Constraints on Quenching of Z 2 Massive Galaxies from the Evolution of the Average Sizes of Star-forming and Quenched Populations in COSMOS

• Published in: The Astrophysical journal Vol. 839; no. 2; pp. 71 - 85
• Main Authors: Faisst, A. L., Carollo, C. M., Capak, P. L., Tacchella, S., Renzini, A., Ilbert, O., McCracken, H. J., Scoville, N. Z.
• Format: Journal Article
• Language: English
• Published: Philadelphia The American Astronomical Society 20.04.2017; IOP Publishing
• Subjects: Astronomical models; Astrophysics; ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; CALIBRATION; Compaction; Evolution; Galactic evolution; GALAXIES; galaxies: evolution; galaxies: fundamental parameters; galaxies: structure; Hubble Space Telescope; Image resolution; INHIBITION; MASS; Power law; Quenching; SPACE; Space telescopes; Star & galaxy formation; STAR EVOLUTION; Star formation; STARS; Stars & galaxies; Stellar evolution; UNIVERSE
• ISSN: 0004-637X; 1538-4357
• DOI: 10.3847/1538-4357/aa697a

We use >9400 quiescent and star-forming galaxies at z 2 in COSMOS/UltraVISTA to study the average size evolution of these systems, with focus on the rare ultra-massive population at . The large 2 square degree survey area delivers a sample of ∼400 such ultra-massive systems. Accurate sizes are derived using a calibration based on high-resolution images from the Hubble Space Telescope. We find that at these very high masses, the size evolution of star-forming and quiescent galaxies is almost indistinguishable in terms of normalization and power-law slope. We use this result to investigate possible pathways of quenching massive m > M* galaxies at z < 2. We consistently model the size evolution of quiescent galaxies from the star-forming population by assuming different simple models for the suppression of star formation. These models include an instantaneous and delayed quenching without altering the structure of galaxies and a central starburst followed by compaction. We find that instantaneous quenching reproduces the observed mass-size relation of massive galaxies at z > 1 well. Our starburst+compaction model followed by individual growth of the galaxies by minor mergers is preferred over other models without structural change for galaxies at z > 0.5. None of our models is able to meet the observations at m > M* and z < 1 without significant contribution of post-quenching growth of individual galaxies via mergers. We conclude that quenching is a fast process in galaxies with m ≥ 1011 M , and that major mergers likely play a major role in the final steps of their evolution.