3C28 in Abell 115- A Radio Source With a Twist

摘要

Abell 115 contains two merging subclusters separated by about 900 kpc. The northern subcluster (hereafter, A115-N) contains a bright central galaxy that hosts the radio source 3C28 which has a remarkable morphology. Although there is no detectable active nucleus, two prominent jets connect to a pair of radio lobes, each of which exhibits a radio tail. We combine Chandra X-ray and VLA radio observations to study the gas motions in and around Al I5-N. We use the Chandra data to estimate the velocity of A115-N with respect to the ambient intracluster medium as well as the velocity of the gas within the subcluster A115-N. We suggest that the motion of A115-N through the cluster induces counter-rotating vortices in the subcluster gas that explain the unique morphology of 3C28 with its two tails pointing in the direction of motion for Al 15-N. We compare the X-ray gas circulation time within A115-N with the timescale computed from the spectral aging of the radio-emitting plasma and discuss the implications of these observations for the lifetimes of radio sources in gaseous atmospheres.