A ${}^{13}$CO Detection in a Brightest Cluster Galaxy

Abstract

We present ALMA Cycle 4 observations of CO(1-0), CO(3-2), and ${}^{13}$CO(3-2) line emission in the brightest cluster galaxy of RXJ0821+0752. This is one of the first detections of ${}^{13}$CO line emission in a galaxy cluster. Half of the CO(3-2) line emission originates from two clumps of molecular gas that are spatially offset from the galactic center. These clumps are surrounded by diffuse emission that extends $8\mathrm{kpc}$ in length. The detected ${}^{13}$CO emission is confined entirely to the two bright clumps, with any emission outside of this region lying below our detection threshold. Two distinct velocity components with similar integrated fluxes are detected in the ${}^{12}$CO spectra. The narrower component ($60\mathrm{km}{\mathrm{s}}^{-1}$ FWHM) is consistent in both velocity centroid and linewidth with ${}^{13}$CO(3-2) emission, while the broader ($130-160\mathrm{km}{\mathrm{s}}^{-1}$), slightly blueshifted wing has no associated ${}^{13}$CO(3-2) emission. A simple local thermodynamic model indicates that the ${}^{13}$CO emission traces $2.1\times 10^9{\mathrm{M}}_{\odot }$ of molecular gas. Isolating the ${}^{12}$CO velocity component that accompanies the ${}^{13}$CO emission yields a CO-to-H${}_2$ conversion factor of ${\alpha }_{\mathrm{CO}}=2.3{\mathrm{M}}_{\odot }(\mathrm{K}\mathrm{km}{\mathrm{s}}^{-1}{)}^{-1}$, which is a factor of two lower than the Galactic value. Adopting the Galactic CO-to-H${}_2$ conversion factor in brightest cluster galaxies may therefore overestimate their molecular gas masses by a factor of two. This is within the object-to-object scatter from extragalactic sources, so calibrations in a larger sample of clusters are necessary in order to confirm a sub-Galactic conversion factor.

11 pages, 5 figures, accepted by ApJ

References in corpus (18)

• Heating Hot Atmospheres with Active Galactic Nuclei
• Massive molecular outflows and negative feedback in ULIRGs observed by Herschel-PACS
• Extreme gas kinematics in the z=2.2 powerful radio galaxy MRC1138-262: Evidence for efficient AGN feedback in the early Universe?
• An Infrared Survey of Brightest Cluster Galaxies. II: Why are Some Brightest Cluster Galaxies Forming Stars?
• The Regulation of Cooling and Star Formation in Luminous Galaxies by AGN Feedback and the Cooling-Time/Entropy Threshold for the Onset of Star Formation
• Investigating AGN Heating in a Sample of Nearby Clusters
• An Entropy Threshold for Strong H-alpha and Radio Emission in the Cores of Galaxy Clusters
• Cold molecular gas in the Perseus cluster core - Association with X-ray cavity, Halpha filaments and cooling flow -
• Molecular gas in extreme star-forming environments: the starbursts Arp220 and NGC6240 as case studies
• Jet acceleration of the fast molecular outflows in the Seyfert galaxy IC5063
• Revealing the physical properties of molecular gas in Orion with a large scale survey in J=2-1 lines of 12CO, 13CO and C18O
• Formation of cold filaments in cooling flow clusters
• Molecular Gas in the X-ray Bright Group NGC 5044 as Revealed by ALMA
• ALMA observations of massive molecular gas filaments encasing radio bubbles in the Phoenix cluster
• On carbon and oxygen isotope ratios in starburst galaxies: New data from NGC253 and Mrk231 and their implications
• An infrared survey of brightest cluster galaxies: Paper I
• ALMA reveals optically thin, highly excited CO gas in the jet-driven winds of the galaxy IC5063
• Molecular Gas Along a Bright H-alpha Filament in 2A 0335+096 Revealed by ALMA

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