Comprehensive X-ray Study of Giant Radio Galaxies with XMM-Newton and Chandra

Abstract

We present a systematic X-ray spectral analysis of 27 giant radio galaxies (GRGs) using archival \textit{XMM-Newton} and \textit{Chandra} data. Roughly 44\% of the sample show intrinsic absorption ($N_{\mathrm{H},\mathrm{int}}\gtrsim 10^{21}{\mathrm{cm}}^{-2}$), while several exhibit narrow Fe K$\hat{I}\pm$ emission lines with equivalent widths up to $\sim$570 eV. Soft X-ray features are also common, including thermal plasma emission (kT$\sim 0.2$--0.8 keV) and ionized absorbers, in some cases consistent with high-velocity outflows. The photon indices are typically hard (median $\hat{I}“\sim 1.6$), in line with radio-loud AGN. A comparison between nuclear X-ray luminosity and extended radio power shows that many sources host relatively strong X-ray cores compared to their lobes, pointing toward possible restarted nuclear activity. For 10 GRGs with published black hole masses, we explore preliminary relations with X-ray luminosity, Eddington ratio, and photon index. We find a positive trend between $M_{\mathrm{BH}}$ and $L_{2-10\mathrm{keV}}$, while Eddington ratios show no clear dependence on mass. A tentative negative relation between $\hat{I}{»}_{\mathrm{Edd}}$ and $\hat{I}“$ hints at inefficient accretion, although confirmation will require larger samples. Overall, GRGs display diverse nuclear conditions and accretion states, supporting scenarios where obscuration, episodic or restarted activity, and low-efficiency accretion shape their long-term evolution.

Accepted for publication in JHEAp , 21 pages, 7 figures, 12 tables

Topics & keywords