C I and CO in nearby spiral galaxies

We present new neutral atomic carbon [C I ] ( 3 P 1 ? 0 ) mapping observations within the inner ?7 kpc and ?4 of disks NGC 3627 4321 at a spatial resolution 190 pc 270 pc, respectively, using Atacama Large Millimeter/Submillimeter Array (ALMA) Compact (ACA). combine these with CO(2?1) data from PHANGS-ALMA, literature CO for two other starburst and/or active galactic nucleus (AGN) galaxies (NGC 1808, 7469) aim studying: (a) distributions C emission; (b) observed line ratio R /CO = [ ](1?0 / CO(2?1 as function various properties; (c) abundance /CO]. find excellent correspondence between emission nearly uniform ? 0.1 across majority star-forming 4321. However, strongly varies ?0.05 center to > 0.2 ? 0.5 in 1808’s starbursting 7469’s an X-ray-luminous AGN. Meanwhile, does not obviously vary ? U ?, which is predictions photodissociation-dominated region (PDR) models. also mildly decreasing value increasing metallicity over 0.7 0.85 Z ? , consistent literature. Assuming typical interstellar medium (ISM) conditions representing giant molecular clouds, regions, strong environments, we calculated (non)local-thermodynamic-equilibrium radiative transfer estimated /CO] be ?0.1 4321, similar previous large-scale findings Galactic studies. this likely experiences substantial increase, up ?1 ?1 5 AGN respectively. This result expectations cosmic-ray dominated (CRDR) X-ray (XDR) chemistry. Finally, do robust evidence generally CO-dark-and-C -bright gas disk areas probed.