One of the simulated galaxies with CDM (left) and SIDM-1 (right), at redshift zero. With CDM, the total mass (gas + stars + dark matter) is 7.24 × 10¹¹ M_⊙, the stellar mass is 1.04 × 10¹⁰ M_⊙, and the dark matter mass is 6.50 × 10¹¹ M_⊙. With SIDM-1, the total mass is 8.73 × 10¹¹ M_⊙, the stellar mass is 3.89 × 10¹⁰ M_⊙, and the dark matter mass is 7.39 × 10¹¹ M_⊙. These masses are calculated using Pynbody, and include all particles that are gravitationally bound to the halo (A. Pontzen et al. 2013). Pynbody uses a stellar population model to estimate the stellar luminosity in different wavelength bands, from which it determines the apparent colors in the images. The colors are set by mapping red, green, and blue to the I (infrared), V (visible), and U (ultraviolet) bands, respectively. Here, the clearly visible differences are primarily due to the effects of SIDM-1 on the star formation history. As SIDM-1 delays the growth of black holes via mergers, star formation is not suppressed to the same degree.