ALMA observations of the dense and shocked gas in the nuclear region of NGC4038 (Antennae galaxies)

Junko Ueda, Yoshimasa Watanabe, Daisuke Iono, David J. Wilner, Giovanni G. Fazio, Satoshi Ohashi, Ryohei Kawabe, Toshiki Saito, Shinya Komugi

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13 Citations (Scopus)


We present 1"(>100pc) resolution maps of millimeter emission from five molecules-CN, HCN, HCO+, CH3OH, and HNCO-obtained towards NGC4038, which is the northern galaxy of the mid-stage merger, Antennae galaxies, with the Atacama Large Millimeter/submillimeter Array. Three molecules (CN, CH3OH, and HNCO) were detected for the first time in the nuclear region of NGC4038. High-resolution mapping reveals a systematic difference in distributions of different molecular species and continuum emission. Active star-forming regions identified by the 3 mm and 850 μm continuum emission are offset from the gas-rich region associated with the HCN (1-0) and CO (3-2) peaks. The CN (1-0)/HCN (1-0) line ratios are enhanced (CN/HCN ≈ 0.8-1.2) in the star-forming regions, suggesting that the regions are photon dominated. The large molecular gas mass (108 M) within a 0".6 (∼60pc) radius of the CO (3-2) peak and a high dense gas fraction (>20%) suggested by the HCN (1-0)/CO (3-2) line ratio may signify a future burst of intense star formation there. The shocked gas traced in the CH3OH and HNCO emission indicates sub-kpc-scale molecular shocks. We suggest that the molecular shocks may be driven by collisions between inflowing gas and the central massive molecular complex.

Original languageEnglish
Article number6
JournalPublications of the Astronomical Society of Japan
Issue number1
Publication statusPublished - 2017 Feb 1
Externally publishedYes


  • Galaxies: individual (NGC 4038)
  • Galaxies: interactions
  • Radio lines: galaxies

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science


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