Assessment of the near infrared identification of carbon stars II. The local group galaxies IC 1613 and NGC 3109

摘要

Context. Thousands of C stars have been identified in Local Group galaxies using narrow band photometry. To survey C stars at larger distances and alternative to the narrow-band approach is needed.Aims. We obtain, from ESO Archive data, NIR magnitudes and colours of previously known C stars in two dwarf irregular Local Group galaxies, namely IC 1613 and NGC 3109.Methods. We compare the NIR magnitudes and colours of the C star populations, previously identified from narrow band techniques to estimate the star formation history of their intermediate-age populations.Results. We demonstrate that the photometric properties of C stars show a wider range in the NIR than in the optical. As confirmed by models we see, among the four galaxies investigated with a 0.7 dex metallicity range, little if any metallicity effect in the C star colour distribution.