The Araucaria Project: The Local Group Galaxy WLM—Distance and Metallicity from Quantitative Spectroscopy of Blue Supergiants

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 red giant branch. This difference is within the 1 σ 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.

Based on VLT observations for ESO Large Program 171.D-0004.