Stellar mass functions of galaxies in the Millennium and Millennium-II simulations. Each panel shows the distribution of galaxy stellar masses in \(z=0\) halos in a narrow range of masses (as shown above each panel), normalized to show the average number of galaxies within a single \(z=0\) halo. Solid lines indicate masses of central galaxies, while dashed lines indicate satellite galaxies. Red lines show results for higher resolution, unaugmented (but pruned) Millennium simulation trees, blue lines show results for unaugmented (but pruned) Millennium-II simulation trees, and green lines show results for Millennium trees augmented to match the resolution of the Millennium-II trees. Shaded bands indicate 1-σ Poisson errors on the mass functions arising from the finite number of merger trees analyzed.