X-ray study of the environmental impact on the initial stages of a radio source evolution

Compact Symmetric Objects (CSOs) are thought to be among the progenitors of large-scale radio galaxies. They show radio features typically observed in large-scale radio galaxies (jets, lobes, hot spots), but contained within the central 1 kpc region of the host galaxy. Because the CSOs are symmetric and not affected by beaming, their linear radio size can be translated into the source age if one measures the expansion velocity of the radio source. However, if the jet expansion is disturbed, e.g. by a dense interstellar medium (ISM), the ages derived this way may be biased. Until now we did not have means to discriminate between confined and non-confined radio sources. We present our X-ray studies of CSOs performed with XMM-Newton and Chandra. For the first time, the data reveal the evidence in favor of the hypothesis that in a sub-population of CSOs the medium is Compton Thick and the radio jets may be confined. Thus their kinematic ages may be underestimated. We discuss the implications of our results on the high energy emission models of CSOs, the earliest stages of the radio source evolution, jet interactions with the ISM, diversity of the environments in which the jets expand, and jet-galaxy co-evolution.