The Dependence of Halo Mass on Galaxy Size at Fixed Stellar Mass Using Weak Lensing

TL;DR

This study uses weak lensing to explore how galaxy size at fixed stellar mass correlates with dark matter halo mass, revealing larger galaxies tend to reside in more massive haloes, especially among luminous red galaxies.

Contribution

It introduces a novel analysis linking galaxy size and halo mass at fixed stellar mass using weak lensing and Sersic profile fitting, providing new insights into galaxy-halo relationships.

Findings

Larger galaxies at fixed stellar mass have more massive haloes.

The size-halo mass relationship is strongest for luminous red galaxies.

Simulations suggest satellites show greater scatter in this relationship.

Abstract

Stellar mass has been shown to correlate with halo mass, with non-negligible scatter. The stellar mass-size and luminosity-size relationships of galaxies also show significant scatter in galaxy size at fixed stellar mass. It is possible that, at fixed stellar mass and galaxy colour, the halo mass is correlated with galaxy size. Galaxy-galaxy lensing allows us to measure the mean masses of dark matter haloes for stacked samples of galaxies. We extend the analysis of the galaxies in the CFHTLenS catalogue by fitting single S\'{e}rsic surface brightness profiles to the lens galaxies in order to recover half-light radius values, allowing us to determine halo masses for lenses according to their size. Comparing our halo masses and sizes to baselines for that stellar mass yields a differential measurement of the halo mass-galaxy size relationship at fixed stellar mass, defined as $M_{h}(M_{*}) \propto r_{\mathrm{eff}}^{\eta}(M_{*})$. We find that on average, our lens galaxies have an $\eta = 0.42\pm0.12$, i.e. larger galaxies live in more massive dark matter haloes. The $\eta$ is strongest for high mass luminous red galaxies (LRGs). Investigation of this relationship in hydrodynamical simulations suggests that, at a fixed $M_{*}$, satellite galaxies have a larger $\eta$ and greater scatter in the $M_{\mathrm{h}}$ and $r_{\mathrm{eff}}$ relationship compared to central galaxies.