The ESO-Spitzer Imaging extragalactic Survey (ESIS) II. VIMOS I, z wide field imaging of ELAIS-S1 and selection of distant massive galaxies

Abstract

Context. The ESO-Spitzer Imaging extragalactic Survey (ESIS) is the optical follow up of the Spitzer Wide-area Infra-Red Extragalactic survey (SWIRE) in the ELAIS-S1 region of the sky. Aims. In the era of observational cosmology, the main efforts are focused on the study of galaxy evolution and its environmental dependence. Wide area, multiwavelength, extragalactic surveys are needed in order to probe sufficiently large volumes, minimize cosmic variance and find significant numbers of rare objects. Methods. We present VIMOS I and z band imaging belonging to the ESIS survey. A total of ~4 deg^2 was targeted in I and ~1 deg^2 in z. Accurate data processing includes removal of fringing, and mosaicking of the complex observing pattern. Completeness levels and photometric uncertainties are estimated through simulations. The multi-wavelength data available in the area are exploited to identify high-redshift galaxies, using the IR-peak technique. Results. More than 300 000 galaxies have been detected in the I band and ~50 000 in the z band. Object coordinates are defined within an uncertainty of ~0.2 arcsec rms, with respect to GSC 2.2. We reach a 90% average completeness at 23.1 and 22.5 mag (Vega) in the I and z bands, respectively. On the basis of IRAC colors, we identify galaxies having the 1.6 $\mu$m stellar peak shifted to z = 1-3. The new I, z band data provide reliable constraints to help avoid low-redshift interlopers and reinforce this selection. Roughly 1000 galaxies between z = 2-3 are identified over the ESIS ~4 deg^2, at the SWIRE 5.8 $\mu$m depth (25.8 $\mu$Jy at 3$\sigma$). These are the best galaxy candidates to dominate the massive tail ( M > 1011 $M_\odot$) of the z > 2 mass function.

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