The Megamaser Cosmology Project


Dark Energy (DE) accounts for 74% of the mass-energy of the universe, dominates its present expansion, and determines its ultimate fate. Understanding DE may be the most important problem in fundamental physics today. The best complement to the CMB to constrain the DE equation of state parameter w would be a measurement of H 0 to better than 3% (Hu, 2005). The best prospect for reaching such accuracy involves measuring direct geometric distances to circumnuclear masers in galaxies well into the Hubble flow, 50--200 Mpc distant. The Megamaser Cosmology Project (MCP) aims to find suitable masers and measure their distances using the maser technique pioneered on NGC 4258. Our successful pilot programs have demonstrated the feasibility of measuring distances to such faint, distant masers using the GBT and the HSA. The MCP is an ambitious ``Large Project'' that aims to measure H 0 directly with 3% accuracy within about 5 years.

Name Other * Institution Email Phone
Jim Braatz PI NRAO - CV work: 434-296-0251 home: 434 973-4453
Lincoln Greenhill CfA 617 495-7194
Jim Condon NRAO-CV (434) 296-0322
Mark Reid Center for Astrophysics 617 495-7470
Chris Henkel Max-Planck-Institut fur Radioa 49-228-525-305
Fred Lo NRAO-CV 434-296-0221
* PI = Principal Investigator; CO = Contact author; T = Thesis observations; S = Student

Front Ends
Gregorian K(18.0 to 26.5 GHz)

Back Ends
VLBA recorder and DAR

Type of Observing
Monitor Very Long Baseline Interferometry Triggered Transient

Switching Type

Processor (correlator)

Allotted time 380.00 hours

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Updated 09/19/2007