Journal
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
Volume 493, Issue 4, Pages 6011-6032Publisher
OXFORD UNIV PRESS
DOI: 10.1093/mnras/staa610
Keywords
galaxies: clusters: general; galaxies: evolution; galaxies: high-redshift; galaxies: star formation; galaxies: stellar content
Categories
Funding
- Science and Technology Facilities Council (STFC)
- George P. and Cynthia Woods Mitchell Institute for Fundamental Physics and Astronomy at Texas AM University
- National Science Foundation [AST-1517863]
- HST program [GO-15294]
- NASA Astrophysics Data Analysis Program (ADAP) [80NSSC17K0019]
- NASA through Space Telescope Science Institute [GO-15294]
- NASA [NAS5-26555]
- Cosmic Dawn Center by the Danish National Research Foundation
- BASAL Center for Astrophysics and Associated Technologies (CATA) [AFB-170002]
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Minor mergers have been proposed as the driving mechanism for the size growth of quiescent galaxies with decreasing redshift. The process whereby large star-forming galaxies quench and join the quiescent population at the large size end has also been suggested as an explanation for this size growth. Given the clear association of quenching with clusters, we explore this mechanism by studying the structural properties of 23 spectroscopically identified recently quenched (or 'post-starburst' (PSB)) cluster galaxies at z similar to 1. Despite clear PSB spectral signatures implying rapid and violent quenching, 87 per cent of these galaxies have symmetric, undisturbed morphologies in the stellar continuum. Remarkably, they follow a mass-size relation lying midway between the star-forming and quiescent field relations, with sizes 0.1 dex smaller than z similar to 1 star-forming galaxies at log(M-*/M-circle dot) = 10.5. This implies a rapid change in the light profile without directly effecting the stellar distribution, suggesting changes in the mass-to-light ratio gradients across the galaxy are responsible. We develop fading toy models to explore how star-forming galaxies move across the mass-size plane as their stellar populations fade to match those of the PSBs. 'Outside-in' fading has the potential to reproduce the contraction in size and increase in bulge-dominance observed between star-forming and PSB cluster galaxies. Since cluster PSBs lie on the large size end of the quiescent mass-size relation, and our previous work shows cluster galaxies are smaller than field galaxies, the sizes of quiescent galaxies must grow both from the quenching of star-forming galaxies and dry minor mergers.
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