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arXiv · 1408.4453

A Compton thick AGN in the barred spiral NGC 4785

P. Gandhi·S. Yamada·C. Ricci·D. Asmus·R. F. Mushotzky·Y. Ueda·Y. Terashima·V. La Parola
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Abstract

We present X-ray observations of the active galactic nucleus (AGN) in NGC 4785. The source is a local Seyfert 2 which has not been studied so far in much detail. It was recently detected with high significance in the 15-60 keV band in the 66 month Swift/BAT all sky survey, but there have been no prior pointed X-ray observations of this object. With Suzaku, we clearly detect the source below 10 keV, and find it to have a flat continuum and prominent neutral iron fluorescence line with equivalent width >~1 keV. Fitting the broadband spectra with physical reflection models shows the source to be a bona fide Compton thick AGN with Nh of at least 2x10^{24} cm^{-2} and absorption-corrected 2-10 keV X-ray power L(2-10) ~ few times 10^{42} erg s^{-1}. Realistic uncertainties on L(2-10) computed from the joint confidence interval on the intrinsic power law continuum photon index and normalization are at least a factor of 10. The local bona fide Compton thick AGN population is highly heterogeneous in terms of WISE mid-infrared source colours, and the nucleus of NGC 4785 appears especially sub-dominant in the mid-infrared when comparing to other Compton thick AGN. Such sources would not be easily found using mid-infrared selection alone. The extent of host galaxy extinction to the nucleus is not clear, though NGC 4785 shows a complex core with a double bar and inner disk, adding to the list of known Compton thick AGN in barred host galaxies.

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P. Gandhi, S. Yamada, C. Ricci, D. Asmus, R. F. Mushotzky, Y. Ueda, Y. Terashima, V. La Parola. 2014-08-19. A Compton thick AGN in the barred spiral NGC 4785. https://doi.org/10.1093/mnras%2Fstv344

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