NASA/IPAC EXTRAGALACTIC DATABASE
Date and Time of the Query: 2019-03-23 T01:14:08 PDT
Help | Comment | NED Home

For refcode 2012ApJ...755....5G:
Retrieve 20 NED objects in this reference.
Please click here for ADS abstract

NED Abstract

Copyright by American Astronomical Society. Reproduced by permission
2012ApJ...755....5G Deep Silicate Absorption Features in Compton-thick Active Galactic Nuclei Predominantly Arise due to Dust in the Host Galaxy Goulding, A. D.; Alexander, D. M.; Bauer, F. E.; Forman, W. R.; Hickox, R. C.; Jones, C.; Mullaney, J. R.; Trichas, M. Abstract. We explore the origin of mid-infrared (mid-IR) dust extinction in all 20 nearby (z < 0.05) bona fide Compton-thick (N_H_ > 1.5 x 10^24^ cm^--2^) active galactic nuclei (AGNs) with hard energy (E > 10 keV) X-ray spectral measurements. We accurately measure the silicate absorption features at lambda ~ 9.7 micron in archival low-resolution (R ~ 57-127) Spitzer Infrared Spectrograph spectroscopy, and show that only a minority (~45%) of nearby Compton-thick AGNs have strong Si-absorption features (S_9.7_ = ln (f_int_/f_obs_) >~ 0.5) which would indicate significant dust attenuation. The majority (~60%) are star formation dominated (AGN:SB < 0.5) at mid-IR wavelengths and lack the spectral signatures of AGN activity at optical wavelengths, most likely because the AGN emission lines are optically extinguished. Those Compton-thick AGNs hosted in low-inclination-angle galaxies exhibit a narrow range in Si-absorption (S_9.7_ ~ 0-0.3), which is consistent with that predicted by clumpy-torus models. However, on the basis of the IR spectra and additional lines of evidence, we conclude that the dominant contribution to the observed mid-IR dust extinction is dust located in the host galaxy (i.e., due to disturbed morphologies, dust lanes, galaxy inclination angles) and not necessarily a compact obscuring torus surrounding the central engine. Key words: galaxies: active, galaxies: Seyfert, infrared: galaxies, X-rays: galaxies
Retrieve 20 NED objects in this reference.
Please click here for ADS abstract

Back to NED Home