NuSTAR Uncovers an Extremely Local Compton-thick AGN in NGC 4968
Abstract
We present the analysis of Chandra and NuSTAR spectra of NGC 4968, a local (D44 Mpc) 12m-selected Seyfert 2 galaxy, enshrouded within Compton-thick layers of obscuring gas. We find no evidence of variability between the Chandra and NuSTAR observations (separated by 2 years), and between the two NuSTAR observations (separated by 10 months). Using self-consistent X-ray models, we rule out the scenario where the obscuring medium is nearly spherical and uniform, contradicting the results implied by the 10 keV Chandra spectrum. The line-of-sight column density, from intervening matter between the source and observer that intercepts the intrinsic AGN X-ray emission, is well within the Compton-thick regime, with a minimum column density of cm. The average global column density is high ( cm), with both Compton-thick and Compton-thin solutions permitted depending on the X-ray spectral model. The spectral models provide a range of intrinsic AGN continuum parameters and implied 2-10 keV luminosities (), where the higher end of is consistent with expectations from the 12m luminosity ( erg s). Compared with Compton-thick AGN previously observed by {\it NuSTAR}, NGC 4968 is among the most intrinsically X-ray luminous. However, despite its close proximity and relatively high intrinsic X-ray luminosity, it is undetected by the 105 month Swift-BAT survey, underscoring the importance of multi-wavelength selection for obtaining the most complete census of the most hidden black holes.
Cite
@article{arxiv.1911.05813,
title = {NuSTAR Uncovers an Extremely Local Compton-thick AGN in NGC 4968},
author = {Stephanie M. LaMassa and Tahir Yaqoob and Peter G. Boorman and Panayiotis Tzanavaris and N. A. Levenson and Poshak Gandhi and Andrew F. Ptak and Timothy M. Heckman},
journal= {arXiv preprint arXiv:1911.05813},
year = {2020}
}
Comments
accepted for publication in ApJ; 20 pages, 8 figures