Mapping the distribution of luminous and dark matter in strong lensing galaxies

TL;DR

This study combines stellar population synthesis and gravitational lensing to map luminous and dark matter in strong lensing galaxies, revealing dark matter's increasing role beyond galaxy cores and its correlation with galaxy mass.

Contribution

It introduces a combined methodology using two independent techniques to analyze dark and luminous matter distribution in strong lensing galaxies, expanding understanding across different redshifts.

Findings

Dark matter is absent in galaxy cores.

Dark matter contribution increases beyond the effective radius.

More massive galaxies tend to have higher dark matter content.

Abstract

We present the distribution of luminous and dark matter in a set of strong lensing (early-type) galaxies. By combining two independent techniques - stellar population synthesis and gravitational lensing - we can compare the baryonic and dark matter content in these galaxies within the regions that can be probed using the images of the lensed background source. Two samples were studied, extracted from the CASTLES and SLACS surveys. The former probes a wider range of redshifts and allows us to explore the mass distribution out to ~5Re. The high resolution optical images of the latter (using HST/ACS) are used to show a pixellated map of the ratio between total and baryonic matter. We find dark matter to be absent in the cores of these galaxies, with an increasing contribution at projected radii R>Re. The slopes are roughly compatible with an isothermal slope (better interpreted as an adiabatically contracted NFW profile), but a large scatter in the slope exists among galaxies. There is a trend suggesting most massive galaxies have a higher content of dark matter in the regions probed by this analysis.