The Megamaser Cosmology Project. XI. A Geometric Distance to CGCG 074-064
D. W. Pesce, J. A. Braatz, M. J. Reid, J. J. Condon, F. Gao, C. Henkel, C. Y. Kuo, K. Y. Lo, W. Zhao
Abstract
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 Green Bank Telescope and the Very Large Array, 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 High-Sensitivity Array to make a high-sensitivity very long baseline interferometric 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 and a geometric distance to the system of Mpc. Assuming a cosmic microwave background-frame recession velocity of 7308 ± 150 km s −1 , we constrain the Hubble constant to (stat.) ± 1.4 (sys.) km s −1 Mpc −1 .