학술논문
Mapping the circumnuclear regions of the Circinus galaxy with the Imaging X-ray Polarimetry Explorer
Document Type
Working Paper
Author
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.; Dovčiak, 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.
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Subject
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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 $28 \pm 7$ per cent (at 68 per cent confidence level) for the neutral reflector, with a polarization angle of $18{\deg} \pm 5{\deg}$, 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{\deg}-55{\deg}. 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.
Comment: 9 pages, accepted for publication in MNRAS, authors list updated
Comment: 9 pages, accepted for publication in MNRAS, authors list updated