Bottom panels: the luminosity function of galaxies in the central region (within  ~700 kpc of the cluster center) of XMMU J2235, in the z, H and K_s bands. Solid symbols show binned counts (with 1σ errors, see text for details), and black lines show the best-fit Schechter function as determined for magnitudes brighter than  ~M^∗ + 2. Confidence levels (1, 2, 3σ) on the two relevant parameters (characteristic magnitude M^∗ and faint end slope α) are plotted in the small insets. In the central panel (H band LF) and corresponding inset, the gray lines show the best-fit Schechter function and confidence levels for the fit down to  ~M^∗ + 4. The formal best-fit values and 1σ errors for M^∗ and α, as fitted down to  ~M^∗ + 2, in the three passbands are: , α_z = −0.95 ± 0.6, , (, down to  ~M^∗ + 4), , . Upper panels: the evolution of M^∗ with redshift as observed in the z, H and K_s band, according to Kodama & Arimoto (1997) models, for three formation redshifts z_f = 2, 3, 5. Solid symbols show M^∗ (and errors) as determined from the LFs in the lower panels.