The MAGPI Survey: the subtle role of environment and not-so-subtle impact of generations of stars on galaxy dynamics

TL;DR

This study investigates how environment subtly influences galaxy dynamics at intermediate redshift, revealing a specific correlation between the high-order kinematic parameter $h_4$ and group mass, beyond effects of age and stellar mass.

Contribution

It demonstrates that environment has a measurable impact on galaxy dynamics, specifically on the $h_4$ parameter, using advanced statistical analysis on intermediate redshift galaxy data.

Findings

Mean $h_4$ correlates with group dynamical mass.

Spin parameter $ ext{lambda}_{R_e}$ strongly correlates with galaxy age.

Environmental effects are detectable after controlling for stellar age and mass.

Abstract

The stellar age and mass of galaxies have been suggested as the primary determinants for the dynamical state of galaxies, with environment seemingly playing no or only a very minor role. We use a sample of 77 galaxies at intermediate redshift (z~0.3) in the Middle-Ages Galaxies Properties with Integral field spectroscopy (MAGPI) Survey to study the subtle impact of environment on galaxy dynamics. We use a combination of statistical techniques (simple and partial correlations and principal component analysis) to isolate the contribution of environment on galaxy dynamics, while explicitly accounting for known factors such as stellar age, star formation histories and stellar masses. We consider these dynamical parameters: high-order kinematics of the line-of-sight velocity distribution (parametrised by the Gauss-Hermite coefficients $h_3$ and $h_4$), kinematic asymmetries $V_{\rm asym}$ derived using kinemetry and the observational spin parameter proxy $\lambda_{R_e}$. Of these, the mean $h_4$ is the only parameter found to have a significant correlation with environment as parametrised by group dynamical mass. This correlation exists even after accounting for age and stellar mass trends. Finally, we confirm that variations in the spin parameter $\lambda_{R_e}$ are most strongly (anti-)correlated with age as seen in local studies, and show that this dependence is well-established by z~0.3.