A multi-wavelength strong lensing analysis of baryons and dark matter in the dynamically active cluster AC 114

TL;DR

This study presents a multi-wavelength strong lensing analysis of the galaxy cluster AC 114, revealing the distribution and dynamics of dark matter, gas, and galaxies, and demonstrating the importance of including baryonic components in lensing models.

Contribution

It introduces a parametric multi-wavelength lensing method that incorporates gas and galaxy data, providing new insights into cluster dynamics and matter distribution.

Findings

Dark matter distribution is shifted and rotated relative to gas.

Dark matter aligns with galaxy density, indicating collisionless behavior.

Cluster shows signs of dynamical activity and develops in the plane of the sky.

Abstract

Strong lensing studies can provide detailed mass maps of the inner regions even in dynamically active galaxy clusters. It is shown that proper modelling of the intracluster medium, i.e. the main baryonic component, can play an important role. In fact, the addition of a new contribution accounting for the gas can increase the statistical significance of the lensing model. We propose a parametric method for strong lensing analyses which exploits multi-wavelength observations. The mass model accounts for cluster-sized dark matter halos, galaxies (whose stellar mass can be obtained from optical analyses) and the intracluster medium. The gas distribution is fitted to lensing data exploiting prior knowledge from X-ray observations. This gives an unbiased look at each matter component and allows us to study the dynamical status of a cluster.}The method has been applied to AC 114, an irregular X-ray cluster. We find positive evidence for dynamical activity, with the dark matter distribution shifted and rotated with respect to the gas. On the other hand, the dark matter follows the galaxy density both for shape and orientation, which hints at its collisionless nature. The inner region (< 250kpc) is under-luminous in optical bands whereas the gas fraction (~20+- 5%) slightly exceeds typical values. Evidence from lensing and X-ray suggests that the cluster develops in the plane of the sky and is not affected by the lensing over-concentration bias. Despite the dynamical activity, the matter distribution seems to be in agreement with predictions from N-body simulations. An universal cusped profile provides a good description of either the overall or the dark matter distribution whereas theoretical scaling relations seem to be nicely fitted.