The Cavity of 3CR 196.1: Hα Emission Spatially Associated with an X-Ray Cavity

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 active galactic nuclei (AGN) outbursts. We present results of the comparison between Chandra and Very Large Telescope Multi-Unit Spectroscopic Explorer data for the inner region of the galaxy cluster, on a scale of tens of kpc. We discovered Hα + [N II]λ6584 emission spatially associated with the X-ray cavity (at ~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 (10⁴ < T ≤ 10⁷ K) AGN outflows. We also found that the Hα, [N II]λ λ6548, 6584, and [S II]λ λ6718, 6733 emission lines show an additional redward component, at ~1000 km s^-1 from rest frame, with no detection in Hβ or [O III]λ λ4960, 5008. We believe the most likely explanation for this redward component is the presence of a background gas cloud as there appears to be a discrete difference of velocities between this component and the rest frame.