The Araucaria Project: the Local Group Galaxy WLM--Distance and metallicity from quantitative spectroscopy of blue Supergiants

TL;DR

This study uses quantitative spectroscopy of blue supergiants in the WLM galaxy to determine its distance and metallicity, providing results consistent with other methods within uncertainties.

Contribution

It introduces a spectroscopic method to measure galaxy distances and metallicities using blue supergiants, complementing traditional photometric techniques.

Findings

Distance modulus of 24.99 mag (995 Kpc) with 0.10 mag uncertainty.

Average stellar metallicity of -0.87 dex relative to solar.

Spectroscopic analysis yields consistent results with other distance indicators.

Abstract

The quantitative analysis of low resolution spectra of A and B supergiants is used to determine a distance modulus of 24.99 +/- 0.10 mag (995 +/- 46 Kpc) to the Local Group galaxy WLM. The analysis yields stellar effective temperatures and gravities, which provide a distance through the Flux weighted Gravity--Luminosity Relationship (FGLR). Our distance is 0.07 mag larger than the most recent results based on Cepheids and the tip of the RGB. This difference is within the 1-sigma overlap of the typical uncertainties quoted in these photometric investigations. In addition, non-LTE spectral synthesis of the rich metal line spectra (mostly iron, chromium and titanium) of the A supergiants is carried out, which allows the determination of stellar metallicities. An average metallicity of -0.87 +/- 0.06 dex with respect to solar metallicity is found.