A strong lensing model of the galaxy cluster PSZ1 G311.65-18.48

TL;DR

This paper develops a detailed strong lensing model of the galaxy cluster PSZ1 G311.65-18.48 using multi-band Hubble and VLT/MUSE data, accurately reproducing multiple images and revealing the cluster's shape and lensing properties.

Contribution

The study introduces a comprehensive parametric lensing model incorporating spectroscopic data, improving image identification and cluster mass estimation.

Findings

Model achieves 0.14'' positional accuracy for multiple images.

Cluster has a large Einstein radius of 29'' at z=2.3702.

Sunburst Arc exhibits up to 12-fold imaging due to caustic complexity.

Abstract

We present a strong lensing analysis of the galaxy cluster PSZ1 G311.65-18.48 (z=0.443) using multi-band observations with Hubble Space Telescope, complemented with VLT/MUSE spectroscopic data. The MUSE observations provide redshift estimates for the lensed sources and help reducing the mis-identification of the multiple images. Spectroscopic data are also used to measure the inner velocity dispersions of 15 cluster galaxies and calibrate the scaling relations to model the subhalo cluster component. The model is based on 62 multiple images grouped in 17 families belonging to 4 different sources. The majority of them are multiple images of compact stellar knots belonging to a single star-forming galaxy at z=2.3702. This source is strongly lensed by the cluster to form the Sunburst Arc system. To accurately reproduce all the multiple images, we build a parametric mass model, which includes both cluster-scale and galaxy-scale components. The resulting model has a r.m.s. separation between the model-predicted and the observed positions of the multiple images of only 0.14''. We conclude that PSZ1 G311.65-18.48 has a relatively round projected shape and a large Einstein radius (29'' for z_s = 2.3702), which could indicate that the cluster is elongated along the line of sight. The Sunburst Arc source is located at the intersection of a complex network of caustics, which explains why parts of the arc are imaged with unprecedented multiplicity (up to 12 times).