Discovery of face-on counterparts of chain galaxies in the Tadpole Advanced Camera for Surveys field

Abstract

The background field of the Tadpole galaxy image taken with the Hubble Space Telescope Advanced Camera for Surveys contains 87 clump clusters that are probably low-inclination versions of the 69 chain galaxies that we found in a previous paper. This conclusion follows from the similarity in colors and apparent magnitudes of the brightest clumps in the clump clusters and chain galaxies and from the similarity between the distribution of axial ratios for the combined sample and the distribution for normal disk galaxies. These distributions are consistent with chains and clump clusters being disks viewed at random angles with intrinsic axial ratios of 0.1-0.2 or less. The disks appear to be gas-rich galaxies at z = 1-2 that are forming an early generation of stars in a small number of very large star complexes.