The cavity of 3CR 196.1: H$\alpha$ emission spatially associated with an X-ray cavity

Abstract

We present a multifrequency analysis of the radio galaxy 3CR 196.1 ($z = 0.198$), associated with the brightest galaxy of the cool core cluster CIZAJ0815.4-0303. This nearby radio galaxy shows a hybrid radio morphology and an X-ray cavity, all signatures of a turbulent past activity, potentially due to merger events and AGN outbursts. We present results of the comparison between $Chandra$ and VLT/MUSE data for the inner region of the galaxy cluster, on a scale of tens of kpc. We discovered H$\alpha$ + [N II]$\lambda6584$ emission spatially associated with the X-ray cavity (at $\sim$10 kpc from the galaxy nucleus) instead of with its rim. This result differs from previous discoveries of ionized gas surrounding X-ray cavities in other radio galaxies harbored in galaxy clusters and could represent the first reported case of ionized gas filling an X-ray cavity, either due to different AGN outbursts or to the cooling of warm ($10^4<T\leq10^7$ K) AGN outflows. We also found that the H$\alpha$, [N II]$\lambda\lambda6548,6584$ and [S II]$\lambda\lambda6718,6733$ emission lines show an additional redward component, at $\sim$1000 km$\,$s$^{-1}$ from rest frame, with no detection in H$\beta$ or [O III]$\lambda\lambda4960,5008$. We believe the most likely explanation for this redward component is the presence of a background gas cloud since there appears to be a discrete difference in velocities between this component and the rest frame.