Cosmological Goal of SAMURAI

Cosmological Goal: Constrain the nature of dark energy by making the most accurate measurement of the Hubble constant.

• Measure distances to Active Galactic Nuclei (AGNs) containing water megamasers.
• Collect VLBI and single-dish monitoring data for a sample of maser AGNs judged to be optimal for distance measurement.
• Measure geometric distances to 7 AGNs.

• Estimate Hubble's constant.
• Combine distance measurements and recessional velocities for 7 AGNs.
• Correct for galaxy peculiar motions to reduce systematics.
• Estimate H₀ with 1-2% accuracy.

• Constrain the nature of dark energy.
• Combine SAMURAI estimate of H₀ with other cosmological data to constrain the equation of state parameter, w, with better than a few percent accuracy.
• Discriminate among physical models of dark energy.

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