2021ApJ...908..135S

We examine the Fundamental Plane (FP) and mass-to-light ratio (M/L) scaling relations using the largest sample of massive quiescent galaxies at 1.5 < z < 2.5 to date. The FP (r_e, σ_e, I_e) is established using 19 UVJ quiescent galaxies from COSMOS with Hubble Space Telescope H_F160W rest-frame optical sizes and X-shooter absorption line-measured stellar velocity dispersions. For a very massive, log(M_*/M_☉)> 11.26, subset of eight quiescent galaxies at z > 2, from Stockmann et al., we show that they cannot passively evolve to the local Coma cluster relation alone and must undergo significant structural evolution to mimic the sizes of local massive galaxies. The evolution of the FP and M/L scaling relations, from z = 2 to present day, for this subset are consistent with passive aging of the stellar population and minor merger structural evolution into the most massive galaxies in the Coma cluster and other massive elliptical galaxies from the MASSIVE Survey. Modeling the luminosity evolution from minor merger-added stellar populations favors a history of merging with "dry" quiescent galaxies.