Candidate Massive Galaxies at $z \sim 4$ in the Dark Energy Survey
Creators: name: Guarnieri, Pierandrea
name: Maraston, Claudia
name: Thomas, Daniel
name: Pforr, Janine
name: Gonzalez-Perez, Violeta
name: Etherington, James
name: Carlsen, Joakim
name: Morice-Atkinson, Xan
name: Conselice, Christopher J.
name: Gschwend, Julia
name: Kind, Matias Carrasco
name: Abbott, Tim
name: Allam, Sahar
name: Brooks, David
name: Burke, David
name: Rosell, Aurelio Carnero
name: Carretero, Jorge
name: Cunha, Carlos
name: ďAndrea, Chris
name: da Costa, Luiz
name: De Vincente, Juan
name: DePoy, Darren
name: Diehl, H. Thomas
name: Doel, Peter
name: Frieman, Josh
name: Garcia-Bellido, Juan
name: Gruen, Daniel
name: Gutierrez, Gaston
name: Hanley, Dominic
name: Hollowood, Devon
name: Honscheid, Klaus
name: James, David
name: Jeltema, Tesla
name: Kuehn, Kyler
name: Lima, Marcos
name: Maia, Marcio A. G.
name: Marshall, Jennifer
name: Martini, Paul
name: Melchior, Peter
name: Menanteau, Felipe
name: Miquel, Ramon
name: Malagon, Andres Plazas
name: Richardson, Samuel
name: Romer, Kathy
name: Sanchez, Eusebio
name: Scarpine, Vic
name: Schindler, Rafe
name: Sevilla, Ignacio
name: Smith, Mathew
name: Soares-Santos, Marcelle
name: Sobreira, Flavia
name: Suchyta, Eric
name: Tarle, Gregory
name: Walker, Alistair
name: Wester, William
Publisher: name: arXiv
Year: 2018
Subjects: subject: Astrophysics of Galaxies (astro-ph.GA)
subject: FOS: Physical sciences
subject: FOS: Physical sciences

description: 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.
description: 24 pages (41 with appendix), 16 figures, MNRAS in press