The Megamaser Cosmology Project (MCP)
Project OverviewThe Megamaser Cosmology Project (MCP) is an NRAO Key Science Project to measure the Hubble Constant, H0, by determining geometric distances to circumnuclear 22 GHz H2O megamasers in galaxies well into the Hubble flow. In combination with the recent, exquisite observations of the Cosmic Microwave Background (CMB) by WMAP and Planck, these measurements provide a direct test of the standard cosmological model and constrain the equation of state of dark energy. The MCP has so far determined H0 = 73.9 ± 3.0 km/s/Mpc (Pesce et al. 2020) based on measurements of 5 megamaser galaxies in the Hubble flow. Work on additional galaxies is in progress, and we expect a slight improvement in the uncertainties on the measurement of H0 when the project is completed around Spring 2021. Our measurement so far is in agreement with other recent measurements based on local measurements in the universe (e.g. Riess et al. ).
Main Results of MCP to Date