The distance to the Fornax Dwarf Spheroidal Galaxy

TL;DR

This study refines the distance to the Fornax dwarf spheroidal galaxy using multiple stellar population indicators, achieving consistent results across different methods and confirming previous measurements.

Contribution

It introduces a new method to measure the Tip of the Red Giant Branch distance and provides a comprehensive comparison of multiple stellar indicators for distance estimation.

Findings

Distance modulus from TRGB: 20.71 ± 0.07

Distance modulus from Horizontal Branch: 20.72 ± 0.06

Weighted mean distance modulus: 20.72 ± 0.04

Abstract

A large multicolour, wide-field photometric database of the Fornax dwarf spheroidal galaxy has been analysed using three different methods to provide revised distance estimates based on stellar populations in different age intervals. The distance to Fornax was obtained from the Tip of the Red Giant Branch measured by a new method, and using the luminosity of Horizontal Branch stars and Red Clump stars correc ted for stellar population effects. Assuming a reddening $E(B-V)=0.02$, the following distance moduli were derived: $(m-M)_0=20.71 \pm 0.07$ based on the Tip of the Red Giant Branch, $(m-M)_0=20.72 \pm 0.06$ from the level of the Horizontal Branch, and $(m-M)_0=20.73 \pm 0.09$ using the Red Clump method. The weighted mean distance modulus to Fornax is $(m-M)_0=20.72 \pm 0.04$. All these measurements agree within the errors, and are fully consistent with previous determinations and with the distance measurements obtained in a companion paper from near-infrared colour-magnitude diagrams.