2018/03/29 by C. D. Wilson, Christine D. Wilson · 17 citations
Physics and Astronomy · #Active galactic nucleus #Astronomy #Astrophysics #Astrophysics and Cosmic Phenomena #Astrophysics and Star Formation Studies #Emission spectrum #Galaxies: Formation, Evolution, Phenomena #Galaxy #Line (geometry) #Luminous infrared galaxy #Millimeter #Optics #Physics #Spectral line #Ultraviolet #astro-ph.GA
paper · pdf · doi:10.1093/mnras/sty845
published in Monthly Notices of the Royal Astronomical Society 477(3), 2926-2942 (Oxford University Press) · accepted to MNRAS; 17 pages, 10 figures
arxiv created 2018/03/29 · openalex publication_date 2018/03/29 · arxiv updated 2018/04/11 · openalex created_date 2025/10/10 · openalex updated_date 2026/08/05
We describe an archival project using Cycle 0 data from the Atacama Large Millimeter/submillimeter Array to survey the CO/CN line ratio in 17 nearby galaxies. CN is an interesting molecule that traces dense gas exposed to ultraviolet radiation and its N = 1 − 0 lines can be observed simultaneously with the CO J = 1 − 0 line. We identify eight galaxies with distances <200 Mpc for which both lines are detected. Signal-to-noise ratio matched CO/CN ratios range from as low as 7 to as high as 65, while ratios using the total detected flux range from 20 to 140. Spatial variations greater than a factor of 3 are seen in several galaxies. These line ratio changes are likely due to changes in the [CN]/[H2] abundance ratio and/or the CN excitation. Additional measurements of the warm gas pressure and the CN excitation should help to distinguish between these two possibilities. Three of the four active galactic nuclei in our sample show CO/CN line ratios that are roughly a factor of 2–3 larger than those seen in starburst-dominated regions, which may be in conflict with models of molecular abundances in X-ray-dominated regions.