A Precise Distance to IRAS 00420+5530 via H2O Maser Parallax with the VLBA
ASTROPHYSICAL JOURNAL(2009)
摘要
We have used the Very Long Baseline Array to measure the annual parallax of the H2O masers in the star-forming region IRAS 00420+5530. This measurement yields a direct distance estimate of 2.17 +/- 0.05 kpc (an error of less than 3%), which disagrees substantially with the standard kinematic distance estimate of similar to 4.6 kpc (according to the rotation curve of Brand & Blitz), as well as most of the broad range of distances (1.7-7.7 kpc) used in various astrophysical analyses in the literature. The three-dimensional space velocity of IRAS 00420+5530 at this new, more accurate distance implies a substantial noncircular and anomalously slow Galactic orbit, consistent with similar observations of W3(OH) (Xu et al. and Hachisuka et al.), as well as line-of-sight velocity residuals in the rotation curve analysis of Brand & Blitz. The Perseus spiral arm of the Galaxy is thus more than a factor of 2 closer than previously presumed, and exhibits motions substantially at odds with axisymmetric models of the rotating Galaxy.
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关键词
astrometry,Galaxy: structure,masers,stars: distances,stars: individual (IRAS 00420+5530),techniques: interferometric
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