JWST LEGGOS Survey

LEGGOS I Submitted — Khullar et al. 2026

LEGGOS LEnsing and Galaxy Growth:
Observing Substructures

A JWST survey resolving clumpy star formation and quenching in eight gravitationally lensed galaxies at z = 2–4, probing 10–200 pc physical scales in unprecedented detail with NIRSpec/Integral Field Spectroscopy and NIRCam Imaging.

Explore the Science Read the Papers →

LEGGOS mosaic — all eight JWST NIRCam lensed galaxy targets

JWST NIRCam RGB mosaics of all eight LEGGOS targets. Gold squares mark NIRSpec/IFS footprints. Eight lensed arcs at cosmic noon, hosting >300 resolved clumps at 10–200 pc physical scales.

Gravitational lensing — how it works

Gravitational lensing animation — light rays bending around a massive galaxy

SGAS 2111−0114 · z = 2.86

SGAS 2111-0114 JWST NIRCam with critical curve

Science

What physics is LEGGOS aiming to understand?

By combining JWST's resolving power with the natural magnification of gravitational lensing, LEGGOS addresses open questions about how galaxies build up — and shut down — their stellar mass at cosmic noon.

Star-forming clumps

What are star-forming clumps, and how do they form?

Giant clumps at z ≈ 2–3 may trace disk fragmentation driven by turbulent gas accretion, or merger-induced starburst events. LEGGOS resolves individual clumps at 10–200 pc scales with NIRSpec IFS spectroscopy, measuring ages, metallicities, and ionization conditions.

Clump migration & quenching

Do clumps migrate inward and trigger central quenching?

In the "clumpy bulge" model, gas-rich clumps spiral inward via dynamical friction, depositing enriched material that quenches the host. We measure stellar population gradients to test whether inner regions are older and more metal-rich.

Lyman continuum leakage

Can high-z clumps produce ionizing radiation that escapes?

The Sunburst Arc (z = 2.37) is the most magnified LyC leaker known. LEGGOS maps its ionization structure with NIRSpec IFS, probing density-bounded H II regions — a mechanism relevant to cosmic reionization at z > 6.

Galaxy-scale feedback

How does feedback regulate star formation across the disc?

NIRSpec IFS of [O III], Hα, and [N II] across each target constrains ionization and metallicity gradients. Combined with lens models at physical scales, we test whether stellar feedback efficiently quenches clumps or the broader disc.

Survey Design

Programs

GO 4125 (Cycle 2), GO 3843 (Cycle 2), GO 2555

Spectroscopy

NIRSpec IFS G235M/G395M; R ≈ 1000

Imaging

NIRCam F115W, F210M, F444W (RGB)

Lens Modeling

Parametric models per target; source-plane reconstruction at 10–200 pc

Data Status

MAST Archive ↗ Zenodo ↗

Redshift Range

z = 2.370 – 3.625

Magnification

μ ≈ 5–40 per target

Targets

Eight lensed galaxies at cosmic noon

Each target is a gravitationally lensed galaxy at z = 2–4, magnified by a foreground cluster into a bright extended arc — enabling rest-frame optical IFS at sub-100 pc resolution.

SGAS 1110+6459

z = 2.481

GO 4125 · GO 3843

SGAS 1527+0652

z = 2.762

GO 4125

Sunburst Arc

z = 2.370

GO 2555

SGAS 1429+1202

z = 2.825

GO 4125

SGAS 2111−0114

z = 2.858

GO 4125

SGAS 1050+0017

z = 3.625

GO 4125

Cosmic Eye

z = 3.074

GO 4125

SGAS 1226+2150

z = 2.926

GO 1355

Collaboration

The LEGGOS Team

Led by astronomers across institutions on three continents.

NIRSpec / IFS Spectroscopy

NIRCam Photometry

Stellar Pop. Synthesis & ML Modeling

Lens Modeling

Taylor Hutchison

Co-I · NIRSpec Lead

NASA Goddard / UMBC

Brian Welch

Co-I · NIRSpec Lead

ISSI

Michael Florian

Survey Co-PI · NIRCam Lead

University of Arizona

Gourav Khullar

Survey Co-PI · SED Fitting & ML Lead

U. of Washington

Julissa Sarmiento

Graduate Researcher

U. of Washington

Keren Sharon

Co-I · Lens Modeling Lead

U. of Michigan

Jane R. Rigby

Co-Investigator

NASA Goddard SFC

Matthew B. Bayliss

Co-PI

U. of Cincinnati

Mike Gladders

Co-Investigator

UChicago

Dylan Berry

Graduate Researcher

U. of Washington

Alex Ross

Graduate Researcher

U. of Washington

Guillaume Mahler

Co-Investigator

U. of Liège

Emil Rivera-Thorsen

Co-I · IFU Pipeline Lead

Stockholm University

Nikko Cleri

Co-Investigator

Penn State

Håkon Dahle

Co-Investigator

University of Oslo

Rion Oh

Graduate Researcher

UWashington / KAIST

Pedram Abedi

Co-Investigator

U. of Michigan

Catherine Cerny (UMichigan) Aleena Ebey (UCincinnati) Cole Panzer (UCincinnati) Amrit Srivastava (UArizona) J.W. Kulp (UArizona) Connor Luettgenau (Penn State) Sedona Price (STScI) Erik Solhaug (UChicago) Suhyeon Choe (Stockholm)

John Chisholm (UT Austin) Rachel Bezanson (UPittsburgh) Keunho Kim (IPAC) Isaac Sierra (UC Davis) Riley Owens (Berkeley) Josh Roberson (UCincinnati) Evgenia Lamprou (Stockholm) Jacqueline Antwi-Danso (Toronto) Arianna Long (UWashington)

Irene Shivaei (INTA-CIS, Spain) Aliza Beverage (Carnegie) David Setton (Princeton) Alaina Einsig (UMichigan) Grace Olivier (Carnegie) Kate Napier (Rubin/LSST) Jess Werk (UWashington) Kate Whitaker (UMass.) Tim Miller (NorthWestern)

Publications

LEGGOS & Related Papers

Click any paper to view details, abstract, and author list.

LEGGOS Survey Papers

LEGGOS I

The JWST LEGGOS Survey: Unpacking the Nature of Clumpy Star Formation and Quenching in Gravitationally Lensed Galaxies beyond Cosmic Noon

Khullar, Florian, Bayliss, Hutchison, Welch, Sharon, Rigby et al.arXiv:2606.20845

2026→

LEGGOS II

A Strong Lens Model and Source-Plane Projection of SGASJ111020.0+645950.8 at z=2.48

Abedi, Sharon, Hutchison, Bayliss, Florian, Khullar et al.arXiv:2606.20804

2026→

LEGGOS III

Mapping Star Formation and Dust with SUMAC, a UMAP and Clustering Framework

Ross, Khullar, Hutchison, Berry, Rivera-Thorsen, Mahler, Welch et al.arXiv:2606.20801

2026→

LEGGOS IV

A Shocking Lack of Evidence for Shocks at Sub-kiloparsec Scales at 2 < z < 4

Cleri, Hutchison, Welch, Khullar, Bayliss, Dahle, Florian, Gladders et al.arXiv:2609.07850

2026→

LEGGOS V

Direct Abundances of N, O, Ne, S, and Ar in Five Lensed Galaxies at Cosmic Noon

Welch, Khullar, Hutchison, Sharon, Abedi, Bayliss, Florian, Berry, Cleri et al.arXiv:2609.07851

2026→

Sunburst Arc

2026

The Sunburst Arc with JWST. IV. The Importance of Interaction, Turbulence, and Feedback for Lyman-continuum Escape

Rivera-Thorsen, Welch, Hutchison et al.2026ApJ..1000..204R

2026→

2025

The Sunburst Arc with JWST. II. Observations of an Eta Carinae Analog at z = 2.37

Choe, Rivera-Thorsen, Dahle et al.2025A&A...698A..16C

2025→

2025

Deciphering Spatially Resolved Lyman-Alpha Profiles in Reionization Analogs: The Sunburst Arc at Cosmic Noon

Solhaug, Chen, Rivera-Thorsen et al.2025OJAp....8E..35S

2025→

2025

The Sunburst Arc with JWST. III. An Abundance of Direct Chemical Abundances

Welch, Rivera-Thorsen, Rigby et al.2025ApJ...980...33W

2025→

2024

The Sunburst Arc with JWST. I. Detection of Wolf-Rayet Stars Injecting Nitrogen into a Low-metallicity, z=2.37 Proto-globular Cluster

Rivera-Thorsen, Chisholm, Welch et al.2024A&A...690A.269R

2024→

Waz Arc (COOL J1241+2219)

2025

JWST & the Waz Arc I: Spatially Resolving the Physical Conditions within a Post-Starburst Galaxy at Redshift 5 with NIRSpec IFS

Hutchison, Khullar, Rigby, Welch, Florian, Sharon et al.arXiv:2512.02000

2025→

2024

COOL-LAMPS VI: Lens Model and New Constraints on the Properties of COOL J1241+2219, a Bright z=5 Lyman Break Galaxy

Klein, Sharon, Napier, Gladders, Khullar, Bayliss, Dahle et al.arXiv:2401.10168

2024→

2021

COOL-LAMPS I: An Extraordinarily Bright Lensed Galaxy at Redshift 5.04

Khullar, Gladders, Bayliss, Sharon, Dahle et al.arXiv:2011.06601

2021→

JWST ERS TEMPLATES

2025

JWST Early Release Science Program TEMPLATES: Targeting Extremely Magnified Panchromatic Lensed Arcs and Their Extended Star Formation

Rigby, Vieira, Phadke, Hutchison, Welch, Bayliss, Florian, Gladders, Khullar, Sharon et al.2025ApJ...978..108R

2025→

2024

TEMPLATES: A Robust Outlier Rejection Method for JWST/NIRSpec Integral Field Spectroscopy

Hutchison, Welch, Rigby et al.2024PASP..136d4503H

2024→

2024

TEMPLATES: Direct Abundance Constraints for Two Lensed Lyman-break Galaxies

Welch, Olivier, Hutchison et al.2024ApJ...975..196W

2024→

2023

JWST's TEMPLATES for Star Formation: The First Resolved Gas-phase Metallicity Maps of Dust-obscured Star-forming Galaxies at z~4

Birkin, Hutchison, Welch et al.2023ApJ...958...64B

2023→

2023

TEMPLATES: Tests of NIRSpec Observing Strategy, using SGAS1723

Welch, Rigby, Hutchison et al.2023RNAAS...7...17W

2023→

2022

HST-Based Lens Model of SDSS J1226+2152, in Preparation for JWST-ERS TEMPLATES

Sharon, Cerny, Rigby et al.arXiv:2207.05709

2022→

Resources

Related surveys & tools

🌌

MEGaSaURA

Magellan rest-frame UV spectra for 7 of the 8 LEGGOS targets — the foundational spectroscopic atlas on which LEGGOS builds.

🔭

UNCOVER

JWST Treasury survey of the Abell 2744 cluster field, complementary deep NIRCam imaging overlapping with LEGGOS science goals.

⭐

GLIMPSE

Gravitational Lensing Investigations of Mass, Phenomenology, and Structure of Emission — lensed galaxy spectroscopy with VLT/MUSE and JWST.

🌠

PHANGS / FEAST

Local-universe analogue surveys from JWST and Hubble providing resolved clump templates at z = 0 for comparison with LEGGOS.

Access the LEGGOS data

All reduced data, lens models, and pipeline code are publicly available through MAST and Zenodo.

MAST Archive Contact the Team

Contact

Get in touch

Survey PIs

gkhullar@uw.edu — Gourav Khullar florianm@arizona.edu — Michael Florian

Data & Code

Zenodo — Survey logo & assets MAST — JWST data archive GO-4125 · GO-3843 · GO-2555