Constraining Resolved Extragalactic R21 Variation with Well-calibrated ALMA Observations
The result's identifiers
Result code in IS VaVaI
<a href="https://www.isvavai.cz/riv?ss=detail&h=RIV%2F67985815%3A90106%2F25%3A00646702" target="_blank" >RIV/67985815:90106/25:00646702 - isvavai.cz</a>
Result on the web
<a href="https://doi.org/10.3847/1538-4357/addf4c" target="_blank" >https://doi.org/10.3847/1538-4357/addf4c</a>
DOI - Digital Object Identifier
<a href="http://dx.doi.org/10.3847/1538-4357/addf4c" target="_blank" >10.3847/1538-4357/addf4c</a>
Alternative languages
Result language
angličtina
Original language name
Constraining Resolved Extragalactic R21 Variation with Well-calibrated ALMA Observations
Original language description
CO(1-0) and CO(2-1) are commonly used as bulk molecular gas tracers. The CO line ratios (especially CO(2-1)/ CO(1-0)-R21) vary within and among galaxies, yet previous studies on R21 and alike often rely on measurements constructed by combining data from facilities with substantial relative calibration uncertainties that have the same order as physical line ratio variations. Hence, robustly determining systematic R21 variations is challenging. Here, we compare CO(1-0) and CO(2-1) mapping data from ALMA for 14 nearby galaxies, at a common physical resolution of 1.7 kpc. Our data set includes new ALMA (7 m+TP) CO(1-0) maps of 12 galaxies. We investigate R21 variation to understand its dependence on global galaxy properties, kiloparsec-scale environmental factors, and its correlation with star formation rate (SFR) surface density and metallicity. We find that the galaxy-to-galaxy scatter is 0.05 dex. This is lower than previous studies, which reported over 0.1 dex variation, likely reflecting significant flux calibration uncertainties in single-dish surveys. Within individual galaxies, R21 has a typical mean value of similar to 0.64 and 0.1 dex variation, with an increase to similar to 0.75 toward galactic centers. We find strong correlations between R21 and various galactic parameters, particularly SFR surface density, which shows a power-law slope of 0.10-0.11 depending on the adopted binning/fitting methods. Our findings suggest that, for studies covering main-sequence galaxy samples, assuming a fixed R21 = 0.64 does not significantly bias kiloparsec-scale molecular gas mass estimates from CO(2-1). Instead, systematic uncertainties from flux calibration and the CO-to-H2 conversion factor account for more systematic scatter of CO-derived molecular gas properties
Czech name
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Czech description
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Classification
Type
J<sub>imp</sub> - Article in a specialist periodical, which is included in the Web of Science database
CEP classification
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OECD FORD branch
10308 - Astronomy (including astrophysics,space science)
Result continuities
Project
—
Continuities
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Others
Publication year
2025
Confidentiality
S - Úplné a pravdivé údaje o projektu nepodléhají ochraně podle zvláštních právních předpisů
Data specific for result type
Name of the periodical
Astrophysical Journal
ISSN
0004-637X
e-ISSN
1538-4357
Volume of the periodical
988
Issue of the periodical within the volume
2
Country of publishing house
GB - UNITED KINGDOM
Number of pages
23
Pages from-to
162
UT code for WoS article
001533803800001
EID of the result in the Scopus database
2-s2.0-105011296233