The Megamaser Cosmology Project. X. High-resolution Maps and Mass Constraints for SMBHs

W. Zhao, J. A. Braatz, J. J. Condon, K. Y. Lo, M. J. Reid, C. Henkel, D. W. Pesce, J. E. Greene, F. Gao, C. Y. Kuo, C. M.V. Impellizzeri

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23 Scopus citations


We present high-resolution (submas) Very Long Baseline Interferometry maps of nuclear H2O megamasers for seven galaxies. In UGC 6093, the well-aligned systemic masers and high-velocity masers originate in an edge-on, flat disk and we determine the mass of the central supermassive black holes (SMBH) to be M SMBH = 2.58 ×107 M o (±7%). For J1346+5228, the distribution of masers is consistent with a disk, but the faint high-velocity masers are only marginally detected, and we constrain the mass of the SMBH to be in the range (1.5-2.0) ×107 M o. The origin of the masers in Mrk 1210 is less clear, as the systemic and high-velocity masers are misaligned and show a disorganized velocity structure. We present one possible model in which the masers originate in a tilted, warped disk, but we do not rule out the possibility of other explanations including outflow masers. In NGC 6926, we detect a set of redshifted masers, clustered within a parsec of each other, and a single blueshifted maser about 4.4 pc away, an offset that would be unusually large for a maser disk system. Nevertheless, if it is a disk system, we estimate the enclosed mass to be M SMBH < 4.8 ×107 M o. For NGC 5793, we detect redshifted masers spaced about 1.4 pc from a clustered set of blueshifted features. The orientation of the structure supports a disk scenario as suggested by Hagiwara et al. We estimate the enclosed mass to be M SMBH < 1.3 ×107 M o. For NGC 2824 and J0350-0127, the masers may be associated with parsec- or subparsec-scale jets or outflows.

Original languageEnglish (US)
Article number124
JournalAstrophysical Journal
Issue number2
StatePublished - Feb 20 2018

All Science Journal Classification (ASJC) codes

  • Astronomy and Astrophysics
  • Space and Planetary Science


  • accretion, accretion disks
  • galaxies: ISM
  • galaxies: Seyfert
  • galaxies: active
  • galaxies: nuclei


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