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Issue A&A
Volume 437, Number 1, July I 2005
Page(s) 61 - 68
Section Extragalactic astronomy
DOI http://dx.doi.org/10.1051/0004-6361:20052692



A&A 437, 61-68 (2005)
DOI: 10.1051/0004-6361:20052692

Near-IR photometry of asymptotic giant branch stars in the dwarf elliptical galaxy NGC 185

A. Kang1, 2, Y.-J. Sohn1, 2, J. Rhee1, 2, M. Shin1, M.-S. Chun1 and Ho-Il Kim3

1  Department of Astronomy, Yonsei University, Seoul 120-749, Korea
    e-mail: sohnyj@yonsei.ac.kr;breeze82@galaxy.yonsei.ac.kr
2  Center for Space Astrophysics, Yonsei University, Seoul 120-749, Korea
3  Korea Astronomy and Space Science Institute, Daejeon 305-348, Korea

(Received 13 January 2005 / Accepted 4 March 2005 )

Abstract
J, H and K' images obtained with the Canada-France-Hawaii Telescope were used to investigate the stellar contents of the asymptotic giant branch (AGB) in the dwarf elliptical galaxy NGC 185. The bright parts of (K, J-K) and (K, H-K) color-magnitude diagrams consist of a group of bright blue stars, a dominant population of M-giants and a red C star population. There were 73 C stars with a mean magnitude of $\langle K\rangle = 16.26\pm0.38$, corresponding to $\langle M_K\rangle = -7.93$, and mean colors of $\langle (J-K)_0\rangle = 2.253$ and $\langle (H-K)_0\rangle = 0.865$. The number ratio of C stars to M-giants was estimated to be $0.11\pm0.04$ without any radial gradient from the center of NGC 185. The (J-K) and (H-K) color distributions of AGB stars showed an M-giant peak and blue and red tails, where the latter two correspond to AGB stars younger than those along M-giant peak and C stars. The bolometric luminosity functions of M-giants and C stars indicate that the M-giant AGB sequence has terminated at $M_{\rm bol} = -6.2$, while the most luminous C star has $M_{\rm bol} = -5.5$. The bolometric luminosity function of C stars in NGC 185 is very similar to that of recent literature values derived from Vi band photometry. The logarithmic slope of the luminosity function for bright M-giant stars was estimated to be $0.83\pm0.02$ in K band. Theoretical isochrone models, compared with the observed near-infrared photometric properties of AGB stars, indicate that star formation in NGC 185 has a wide range of ages with possibly two different epochs of star formation.


Key words: galaxies: individual: NGC 185 -- galaxies: stellar content -- stars: AGB and post-AGB

SIMBAD Objects in preparation
Tables at the CDS



© ESO 2005

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