The Tip of Red Giant Branch Distances to Nearby Dwarf Galaxies WLM and Sextans A with JWST

TL;DR

This study uses JWST to measure distances to dwarf galaxies WLM and Sextans A via the TRGB method, achieving high precision and confirming previous results, with potential to improve cosmic distance calibration.

Contribution

First application of JWST's high-resolution imaging to measure TRGB distances to dwarf galaxies, enhancing accuracy and establishing new calibration anchors.

Findings

Distance uncertainties are below 3%.

Results agree with previous TRGB, Cepheid, and JAGB measurements.

Potential to reduce TRGB distance uncertainty below 2%.

Abstract

Distance measurements to extragalactic systems that are both accurate and precise are cornerstones of modern astrophysics, underpinning the calibration of standard candles and the determination of the Hubble constant. Dwarf galaxies, such as Wolf-Lundmark-Melotte (WLM) and Sextans A, provide valuable laboratories for testing distance scales across different stellar populations. In this work, we utilize the high sensitivity and spatial resolution of the James Webb Space Telescope (JWST) to measure the distances to WLM and Sextans A using the tip of the red giant branch (TRGB) method. Adopting the TRGB absolute magnitude calibrated by NGC 4258, we determine distance moduli of $\mu_{\mathrm{0,WLM}} = 24.977 \pm 0.018 (\mathrm{stat}) \pm 0.056 (\mathrm{sys})$ mag for WLM and $\mu_{\mathrm{0,SexA}} = 25.740 \pm 0.011 (\mathrm{stat}) \pm 0.057 (\mathrm{sys})$ mag for Sextans A. Our results are consistent within a 3% distance uncertainty with previous measurements based on TRGB, Cepheids, and J-Region Asymptotic Giant Branch (JAGB) methods. With improved distance measurements in the future, these two galaxies have the potential to serve as additional anchor points for TRGB calibration, aiming to reduce the TRGB-based distance uncertainty to below 2%.