The Size Evolution of Passive Galaxies: Observations from the Wide Field Camera 3 Early Release Science Program
astro-ph.CO
/ Authors
R. E. Ryan, P. J. McCarthy, S. H. Cohen, H. Yan, N. P. Hathi, A. M. Koekemoer, M. J. Rutkowski, M. R. Mechtley, R. A. Windhorst, R. W. O'Connell
and 21 more authors
B. Balick, H. E. Bond, H. Bushouse, D. Calzetti, R. M. Crockett, M. Disney, M. A. Dopita, J. A. Frogel, D. N. B. Hall, J. A. Holtzman, S. Kaviraj, R. A. Kimble, J. MacKenty, M. Mutchler, F. Paresce, A. Saha, J. I. Silk, J. Trauger, A. R. Walker, B. C. Whitmore, E. Young
/ Abstract
We present results on the size evolution of passively evolving galaxies at 1<z<2 drawn from the Wide Field Camera 3 Early Release Science program. Our sample was constructed using an analog to the passive BzK selection criterion, which isolates galaxies with little or no on-going star formation at z>1.5. We identify 30 galaxies in ~40 square arcmin to H<25 mag. We supplement spectroscopic redshifts from the literature with photometric redshifts determined from the 15-band photometry from 0.22-8 micron. We determine effective radii from Sersic profile fits to the H-band image using an empirical PSF. We find that size evolution is a strong function of stellar mass, with the most massive (M* ~ 10^11 Msol) galaxies undergoing the most rapid evolution from z~2 to the present. Parameterizing the size evolution as (1+z)^{-alpha}, we find a tentative scaling between alpha and stellar mass of alpha ~ -1.8+1.4 log(M*/10^9 Msol). We briefly discuss the implications of this result for our understanding of the dynamical evolution of the red galaxies.