Mapping the circumnuclear regions of the Circinus galaxy with the Imaging X-ray Polarimetry Explorer. Issue 1 (9th November 2022)

• Record Type: Journal Article
• Authors: Ursini, F; Marinucci, A; Matt, G; Bianchi, S; Marin, F; Marshall, H L; Middei, R; Poutanen, J; Rogantini, D; De Rosa, A; Di Gesu, L; García, J A; Ingram, A; Kim, D E; Krawczynski, H; Puccetti, S; Soffitta, P; Svoboda, J; Tombesi, F; Weisskopf, M C; Barnouin, T; Perri, M; Podgorny, J; Ratheesh, A; Zaino, A; Agudo, I; Antonelli, L A; Bachetti, M; Baldini, L; Baumgartner, W H; Bellazzini, R; Bongiorno, S D; Bonino, R; Brez, A; Bucciantini, N; Capitanio, F; Castellano, S; Cavazzuti, E; Ciprini, S; Costa, E; Del Monte, E; Di Lalla, N; Di Marco, A; Donnarumma, I; Doroshenko, V; Dovciak, M; Ehlert, S R; Enoto, T; Evangelista, Y; Fabiani, S; Ferrazzoli, R; Gunji, S; Heyl, J; Iwakiri, W; Jorstad, S G; Karas, V; Kitaguchi, T; Kolodziejczak, J J; La Monaca, F; Latronico, L; Liodakis, I; Maldera, S; Manfreda, A; Marscher, A P; Mitsuishi, I; Mizuno, T; Muleri, F; Ng, C Y; O'Dell, S L; Omodei, N; Oppedisano, C; Papitto, A; Pavlov, G G; Peirson, A L; Pesce-Rollins, M; Petrucci, P-O; Pilia, M; Possenti, A; Ramsey, B D; Rankin, J; Romani, R W; Sgrò, C; Slane, P; Spandre, G; Tamagawa, T; Tavecchio, F; Taverna, R; Tawara, Y; Tennant, A F; Thomas, N E; Trois, A; Tsygankov, S S; Turolla, R; Vink, J; Wu, K; Xie, F; Zane, S;
• Is Part Of: Monthly notices of the Royal Astronomical Society. Volume 519:Issue 1(2023)
• Page Start: 50
• Page End: 58
• Publication Date: 2022-11-09
• Subjects: polarization -- scattering -- galaxies: active -- galaxies: individual: Circinus -- galaxies: Seyfert -- X-rays: galaxies; Astronomy -- Periodicals; Periodicals; 520.5
• DOI: 10.1093/mnras/stac3189
• Languages: English
• ISSNs: 0035-8711

Abstract

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.