X-ray properties of the Youngest Radio Sources and their Environments

Abstract

We present the first results from our X-ray study of young radio sources classified as compact symmetric objects (CSOs). Using the Chandra X-ray Observatory we observed six CSOs for the first time in X-rays, and re-observed four CSOs already observed with XMM-Newton or BeppoSAX. We also included six other CSOs with archival data to built a pilot study of a sample of the 16 CSO sources observed in X-rays to date. All the sources are nearby, $z\lt 1$, and the age of their radio structures ($\lt 3000$ yr) has been derived from the expansion velocity of their hot spots. Our results show the heterogeneous nature of the CSOs' X-ray emission, indicating a complex environment associated with young radio sources. The sample covers a range in X-ray luminosity, ${L}_{2\mbox{--}10\mathrm{keV}}\sim {10}^{41}$–1045 erg s−1, and intrinsic absorbing column density of ${N}_{{\rm{H}}}\simeq {10}^{21}$–1022 cm−2. In particular, we detected extended X-ray emission in 1718−649; a hard photon index of ${\rm{\Gamma }}\simeq 1$ in 2021+614 and 1511+0518 consistent with either a Compton-thick absorber or non-thermal emission from compact radio lobes, and in 0710+439 an ionized iron emission line at ${E}_{\mathrm{rest}}=(6.62\pm 0.04)$ keV and EW $\sim 0.15$–1.4 keV, and a decrease by an order of magnitude in the 2–10 keV flux since the 2008 XMM-Newton observation in 1607+26. We conclude that our pilot study of CSOs provides a variety of exceptional diagnostics and highlights the importance of deep X-ray observations of large samples of young sources. This is necessary in order to constrain theoretical models for the earliest stage of radio source evolution and to study the interactions of young radio sources with the interstellar environment of their host galaxies.