Presentation #106.27 in the session “AGN (Poster)”.
There are fewer high-z radio galaxies than expected from the number of high-z blazars. The discrepancy has been attributed to the increased energy density of the cosmic microwave background, which makes inverse-Compton cooling dominant over synchrotron emission and would suppress radio lobes in favor of X-ray lobes. However, prior investigations of high-z radio galaxies have arrived at discrepant conclusions. Here we show that, when considering lobes and hot spots and/or jets separately, high-z radio galaxies (1.3 < z < 4.3) exhibit the expected X-ray enhancement and are close to equipartition. In this situation, it is difficult to suppress synchrotron emission from the highly magnetized jets and hot spots up to at least z>6. The dearth of high-z radio galaxies may instead be an artifact of an incorrect radio-loud quasar evolution luminosity function or radio-loud fraction.