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Chan, Jeffrey C. C., Beifiori, Alessandra, Saglia, Roberto P., Mendel, J. Trevor, Stott, John P., Bender, Ralf, Galametz, Audrey, Wilman, David J., Cappellari, Michele, Davies, Roger L., Houghton, Ryan C. W., Prichard, Laura J., Lewis, Ian J., Sharples, Ray and Wegner, Michael (2018): The KMOS Cluster Survey (KCS). II. The Effect of Environment on the Structural Properties of Massive Cluster Galaxies at Redshift 1.39 < z < 1.61. In: Astrophysical Journal, Vol. 856, No. 1, 8

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We present results on the structural properties of massive passive galaxies in three clusters at 1.39. <. z. <. 1.61 from the KMOS Cluster Survey. We measure light-weighted and mass-weighted sizes from optical and nearinfrared Hubble Space Telescope imaging and spatially resolved stellar mass maps. The rest-frame R-band sizes of these galaxies are a factor of similar to 2-3 smaller than their local counterparts. The slopes of the relation between the stellar mass and the light-weighted size are consistent with recent studies in clusters and the field. Their massweighted sizes are smaller than the rest-frame R-band sizes, with an average mass-weighted to light-weighted size ratio that varies between similar to 0.45 and 0.8 among the clusters. We find that the median light-weighted size of the passive galaxies in the two more evolved clusters is similar to 24% larger than that for field galaxies, independent of the use of circularized effective radii or semimajor axes. These two clusters also show a smaller size ratio than the less evolved cluster, which we investigate using color gradients to probe the underlying M*/LH160 gradients. The median color gradients are del(z) -H similar to -0.4 mag dex(-1), twice the local value. Using stellar populations models, these gradients are best reproduced by a combination of age and metallicity gradients. Our results favor the minor merger scenario as the dominant process responsible for the observed galaxy properties and the environmental differences at this redshift. The environmental differences support that clusters experience accelerated structural evolution compared to the field, likely via an epoch of enhanced minor merger activity during cluster assembly.

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