Red Supergiants as Cosmic Abundance Probes

¹ Astrophysics Research Institute, Liverpool John Moores University, Egerton Wharf, Birkenhead CH41 1LD, UK
² Institute for Astronomy, University of Hawaii, 2680 Woodlawn Drive, Honolulu, HI, 96822, USA
³ Laboratoire Univers et Particules de Montpellier, Université Montpellier 2, CNRS, 34095 Montpellier, France
⁴ Max-Planck-Institute for Astrophysics, Karl-Schwarzschild-Str.1, 85741 Garching, Germany
⁵ UK Astronomy Technology Centre, Royal Observatory Edinburgh, Blackford Hill, Edinburgh EH9 3HJ, UK

Abstract

The chemical abundances of galaxies provide key constraints to models of their formation and evolution. Unfortunately, the standard method of determining abundances, from the strong emission lines of Hii-regions, is well-known to be subject to large systematic errors, particularly at high metallicities. To address this problem we are currently working on a project to measure a galaxy’s chemical abundances from spectral analysis of individual RSGs. By focussing on a spectral window in the J-band which contains few molecular lines, we are able to derive accurate chemical abundances from relatively low resolution data. In fact, we show that this technique can operate at distances of 3–4 Mpc using the VLT, and a factor of 10 further if we target massive RSG-dominated star clusters. Furthermore, in the ELT-era, we show that we can perform abundance analysis on individual stars out to 70 Mpc, and redshifts of 0.1 for star clusters.