We present the analysis of the fundamental plane ( FP ) for a sample of 19 massive red-sequence galaxies ( M _ { \star } > 4 \times 10 ^ { 10 } M _ { \odot } ) in 3 known overdensities at 1.39 < z < 1.61 from the KMOS Cluster Survey , a guaranteed time program with spectroscopy from the K-band Multi-Object Spectrograph ( KMOS ) at the VLT and imaging from the Hubble Space Telescope .
As expected , we find that the FP zero-point in B band evolves with redshift , from the value 0.443 of Coma to -0.10 \pm 0.09 , -0.19 \pm 0.05 , -0.29 \pm 0.12 for our clusters at z = 1.39 , z = 1.46 , and z = 1.61 , respectively .
For the most massive galaxies ( \log M _ { \star } / M _ { \odot } > 11 ) in our sample , we translate the FP zero-point evolution into a mass-to-light-ratio M / L evolution finding \Delta \log M / L _ { B } = ( -0.46 \pm 0.10 ) z , \Delta \log M / L _ { B } = ( -0.52 \pm 0.07 ) z , to \Delta \log M / L _ { B } = ( -0.55 \pm 0.10 ) z , respectively .
We assess the potential contribution of the galaxies structural and stellar velocity dispersion evolution to the evolution of the FP zero-point and find it to be \sim 6-35 % of the FP zero-point evolution .
The rate of M / L evolution is consistent with galaxies evolving passively .
By using single stellar population models , we find an average age of 2.33 ^ { +0.86 } _ { -0.51 } Gyr for the \log M _ { \star } / M _ { \odot } > 11 galaxies in our massive and virialized cluster at z = 1.39 , 1.59 ^ { +1.40 } _ { -0.62 } Gyr in a massive but not virialized cluster at z = 1.46 , and 1.20 ^ { +1.03 } _ { -0.47 } Gyr in a protocluster at z = 1.61 .
After accounting for the difference in the age of the Universe between redshifts , the ages of the galaxies in the three overdensities are consistent within the errors , with possibly a weak suggestion that galaxies in the most evolved structure are older .