X-ray polarization measurement of the gold standard of radio-quiet active galactic nuclei : NGC 1068

Abstract

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 for a net exposure time of 1.15 Ms on the target, in addition to two ~ 10 ks each Chandra snapshots in order to account for the potential impact of several ultraluminous X-ray source (ULXs) within IXPE's field-of-view. We measured a 2 - 8 keV polarization degree of 12.4% +/- 3.6% and an electric vector polarization angle of 101° +/- 8° at 68% confidence level. If we exclude the spectral region containing the bright Fe K lines and other soft X-ray lines where depolarization occurs, the polarization fraction rises up to 21.3% +/- 6.7% 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 multi-wavelength 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 polarization angle orientation with respect to the radio-jet and 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 object is now feasible thanks to X-ray polarimetry.

9 pages, 5 figures, 2 tables, submited to A&A

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• Thermal imaging of dust hiding the black hole in the Active Galaxy NGC 1068
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• X-ray reflection in the nearby Seyfert 2 galaxy NGC 1068
• Probing the circumnuclear absorbing medium of the buried AGN in NGC 1068 through NuSTAR observations
• Discovery and Rapid Follow-up Observations of the Unusual Type II SN 2018ivc in NGC 1068
• A Multi-Wavelength View on the Rapidly-Evolving Supernova 2018ivc: An Analog of SN IIb 1993J but Powered Primarily by Circumstellar Interaction
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Cited by in corpus (4)

• Studying geometry of the ultraluminous X-ray pulsar Swift J0243.6+6124 using X-ray and optical polarimetry
• A systematic study of the ultra-fast outflow responses to luminosity variations in active galactic nuclei
• Detection of Compton scattering in the jet of 3C 84
• A multi-wavelength view of the multi-messenger sources NGC 1068 and PKS 1502+1061