The MALATANG Survey: The L GAS-L IR Correlation on Sub-kiloparsec Scale in Six Nearby Star-forming Galaxies as Traced by HCN J = 4 → 3 and HCO+ J = 4 → 3

Qing Hua Tan, Yu Gao, Zhi Yu Zhang, Thomas R. Greve, Xue Jian Jiang, Christine D. Wilson, Chen Tao Yang, Ashley Bemis, Aeree Chung, Satoki Matsushita, Yong Shi, Yi Ping Ao, Elias Brinks, Malcolm J. Currie, Timothy A. Davis, Richard De Grijs, Luis C. Ho, Masatoshi Imanishi, Kotaro Kohno, Bumhyun LeeHarriet Parsons, Mark G. Rawlings, Dimitra Rigopoulou, Erik Rosolowsky, Joanna Bulger, Hao Chen, Scott C. Chapman, David Eden, Walter K. Gear, Qiu Sheng Gu, Jin Hua He, Qian Jiao, Dai Zhong Liu, Li Jie Liu, Xiao Hu Li, Michał J. Michałowski, Quang Nguyen-Luong, Jian Jie Qiu, Matthew W.L. Smith, Giulio Violino, Jian Fa Wang, Jun Feng Wang, Jun Zhi Wang, Sherry Yeh, Ying He Zhao, Ming Zhu

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Abstract

We present HCN J = 4→3 and HCO+ J = 4→3 maps of six nearby star-forming galaxies, NGC 253, NGC 1068, IC 342, M82, M83, and NGC 6946, obtained with the James Clerk Maxwell Telescope as part of the MALATANG survey. All galaxies were mapped in the central 2×2 region at 14 (FWHM) resolution (corresponding to linear scales of ∼0.2-1.0 kpc). The LIR-Ldense relation, where the dense gas is traced by the HCN J = 4→3 and the HCO+ J = 4→3 emission, measured in our sample of spatially resolved galaxies is found to follow the linear correlation established globally in galaxies within the scatter. We find that the luminosity ratio, LIR/Ldense, shows systematic variations with LIR within individual spatially resolved galaxies, whereas the galaxy-integrated ratios vary little. A rising trend is also found between LIR/Ldense ratio and the warm-dust temperature gauged by the 70 μm/100 μm flux ratio. We find that the luminosity ratios of IR/HCN (4-3) and IR/HCO+ (4-3), which can be taken as a proxy for the star formation efficiency (SFE) in the dense molecular gas (SFEdense), appear to be nearly independent of the dense gas fraction ( fdense) for our sample of galaxies. The SFE of the total molecular gas (SFEmol) is found to increase substantially with fdense when combining our data with those on local (ultra)luminous infrared galaxies and high-z quasars. The mean LHCN(4-3) LHCO+(4-3) line ratio measured for the six targeted galaxies is 0.9±0.6. No significant correlation is found for the L'HCN(4-3) L'HCO+(4-3) ratio with the star formation rate as traced by LIR, nor with the warm-dust temperature, for the different populations of galaxies.

Original languageEnglish
Article number165
JournalAstrophysical Journal
Volume860
Issue number2
DOIs
Publication statusPublished - 2018 Jun 20

All Science Journal Classification (ASJC) codes

  • Astronomy and Astrophysics
  • Space and Planetary Science

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    Tan, Q. H., Gao, Y., Zhang, Z. Y., Greve, T. R., Jiang, X. J., Wilson, C. D., Yang, C. T., Bemis, A., Chung, A., Matsushita, S., Shi, Y., Ao, Y. P., Brinks, E., Currie, M. J., Davis, T. A., Grijs, R. D., Ho, L. C., Imanishi, M., Kohno, K., ... Zhu, M. (2018). The MALATANG Survey: The L GAS-L IR Correlation on Sub-kiloparsec Scale in Six Nearby Star-forming Galaxies as Traced by HCN J = 4 → 3 and HCO+ J = 4 → 3. Astrophysical Journal, 860(2), [165]. https://doi.org/10.3847/1538-4357/aac512