Guarnieri, Pierandrea and Maraston, Claudia and Thomas, Daniel and Pforr, Janine and Gonzalez-Perez, Violeta and Etherington, James and Carlsen, Joakim and Morice-Atkinson, Xan and Conselice, Christopher J. and Gschwend, Julia and Kind, Matias Carrasco and Abbott, Tim and Allam, Sahar and Brooks, David and Burke, David and Rosell, Aurelio Carnero and Carretero, Jorge and Cunha, Carlos and ďAndrea, Chris and Costa, Luiz da and Vincente, Juan De and DePoy, Darren and Diehl, H. Thomas and Doel, Peter and Frieman, Josh and Garcia-Bellido, Juan and Gruen, Daniel and Gutierrez, Gaston and Hanley, Dominic and Hollowood, Devon and Honscheid, Klaus and James, David and Jeltema, Tesla and Kuehn, Kyler and Lima, Marcos and Maia, Marcio A. G. and Marshall, Jennifer and Martini, Paul and Melchior, Peter and Menanteau, Felipe and Miquel, Ramon and Malagon, Andres Plazas and Richardson, Samuel and Romer, Kathy and Sanchez, Eusebio and Scarpine, Vic and Schindler, Rafe and Sevilla, Ignacio and Smith, Mathew and Soares-Santos, Marcelle and Sobreira, Flavia and Suchyta, Eric and Tarle, Gregory and Walker, Alistair and Wester, William (2019) Candidate Massive Galaxies at z~4 in the Dark Energy Survey. Monthly Notices of the Royal Astronomical Society, 483 (3). pp. 3060-3081. ISSN 0035-8711
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Abstract
Using stellar population models, we predicted that the Dark Energy Survey (DES) - due to its special combination of area (5000 deg. sq.) and depth ($i = 24.3$) - would be in the position to detect massive ($\gtrsim 10^{11}$ M$_{\odot}$) galaxies at $z \sim 4$. We confront those theoretical calculations with the first $\sim 150$ deg. sq. of DES data reaching nominal depth. From a catalogue containing $\sim 5$ million sources, $\sim26000$ were found to have observed-frame $g-r$ vs $r-i$ colours within the locus predicted for $z \sim 4$ massive galaxies. We further removed contamination by stars and artefacts, obtaining 606 galaxies lining up by the model selection box. We obtained their photometric redshifts and physical properties by fitting model templates spanning a wide range of star formation histories, reddening and redshift. Key to constrain the models is the addition, to the optical DES bands $g$, $r$, $i$, $z$, and $Y$, of near-IR $J$, $H$, $K_{s}$ data from the Vista Hemisphere Survey. We further applied several quality cuts to the fitting results, including goodness of fit and a unimodal redshift probability distribution. We finally select 233 candidates whose photometric redshift probability distribution function peaks around $z\sim4$, have high stellar masses ($\log($M$^{*}$/M$_{\odot})\sim 11.7$ for a Salpeter IMF) and ages around 0.1 Gyr, i.e. formation redshift around 5. These properties match those of the progenitors of the most massive galaxies in the local universe. This is an ideal sample for spectroscopic follow-up to select the fraction of galaxies which is truly at high redshift. These initial results and those at the survey completion, which we shall push to higher redshifts, will set unprecedented constraints on galaxy formation, evolution, and the re-ionisation epoch.