Investigating source confusion in PMN J1603$-$4904

TL;DR

This study uses Chandra X-ray observations to confirm that PMN J1603-4904 is a genuine gamma-ray bright young radio galaxy, ruling out source confusion within the Fermi/LAT positional uncertainty.

Contribution

The paper provides the first X-ray confirmation that PMN J1603-4904 is a true gamma-ray emitting young radio galaxy, clarifying its nature among similar objects.

Findings

No other X-ray sources in the Fermi/LAT error ellipse.

PMN J1603-4904's X-ray flux and spectrum support its identification.

Confirmed as the second gamma-ray bright young radio galaxy.

Abstract

PMN J1603$-$4904 is a likely member of the rare class of $\gamma$-ray emitting young radio galaxies. Only one other source, PKS 1718$-$649, has been confirmed so far. These objects, which may transition into larger radio galaxies, are a stepping stone to understanding AGN evolution. It is not completely clear how these young galaxies, seen edge-on, can produce high-energy $\gamma$-rays. PMN J1603$-$4904 has been detected by TANAMI Very Long Baseline Interferometry (VLBI) observations and has been followed-up with multiwavelength observations. A Fermi/LAT $\gamma$-ray source has been associated with it in the LAT catalogs. We have obtained Chandra observations of the source in order to consider the possibility of source confusion, due to the relatively large positional uncertainty of Fermi/LAT. The goal was to investigate the possibility of other X-ray bright sources in the vicinity of PMN J1603$-$4904 that could be counterparts to the $\gamma$-ray emission. With Chandra/ACIS, we find no other sources in the uncertainty ellipse of Fermi/LAT data, which includes an improved localization analysis of 8 years of data. We further study the X-ray fluxes and spectra. We conclude that PMN J1603$-$4904 is indeed the second confirmed $\gamma$-ray bright young radio galaxy.