# The Carousel Lens II: Cosmological Constraints with GIGA-Lens

**Authors:** Felipe Urcelay, Xiaosheng Huang, William Sheu, Jackson H. O'Donnell, Tesla Jeltema, Demetrius Y. Williams, Sean Xu, Shrihan Agarwal, Greg Aldering, David Álvarez-García, Harsh Ambardekar, Tania M. Barone, Fuyan Bian, Adam S. Bolton, Aleksandar Cikota, Gerrit S. Farren, Karl Glazebrook, Taylor Hoyt, Aniket Jain, Tucker Jones  
**arXiv:** [2602.16077](https://arxiv.org/abs/2602.16077)  
**Date:** 2026-02-17  
**Summary page:** https://www.summarizepaper.com/en/paper/2602.16077v1/

## Key points

- Understanding dark matter and dark energy in cosmology is a challenging question.
- Strong gravitational lenses with multiple source planes provide a unique perspective on cosmological parameters.
- The ratio of deflection angles at different redshifts depends on angular-diameter distances, offering constraints on factors like matter density ($Ω_m$) and the equation of state for dark energy ($w$).
- Recent work on the Carousel Lens has provided new cosmological insights due to its relaxed core and rich array of extended images, making it well-suited for inference.
- Constraints within the $w$CDM framework derived from the Carousel Lens data are $Ω_m = 0.34^{+0.16}_{-0.13}$ and $w = -1.31^{+0.35}_{-0.32}$, accounting for statistical uncertainties and systematic errors.
- Including additional higher-redshift sources could enhance constraining power by approximately 80%.
- Results from the Carousel Lens alone in an evolving dark energy model yield constraints comparable to those from CMB observations, offering an independent avenue alongside other analyses.
- Limitations are primarily driven by systematic uncertainties, but future advancements are anticipated through reductions in systematics and integration of high-resolution imaging data from higher-redshift sources.

## Summary

In the field of cosmology, understanding the nature of dark matter and dark energy remains a central and challenging question. One method of probing these mysteries is through strong gravitational lenses with multiple source planes, which offer a unique geometric perspective on cosmological parameters. Specifically, the ratio of deflection angles at different redshifts depends solely on angular-diameter distances, providing constraints on important factors such as the matter density ($Ω_m$) and the equation of state for dark energy ($w$). Historically, constraints derived from this technique have trailed behind those obtained from other methods such as Cosmic Microwave Background (CMB) observations, Type Ia Supernovae (SNe Ia), and Baryon Acoustic Oscillations (BAO). However, recent work has presented new cosmological insights from the Carousel Lens, a cluster-scale gravitational lens featuring over 40 extended images from 11 spectroscopically confirmed sources. This lens stands out due to its relaxed core and rich array of extended images behind the main halo, making it particularly well-suited for cosmological inference. Utilizing the GIGA-Lens pipeline, researchers constructed a detailed pixel-level lens model incorporating six sources detected by the Hubble Space Telescope (HST) and four mass components. From this model, they derived constraints within the $w$CDM framework: $Ω_m = 0.34^{+0.16}_{-0.13}$ and $w = -1.31^{+0.35}_{-0.32}$ solely from data provided by the Carousel Lens. These constraints account for both statistical uncertainties and systematic errors. Furthermore, projections suggest that including four additional higher-redshift sources with similar fractional uncertainties could enhance constraining power by approximately 80%, bringing precision levels closer to those achieved by CMB and SNe Ia studies. In an evolving dark energy model ($w_0w_a$CDM), results from the Carousel Lens alone yield constraints comparable to those obtained from CMB observations, offering an independent and complementary avenue alongside SN Ia and BAO analyses. While current limitations are primarily driven by systematic uncertainties – quantified through simulations – findings demonstrate that multi-source-plane cluster lenses like the Carousel Lens hold promise in delivering competitive cosmological constraints. Future advancements are anticipated through reductions in systematics and integration of additional high-resolution imaging data from known or newly discovered higher-redshift sources.