Recent studies have indicated that the ratio between half-mass and half-light radii, r (mass)/r (light), varies significantly as a function of stellar mass and redshift, complicating the interpretation of the ubiquitous r (light) - M (*) relation. To investigate, in this study we construct the light and color profiles of & SIM;3000 galaxies at 1 < z < 2 with logM*/M & ODOT;> 10.25 imcascade, a Bayesian implementation of the Multi-Gaussian Expansion (MGE) technique. imcascade flexibly represents galaxy profiles using a series of Gaussians, free of any a priori parameterization. We find that both star-forming and quiescent galaxies have, on average, negative color gradients. For star-forming galaxies, we find steeper gradients that evolve with redshift and correlate with dust content. Using the color gradients as a proxy for gradients in the M/L ratio, we measure half-mass radii for our sample of galaxies. There is significant scatter in individual r (mass)/r (light) ratios, which is correlated with variation in the color gradients. We find that the median r (mass)/r (light) ratio evolves from 0.75 at z = 2 to 0.5 at z = 1, consistent with previous results. We characterize the r (mass) - M (*) relation, and we find that it has a shallower slope and shows less redshift evolution than the r (light) - M (*) relation. This applies both to star-forming and quiescent galaxies. We discuss some of the implications of using r (mass) instead of r (light), including an investigation of the size-inclination bias and a comparison to numerical simulations.
