J/A+A/454/717 Near-IR photometry of C and AGB stars in NGC 6822 (Kang+, 2006)
The evolved asymptotic giant branch stars in the central bar of the dwarf
irregular galaxy NGC 6822.
Kang A., Sohn Y.-J., Kim H.-I., Rhee J., Kim J.-W., Hwang N., Lee M.G,
Kim Y.-C., Chun M.-S.
<Astron. Astrophys. 464, 717 (2006)>
=2006A&A...454..717K 2006A&A...454..717K
ADC_Keywords: Galaxies, photometry ; Stars, giant ; Stars, carbon ;
Photometry, infrared
Keywords: galaxies: individual: NGC 6822 - galaxies: stellar content -
stars: AGB and post-AGB
Abstract:
Images of JHK and gi obtained with the Canada-France-Hawaii Telescope
are used to investigate the stellar contents of the resolved
asymptotic giant branch (AGB) population in the area of 3.6'x6.3' on
the central bar of the dwarf irregular galaxy NGC 6822. The upper
envelope of near-infrared (J-K, K) and (H-K, K) color-magnitude
diagrams (CMDs) shows four components of main-sequence stars,
foreground stars, massive supergiants, and AGB stars. These components
are also noticeable in the bright part of (g-i, g) CMD. We select AGB
stars in NGC 6822 from the (g-K, g) CMD, which has a long spectral
wavelength base line in the color index. There are 141 C stars with a
mean absolute magnitude of <MK≥-7.60±0.50, and with mean colors
of <(J-K)o≥1.77±0.41, and <(H-K)o≥0.75±0.28. The number
ratio of C stars to M-giants (C/M) is estimated as 0.27±0.03, while
the northern part of the bar has a somewhat lower C/M ratio than the
southern part. The (J-K) and (H-K) color distributions of AGB stars
contain a main peak of M-giant stars and a red tail of C stars. The
broad color distributions for M-giants indicate that NGC 6822 has a
wide range of intermediate ages with a peak at log(tyr)∼9.0. The
MK luminosity function (LF) for C stars in the central bar of
NGC 6822 is likely to be a Gaussian distribution, while the LF of C
stars in the southern part is slightly skewed to the brighter side
than in northern part. The mean bolometric magnitude of 141 C stars in
NGC 6822 is <Mbol≥-4.36±0.54. The bolometric LF for M-giants
extends up to Mbol=-6.5, while the one for C stars spans
-5.8<Mbol←3.5.
Description:
Table 2 lists the equatorial coordinates, near-infrared photometric
properties of 141 C stars, and color indices in RI bands of
cross-identified C stars with Letarte et al. (2002, Cat.
J/AJ/123/832).
Table 3 lists those of the rest 522 M-giants of AGB stars.
File Summary:
--------------------------------------------------------------------------------
FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
table2.dat 108 141 Coordinates and photometric properties for
141 C stars
table3.dat 96 522 Coordinates and photometric properties for
522 M-giant stars
--------------------------------------------------------------------------------
See also:
J/AJ/123/832 : C star population in NGC 6822 (Letarte+, 2002)
Byte-by-byte Description of file: table2.dat table3.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
2- 4 I3 --- Seq [1/522] Sequential number of C star (table2)
or M-giant star (table3)
7- 8 I2 h RAh Right Ascension J2000 (hours)
10- 11 I2 min RAm Right Ascension J2000 (minutes)
13- 17 F5.2 s RAs Right Ascension J2000 (seconds)
19 A1 --- DE- Declination J2000 (sign)
20- 21 I2 deg DEd Declination J2000 (degrees)
23- 24 I2 arcmin DEm Declination J2000 (minutes)
26- 29 F4.1 arcsec DEs Declination J2000 (seconds)
32- 37 F6.3 mag Kmag K band magnitude
39- 43 F5.3 mag e_Kmag Error of K magnitude
46- 50 F5.3 mag J-K (J-K) color index
52- 56 F5.3 mag e_J-K Error of (J-K) color index
59- 63 F5.3 mag H-K (H-K) color index
65- 69 F5.3 mag e_H-K Error of (H-K) color index
72- 77 F6.3 mag gmag g band magnitude
79- 83 F5.3 mag e_gmag Error of g magnitude
85- 90 F6.3 mag g-i (g-i) color index
92- 96 F5.3 mag e_g-i Error of (g-i) color index
99-103 F5.3 mag R-I ? (R-I) color index by Letarte et al., 2002,
Cat. J/AJ/123/832 (1)
106-108 I3 --- [LDB2002] ? ID number of Letarte et al., 2002,
Cat. J/AJ/123/832 (1)
--------------------------------------------------------------------------------
Note (1): Only for table2.dat objects.
--------------------------------------------------------------------------------
Acknowledgements:
Aram Kang, breeze82(at)galaxy.yonsei.ac.kr
(End) Patricia Vannier [CDS] 16-Mar-2006