# Measuring Cosmological Distances Using Cluster Edges as a Standard Ruler

**Authors:** Erika L. Wagoner, Eduardo Rozo, Han Aung, Daisuke Nagai  
**arXiv:** [2010.11324](https://arxiv.org/abs/2010.11324)  
**Date:** 2020-10-21  
**Summary page:** https://www.summarizepaper.com/en/arxiv-id/2010.11324v1/

## Key points

- Study explores a novel method to measure cosmological distances using galaxy clusters
- Line-of-sight velocity dispersion profile of clusters exhibits a distinct "kink"
- Researchers propose using this feature as a gravity-calibrated standard ruler
- Amplitude of velocity dispersion data can infer physical size of the cluster
- Angular scale of the "kink" can be translated into a distance measurement
- Method validated by assuming calibration from simulations
- Forecasted to measure Hubble constant with 3% precision using existing data from SDSS
- Technique can be implemented with DESI for more precise measurement at 1.3%
- Incorporating cosmological supernova data improves uncertainty to 0.7%
- Innovative approach for measuring cosmological distances in galaxy clusters' velocity dispersion profiles
- Potential application holds promise for improving understanding of cosmic expansion and refining measurements of fundamental cosmological parameters like the Hubble constant

## Summary

In their study titled "Measuring Cosmological Distances Using Cluster Edges as a Standard Ruler," Erika L. Wagoner, Eduardo Rozo, Han Aung, and Daisuke Nagai explore a novel method to measure cosmological distances using the line-of-sight velocity dispersion profile of galaxy clusters. They observe that this profile exhibits a distinct "kink" that corresponds to the spatial extent of orbiting galaxies within the cluster. The researchers propose utilizing this feature as a gravity-calibrated standard ruler. They explain that the amplitude of the velocity dispersion data can be used to infer the physical size of the cluster. By observing the angular scale of the "kink" in the profile, they can translate it into a distance measurement to the cluster. To validate their approach, they assume that the relation between cluster radius and cluster velocity dispersion can be calibrated from simulations. With existing data from the Sloan Digital Sky Survey (SDSS), they forecast that they will be able to measure the Hubble constant with 3% precision using this method. Furthermore, they discuss implementing their technique with data from the Dark Energy Spectroscopic Instrument (DESI), which would result in a more precise measurement of the Hubble constant at 1.3%. Additionally, by incorporating cosmological supernova data into their analysis, they improve the uncertainty of DESI's measurement even further to 0.7%. Overall, this study presents an innovative approach for measuring cosmological distances by leveraging features in galaxy clusters' velocity dispersion profiles. The potential application of this method with existing and future observational datasets holds promise for improving our understanding of cosmic expansion and refining measurements of fundamental cosmological parameters like the Hubble constant.