¹³CO/C¹⁸O Gradients across the Disks of Nearby Spiral Galaxies
Date
2017
Authors
Jimenez-Donaire, Maria J.
Cormier, Diane
Bigiel, Frank
Leroy, Adam K
Gallagher, Molly
Krumholz, Mark
Usero, Antonio
Hughes, Annie
Kramer, Carsten
Meier, David
Journal Title
Journal ISSN
Volume Title
Publisher
Institute of Physics Publishing Ltd.
Abstract
We use the IRAM Large Program EMPIRE and new high-resolution ALMA data to measure 13CO(1-0)/C18O(1-0)
intensity ratios across nine nearby spiral galaxies. These isotopologues of 12CO are typically optically thin across
most of the area in galaxy disks, and this ratio allows us to gauge their relative abundance due to chemistry or
stellar nucleosynthesis effects. Resolved 13CO/C18O gradients across normal galaxies have been rare due to the
faintness of these lines. We find a mean 13CO/C18O ratio of 6.0 ± 0.9 for the central regions of our galaxies. This
agrees well with results in the Milky Way, but differs from results for starburst galaxies (3.4 ± 0.9) and
ultraluminous infrared galaxies (1.1 ± 0.4). In our sample, the 13CO/C18O ratio consistently increases with
increasing galactocentric radius and decreases with increasing star formation rate surface density. These trends
could be explained if the isotopic abundances are altered by fractionation; the sense of the trends also agrees with
those expected for carbon and oxygen isotopic abundance variations due to selective enrichment by massive stars.
Description
Keywords
galaxies: ISM, ISM: molecules, radio lines: galaxies
Citation
Collections
Source
Astrophysical Journal Letters
Type
Journal article
Book Title
Entity type
Access Statement
Open Access