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The Subaru Seminar is usually held in Room 104 of the Hilo Base Facility, adjacent to the main lobby. Everyone is welcome to attend. If you are interested in giving a seminar, please contact Subaru seminar organizers (Tadayuki Kodama, Kumiko S. Usuda, Naoyuki Tamura, Tomonori Usuda) by email : (please change"_at" to @).

June 27, Thursday, at 11:00 am

" Mega-maser Cosmology Project "

Fred K. Y. Lo


Better measurements of Ho - 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 Ho 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 discovered 9 new mega-maser disks in Sy2 nuclei suitable for distance determination.  A geometric distance measurement to a galaxy at 140 Mpc, via micro-arc-second astrometry of its circum-nuclear mega-maser disk, has been demonstrated.  The current status of the MCP measurements of Ho, and future prospects, will be described. 

The MCP also enables 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 in the mega-maser galaxy bulges raise questions about the validity of the well-known M-σ relation of BH mass and the spherical component of galaxies.  The relationship of the thin Keplerian accretion disks delineated by the mega-masers with the obscuring material of the AGN will also be briefly discussed.

Time permitting, other key projects at the NRAO will be also described.

Seminars are also held at JAC, CFHT, and IfA.

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