An extended XMM-Newton observation of the Seyfert galaxy NGC 4051. II. Soft X-ray emission from a limb-brightened shell of post-shock gas

TL;DR

This study analyzes extended XMM-Newton observations of NGC 4051, revealing complex outflow structures, broad emission lines from a limb-brightened shell of post-shock gas, and variable recombination continua linked to the continuum flux.

Contribution

It provides new insights into the structure and variability of post-shock gas and outflows in Seyfert galaxies through detailed spectral analysis.

Findings

Detection of broad emission lines consistent with limb-brightened shell emission

Recombination continua vary with continuum flux, indicating ionized flow scaling

Complex absorption spectrum with multiple outflow velocities and ionization states

Abstract

An extended XMM-Newton observation of the Seyfert I galaxy NGC 4051 in 2009 revealed a complex absorption spectrum, with a wide range of outflow velocities and ionisation states.The main velocity and ionisation structure was interpreted in Paper I in terms of a decelerating, recombining flow resulting from the shocking of a still higher velocity wind colliding with the ISM or slower moving ejecta. The high sensitivity of the XMM-Newton observation also revealed a number of broad emission lines, all showing evidence of self-absorption near the line cores. The line profiles are found here to be consistent with emission from a limb-brightened shell of post-shock gas building up ahead of the contact discontinuity. While the broad emission lines remain quasi-constant as the continuum flux changes by an order of magnitude, recombination continua of several H- and He-like ions are found to vary in response to the continuum, providing an important key to scaling the ionised flow.