Investigating the growing population of massive quiescent galaxies at cosmic noon
Sydney Sherman, Shardha Jogee, Jonathan Florez, Matthew L. Stevans, Lalitwadee Kawinwanichakij, Isak Wold, Steven L. Finkelstein, Casey Papovich, Robin Ciardullo, C. Gronwall, S. A. Cora, Tomás Hough, Cristian A Vega-Martínez
Abstract
ABSTRACT We explore the build-up of quiescent galaxies using a sample of 28 469 massive (M⋆ ≥ 1011 M⊙) galaxies at redshifts 1.5 < $z$ < 3.0, drawn from a 17.5 deg2 area (0.33 Gpc3 comoving volume at these redshifts). This allows for a robust study of the quiescent fraction as a function of mass at 1.5 < $z$ < 3.0 with a sample ∼40 times larger at log(M⋆/$\rm M_{\odot })\ge 11.5$ than previous studies. We derive the quiescent fraction using three methods: specific star formation rate, distance from the main sequence, and UVJ colour–colour selection. All three methods give similar values at 1.5 < $z$ < 2.0, however the results differ by up to a factor of 2 at 2.0 < $z$ < 3.0. At redshifts 1.5 < $z$ < 3.0, the quiescent fraction increases as a function of stellar mass. By $z$ = 2, only 3.3 Gyr after the big bang, the universe has quenched ∼25 per cent of M⋆ = 1011 M⊙ galaxies and ∼45 per cent of M⋆ = 1012 M⊙ galaxies. We discuss physical mechanisms across a range of epochs and environments that could explain our results. We compare our results with predictions from hydrodynamical simulations SIMBA and IllustrisTNG and semi-analytic models (SAMs) SAG, SAGE, and Galacticus. The quiescent fraction from IllustrisTNG is higher than our empirical result by a factor of 2–5, while those from SIMBA and the three SAMs are lower by a factor of 1.5–10 at 1.5 < $z$ < 3.0.