A shock-induced pair of superbubbles in the high-redshift powerful radio galaxy MRC 0406-244

We present new optical spectroscopy of the high-redshift powerful radio galaxy MRC 0406-244 at redshift of 2.429. We find that the two extensions toward the northwest and southeast probed in the rest-frame ultraviolet image are heated mainly by the nonthermal continuum of the active galactic nucleus. However, each extension shows a shell-like morphology, suggesting that they are a pair of superbubbles induced by the superwind activity rather than by the interaction between the radio jet and the ambient gas clouds. If this is the case, the intense starburst responsible for the formation of superbubbles could occur similar to1 x 10(9) yr ago. On the other hand, the age of the radio jets may be on the order of similar to 10(6) yr, being much shorter than the starburst age. Therefore, the two events, i.e., the starburst and the radio jet activities, are independent phenomena. However, their directions of the expanding motions could be governed by the rotational motion of the gaseous component in the host galaxy. This idea appears to explain the alignment effect of MRC 0406-244.