Morphology and Stellar Populations in the Gas-Rich, Giant LSBGs

An unexpected characteristic of low surface brightness galaxies (LSBGs) is that a significant number are massive and possess substantial amounts of atomic gas. We present preliminary results of an ongoing program to obtain BVRIJHK imaging, along with some nuclear spectroscopy, of a well-defined sample of LSBGs which are gas-rich and of similar size to giant, high surface brightness spiral galaxies (HSBGs). These LSBGs span the entire range of Hubble disk morphologies. While their disks are bluer, on average, than comparable HSBGs, the optical morphology of massive LSBGs indicates that many of these systems have undergone previous star formation episodes. They typically have long disk scale lengths, and range from $M_B = -16 to -22 (H_0 = 75 km/s Mpc^{-1})$. About half of the LSBGs with bulges show evidence of nuclear activity, and $\sim 30%$ have appear to be barred. These massive, gas-rich LSBGs apparently have varied, and often complex, evolutionary histories.