2016ApJ...820..118Z

In this paper, we report our high-resolution (0".20x0".14 or ∼70x49 pc) observations of the CO(6-5) line emission, which probes warm and dense molecular gas, and the 434 µm dust continuum in the nuclear region of NGC 7130, obtained with the Atacama Large Millimeter Array (ALMA). The CO line and dust continuum fluxes detected in our ALMA observations are 1230±74 Jy km/s and 814±52 mJy, respectively, which account for 100% and 51% of their total fluxes. We find that the CO(6-5) and dust emissions are generally spatially correlated, but their brightest peaks show an offset of ∼70 pc, suggesting that the gas and dust emissions may start decoupling at this physical scale. The brightest peak of the CO(6-5) emission does not spatially correspond to the radio continuum peak, which is likely dominated by an active galactic nucleus (AGN). This, together with our additional quantitative analysis, suggests that the heating contribution of the AGN to the CO(6-5) emission in NGC 7130 is negligible. The CO(6-5) and the extinction-corrected Pa-α maps display striking differences, suggestive of either a breakdown of the correlation between warm dense gas and star formation at linear scales of <100 pc or a large uncertainty in our extinction correction to the observed Pa-α image. Over a larger scale of ∼2.1 kpc, the double-lobed structure found in the CO(6-5) emission agrees well with the dust lanes in the optical/near-infrared images.