Near-infrared photometry of bright elliptical galaxies

High-quality visual-infrared color profiles have been determined for elliptical galaxies for the first time. Surface photometry in J and K is presented for 12 bright elliptical galaxies, and the results have been combined with CCD data in visual passbands. It is shown that the galaxies become bluer in V-K by an average of 0.16 mag/dex with increasing radius. There is a strong correlation between radial color gradients in U-V, B-V, and V-K for 11 of the galaxies. Models to interpret the color profiles are constructed which indicate that the stellar populations in elliptical galaxies can be explained by a single burst population with a contribution of a few percent of the light in V from blue stars. Metallicity is a possible candidate for the parameter causing radial color gradients