XRISM Spectroscopy of the Fe Kα Emission Line in the Seyfert Active Galactic Nucleus NGC 4151 Reveals the Disk, Broad-line Region, and Torus

Article Article scientifique Article XRISM Spectroscopy of the Fe Kα Emission Line in the Seyfert Active Galactic Nucleus NGC 4151 Reveals the Disk, Broad-line Region, and Torus eng 2024-09-19 2024-09-19 XRISM Collaboration collaborator Audard Marc 0000-0003-4721-034X 646393 Département d'astronomie (ASTRO) collaborator Eckert Dominique 0000-0001-7917-3892 515027 Département d'astronomie (ASTRO) collaborator Paltani Stéphane 0000-0002-8108-9179 27695 Département d'astronomie (ASTRO) collaborator Gerolymatou Dimitra 978455 Département d'astronomie (ASTRO) L25 10.3847/2041-8213/ad7397 2041-8205 https://iopscience.iop.org/article/10.3847/2041-8213/ad7397 We present an analysis of the first two XRISM/Resolve spectra of the well-known Seyfert-1.5 active galactic nucleus (AGN) in NGC 4151, obtained in 2023 December. Our work focuses on the nature of the narrow Fe K α emission line at 6.4 keV, the strongest and most common X-ray line observed in AGN. The total line is found to consist of three components. Even the narrowest component of the line is resolved with evident Fe K α ,1 (6.404 keV) and K α ,2 (6.391 keV) contributions in a 2:1 flux ratio, fully consistent with neutral gas with negligible bulk velocity. Subject to the limitations of our models, the narrowest and intermediate-width components are consistent with emission from optically thin gas, suggesting that they arise in a disk atmosphere and/or wind. Modeling the three line components in terms of Keplerian broadening, they are readily associated with (1) the inner wall of the “torus,” (2) the innermost optical “broad-line region” (or “X-ray BLR”), and (3) a region with a radius of r ≃ 100 GM / c 2 that may signal a warp in the accretion disk. Viable alternative explanations of the broadest component include a fast-wind component and/or scattering; however, we find evidence of variability in the narrow Fe K α line complex on timescales consistent with small radii. The best-fit models are statistically superior to simple Voigt functions, but when fit with Voigt profiles the time-averaged lines are consistent with a projected velocity broadening of FWHM = 1600 − 200 + 400 km s − 1 . Overall, the resolution and sensitivity of XRISM show that the narrow Fe K line in AGN is an effective probe of all key parts of the accretion flow, as it is currently understood. We discuss the implications of these findings for our understanding of AGN accretion, future studies with XRISM, and X-ray-based black hole mass measurements. Dewey 520 United States Department of Energy DE-AC52- 07NA27344 NASA 80GSFC21M0002 JSPS KAKENHI JP22H00158 JSPS KAKENHI JP22H01268 JSPS KAKENHI JP22K03624 JSPS KAKENHI JP23H04899 JSPS KAKENHI JP23H04899 JSPS KAKENHI JP24K00638 JSPS KAKENHI JP24K17105 JSPS KAKENHI JP21K13958 JSPS KAKENHI JP21H01095 JSPS KAKENHI JP23K20850 JSPS KAKENHI JP24H00253 JSPS KAKENHI JP21K03615 JSPS KAKENHI JP24K00677 JSPS KAKENHI JP20K14491 JSPS KAKENHI JP23H00151 JSPS KAKENHI JP19K21884 JSPS KAKENHI JP20H01947 JSPS KAKENHI JP20KK0071 JSPS KAKENHI JP23K20239 JSPS KAKENHI JP24K00672 JSPS KAKENHI JP24K17104 JSPS KAKENHI JP24K17093 JSPS KAKENHI JP20K04009 JSPS KAKENHI JP21H04493 JSPS KAKENHI JP20H01946 JSPS KAKENHI JP23K13154 JSPS KAKENHI JP19K14762 JSPS KAKENHI JP20H05857 JSPS KAKENHI JP23K03459 NASA 80NSSC20K0733 NASA 80NSSC18K0978 NASA 80NSSC20K0883 NASA 80NSSC20K0737 NASA 80NSSC24K0678 NASA 80NSSC18K1684 NASA 80NNSC22K1922 NSF 2205918 STFC ST/T000244/1 Canadian Space Agency 18XARMSTMA. 945 AT JSPS Core-to-Core Program JPJSCCA20220002 26 Département d'astronomie 12 false The astrophysical journal. Letters 973 1 a4d495df-8b0f-4930-8aab-f78c0b54d088 Article (Published version) Public Audard_2024_ApJL_973_L25.pdf 1661427 application/pdf CC BY-4.0 31752003b54d0bb43c418b5a8a95730ce3a4130ac5a4cffb988df964a5972cac openAccess Faculté des sciences / Département d'astronomie

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