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

¹ DIFA – Dipartimento di Fisica e Astronomia, Università di Bologna, via Gobetti 93/2, 40129 Bologna, Italy
e-mail: giada.pignataro@studio.unibo.it
² INAF – OAS, Osservatorio di Astrofisica e Scienza dello Spazio di Bologna, via Gobetti 93/3, 40129 Bologna, Italy
³ Dipartimento di Fisica, Università degli Studi di Milano, via Celoria 16, 20133 Milano, Italy
⁴ Dark Cosmology Centre, Niels Bohr Institute, University of Copenhagen, Jagtvej 128, 2200 Copenhagen, Denmark
⁵ Dipartimento di Fisica e Scienze della Terra, Università degli Studi di Ferrara, via Saragat 1, 44122 Ferrara, Italy
⁶ INAF – Osservatorio Astronomico di Capodimonte, Via Moiariello 16, 80131 Napoli, Italy
⁷ Cosmic Dawn Center, Niels Bohr Institute, University of Copenhagen, Juliane Maries Vej 30, 2100 Copenhagen Ø, Denmark
⁸ Max-Planck-Institut für Astrophysik, Karl-Schwarzschild-Str. 1, 85748 Garching, Germany
⁹ INAF – Osservatorio Astronomico di Trieste, via G. B. Tiepolo 11, 34143 Trieste, Italy
¹⁰ INAF – Osservatorio Astrofisico di Arcetri, Largo E. Fermi, 50125 Firenze, Italy

Received: 18 June 2021
Accepted: 22 September 2021

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 to reduce misidentification 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 four 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 built a parametric mass model, which includes both cluster-scale and galaxy-scale components. The resulting model has a rms 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).