Hot Molecular Gas in the Nuclear Region of IC 342

Abstract

We present the first interferometric detection of extragalactic NH_3(6,6) emission in the nearby galaxy IC 342 made using the VLA. The data have a resolution of 7.8''x 5.0'' and trace hot (T ~ 412 K) and dense (> 10^{4} cm^{-3}) molecular gas. We have covered a 170''x 300'' area, and detect two very strong line emission peaks, likely associated with the two strongest star formation regions of the central part of the galaxy. We compare these emission peaks to CO (1-0) and (2-1) emission data, which are the most abundant CO transitions and trace spatially extended emission. The NH_3(6,6) emission is also compared to emission data from three high-density, nitrogen bearing tracers: HNC(1-0), HC_3N(10-9) and N_2H^{+}. Our results suggest that the molecular mass in the nuclear region of IC 342 has at least two different components, a dense and cold component and a less dense and hotter component.