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Beifiori, Alessandra; Mendel, J. Trevor; Chan, Jeffrey C. C.; Saglia, Roberto P.; Bender, Ralf; Cappellari, Michele; Davies, Roger L.; Galametz, Audrey; Houghton, Ryan C. W.; Prichard, Laura J.; Smith, Russell; Stott, John P.; Wilman, David J.; Lewis, Ian J.; Sharples, Ray; Wegner, Michael (2017): The KMOS Cluster Survey (KCS). I. The Fundamental Plane and the Formation Ages of Cluster Galaxies at Redshift 1.4 < Z < 1.6. In: Astrophysical Journal, Vol. 846, No. 2, 120
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Abstract

We present the analysis of the fundamental plane (FP) for a sample of 19 massive red-sequence galaxies (M-star > 4 x 10(10) M-circle dot) in three known overdensities at 1.39 < z < 1.61 from the K-band Multi-object Spectrograph (KMOS) Cluster Survey, a guaranteed-time program with spectroscopy from the 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 +/- 0.09, -0.19 +/- 0.05, and -0.29 +/- 0.12 for our clusters at z = 1.39, z = 1.46, and z = 1.61, respectively. For the most massive galaxies (logM(star)/M-circle dot > 11) in our sample, we translate the FP zero-point evolution into a mass-to-light-ratio M/ L evolution, finding Delta logM/L-B =(-0.46 +/- 0.10) z, Delta logM/L-B =(-0.52 +/- 0.07) z, to Delta logM/L-B =(-0.55 +/- 0.10) z, respectively. We assess the potential contribution of the galaxy structural and stellar velocity dispersion evolution to the evolution of the FP zero-point and find it to be similar to 6%-35% of the FP zero-point evolution. The rate of M/L evolution is consistent with galaxies evolving passively. Using single stellar population models, we find an average age of 2.33(-0.51)(+0.86) Gyr for the logM(star)/M-circle dot > 11 galaxies in our massive and virialized cluster at z= 1.39,1.59(-0.62)(+1.40) Gyr in a massive but not virialized cluster at z = 1.46, and 1.20(-0.47)(+1.03) 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.