The Cosmic Telescope that Lenses the Sunburst Arc, PSZ1 G311.65-18.48: Strong Gravitational Lensing model and Source Plane Analysis

TL;DR

This paper models the strong gravitational lensing effect of galaxy cluster PSZ1 G311.65-18.48 on the Sunburst Arc, revealing detailed source properties, magnification factors, and the cluster's mass distribution, with implications for understanding LyC emission.

Contribution

It provides a detailed strong lensing model of the cluster and source, including source size, magnification, and system configuration, using multi-wavelength data for the first time in this context.

Findings

Magnification of ~13x for the main images of the Sunburst Arc

Source size constrained to less than 50 parsecs

Identification of a possible interacting galaxy system within 6 kpc

Abstract

We present a strong lensing analysis of the cluster PSZ1 G311.65-18.48, based on Hubble Space Telescope imaging, archival VLT/MUSE spectroscopy, and Chandra X-ray data. This cool-core cluster (z=0.443) lenses the brightest lensed galaxy known, dubbed the "Sunburst Arc" (z=2.3703), a Lyman continuum (LyC) emitting galaxy multiply-imaged 12 times. We identify in this field 14 additional strongly-lensed galaxies to constrain a strong lens model, and report secure spectroscopic redshifts of four. We measure a projected cluster core mass of M(<250 kpc)=2.93+0.01/-0.02x10^14M_sun. The two least-magnified but complete images of the Sunburst Arc's source galaxy are magnified by ~13x, while the LyC clump is magnified by ~4-80x. We present time delay predictions and conclusive evidence that a discrepant clump in the Sunburst Arc, previously claimed to be a transient, is not variable, thus strengthening the hypothesis that it results from an exceptionally high magnification. A source plane reconstruction and analysis of the Sunburst Arc finds its physical size to be 1x2 kpc, and that it is resolved in three distinct directions in the source plane, 0, 40, and 75 degrees (east of North). We place an upper limit of r <~ 50 pc on the source plane size of unresolved clumps, and r<~ 32 pc for the LyC clump. Finally, we report that the Sunburst Arc is likely in a system of two or more galaxies separated by <~6 kpc in projection. Their interaction may drive star formation and could play a role in the mechanism responsible for the leaking LyC radiation.