Near-IR photometry of asymptotic giant branch stars in the dwarf elliptical galaxy NGC 185
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
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
and 
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 
, corresponding to 
,
and mean colors of 
and 
. The number ratio of C stars to
M-giants was estimated to be 
without any radial gradient from the center of NGC 185.
The 
and 
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 
, while the most luminous C star
has 
. 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 
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
© ESO, 2005