XMM-Newton Detection of a Compton-thick AGN in the 1-Jy ULIRG/LINER F04103-2838

TL;DR

This paper reports the detection of a Compton-thick AGN in the ULIRG F04103-2838 using XMM-Newton, revealing a strong Fe Kalpha line and a dominant hard X-ray component indicative of a heavily obscured active nucleus.

Contribution

It provides the first clear X-ray evidence of a Compton-thick AGN in F04103-2838, demonstrating the effectiveness of XMM-Newton in identifying obscured AGN in ULIRGs.

Findings

Detection of a strong Fe Kalpha line at 6.4 keV with an equivalent width of 1.6 keV.

Identification of a Compton-thick AGN with intrinsic luminosity ~10^44 erg/s.

X-ray spectrum resembles that of NGC 6240 despite different merger states.

Abstract

We report on the detection of Fe Kalpha emission in F04103$-$2838, an ultraluminous infrared galaxy (ULIRG; log[L$_{\rm IR}$/L$_\odot$] $\ge$ 12) that is optically classified as a LINER. Previous {\it Chandra} observations suggested the presence of both a starburst and an AGN in this source. A deeper ($\sim$20 ksec) {\it XMM-Newton} spectrum reveals an Fe Kalpha line at rest frame energy $\sim$6.4 keV, consistent with cold neutral iron. The best-fit spectral model indicates the Fe Kalpha line has an equivalent width of $\sim$1.6 keV. The hard X-ray emission is dominated by a Compton-thick AGN with intrinsic 0.2--10 keV luminosity $\sim10^{44}$ ergs s$^{-1}$, while the soft X-ray emission is from $\sim$0.1 keV gas attributed to the starburst. The X-ray spectrum of this source bears a striking resemblance to that of the archetypal luminous infrared galaxy NGC 6240 despite differences in merger state and infrared properties.