XRISM Spectroscopy of Accretion-Driven Wind Feedback in NGC 4151

TL;DR

This study uses XRISM X-ray spectroscopy to analyze the complex, multi-phase winds in galaxy NGC 4151, revealing fast, stratified outflows with significant kinetic power capable of influencing galaxy evolution.

Contribution

First detailed photoionization analysis of NGC 4151's accretion-driven winds using XRISM, identifying multiple wind components and their properties with high spectral resolution.

Findings

Detection of multiple wind components including UFOs, VFOs, and WAs.

Wind kinetic luminosities exceed thresholds for galaxy feedback.

Evidence of wind asymmetry and variability.

Abstract

The hottest, most ionized, and fastest winds driven by accretion onto massive black holes have the potential to reshape their host galaxies. Calorimeter-resolution X-ray spectroscopy is the ideal tool to understand this feedback mode, as it enables accurate estimates of physical characteristics needed to determine the wind's kinetic power. We report on a photoionization analysis of five observations of the Seyfert-1.5 galaxy NGC 4151, obtained with XRISM/Resolve in 2023 and 2024. In the Fe K band, individual spectra require as many as six wind absorption components. Slow "warm absorbers" (WAs, $v_{\mathrm{out}} \sim 100 - 1000~\mathrm{km~s^{-1}}$), very fast outflows (VFOs, $v_{\mathrm{out}} \sim 10^3~{\rm km}~{\rm s}^{-1} - 10^4~{\rm km}~{\rm s}^{-1}$), and ultra-fast outflows (UFOs, $v_{\mathrm{out}} \sim 10^4~{\rm km}~{\rm s}^{-1} - 10^5~{\rm km}~{\rm s}^{-1}$ or $0.033 - 0.33~c$) are detected simultaneously, and indicate a stratified, multiphase wind. Fast and variable emission components suggest that the wind is axially asymmetric. All of the wind components have mass flow rates comparable to or in excess of the mass accretion rate, though the slowest zones may be "failed" winds that do not escape. Two UFO components have kinetic luminosities that exceed the theoretical threshold of $L_{kin} \geq 0.5\% L_{Edd}$ necessary to strip the host bulge of gas and halt star formation, even after corrections for plausible filling factors. The bulk properties of the observed winds are consistent with magnetocentrifugal driving, where the density depends on radius as $n \propto r^{-1.5}$, but radiative driving and other mechanisms may also be important. Numerous complexities and variability require further analysis.