The Megamaser Cosmology Project. XI. A geometric distance to CGCG 074-064
Abstract
As part of the survey component of the Megamaser Cosmology Project, we have discovered a disk megamaser system in the galaxy CGCG 074-064. Using the GBT and the VLA, we have obtained spectral monitoring observations of this maser system at a monthly cadence over the course of two years. We find that the systemic maser features display line-of-sight accelerations of ~4.4 km s-1 yr-1 that are nearly constant with velocity, while the high-velocity maser features show accelerations that are consistent with zero. We have also used the HSA to make a high-sensitivity VLBI map of the maser system in CGCG 074-064, which reveals that the masers reside in a thin, edge-on disk with a diameter of ~1.5 mas (0.6 pc). Fitting a three-dimensional warped disk model to the data, we measure a black hole mass of 2.42+0.22-0.20 × 107 M and a geometric distance to the system of 87.6+7.9-7.2 Mpc. Assuming a CMB-frame recession velocity of 7308 150 km s-1, we constrain the Hubble constant to H0 = 81.0+7.4-6.9 (stat.) 1.4 (sys.) km s-1 Mpc-1.