Red Supergiants as Cosmic Abundance Probes: The Sculptor Galaxy NGC 300

TL;DR

This study uses J-band spectroscopy of red supergiants in NGC 300 to measure metallicity and its gradient, demonstrating the method's effectiveness beyond the Local Group.

Contribution

First application of J-band spectroscopic technique to red supergiants outside the Local Group for metallicity measurement.

Findings

Central metallicity of [Z]= -0.03 +/- 0.05

Metallicity gradient of -0.083 +/- 0.014 dex/kpc

Method aligns with previous blue supergiant and H II-region studies

Abstract

We present a quantitative spectroscopic study of twenty-seven red supergiants in the Sculptor Galaxy NGC 300. J-band spectra were obtained using KMOS on the VLT and studied with state of the art synthetic spectra including NLTE corrections for the strongest diagnostic lines. We report a central metallicity of [Z]= -0.03 +/- 0.05 with a gradient of -0.083 +/- 0.014 [dex/kpc], in agreement with previous studies of blue supergiants and H II-region auroral line measurements. This result marks the first application of the J-band spectroscopic method to a population of individual red supergiant stars beyond the Local Group of galaxies and reveals the great potential of this technique.