HIGHMASS—HIGH H i MASS, H i-RICH GALAXIES AT Z ∼ 0: COMBINED H i AND H₂ OBSERVATIONS

Abstract

ABSTRACT We present resolved and CO observations of three galaxies from the HIghMass sample, a sample of -massive ( ), gas-rich ( in the top 5% for their M * ) galaxies identified in the ALFALFA survey. Despite their high gas fractions, these are not low-surface-brightness galaxies and have typical specific star formation rates (SFR ) for their stellar masses. The three galaxies have normal SFRs for their masses, but unusually short star formation efficiency scale lengths, indicating that the star formation bottleneck in these galaxies is in the conversion of to , not in converting to stars. In addition, their dark matter spin parameters ( λ ) are above average, but not exceptionally high, suggesting that their star formation has been suppressed over cosmic time but is now becoming active, in agreement with prior H α observations.