type 1s and 3 type 2s) are Compton-thin. Using the median values of Rx Compton−thin and Rx Compton−thick in this sample, we estimated the absorption correction factor f cor ∼ 70, which is close to the one reported in Panessa et al (2006) by using similar flux diagnostic method but considering the flux ratios of Seyfert type 1s and type 2s rather than that of Compton-thick and Compton-thin sources. We caution that the true value of the correction factor ( f cor ) may be different for different sources depending upon the true value of the absorbing column density.…”

Faint high-redshift AGN in theChandradeep field south: the evolution of the AGN luminosity function and black hole demography

“…The largest uncertainty in the AGN luminosity function is in the fraction of Compton thick AGN. The fraction of these objects in the local Universe is high: 30-50% of the optically selected Seyfert 2 galaxies can be Compton thick (≈1/4−1/3 of the full AGN population, Risaliti et al (1999), Panessa et al (2006), a result confirmed by hard X-ray selection, see Malizia et al 2009). At higher redshift, the fraction of Compton thick AGN is more uncertain, but it can be as high as one third of the full AGN population (Fiore et al , 2009), or even higher (Daddi et al 2007;Treister et al 2010).…”

Tidal disruption of a super-Jupiter by a massive black hole

“…The [O III] line intensity in NGC 4845 is 5.40 × 10 −15 erg s −1 (Ho et al 1997). According to the X-ray -[O III] λ5007 relationship (Panessa et al 2006) the estimated unabsorbed 2-10 keV flux should be 6 × 10 −14 erg s −1 . However, since the X-ray flux observed in January 2011 was almost 1000 times larger (Table 4), the absorption explanation is ruled out.…”