1302.5115 (C. M. Carollo et al.)

Newly-quenched galaxies as the cause for the apparent evolution in average size of the population    [PDF]

C. M. Carollo, T. J. Bschorr, A. Renzini, S. J. Lilly, P. Capak, A. Cibinel, O. Ilbert, M. Onodera, N. Scoville, E. Cameron, B. Mobasher, D. Sanders, Y. Taniguchi

We study the number densities of quenched early-type galaxies (Q-ETGs) of a given size in a homogeneous COSMOS sample over the interval 1 < z < 0.2. At 10^{10.5}10^{11} Msun we find a decrease by 30-40%. In both mass bins, the increase of the median sizes of Q-ETGs with time is primarily caused by the addition of larger Q-ETGs. At all masses, compact Q-ETGs become redder towards later epochs, with a (U-V) color difference which is consistent with a passive evolution of their stellar populations. At all epochs, the larger Q-ETGs have colors that are systematically bluer than those of the more compact Q-ETGs, suggesting that the former are younger than the latter. The sizes and number of the star-forming galaxies over the same redshift interval also support the idea that new Q-ETGs are responsible for the growth in the median size of the population at a given mass. The sizes of the new members of the population appear to scale as roughly (1+z)^{-1}. We conclude that the dominant cause of the apparent size evolution of the population of Q-ETGs is the addition at later epochs of larger galaxies. [abridged]

View original: http://arxiv.org/abs/1302.5115