A Study of Massive and Evolved Galaxies at z>3
I use deep data taken as part of the Hubble Space Telescope (HST) Wide Field Camera 3 (WFC3) observations by the Cosmic Assembly Near-infrared Deep Extragalactic Legacy Survey (CANDELS) along with ground-based and Spitzer Space Telescope data to identify massive and evolved galaxies at z>3. This is performed using the strength of the Balmer break feature at rest-frame 3648A, which is an age dependent diagnostic of the stellar population, to develop a Balmer Break Galaxy (BBG) selection. Fitting the spectral energy distribution (SED) of the candidates show that these systems have average estimated ages of ~ 800 Myr and average stellar masses of ~ 5 x10^10 M_sun, consistent with being old and massive. I find a number density of ~ 3.2 x 10^-5 Mpc^-3 for these systems corresponding to a mass density of ~ 2.0 x 10^6 M_sun/Mpc^3 at 3 3 are far more compact than lower redshift early type galaxies. Using the GALFIT measured sizes, I confirm that the physical size of the early type galaxies evolve rapidly with redshift according to: R_e proportional to (1+z)^-1.48 out to z ~ 3.3.