Stellar Properties of Asymptotic Giant Branch Stars in the Dwarf Irregular Galaxy IC 1613

摘要

Broadband near-infrared images obtained with the WIRCam array of the Canada-France-Hawaii Telescope are used to investigate the properties of resolved asymptotic giant branch (AGB) stars in the dwarf irregular galaxy IC 1613. Combining our JHK_S data with optical photometric data, AGB stars were selected in color-magnitude diagrams covering a wide range of wavelength. We examined the distribution of AGB stars in the (J-K_s, H-K_s) color-color diagram, and distinguished 140 carbon-rich and 306 oxygen-rich M giant AGB stars. The number ratio of C stars to M giants (C/M) was estimated, and the metallicity of IC 1613 was derived using the C/M ratio. We also examined the local C/M ratio as a function of radial distance from the center of the galaxy, and found a small negative gradient.