Title:
A geometric measurement of H0 by the Megamaser Cosmology Project

Abstract:
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
https://huji.zoom.us/j/84740565269?pwd=R2o3Vk9BUFRGZ0hzT3B6Zm9USmthQT09
Meeting ID: 847 4056 5269
Passcode: w31c0m3