The stellar and dark matter distributions in early-type galaxies measured by stacked weak gravitational lensing

TL;DR

This study uses weak gravitational lensing data from the Hyper Suprime-Cam to analyze the distribution of stellar and dark matter in early-type galaxies, revealing non-zero dark matter cores and constraining the stellar-to-halo mass relation.

Contribution

It provides the first direct weak lensing constraints on the stellar-to-halo mass relation and dark matter core sizes in early-type galaxies.

Findings

Preference for non-zero dark matter core radii in ~10^{11} M_sun galaxies

Results suggest stronger feedback effects than current simulations

Constraints indicate a bottom-heavy stellar initial mass function

Abstract

We investigate stellar mass and central dark matter density profiles of photometric luminous red galaxies with stellar masses of $\sim10^{10}-10^{12}M_\odot$ using weak gravitational lensing measurements from the Hyper Suprime-Cam Subaru Strategic Program data obtained with the Subaru Telescope. By stacking weak lensing signals from a large number of galaxies, we obtain average tangential shear profiles down to $\sim 10\,\mathrm{kpc}/h$, which are fitted assuming a two-component model consisting of stellar and dark matter components to constrain their central dark matter distribution. We find a preference for non-zero core radii of dark matter distributions in galaxies with stellar masses of $\sim 10^{11}M_\odot$. Our results imply a stronger feedback effect than that typically predicted by current hydrodynamical simulations. In addition, we provide a new constraint on the stellar-to-halo mass relation, where both stellar and halo masses are, for the first time, directly constrained by weak gravitational lensing. Our results prefer the stellar initial mass function (IMF) that is more bottom-heavy than the Salpeter IMF.