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Mapping the circumnuclear regions of the Circinus galaxy with the Imaging X-ray Polarimetry Explorer

Abstract : We report on the Imaging X-ray Polarimetry Explorer (IXPE) observation of the closest and X-ray brightest Compton-thick active galactic nucleus (AGN), the Circinus galaxy. We find the source to be significantly polarized in the 2-6 keV band. From previous studies, the X-ray spectrum is known to be dominated by reflection components, both neutral (torus) and ionized (ionization cones). Our analysis indicates that the polarization degree is 28 ± 7 per cent (at 68 per cent confidence level) for the neutral reflector, with a polarization angle of 18 ± 5, roughly perpendicular to the radio jet. The polarization of the ionized reflection is unconstrained. A comparison with Monte Carlo simulations of the polarization expected from the torus shows that the neutral reflector is consistent with being an equatorial torus with a half-opening angle of 45-55. This is the first X-ray polarization detection in a Seyfert galaxy, demonstrating the power of X-ray polarimetry in probing the geometry of the circumnuclear regions of AGNs, and confirming the basic predictions of standard Unification Models.
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https://hal-insu.archives-ouvertes.fr/insu-03850830
Contributor : Olivier Hauss Connect in order to contact the contributor
Submitted on : Monday, November 14, 2022 - 10:45:52 AM
Last modification on : Thursday, November 24, 2022 - 5:02:58 PM

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F. Ursini, A. Marinucci, G. Matt, S. Bianchi, F. Marin, et al.. Mapping the circumnuclear regions of the Circinus galaxy with the Imaging X-ray Polarimetry Explorer. Monthly Notices of the Royal Astronomical Society, 2022, ⟨10.1093/mnras/stac3189⟩. ⟨insu-03850830⟩

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