The link between a galaxy’s structure and its stellar populations.

Abstract

Stellar population parameters correlate with a range of galaxy properties, but it is unclear which relations are causal and which are the result of another underlying trend. The well-established correlations between mass and other galaxy properties are often considered evidence for mass driving a galaxy’s evolution. However, we find that, at fixed mass, stellar population properties show significant dependence on size, indicating that the size of a galaxy is also an important property tracing, and possibly influencing, its evolution. We quantitatively compare trends between various stellar population properties and key galaxy structural parameters --- in particular the galaxy’s mass, gravitational potential, and surface density --- in order to determine which relations are intrinsically tighter and are therefore more likely to reflect a causal relation. We divide our work into three parts focusing on early-type galaxies, star-forming galaxies and micro high-redshift galaxies, respectively. This division reflects both the physical differences between these samples, as well as technical differences in measuring their stellar population properties.