XRISM Spectroscopy of Accretion-Driven Wind Feedback in NGC 4151

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, vₒᵤₜ ∼ 100 − 1000 km s−1 ), very fast outflows (VFOs, vₒᵤₜ ∼ 10³ km s⁻¹ − 10⁴ km s⁻¹), and ultra-fast outflows (UFOs, vₒᵤₜ ∼ 104 km s⁻¹ − 10⁵ km 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 Lₖᵢₙ ≥ 0.5%Lₑ* 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 ∝ r ⁻¹.⁵, but radiative driving and other mechanisms may also be important. Numerous complexities and variability require further analysis.

* = subscript dd