NuSTAR Uncovers an Extremely Local Compton-thick AGN in NGC 4968. (arXiv:1911.05813v1 [astro-ph.HE])
<a href="http://arxiv.org/find/astro-ph/1/au:+LaMassa_S/0/1/0/all/0/1">Stephanie M. LaMassa</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Yaqoob_T/0/1/0/all/0/1">Tahir Yaqoob</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Boorman_P/0/1/0/all/0/1">Peter G. Boorman</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Tzanavaris_P/0/1/0/all/0/1">Panayiotis Tzanavaris</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Levenson_N/0/1/0/all/0/1">N. A. Levenson</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Gandhi_P/0/1/0/all/0/1">Poshak Gandhi</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Ptak_A/0/1/0/all/0/1">Andrew F. Ptak</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Heckman_T/0/1/0/all/0/1">Timothy M. Heckman</a>
We present the analysis of Chandra and NuSTAR spectra of NGC 4968, a local
(D$sim$44 Mpc) 12$mu$m-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 $2times10^{24}$ cm$^{-2}$. The average global column density is
high ($> 3times10^{23}$ cm$^{-2}$), 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 ($L_{rm 2-10keV,intrinsic}$), where the higher end of $L_{rm
2-10keV,intrinsic}$ is consistent with expectations from the 12$mu$m
luminosity ($L_{rm 2-10keV,intrinisc} sim 7times10^{42}$ erg s$^{-1}$).
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.
We present the analysis of Chandra and NuSTAR spectra of NGC 4968, a local
(D$sim$44 Mpc) 12$mu$m-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 $2times10^{24}$ cm$^{-2}$. The average global column density is
high ($> 3times10^{23}$ cm$^{-2}$), 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 ($L_{rm 2-10keV,intrinsic}$), where the higher end of $L_{rm
2-10keV,intrinsic}$ is consistent with expectations from the 12$mu$m
luminosity ($L_{rm 2-10keV,intrinisc} sim 7times10^{42}$ erg s$^{-1}$).
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.
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