Submillimeter Array/Plateau de Bure Interferometer Multiple Line Observations of the Nearby Seyfert 2 Galaxy NGC 1068: Shock-related Gas Kinematics and Heating in the Central 100 pc?
Résumé
We present high angular resolution (0farcs5-2farcs0) observations of the millimeter continuum and the 12CO(J = 3-2), 13CO(J = 3-2), 13CO(J = 2-1), C18O(J = 2-1), HCN(J = 3-2), HCO+(J = 4-3), and HCO+(J = 3-2) line emission in the circumnuclear disk (r = 200 K) and dense (n(H2) sime 104 cm-3) gas constrained from observed molecular line ratios. The HCN abundance in the circumnuclear disk is found to be [HCN]/[12CO] ≈ 10-3.5. This is slightly higher than the abundances derived for Galactic and extragalactic star-forming/starbursting regions. This result lends further support to X-ray-enhanced HCN formation in the circumnuclear disk of NGC 1068 as suggested by earlier studies. The HCO+ abundance ([HCO+]/[12CO] ≈ 10-5) appears to be somewhat lower than that of Galactic and extragalactic star-forming/starbursting regions. When trying to fit the centimeter-to-millimeter continuum emission by different thermal and non-thermal processes, it appears that electron-scattered synchrotron emission yields the best results while thermal free-free emission seems to overpredict the millimeter continuum emission.