Shards: An Optical Spectro-Photometric Survey of Distant Galaxies

Abstract

We present the Survey for High-z Absorption Red and Dead Sources (SHARDS), an ESO/GTC Large Program carried out with the OSIRIS instrument on the 10.4m Gran Telescopio Canarias (GTC). SHARDS is an ultra-deep optical spectro-photometric survey of the GOODS-N field covering 130 arcmin 2 at wavelengths between 500 and 950 nm with 24 contiguous medium-band filters (providing a spectral resolution R∼50). The data reach an AB magnitude of 26.5 (at least at a 3σ level) with sub-arcsec seeing in all bands. SHARDS main goal is obtaining accurate physical properties of intermediate and high-z galaxies using well-sampled optical SEDs with sufficient spectral resolution to measure absorption and emission features, whose analysis will provide reliable stellar population and AGN parameters. Among the different populations of high-z galaxies, SHARDS principal targets are massive quiescent galaxies at z>1, whose existence is one of the major challenges of current hierarchical models of galaxy formation. In this paper, we outline the observational strategy and include a detailed discussion of the special reduction and calibration procedures which should be applied to the GTC/OSIRIS data. An assessment of the SHARDS data quality is also performed. We present science demonstration results about the detection and study of emission-line galaxies (star-forming objects and AGN) at z=0-5. We also analyze the SEDs for a sample of 27 quiescent massive galaxies with spectroscopic redshifts in the range 1.0<z 1.4. We discuss on the improvements introduced by the SHARDS dataset in the analysis of their star formation history and stellar properties. We discuss the systematics arising from the use of different stellar population libraries, typical in this kind of studies. Averaging the results from the different libraries, we find that the UV-to-MIR SEDs of the massive quiescent galaxies at z=1.0-1.4 are well described by an exponentially decaying star formation history with scale τ =100-200 Myr, age around 1.5-2.0 Gyr, solar or slightly sub-solar metallicity, and moderate extinction, A(V)∼0.5 mag. We also find that galaxies with masses above M * are typically older than lighter galaxies, as expected in a downsizing scenario of galaxy formation. This trend is, however, model dependent, i.e., it is significantly more evident in the results obtained with some stellar population synthesis libraries and almost absent in others.

The ALHAMBRA survey: 2D analysis of the stellar populations in massive early-type galaxies atz< 0.3

“…Results from this survey support an inside-out scenario of galaxy formation through different studies (e.g. Pérez et al 2013;Sánchez-Blázquez et al 2014). Using a sample of 107 galaxies, González Delgado et al (2014) study the radial structure of the stellar mass surface density as well as the age distribution as a function of morphology and mass.…”

“…COMBO-17, Wolf et al 2003; ALHAMBRA, Moles et al 2008;PAU, Castander et al 2012; SHARDS, Pérez-González et al 2013: J-PAS, Benitez et al 2014;J-PLUS, Cenarro et al in prep). Half-way between classical photometry and spectroscopy, these surveys will build a formidable legacy data set by delivering low resolution spectroscopy for every pixel over a large area of the sky.…”

Understanding the size growth of massive galaxies through stellar populations

“…The sample is extracted from the Survey for High-z Absorption Red and Dead Sources (SHARDS), a dataset consisting of deep (<26.5AB) photometry through 24 medium band (Δλ ∼150Å) filters over a 130 arcmin 2 region towards the HDFN (Pérez-González et al 2013). Medium band photometric data enables us to achieve accurate photometric redshifts (Δz/(1 + z) ∼ 0.055) without the completeness issues present in spectroscopic surveys.…”

MOSFIRE SPECTROSCOPY OF QUIESCENT GALAXIES AT 1.5 < z < 2.5. I. EVOLUTION OF STRUCTURAL AND DYNAMICAL PROPERTIES

“…A new generation of near-infrared instruments has only recently allowed the possibility of studying rest-frame optical spectra at these early epochs (Onodera et al 2012(Onodera et al , 2014Bedregal et al 2013;Pérez-González et al 2013;Whitaker et al 2013;Krogager et al 2014;Newman et al 2014;Mendel et al 2015). However, only a handful of absorption-line spectra are currently available for individual galaxies in this redshift range van Dokkum et al 2009;Toft et al 2012;van de Sande et al 2013;Barro et al 2016;Hill et al 2016).…”