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NRAO/Socorro Colloquium Series

Fred Lo

NRAO-CV

H0, Mega-masers and AGN

Accurate measurements of the Hubble Constant, H0 - the current expansion rate of the Universe, provide critical independent constraints on dark energy, spatial curvature of the Universe, neutrino physics, and validity of general relativity.  The recent Planck results highlight the necessity of an independent determination of H0 at high accuracy. 

 The Mega-maser Cosmology Project (MCP) aims to determine the Hubble Constant at high accuracy by measuring the angular-diameter distance to galaxies in the Hubble Flow.  The MCP has been observing ~10 mega-maser disks in Sy2 galaxies suitable for such distance determination.  The current status of the MCP measurements of H0 will be briefly updated.

The MCP also provides accurate determination of the central black-hole mass in mega-maser galaxies.  The large intrinsic scatter of BH masses in a narrow range of the velocity dispersion of the mega-maser galaxy bulges adds to the observational richness of the well-known M-σ relation of BH mass and the spherical component of galaxies.  The mega-maser disks also constitute the only resolved imaging of accretion disks around AGN.  The conditions of the thin Keplerian accretion disks delineated by the mega-masers and their relationship with the obscuring material of the AGN will be discussed.


October 8, 2013

4:00pm

Array Operations Center Auditorium

All NRAO employees are invited to attend via video, available in Charlottesville Room 230, Green Bank Room 137 and Tucson N525.

Local Host: Juergen Ott

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