# Galaxy cluster strong lensing cosmography: cosmological constraints from a sample of regular galaxy clusters

**Authors:** G. B. Caminha, S. H. Suyu, C. Grillo, P. Rosati  
**arXiv:** [2110.06232](https://arxiv.org/abs/2110.06232)  
**Date:** 2021-10-12  
**Summary page:** https://www.summarizepaper.com/en/paper/2110.06232v1/

## Key points

- The study investigates the potential of cluster strong lensing cosmography as a probe for understanding the background geometry of the Universe.
- The researchers utilize a sample of five cluster strong lenses to measure cosmological parameters and combine them with data from classical probes.
- Strong lensing alone yields significant constraining power on two key parameters: the total matter density of the Universe ($\Omega_{\rm m}$) and the equation of state parameter for dark energy ($w$).
- When combined with posterior distributions in a flat $w$CDM cosmology, constraints from Cosmic Microwave Background (CMB) improve by factors of 2.5 and 4.0 on $\Omega_{\rm m}$ and $w$, respectively.
- In a scenario where the equation of state for dark energy evolves with redshift, strong lensing constraints are consistent with a cosmological constant ($w=-1$).
- In a curved cosmology, strong lensing can accommodate a wide range of values for the curvature parameter $\Omega_{\rm k}$.
- Strong lensing constraints are complementary to measurements from other cosmological probes such as CMB, baryon acoustic oscillations (BAOs), and Type Ia supernovae (SNe).
- Cluster strong lensing cosmography has potential as an effective tool for future studies into our Universe's background geometry.

## Summary

In the study titled "Galaxy cluster strong lensing cosmography: cosmological constraints from a sample of regular galaxy clusters," authors G. B. Caminha, S. H. Suyu, C. Grillo, and P. Rosati investigate the potential of cluster strong lensing cosmography as a probe for understanding the background geometry of the Universe. They utilize a sample of five cluster strong lenses to measure cosmological parameters and combine them with data from classical probes. The researchers adopt four different cosmological scenarios to assess degeneracies and evaluate the effectiveness of strong-lensing cosmography in constraining the background geometry of the Universe. Their analysis reveals significant constraining power on two key parameters: the total matter density of the Universe ($\Omega_{\rm m}$) and the equation of state parameter for dark energy ($w$). For a flat $w$CDM (cold dark matter) cosmology, they find that strong lensing alone yields $\Omega_{\rm m} = 0.30_{-0.11}^{+0.09}$ and $w=-1.12_{-0.32}^{+0.17}$. Notably, when combined with posterior distributions in this cosmological model, they demonstrate that constraints from the Cosmic Microwave Background (CMB) improve by factors of 2.5 and 4.0 on $\Omega_{\rm m}$ and $w$, respectively. In a scenario where the equation of state for dark energy evolves with redshift, their strong lensing constraints are consistent with a cosmological constant ($w=-1$). Additionally, in a curved cosmology, their analyses indicate that strong lensing can accommodate a wide range of values for the curvature parameter $\Omega_{\rm k}$, specifically $\Omega_{\rm k}=0.28_{-0.21}^{+0.16}$. The authors emphasize that their strong lensing constraints are complementary to and in good agreement with measurements from other cosmological probes such as those derived from observations made using the Cosmic Microwave Background (CMB), baryon acoustic oscillations (BAOs), and Type Ia supernovae (SNe). These findings highlight the potential of cluster strong lensing cosmography as an effective tool for future studies into our Universe's background geometry which has been made possible by recent advancements in observational quality using both space-based telescopes as well as ground-based observatories .