WISDOM project – XVIII. Molecular gas distributions and kinematics of three megamaser galaxies

Fu Heng Liang, Mark D. Smith, Martin Bureau, Feng Gao, Timothy A. Davis, Michele Cappellari, Jacob S. Elford, Jenny E. Greene, Satoru Iguchi, Federico Lelli, Anan Lu, Ilaria Ruffa, Thomas G. Williams, Hengyue Zhang

Research output: Contribution to journalArticlepeer-review

1 Scopus citations


The co-evolution of galaxies and supermassive black holes (SMBHs) underpins our understanding of galaxy evolution, but different methods to measure SMBH masses have only infrequently been cross-checked. We attempt to identify targets to crosscheck two of the most accurate methods, megamaser, and cold molecular gas dynamics. Three promising galaxies are selected from all those with existing megamaser SMBH mass measurements. We present Atacama Large Millimeter/sub-millimeter Array (ALMA) 12CO (2–1) and 230-GHz continuum observations with angular resolutions of ≈0'' . 5. Every galaxy has an extended rotating molecular gas disc and 230-GHz continuum source(s), but all also have irregularities and/or non-axisymmetric features: NGC 1194 is highly inclined and has disturbed and lopsided central 12CO (2–1) emission; NGC 3393 has a nuclear disc with fairly regular but patchy 12CO (2–1) emission with little gas near the kinematic major axis, faint emission in the very centre, and two brighter structures reminiscent of a nuclear ring and/or spiral; NGC 5765B has a strong bar and very bright 12CO (2–1) emission concentrated along two bisymmetric offset dust lanes and two bisymmetric nuclear spiral arms. 12CO (2–1) and 12CO (3–2) observations with the James Clerk Maxwell Telescope are compared with the ALMA observations. Because of the disturbed gas kinematics and the impractically long integration times required for higher angular resolution observations, none of the three galaxies is suitable for a future SMBH mass measurement. None the less, increasing the number of molecular gas observations of megamaser galaxies is valuable, and the ubiquitous disturbances suggest a link between large-scale gas properties and the existence of megamasers.

Original languageEnglish (US)
Pages (from-to)9343-9358
Number of pages16
JournalMonthly Notices of the Royal Astronomical Society
Issue number3
StatePublished - Jan 1 2024

All Science Journal Classification (ASJC) codes

  • Astronomy and Astrophysics
  • Space and Planetary Science


  • individual
  • ISM – galaxies
  • kinematics and dynamics – galaxies
  • masers – galaxies
  • NGC 1194
  • NGC 3393
  • NGC 5765B – galaxies
  • nuclei


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