SEAGLE – III: Towards resolving the mismatch in the dark-matter fraction in early-type galaxies between simulations and observations

ABSTRACT The central dark-matter fraction of galaxies is sensitive to feedback processes during galaxy formation. Strong gravitational lensing has been effective in the precise measurement inside massive early-type galaxies. Here, we compare projected inferred from SLACS (Sloan Lens ACS Survey) strong-lens survey with those obtained Evolution and Assembly GaLaxies their Environment (EAGLE), Illustris, IllustrisTNG hydrodynamical simulations. Previous comparisons some simulations revealed a large discrepancy, considerably higher fractions – by factors ≈2–3 half radius observed as compared simulated report good agreement between EAGLE for both function galaxy’s stellar mass, radius, total mass-density slope. However, are lower than observed. This work consistently assumes Chabrier initial mass (IMF), which suggests that different IMF (although not excluded) necessary resolve this mismatch. differences model Illustris likely dominant cause difference density