Resolving the mid-infrared cores of local Seyferts

We present new photometry of 16 local Seyferts including 6 Compton-thick sources in N-band filters around 12-mu m, obtained with the VISIR instrument on the 8-m Very Large Telescope. The near-diffraction-limited imaging provides the least-contaminated core fluxes for these sources to date. Augmenting these with our previous observations and with published intrinsic X-ray fluxes, we form a total sample of 42 sources for which we find a strong mid-infrared: X-ray (12.3 mu m: 2-10 keV) luminosity correlation. Performing a physically-motivated subselection of sources in which the Seyfert torus is likely to be best-resolved results in the correlation L-MIR proportional to L-X(1.11 +/- 0.07), with a reduction of the scatter in luminosities as compared to the full sample. Consideration of systematics suggests a range of 1.02-1.21 for the correlation slope. The mean 2-keV: 12.3-mu m spectral index (alpha(IX)) is found to be -1.10 +/- 0.01, largely independent of luminosity. Indirectly-computed 12-mu m bolometric corrections range over approximate to 10-30 if a known luminosity trend of X-ray bolometric corrections is assumed. Comparison with ISO data spanning a wider luminosity range suggests that our correlation can be extended into the quasar regime. That unobscured, obscured, and Compton-thick sources all closely follow the same luminosity correlation has important implications for the structures of Seyfert cores. The typical resolution-limit of our imaging corresponds to similar to 70 pc at a median z = 0.01, and we use the tightness of the correlation to place constraints on the dominance of any residual emission sources within these physical scales. An upper-limit for any contaminating star formation of approximate to 40% of the unresolved flux is inferred, on average. We suggest that uncontaminated mid-IR continuum imaging of AGN is an accurate proxy for their intrinsic power.