First X-Ray Polarimetric View of a Low-luminosity Active Galactic Nucleus: The Case of NGC 2110

Le résumé fourni par la source

Abstract Low-luminosity active galactic nuclei (LLAGN) provide a unique view of Comptonization and nonthermal emission from accreting black holes in the low accretion rate regime. However, to decipher the exact nature of the Comptonizing corona in LLAGN, its geometry and emission mechanism must be understood beyond the limits of spectro-timing techniques. Spectropolarimetry offers the potential to break the degeneracies between different coronal emission models. Compton-thin LLAGN provide an opportunity for such spectropolarimetric exploration in the 2–8 keV energy range using the Imaging X-Ray Polarimetry Explorer (IXPE). In this work, we carry out a spectropolarimetric analysis of the first IXPE observation, in synergy with a contemporaneous Nuclear Spectroscopic Telescope Array observation, of an LLAGN: NGC 2110. Using 554.4 ks of IXPE data from 2024 October, we constrain the 99% upper limit on the polarization degree (PD) to be less than 8.3% assuming the corresponding polarization angle (PA) to be aligned with the radio jet, and less than 3.6% if in the perpendicular direction. In the absence of a significant PD detection, the PA remains formally unconstrained, yet the polarization significance contours appear to be aligned with the radio jet, tentatively supporting models in which the corona is radially extended in the plane of the disk. We also carry out detailed Monte Carlo simulations using monk and STOKES codes to test different coronal models against our results and compare the polarization properties between NGC 2110 and brighter Seyferts.

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