2009/02/16 by P. Gandhi, H. Horst, A. Smette +6 · 4 citations
Physics and Astronomy · #Active galactic nucleus #Astrophysical Phenomena and Observations #Galaxies: Formation, Evolution, Phenomena #Galaxy #Luminosity #Photometry (optics) #Quasar #Spectral index #Star formation #Stellar classification #Stellar, planetary, and galactic studies #Torus #astro-ph.CO #astro-ph.GA
paper · pdf · doi:10.1051/0004-6361/200811368
Accepted for publication in Astronomy & Astrophysics
arxiv created 2009/02/16 · openalex publication_date 2009/04/29 · arxiv updated 2015/05/12 · openalex created_date 2016/06/24 · openalex updated_date 2026/08/05
We present new photometry of 16 local Seyferts including 6 Compton-thick sources in <i>N<i/>-band filters around 12-<i>μ<i/>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 <i>μ<i/>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 <i>L<i/><sub>MIR<sub/> <i>L<i/><sub>X<sub/>, 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-<i>μ<i/>m spectral index () is found to be -1.100.01, largely independent of luminosity. Indirectly-computed 12-<i>μ<i/>m bolometric corrections range over <i>≈<i/>10–30 if a known luminosity trend of X-ray bolometric corrections is assumed. Comparison with <i>ISO<i/> 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 ~70 pc at a median , 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 <i>≈<i/>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.