paper

Constraints on Quenching of Massive Galaxies from the Evolution of the average Sizes of Star-Forming and Quenched Populations in COSMOS

arXiv:1703.09234 · doi:10.3847/1538-4357/aa697a

Abstract

We use 9400 quiescent and star-forming galaxies at 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 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 galaxies at . 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 well the observed mass-size relation of massive galaxies at . Our starburstcompaction model followed by individual growth of the galaxies by minor mergers is preferred over other models without structural change for galaxies at . None of our models is able to meet the observations at and with out significant contribution of post-quenching growth of individual galaxies via mergers. We conclude that quenching is a fast process in galaxies with , and that major mergers likely play a major role in the final steps of their evolution.

20 pages, 9 figures, 1 table, accepted for publication in ApJ

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