DISTANCE DETERMINATIONS TO SHIELD GALAXIES FROM HUBBLE SPACE TELESCOPE IMAGING

Here, we measure the distances to the 12 SHIELD galaxies to be between 5 and 12 Mpc by applying the tip of the red giant method to the resolved stellar populations imaged by the Hubble Space Telescope. Based on these distances, the HI masses in the sample range from 4x10 super(6) to 6x10 super(7) M sub([middot in circle]), with a median HI mass of 1x10 super(7) M sub([middot in circle]). The tip of the red giant branch distances are up to 73% farther than flow-model estimates in the ALFALFA catalog. Five of the galaxies are part of the NGC 672 and NGC 784 groups, which together constitute a single structure. One galaxy is part of a larger linear ensemble of nine systems that stretches 1.6 Mpc from end to end. Three galaxies reside in regions with 1-9 neighbors, and four galaxies are truly isolated with no known system identified within a radius of 1 Mpc.