Evidence for Old Stars in the Red Low Surface Brightness Galaxies UGC 6614 and F568-6

Abstract

We present near-Infrared images of low surface brightness galaxies: H band images of UGC 6614 and F568-6 (Malin 2). The H band images show spiral structure so we are confident that we are seeing the galaxy disks as well as the central bulges. The optical-IR colors of these galaxies, $R-H = 2.2\pm 0.2$, $B-H = 3.5-4.2$, are extremely red and are similar to those of many S0 and elliptical galaxies. This represents strong evidence for a component of old stars. Recent studies find that low surface brightness galaxies span a wide range of morphologies and colors. In this context UGC 6614 and F568-6 could be examples of low surface brightness galaxies which have undergone a past epoch of more vigorous star formation.