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  • X-ray polarization measurem...
    Marin, F.; Marinucci, A.; Laurenti, M.; Kim, D.E.; Barnouin, T.; Di Marco, A.; Ursini, F.; Bianchi, S.; Ravi, S.; Marshall, H.L.; Matt, G.; Chen, C.-T.; Gianolli, V.E.; Ingram, A.; Maksym, W.P.; Panagiotou, C.; Podgorny, J.; Puccetti, S.; Ratheesh, A.; Tombesi, F.; Agudo, I.; Antonelli, L.A.; Bachetti, M.; Baldini, L.; Baumgartner, W.; Bellazzini, R.; Bongiorno, S.; Bonino, R.; Brez, A.; Bucciantini, N.; Capitanio, F.; Castellano, S.; Cavazzuti, E.; Ciprini, S.; Costa, E.; De Rosa, A.; Del Monte, E.; Di Gesu, L.; Di Lalla, N.; Donnarumma, I.; Doroshenko, V.; Dovčiak, M.; Ehlert, S.; Enoto, T.; Evangelista, Y.; Fabiani, S.; Garcia, J.; Gunji, S.; Heyl, J.; Iwakiri, W.; Jorstad, S.; Kaaret, P.; Karas, V.; Kislat, F.; Kitaguchi, T.; Kolodziejczak, J.; Krawczynski, H.; La Monaca, F.; Latronico, L.; Liodakis, I.; Madejski, G.; Maldera, S.; Manfreda, A.; Marscher, A.; Massaro, F.; Mitsuishi, I.; Mizuno, T.; Ng, S.; O'Dell, S.; Omodei, N.; Oppedisano, C.; Papitto, A.; Pavlov, G.; Perri, M.; Pesce-Rollins, M.; Petrucci, P.-O.; Pilia, M.; Possenti, A.; Poutanen, J.; Ramsey, B.; Rankin, J.; Roberts, O.; Romani, R.; Sgrò, C.; Slane, P.; Soffitta, P.; Spandre, G.; Tamagawa, T.; Tavecchio, F.; Taverna, R.; Tennant, A.; Thomas, N.; Trois, A.; Tsygankov, S.; Turolla, R.; Vink, J.; Weisskopf, M.; Wu, K.; Xie, F.; Zane, S.

    Astronomy and astrophysics (Berlin), 05/2024
    Journal Article

    NGC 1068 is the most observed radio-quiet active galactic nucleus (AGN) in polarimetry, yet its high-energy polarization has never been probed before due to a lack of dedicated polarimeters. Using the first X-ray polarimeter sensitive enough to measure the polarization of AGNs, we want to probe the orientation and geometric arrangement of (sub)parsec-scale matter around the X-ray source. We used the Imaging X-ray Polarimetry Explorer (IXPE) satellite to measure, for the first time, the 2-8 keV polarization of NGC 1068. We pointed IXPE at the target for a net exposure time of 1.15 Ms, in addition to using two Chandra snapshots of sim 10 ks each in order to account for the potential impact of several ultraluminous X-ray sources (ULXs) within IXPE's field of view. We measured a 2 -- 8 keV polarization degree of 12.4<!PCT!> pm 3.6<!PCT!> and an electric vector polarization angle of 101$^ pm 8$^ at a 68<!PCT!> confidence level. If we exclude the spectral region containing bright Fe K lines and other soft X-ray lines where depolarization occurs, the polarization fraction rises to 21.3<!PCT!> pm 6.7<!PCT!> in the 3.5 -- 6.0 keV band, with a similar polarization angle. The observed polarization angle is found to be perpendicular to the parsec-scale radio jet. Using a combined Chandra and IXPE analysis plus multiwavelength constraints, we estimated that the circumnuclear “torus” may sustain a half-opening angle of 50 -- 55$^ (from the vertical axis of the system). Thanks to IXPE, we have measured the X-ray polarization of NGC 1068 and found comparable results, both in terms of the polarization angle orientation with respect to the radio jet and the torus half-opening angle, to the X-ray polarimetric measurement achieved for the other archetypal Compton-thick AGN: the Circinus galaxy. Probing the geometric arrangement of parsec-scale matter in extragalactic objects is now feasible thanks to X-ray polarimetry.