The Cosmological Unimportance of Low Surface Brightness Galaxies

We have searched for Type Ia supernovae (SNe Ia) in the local (d<~60 Mpc) universe using Northern Sky Variability Survey (NSVS) data collected from the nightly optical surveys of the Robotic Optical Transient Search Experiment (ROTSE) Telescope. It was hoped that SNe Ia would provide a means to find previously unknown low surface brightness (LSB) galaxies or displaced stars that would otherwise be very difficult to detect. The ROTSE data allowed us to survey 19,000 deg² at declinations north of 0°, but we did not find a single SN Ia in a period of time covering roughly 1 year. Using known SNe Ia rates in bright galaxies, we set an upper limit on the optical luminosity density, L_B, of LSBs in the local universe. Using mean LSB baryonic and dynamical mass-to-light ratios, we find 95% upper limits for LSBs of L_B<=2.53×10⁸L_B,solar Mpc^-3, Ω_b<=0.0040, and Ω_m<=0.036. We conclude that LSBs and displaced stars are not a major constituent of matter in the local universe.