The Megamaser Cosmology Project-XII. VLBI imaging of H2O maser emission in three active galaxies and the effect of AGN winds on disc dynamics

Abstract

We present very long baseline interferometry (VLBI) images and kinematics of water maser emission in three active galaxies: NGC 5728, Mrk 1, and IRAS 08452-0011. IRAS 08452-0011, at a distance of ∼200 Mpc, is a triple-peaked H2O megamaser, consistent with a Keplerian rotating disc, indicating a black hole mass of (3.3 ± 0.2) × 107 M⊙. NGC 5728 and Mrk 1 display double-peaked spectra, and VLBI imaging reveals complicated gas kinematics that do not allow for a robust determination of black hole mass. We show evidence that the masers in NGC 5728 are in a wind while the Mrk 1 maser system has both disc and outflow components. We also find that disturbed morphology and kinematics are a ubiquitous feature of all double-peaked maser systems, implying that these maser sources may reside in environments where active galactic nucleus (AGN) winds are prominent at ∼1 pc scale and have significant impact on the masing gas. Such AGNs tend to have black hole masses MBH < 8 × 106 M⊙ and Eddington ratios λEdd ≳ 0.1, while the triple-peaked megamasers show an opposite trend.