Delving into the depths of NGC 3783 with XRISM. I. Kinematic and ionization structure of the highly ionized outflows

TL;DR

This study uses XRISM's high-resolution spectroscopy to analyze the ionization, velocity, and structure of outflows in galaxy NGC 3783, revealing complex, multi-component winds with varying ionization and turbulence.

Contribution

First detailed characterization of highly ionized AGN outflows using XRISM Resolve, uncovering multiple components and complex ionization structures with implications for wind models.

Findings

Detected six outflow components with velocities from 560 to 1170 km/s.

Identified a broad Fe XXVI outflow at 14,300 km/s, with significant kinetic luminosity.

Found that turbulence increases with ionization parameter, indicating complex wind dynamics.

Abstract

We present our study of the XRISM observation of the Seyfert-1 galaxy NGC 3783. XRISM's Resolve microcalorimeter has enabled, for the first time, a detailed characterization of the highly ionized outflows in this active galactic nucleus. Our analysis constrains their outflow and turbulent velocities, along with their ionization parameter ($\xi$) and column density ($N_{\rm H}$). The high-resolution Resolve spectrum reveals a distinct series of Fe absorption lines between 6.4 and 7.8 keV, ranging from Fe XVIII to Fe XXVI. At lower energies, absorption features from Si, S, and Ar are also detected. Our spectroscopy and photoionization modeling of the time-averaged Resolve spectrum uncovers six outflow components, five of which exhibit relatively narrow absorption lines with outflow velocities ranging from 560 to 1170 km/s. In addition, a broad absorption feature is detected, which is consistent with Fe XXVI outflowing at 14,300 km/s (0.05 $c$). The kinetic luminosity of this component is 0.8-3% of the bolometric luminosity. Our analysis of the Resolve spectrum shows that more highly ionized absorption lines are intrinsically broader than those of lower-ionization species, indicating that the turbulent velocity of the six outflow components (ranging from 0 to 3500 km/s) increases with $\xi$. Furthermore, we find that the $N_{\rm H}$ of the outflows generally declines with $\xi$ up to $\log \xi = 3.2$ but rises beyond this point, suggesting a complex ionization structure. The absorption profile of the Fe XXV resonance line is intriguingly similar to UV absorption lines (Ly$\alpha$ and C IV) observed by the HST, from which we infer that the outflows are clumpy in nature. Our XRISM/Resolve results support a "hybrid wind" scenario in which the observed outflows have multiple origins and driving mechanisms. We explore various interpretations of our findings within AGN wind models.