The Asymptotic Giant Branch of NGC 205: The Characteristics of Carbon Stars and M Giants Identified fromJHK′ Images

J, H, and K' images are used to investigate the asymptotic giant branch (AGB)content of the Local Group dwarf elliptical galaxy NGC 205. The AGB on the (K,H-K) and (K, J-K) color-magnitude diagrams consists of two sequences: anear-vertical plume of giants with spectral types K and M, and a red armcontaining C stars. There are 320 C stars with M_bol < -4.1 and J-K > 1.5within 2 arcmin of the nucleus. C stars account for 10% of the integratedluminosity of AGB stars brighter than M_bol = -3.75 near the center of NGC 205,and this is in excellent agreement with what is measured in intermediate-ageclusters in the LMC. The most luminous AGB star has M_bol = -6.5, althoughvariability introduces an uncertainty of a few tenths of a magnitude when usingthis as an estimate of the AGB-tip brightness. Comparisons with models suggestthat the brightest AGB stars formed within the past 0.1 Gyr, and that theprevious episode of star formation occured a few tenths of a Gyr earlier. Theseresults are consistent with star formation in NGC 205 being triggered byinteractions with M31. These data also demonstrate that near-infrared imagingprovides an efficient means of identifying C stars in nearby galaxies.Comment: 16 pages of text; 8 postscript figures; will appear in Ap