Discovery of a [CI]-faint, CO-bright Galaxy: ALMA Observations of the Merging Galaxy NGC 6052

Abstract

We report sensitive [\ion{C}{1}]~${}^3{P}_1$--${}^3{P}_0$ and ${}^{12}$CO~$J$=4--3 observations of the nearby merging galaxy NGC 6052 using the Morita (Atacama Compact) Array of ALMA. We detect ${}^{12}$CO~$J$=4--3 toward the northern part of NGC 6052, but [\ion{C}{1}]~${}^3{P}_1$--${}^3{P}_0$ is not detected with a [\ion{C}{1}]~${}^3{P}_1$--${}^3{P}_0$ to ${}^{12}$CO~$J$=4--3 line luminosity ratio of$\lesssim 0.07$. According to models of photodissociation regions, the unusual weakness of [\ion{C}{1}]~${}^3{P}_1$--${}^3{P}_0$ relative to ${}^{12}$CO~$J$=4--3 can be explained if the interstellar medium has a hydrogen density larger than $10^5{\mathrm{cm}}^{-3}$, conditions that might arise naturally in the ongoing merging process in NGC 6052. Its [\ion{C}{1}]~${}^3{P}_1$--${}^3{P}_0$ emission is also weaker than expected given the molecular gas mass inferred from previous measurements of ${}^{12}$CO~$J$=1--0 and ${}^{12}$CO~$J$=2--1. This suggests that [\ion{C}{1}]~${}^3{P}_1$--${}^3{P}_0$ may not be a reliable tracer of molecular gas mass in this galaxy. NGC 6052 is a unique laboratory to investigate how the merger process impacts the molecular gas distribution.

7 pages, 3 figures, accepted for publication in The Astrophysical Journal Letters

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Cited by in corpus (12)

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• The subthermal excitation of the C{\sc i} lines in the molecular gas reservoirs of galaxies: its significance and potential utility
• The Kiloparsec-scale Neutral Atomic Carbon Outflow in the Nearby Type-2 Seyfert Galaxy NGC 1068: Evidence for Negative AGN Feedback
• An ACA Survey of [CI] ${}^3{P}_1{-}^3{P}_0$, CO $J=4-3$, and Dust Continuum in Nearby U/LIRG
• Metallicity dependence of the CO-to-H${}_2$ and the [CI]-to-H${}_2$ conversion factors in galaxies
• CI and CO in Nearby Spiral Galaxies -- I. Line Ratio and Abundance Variations at ~ 200 pc Scales
• Atomic Carbon in the Central Molecular Zone of the Milky Way : Possible Cosmic-ray Induced Chemistry or Time-Dependent Chemistry Associated with SNR Sagittarius A East
• Ionized Carbon in Galaxies: The [C II] 158 $\mu$m Line as a Total Molecular Gas Mass Tracer Revisited
• Main Sequence to Starburst Transitioning Galaxies: Gamma-ray Burst Hosts at $z\sim 2$
• Tight correlation of star formation with [Ci] and CO lines across cosmic time
• From Non-Detection to Detection: Atacama Compact Array Mosaic Observations of Faint Extended [C I] Emission in NGC 7679