Footprints in the Wind: Probing X-ray Outflows in NGC 7469 using Near-Infrared Emission Lines

AGN winds play an important role in the co-evolution of supermassive black holes and their host galaxies, yet their driving mechanisms and impact on star formation remain subjects of active investigation. Critically, the lack of X-ray Integral Field Units currently limits our ability to acquire spatially resolved velocity information in the X-ray regime. However, instead, this can be achieved using the James Webb Space Telescope. As part of an ongoing investigation of the nuclear feedback processes in the nearby luminous AGN NGC 7469, we present an analysis of the kinematics of the X-ray emitting outflows using near-infrared footprint lines such as [Mg VIII] 3.03 um. These high-ionization emission lines are associated with the same gas analyzed in the X-ray, and thus can be used to probe the footprint of the X-ray wind’s velocity structure and ionization state. Thanks to the wide wavelength range available with JWST we also use nebular (e.g. [S IV] 10.51 um) and coronal (e.g. [Ne V] 14.32 um) emission lines to offer a comprehensive multi-phase view of the outflows. We present mass and kinetic energy outflow rates, and find that while the feedback processes in NGC 7469 are not efficient by theoretical benchmarks, the most massive and energetic component is the high ionization X-ray gas.

💡 Research Summary

This paper presents a groundbreaking study that overcomes a major observational limitation in astrophysics by using the James Webb Space Telescope (JWST) to probe the kinematics of high-energy X-ray outflows from the Active Galactic Nucleus (AGN) in the galaxy NGC 7469. AGN-driven winds are crucial agents of “feedback,” thought to regulate star formation and galaxy evolution, but directly measuring the spatially resolved velocity structure of the hot, X-ray emitting gas has been impossible due to the lack of X-ray integral field units.

The authors introduce and employ the concept of “footprint lines”—specific high-ionization potential (IP > 100 eV) near- and mid-infrared emission lines such as