Size and Spectroscopic Evolution of HectoMAP Quiescent Galaxies

TL;DR

This study analyzes the size and spectroscopic evolution of quiescent galaxies from the HectoMAP survey across redshifts 0.2 to 0.6, revealing insights into galaxy growth mechanisms and progenitor bias effects.

Contribution

It provides a detailed analysis of size-mass relation evolution for quiescent galaxies, distinguishing between newcomers and resident populations, and discusses implications for galaxy growth models.

Findings

Size-mass relation evolution is consistent with minor merger growth.

Newcomers show a steeper size increase with cosmic time.

Progenitor bias influences observed size evolution patterns.

Abstract

The HectoMAP survey provides a complete, mass-limited sample of 30,231 quiescent galaxies with $i-$band Hyper Suprime-Cam Subaru Strategic Program (HSC SSP) imaging that spans the redshift range $0.2 <z < 0.6$. We combine half-light radii based on HSC SSP imaging with redshifts and D$_n4000$ to explore the size - mass relation, $R_{e} = A \times M_{*}^{\alpha}$, and its evolution for the entire HectoMAP quiescent population and for two subsets of the data. Newcomers with $1.5 < \mathrm{D}_n4000 < 1.6$ at each redshift show a steeper increase in $A$ as the universe ages than the population that descends from galaxies that are already quiescent at the survey limit, $z \sim 0.6$ (the resident population). In broad agreement with previous studies, evolution in the size - mass relation both for the entire HectoMAP sample and for the resident population (but not for the newcomers alone) is consistent with minor merger driven growth. For the resident population, the evolution in the size - mass relation is independent of the population age at $z \sim 0.6$. The contrast between the sample of newcomers and the resident population provides insight into the role of commonly termed "progenitor bias" on the evolution of the size - mass relation.