High-Resolution Rotation Curves of Low Surface Brightness Galaxies. II. Mass Models

Abstract

We present mass models for a sample of 30 high-resolution rotation curves of low surface brightness\r galaxies. We fit both pseudoisothermal (core dominated) and cold dark matter (CDM; cusp dominated)\r halos for a wide variety of assumptions about the stellar mass-to-light ratio. We find that the\r pseudoisothermal model provides superior fits. CDM fits show systematic deviations from the data and\r often have a small statistical likelihood of being the appropriate model. The distribution of\r concentration parameters is too broad, and has too low a mean, to be explained by low-density, flat\r CDM (ΛCDM). This failing becomes more severe as increasing allowance is made for stellar mass:\r Navarro, Frenk, & White (NFW) model fits require uncomfortably low mass-to-light ratios. In\r contrast, the maximum disk procedure does often succeed in predicting the inner shape of the\r rotation curves, but it requires uncomfortably large stellar mass-to-light ratios. The data do admit\r reasonable stellar population mass-to-light ratios if halos have cores rather than cusps.