A Weak Fe K$\beta$ Emission Line in the Broad-Line Radio Galaxy 3C 111 Observed with XRISM: An Ionized Wind Absorption Feature?

TL;DR

This study reports the detection of a weak Fe Kβ emission line in 3C 111, likely caused by an ionized wind absorption feature, revealing insights into the outflow velocities and wind power in this galaxy.

Contribution

First high-resolution spectral analysis of 3C 111 revealing a potential ionized wind absorption feature affecting Fe Kβ emission.

Findings

Fe Kβ line significantly weaker than expected from Fe Kα.

Possible blueshifted absorption lines indicating ionized wind velocities of 4600 or 17200 km/s.

Estimated wind kinetic power ranges from 10^41 to 10^44 erg/s, smaller than jet power.

Abstract

We present the results of an observation of the broad-line radio galaxy 3C 111 with the X-Ray Imaging and Spectroscopy Mission (XRISM). The unprecedentedly high spectral resolution of XRISM/Resolve revealed that the Fe K$\beta$ emission line is significantly weaker than expected from the Fe K$\alpha$ line. This feature may be explained by a blueshifted absorption line from an ionized wind overlapping the Fe K$\beta$ energy. The inferred outflow velocity is 4600 km s$^{-1}$ or 17200 km s$^{-1}$, depending on whether the absorption feature is identified as Fe XXVI or Fe XXV, with the current data unable to distinguish between the two interpretations. Based on spectral modeling, the kinetic power of the wind is estimated to lie in the range 10$^{41}$-10$^{44}$ erg s$^{-1}$, although this estimate is subject to large uncertainties primarily due to the poorly constrained location of the absorber. The inferred wind power is smaller than the jet power of 3C 111 ($\sim 3\times 10^{44}$ erg s$^{-1}$), and is broadly consistent with theoretical expectations that the jet power exceeds that of disk winds.