Exploring the CO/CN line ratio in nearby galaxies with the ALMA archive

Abstract

We describe an archival project using Cycle 0 data from the Atacama Large Millimeter/submilleter 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 8 galaxies with distances < 200 Mpc for which both lines are detected. Signal-to-noise 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. 3 of the 4 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.

accepted to MNRAS; 17 pages, 10 figures

References in corpus (4)

• ALMA Reveals the Molecular Medium Fueling the Nearest Nuclear Starburst
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• Warm and Cold Molecular Gas Conditions Modeled in 87 Galaxies Observed by the Herschel SPIRE Fourier Transform Spectrometer
• Molecular Gas Properties in M83 from CO PDFs

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• Zoom-in cosmological hydrodynamical simulation of a star-forming barred, spiral galaxy at redshift z=2
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• Circumnuclear Medium around the Central AGN in a Cool-Core Cluster, Abell 1644-South
• Down but not out: properties of the molecular gas in the stripped Virgo Cluster early-type galaxy NGC4526