  SHARDS, an ESO/GTC Large Program, is an ultra-deep (26.5 mag)
spectro-photometric survey with GTC/OSIRIS designed to select and study massive
passively evolving galaxies at z=1.0-2.3 in the GOODS-N field using a set of 24
medium-band filters (FWHM~17 nm) covering the 500-950 nm spectral range. Our
observing strategy has been planned to detect, for z>1 sources, the prominent
Mg absorption feature (at rest-frame ~280 nm), a distinctive, necessary, and
sufficient feature of evolved stellar populations (older than 0.5 Gyr). These
observations are being used to: (1) derive for the first time an unbiased
sample of high-z quiescent galaxies, which extends to fainter magnitudes the
samples selected with color techniques and spectroscopic surveys; (2) derive
accurate ages and stellar masses based on robust measurements of spectral
features such as the Mg(UV) or D(4000) indices; (3) measure their redshift with
an accuracy Delta(z)/(1+z)<0.02; and (4) study emission-line galaxies
(starbursts and AGN) up to very high redshifts. The well-sampled optical SEDs
provided by SHARDS for all sources in the GOODS-N field are a valuable
complement for current and future surveys carried out with other telescopes
(e.g., Spitzer, HST, and Herschel).
