The high-ionization IR fine-structure lines as bolometric indicators of the AGN power: study of the complete 12 micron AGN sample

Abstract: The high-ionization mid-IR lines, excited in the Narrow Line Regions (NLR) of Active Galactic Nuclei (AGN), barely affected by stellar excitation and dust extinction, trace the AGN bolometric power. We used the complete 12 micron sample of Seyfert galaxies, for which 100/116 objects have reliable 2-10keV observations. The [NeV] and [OIV] mid-IR lines linearly correlate with several AGN bolometric indicators (intrinsic 2-10keV and observed 14-195keV X-ray emission, compact nuclear 12 micron emission, [OIII] 5007A line emission), both in terms of flux and luminosity. No evidence of systematic differences in these correlations is found among the Seyfert populations, including type 1 and type 2, and Compton thick and thin AGN. Nevertheless, we find that a sequence of high-to-low Eddington ratio together with strong-to-weak line excitation (traced by the [OIV]/[Ne II] line ratio) encompasses from type 1 through type 2 AGN to Low Ionization Nuclear Emission Line Region (LINER) galaxies, showing intrinsic differences in these three AGN populations. A positive correlation between the Black Hole Accretion Rate (BHAR) and the Star Formation Rate (SFR) is found, but no correlation between the specific SFR (sSFR) and the ratio BHAR/M_(BH), simply reflecting the fact that the more massive is a galaxy, the more it is forming stars and feeding its central black hole. The JWST telescope, just beginning operations, will allow large samples of AGN to be observed in these lines in the nearby Universe (z<0.9).