astrolunch: Dom Pesce (Harvard-Smithsonian Center for Astrophysics)

Sun, 24/01/2021 - 17:00 to 18:00

A geometric measurement of H0 by the Megamaser Cosmology Project

Water megamasers residing in the accretion disks around supermassive black holes (SMBHs) in active galactic nuclei (AGN) provide unique tools for bypassing the distance ladder and making one-step, geometric distance measurements to their host galaxies.  The Megamaser Cosmology Project (MCP) is a multiyear campaign to find, monitor, and map such AGN accretion disk megamaser systems, with the goal of constraining the Hubble constant to a precision of several percent.  In this talk I will cover the latest results from the MCP.  We have systematically applied an updated disk modeling technique to measure the distances to six megamaser-hosting galaxies, which together constrain the Hubble constant to 73.9 +/- 3.0 km/s/Mpc.  This value relies solely on maser-based distance and velocity measurements, and it does not use any peculiar velocity corrections.  We have explored a variety of different approaches for correcting peculiar velocities, none of which modify this constraint by more than 1-sigma.  Our measurement is independent of distance ladders, the cosmic microwave background, and gravitational lenses, and it corroborates prior indications that the local Hubble constant exceeds the early-Universe prediction.
 Zoom link
Meeting ID: 847 4056 5269
Passcode: w31c0m3