2006ApJ...636L..21V

We measure the evolution of the rest-frame K-band fundamental plane from z=1 to the present by using IRAC imaging of a sample of early-type galaxies in the Chandra Deep Field-South at z∼1 with accurately measured dynamical masses. We find that M/L_Kevolves as Δln(M/L_K)=(-1.18±0.10)z, which is slower than in the B band [Δln(M/L_B)=(-1.46±0.09)z]. In the B band, the evolution has been demonstrated to be strongly mass-dependent. In the K band, we find a weaker trend: galaxies more massive than M=2x10¹¹ M_☉evolve as Δln(M/L_K)=(-1.01±0.16)z; less massive galaxies evolve as Δln(M/L_K)=(-1.27±0.11)z. As expected from stellar population models, the evolution in M/L_Kis slower than the evolution in M/L_B. However, when we make a quantitative comparison, we find that the single-burst Bruzual-Charlot models do not fit the results well, unless large dust opacities are allowed at z=1. Models with a flat IMF fit better; Maraston models with a different treatment of AGB stars fit best. These results show that the interpretation of rest-frame near-IR photometry is severely hampered by model uncertainties and therefore that the determination of galaxy masses from rest-frame near-IR photometry may be harder than was thought before.