RED SUPERGIANT STARS AS COSMIC ABUNDANCE PROBES: KMOS OBSERVATIONS IN NGC 6822

Abstract

We present near-IR spectroscopy of red supergiant (RSG) stars in NGC 6822,\nobtained with the new VLT-KMOS instrument. From comparisons with model spectra\nin the J-band we determine the metallicity of 11 RSGs, finding a mean value of\n[Z] = -0.52 $\\pm$ 0.21 which agrees well with previous abundance studies of\nyoung stars and HII regions. We also find an indication for a low-significance\nabundance gradient within the central 1 kpc. We compare our results with those\nderived from older stellar populations and investigate the difference using a\nsimple chemical evolution model. By comparing the physical properties\ndetermined for RSGs in NGC 6822 with those derived using the same technique in\nthe Galaxy and the Magellanic Clouds, we show that there appears to be no\nsignificant temperature variation of RSGs with respect to metallicity, in\ncontrast with recent evolutionary models.\n