GBT13A-236

The Megamaser Cosmology Project. VI

Abstract

To constrain models of dark energy, a precise measurement of the Hubble constant provides the best complement to observations of the Cosmic Microwave Background. The Megamaser Cosmology Project (MCP) aims to determine Ho to +/- 3% by measuring geometric distances to water vapor megamasers in the Hubble flow. Based on observations of UGC 3789 and NGC 6264, the MCP has so far measured Ho = 72.2 +/- 5.0 km/s/Mpc, a 6.9% accuracy that exceeds the HST Key Project measurement. We will improve our result by measuring additional galaxies. As a second important science result, the MCP is measuring the most precise (< 10%) masses of supermassive black holes in external galaxies by measuring the Keplerian rotation curves from these circumnuclear masers within a parsec of the black hole. We have determined masses for 13 SMBH so far, and these measurements are key to understanding the co-evolution of supermassive black holes and their host galaxies. In this proposal we request GBT, HSA, and VLA time to measure distances to three recently discovered maser disks, continue our successful survey for additional megamasers in AGNs, and map newly-discovered maser disks.

Investigators

Name	Institution
Jim Braatz *	National Radio Astronomy Observatory
Jim Condon	Independent
Violette Impellizzeri	National Radio Astronomy Observatory; Leiden, University of; Joint ALMA Observatory
Feng Gao	Max-Planck-Institut für Radioastronomie
Cheng-Yu Kuo	Virginia, University of; National Sun Yat-sen University
Wei Zhao	Shanghai Astronomical Observatory, CAS; Independent
Jan Wagner	Max-Planck-Institut für Radioastronomie
Eugenia Litzinger	Würzburg, Universität
Jenny Greene	Princeton University
Chris Henkel	Max-Planck-Institut für Radioastronomie
Fred Lo	National Radio Astronomy Observatory
Mark Reid	Center for Astrophysics | Harvard & Smithsonian
Anca Constantin	James Madison University

* indicates the PI