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 radiogalaxy MRC 0406$-$244 at redshift of 2.429. We find that the two extensionstoward NW and SE probed in the rest-frame ultraviolet image are heated mainlyby the nonthermal continuum of the active galactic nucleus. However, eachextension shows a shell-like morphology, suggesting that they are a pair ofsuperbubbles induced by the superwind activity rather than by the interactionbetween the radio jet and the ambient gas clouds. If this is the case, theintense starburst responsible for the formation of superbubbles could occur$\sim 1 \times 10^9$ yr ago. On the other hand, the age of the radio jets maybe of the order of $\sim 10^6$ 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 motionscould be governed by the rotational motion of the gaseous component in the hostgalaxy. This idea appears to explain the alignment effect of MRC 0406$-$244.Comment: 4 pages (emulateapj.sty), Fig. 1 (jpeg) + Fig.2 (eps). Accepted for publications in ApJ (Letters