Near-IR photometry of asymptotic giant branch stars in the dwarf elliptical galaxy NGC 147

Young-Jong Sohn, A. Kang, J. Rhee, M. Shin, M. S. Chun, Ho Il Kim

Research output: Contribution to journalArticle

18 Citations (Scopus)

Abstract

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 = -5.8 mag, 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 ∼2 Gyr.

Original languageEnglish
Pages (from-to)69-77
Number of pages9
JournalAstronomy and Astrophysics
Volume445
Issue number1
DOIs
Publication statusPublished - 2006 Jan 1

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giant stars
carbon stars
M stars
asymptotic giant branch stars
elliptical galaxies
dwarf galaxies
photometry
blue stars
color
histogram
stars
near infrared
color-magnitude diagram
diagram
histograms
brightness
luminosity
gradients
young

All Science Journal Classification (ASJC) codes

  • Space and Planetary Science

Cite this

Sohn, Young-Jong ; Kang, A. ; Rhee, J. ; Shin, M. ; Chun, M. S. ; Kim, Ho Il. / Near-IR photometry of asymptotic giant branch stars in the dwarf elliptical galaxy NGC 147. In: Astronomy and Astrophysics. 2006 ; Vol. 445, No. 1. pp. 69-77.
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abstract = "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 = -5.8 mag, 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 ∼2 Gyr.",
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Near-IR photometry of asymptotic giant branch stars in the dwarf elliptical galaxy NGC 147. / Sohn, Young-Jong; Kang, A.; Rhee, J.; Shin, M.; Chun, M. S.; Kim, Ho Il.

In: Astronomy and Astrophysics, Vol. 445, No. 1, 01.01.2006, p. 69-77.

Research output: Contribution to journalArticle

TY - JOUR

T1 - Near-IR photometry of asymptotic giant branch stars in the dwarf elliptical galaxy NGC 147

AU - Sohn, Young-Jong

AU - Kang, A.

AU - Rhee, J.

AU - Shin, M.

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AU - Kim, Ho Il

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N2 - 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 = -5.8 mag, 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 ∼2 Gyr.

AB - 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 = -5.8 mag, 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 ∼2 Gyr.

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