Astronomy and Astrophysics, volume 445, 69-77 (2006/1-1)
Near-IR photometry of asymptotic giant branch stars in the dwarf elliptical galaxy NGC 147.
SOHN Y.-J., KANG A., RHEE J., SHIN M., CHUN M.-S. and KIM H.-I.
Abstract (from CDS):
Near-infrared J, H and K' images were used to investigate the stellar contents of the asymptotic giant branch (AGB) population in the nearby dwarf elliptical galaxy NGC 147. The obtained (K, J-K) and (K, H-K) color-magnitude diagrams contain stars of AGB and red giant branch populations, where the former consists of a group of bright blue stars, a dominant population of M giant and a red C star population. We identified 91 AGB C stars in NGC 147 with the mean absolute magnitude and colors of <MK≥-7.56, <(J-K)0≥1.81 and <(H-K)0≥0.74. The estimated number ratio of C stars to M giant stars (C/M) is 0.16±0.02. The estimated local C/M ratios of 0.14±0.02 for the inner region (r<70'') and 0.19±0.03 for the outer region (r>70'') indicate a weak radial gradient. The mean bolometric magnitude of 91 C stars in NGC 147 is <Mbol≥-4.32±0.49. The bolometric luminosity function of M giant stars in NGC 147 extends up to Mbol=-5.8mag, and that of only C stars spans -5.6<Mbol←3.5. The color histograms of AGB stars in (J-K) and (H-K) show a main peak containing M giant stars, a red tail containing C stars with a weak excess, and a blue excess possibly due to bright blue foreground stars and AGB stars younger than M giants. The comparison of the theoretical isochrone models with the color distribution and the brightness of AGB stars indicates that most of the bright M giants in NGC 147 were formed at log(tyr)∼8.4 with a range of 8.2∼8.6. Ages of the majority of M giant stars in NGC 147 are similar to those of younger M giant stars in its companion NGC 185, while their formation occurred more recently than the older M giant stars in NGC 185 by ∼2Gyr.
galaxies: individual: NGC 147 - galaxies: stellar content - stars: AGB and post-AGB
VizieR on-line data:
<Available at CDS (J/A+A/445/69): table2.dat>
Table 2: [SKR2006] NN (Nos 1-91).
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