A combined VANDELS and LEGA-C study: the evolution of quiescent galaxy size, stellar mass and age from z = 0.6 to z = 1.3

2022/01/31 by M. L. Hamadouche, Adam C. Carnall, A. C. Carnall +17
Physics and Astronomy · #Astronomy #Astronomy and Astrophysical Research #Astrophysics #Flattening #Galaxies: Formation, Evolution, Phenomena #Galaxy #Metallicity #Physics #Star formation #Stellar mass #Stellar, planetary, and galactic studies #astro-ph.GA

paper · pdf · doi:10.1093/mnras/stac535

14 pages, 9 figures, submitted to MNRAS

arxiv created 2022/02/24 · openalex publication_date 2022/02/24 · openalex created_date 2022/02/25 · arxiv updated 2022/03/09 · openalex updated_date 2026/08/05

Abstract

We study the relationships between stellar mass, size and age within the quiescent population, using two mass-complete spectroscopic samples with \mathrmlog₁₀(M_⋆/\mathrmM_\odot)>10.3, taken from VANDELS at 1.0<z<1.3, and LEGA-C at 0.6<z<0.8. Using robust D_n4000 values, we demonstrate that the well-known 'downsizing' signature is already in place by z≃1.1, with D_n4000 increasing by ≃0.1 across a ≃ 1 dex mass interval for both VANDELS and LEGA-C. We then proceed to investigate the evolution of the quiescent galaxy stellar mass-size relation from z≃1.1 to z≃0.7. We find the median size increases by a factor of 1.9±0.1 at \mathrmlog₁₀(M_⋆/\mathrmM_\odot)=10.5, and see tentative evidence for flattening of the relation, finding slopes of α=0.72±0.06 and α= 0.56±0.04 for VANDELS and LEGA-C respectively. We finally split our sample into galaxies above and below our fitted mass-size relations, to investigate how size and D_n4000 correlate. For LEGA-C, we see a clear difference, with larger galaxies found to have smaller D_n4000 at fixed stellar mass. Due to the faintness and smaller numbers of the VANDELS sample, we cannot confirm whether a similar relation exists at z≃1.1. We consider whether differences in stellar age or metallicity are most likely to drive this size-D_n4000 relation, finding that any metallicity differences are unlikely to fully explain the observed offset, meaning smaller galaxies must be older than their larger counterparts. We find the observed evolution in size, mass and D_n4000 across the ≃2 Gyr from z∼1.1 to z∼0.7 can be explained by a simple toy model in which VANDELS galaxies evolve passively, whilst experiencing a series of minor mergers.

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