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Masers and the Cosmic Distance Scale

  • Mark J. Reid (a1), James M. Moran (a1) and Carl R. Gwinn (a1)

Abstract

Studies of H2O masers have demonstrated the power of VLBI techniques to measure relative positions with sufficient accuracy (∼ 10 μas) to determine proper motions and to estimate distances to maser sources throughout the Galaxy. The distance to four H2O masers have been determined, and the distance to the center of the Galaxy has been determined to be 7.1 ± 1.5 kpc from observations of the H2O masers in Sgr-B2. Proper motion distances for other H2O masers, and possibly for OH masers, may allow the determination of the fundamental parameters describing the size (Ro ) and rotation rate (Θ o ) of the Galaxy with accuracies of better than 10%. Finally, the measurement of the proper motions of H2O masers in nearby galaxies (< 10 Mpc) is feasible and offers the possibility of direct calibration of the extragalactic distance scale.

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References

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Masers and the Cosmic Distance Scale

  • Mark J. Reid (a1), James M. Moran (a1) and Carl R. Gwinn (a1)

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