...VLA

The National Radio Astronomy Observatory is operated by Associated Universities, Inc., under cooperative agreement with the National Science Foundation.

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...object

This object is near the edge of the survey area and was observed far off-axis in only a single field. The position error can be attributed to a recently discovered, very small rotation and scale error in the FIRST grid images that can produce offsets of 44#44 at the edges of grid images. In the coadded images, the resulting position errors cancel and so are extremely small except at the edge of the survey area. The source of the rotation and scaling is under investigation; we speculate that they are due to a combination of frequency shifts from bandpass shape effects and VLA clock errors.

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...catalog.

The position offsets of all but one of the sources are substantially less than 8#8, yet another confirmation of the FIRST astrometric accuracy. In addition, 24 of the 29 sources corresponding to the cores of complex objects also have offsets 61#61, suggesting optical identification of such objects from FIRST positions will be straightforward.

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