The Cosmic Telescope That Lenses the Sunburst Arc, PSZ1 G311.65–18.48: Strong Gravitational Lensing Model and Source Plane Analysis*

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 of them. We measure a projected cluster core mass of M(<250 kpc) = 2.93 − 0.02 + 0.01 × 10 14 M ⊙. The two least magnified but complete images of the Sunburst Arc’s source galaxy are magnified by ∼13×, while the LyC clump is magnified by ∼4–80×. 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° (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.

Nitrogen-enriched, Highly Pressurized Nebular Clouds Surrounding a Super Star Cluster at Cosmic Noon

“…Such magnification variation across a small angular scale 0 5 is not well-described by the large-scale cluster lens, and could be caused by a nearby invisible dark matter subhalo. While lens modeling predicts that image (9) and image (10) should have similar magnifications (Pignataro et al 2021;Sharon et al 2022), photometric measurements from Vanzella et al (2022b) also confirmed a significant flux ratio of 2, albeit lower than those found in this work. This might be a hint for spatial fine structures in the lens model near images (9) and (10).…”

“…While Vanzella et al (2022b) predicted μ r = 1.2-1.3, Diego et al (2022) presented two models with μ r = 1.4, and μ r = 2.1, respectively. The source-plane reconstruction results of Sharon et al (2022) imply μ r = 1.6-2. We use a high fiducial value μ r = 2.…”

“…where μ r is the radial magnification. The angular half-width for the nebula comprised of the low-pressure clouds at larger The absolute magnification factors of the various lensed images are uncertain, as existing lens models reproduce image locations well but not magnification ratios (Sharon et al 2022). There is also uncertainty for μ r , whose value should vary moderately between lensed images.…”

“…It is the brightest known gravitationally lensed starburst galaxy at Cosmic Noon. A lensed compact star-forming clump was found on the arc, which shows twelve different lensed avatars arising from an Einstein ring configuration disrupted by secondary lensing caustics cast by multiple cluster member galaxies (Rivera-Thorsen et al 2019;Pignataro et al 2021;Diego et al 2022;Sharon et al 2022).…”

JWST/NIRCam Probes Young Star Clusters in the Reionization Era Sunrise Arc

“…Pioneering works in the pre-James Webb Space Telescope (JWST) era have already reported on the detection of tiny starforming regions at cosmological distances by combining Hubble Space Telescope (HST) imaging and gravitational lensing (e.g., Ellis et al 2001) that have only recently been recognized as globular cluster precursor (GCP) candidates (Vanzella et al 2017(Vanzella et al , 2019; see also Elmegreen et al 2021;Welch et al 2023), along with the use of deep Very Large Telescope (VLT) Multi Unit Spectroscopic Explorer (MUSE) spectroscopy performed on the Hubble Frontier Fields (e.g., Vanzella et al 2021) or exploiting superlensed arcs like the Sunburst (Rigby et al 2017;Rivera-Thorsen et al 2019;Sharon et al 2022;Vanzella et al 2022a).…”