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Toward a New Distance to the Active Galaxy NGC 4258: II. Centripetal Accelerations and Investigation of Spiral Structure
E. M. L. Humphreys, M. J. Reid, L. J. Greenhill +2
We report measurements of centripetal accelerations of maser spectral components of NGC 4258 for 51 epochs spanning 1994 to 2004. This is the second paper of a series, in which the…
The structure of the accretion disk in NGC 4258 derived from observations of its water vapor masers
Jim Moran, Liz Humphreys, Lincoln Greenhill +2
A wealth of new information about the structure of the maser disk in NGC 4258 has been obtained from a series of 18 VLBA observations spanning three years, as well as from 32 addit…
Imaging the Ionized Disk of the High-Mass Protostar Orion-I
M. J. Reid, K. M. Menten, L. J. Greenhill +1
We have imaged the enigmatic radio source-I (Orion-I) in the Orion-KL nebula with the VLA at 43 GHz with 34 mas angular resolution. The continuum emission is highly elongated and i…
Toward a New Geometric Distance to the Active Galaxy NGC4258: I. VLBI Monitoring of Water Maser Emission
A. L. Argon, L. J. Greenhill, M. J. Reid +2
We report a three year, 18 epoch, VLBI monitoring study of H2O masers in the sub-parsec, warped, accretion disk within the NGC4258 AGN. Our immediate goals are to trace the geometr…