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

Kavli Affiliate: Michael D. Gladders

| First 5 Authors: Keren Sharon, Guillaume Mahler, T. Emil Rivera-Thorsen, Hakon Dahle, Michael D. Gladders

| Summary:

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/-0.02×10^14M_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 1×2 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.

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