Multi-line modelling in nearby galaxies: The link between dense gas and star formation in different environments
1 Observatorio Astronómico Nacional (IGN), C/ Alfonso XII, 3, 28014 Madrid, Spain
Published online: 7 September 2022
The J=1–0 lines of HCN and HCO+ have become the default tracers of dense molecular gas in external galaxies. To study the relation between HCN and HCO+ emission and density, we have mapped their J=3–2 lines with the ALMA Compact Array (ACA) in the nearby star-forming galaxies NGC3351, NGC3627, and NGC4321. Combined with archival line maps of HCN(1–0), HCO+(1–0), CO(1–0), and CO(2–1), we use this data set to: (1) compare the excitation of dense gas tracers in normal and starburst/AGN galaxies; (2) explore how line ratios vary across galaxy disks; (3) infer the density distribution and other cloud properties on a pixel-by-pixel basis through a physically-motivated radiative transfer model.
© The Authors, Published by EDP Sciences, 2022
This is an Open Access article distributed under the terms of the Creative Commons Attribution License 4.0 (http://creativecommons.org/licenses/by/4.0/).