THE DETECTION OF AN EXTENDED MOVING GROUP NEAR THE GALACTIC DISK

A radial velocity survey (median velocity precision approximately 1.0 km s-1) for 879 field stars in the direction (l,b) = (277-degrees,9-degrees) has been undertaken with the bench-mounted spectrograph, ARGUS, and echelle grating at the CTIO 4.0 m telescope. The radial velocity histogram shows a marked overabundance of stars in the range 74.0-76.0 km s-1. We observe 18 stars in this interval, whereas only five such stars (within our approximately 1-degrees field) are expected on the basis of the Institute for Advanced Study Galaxy Model. Monte Carlo simulations indicate that this feature is significant at better than the 99% level. B, V CCD photometry is available for four of the 18 stars-the remaining stars have B, V magnitudes determined from APM scans of B(J) and R UK-Schmidt plates. Although the scatter in the photometry is appreciable, 14 of the stars occupy a roughly horizontal locus in the field color-magnitude diagram. Various considerations lead us to suspect that they are giants in an extended moving group at a common distance in the range 6-12 kpc.