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

Kang, A.; Sohn, Young-Jong; Rhee, J.; Shin, Meong Cheol; Chun, Mun-Suk; Kim, Ho Il

doi:10.1051/0004-6361:20052692

Cited by 23 publications

(85 citation statements)

References 44 publications

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“…The logarithmic slope of the M K s LF for the M-giant stars was measured to be 1.59 ± 0.26 by performing a least-squares fit to the magnitude of −7.7 < M K s < −6.8. The slope of the LF for the M-giant stars in IC 1613 is comparable with the slope of 1.12 ± 0.03 for NGC 6822 , but is much steeper than our previous results of slopes for dwarf elliptical galaxies, that is, 0.79 ± 0.02 for NGC 147 , 0.83 ± 0.02 for NGC 185 (Kang et al 2005), and 0.84 ± 0.01 for NGC 205 (Jung et al 2012). This comparison indicates that the dwarf irregular galaxies probably have a star-forming history for M-giant stars different from that of dwarf elliptical galaxies.…”

Section: Color Distribution and Luminosity Function Of The Agb Starssupporting

confidence: 81%

“…8, the bolometric LF of the M-giant stars extends to M bol = −4.5, and that of the C stars spans −5.7 < M bol < −2.8. The average bolometric magnitude of the C stars is M bol = −4.28 ± 0.47, which is comparable with those of C stars in dwarf galaxies, that is, M bol = −4.50 ± 0.42 in NGC 185 (Kang et al 2005), M bol = −4.32 ± 0.49 in NGC 147 , M bol = −4.24 ± 0.55 in NGC 205 (Jung et al 2012), and M bol = −4.36±0.54 in NGC 6822 ).…”

Section: Color Distribution and Luminosity Function Of The Agb Starsmentioning

confidence: 57%

“…The broad color distribution of the AGB stars indicates that the AGB stars have a wide range of ages and metallicities. In our previous studies (Kang et al 2005Sohn et al 2006;Jung et al 2012), the age ranges for the AGB stars in NGC 185, NGC 147, NGC 6822, and NGC 205 were inferred: two epochs of star formation with log (t yr ) ∼ 9.0−9.4 and 7.8−8.5 for NGC 185 (Kang et al 2005), a range of age with log (t yr ) ∼ 8.2−8.6 for NGC 147 ), a range of age with log (t yr ) ∼ 8.0−10.0 for NGC 6822 , and an epoch of age with log (t yr ) ∼ 9.0−9.7 for NGC 205 (Jung et al 2012). Davidge (2005) also examined the age range for the M-giant stars in NGC 147, NGC 185, and NGC 205 by comparing the (J−K) and (H−K) color distributions of the M-giant stars between −7.6 < M K < −7.2 with the color values at M K = −7.4 of the theoretical Girardi et al (2002) isochrones with ages of Fig.…”

Section: Color Distribution and Luminosity Function Of The Agb Starsmentioning

confidence: 88%

“…More recently, Sibbons et al (2015) also derived the metallicity of [Fe/H] = −1.26±0.07 for IC 1613 from their C/M ratio. In our previous studies, the C/M ratios of three dwarf elliptical galaxies and one dwarf irregular galaxy were estimated as 0.11 ± 0.01 for NGC 185 (Kang et al 2005), 0.16 ± 0.02 for NGC 147 , 0.15 ± 0.01 for NGC 205 (Jung et al 2012), and 0.27 ± 0.03 for NGC 6822 . We note that Sibbons et al (2012) estimated the C/M ratio for NGC 6822 with different criteria for the selection and identification of the AGB populations and found that this value was 0.62±0.03.…”

Section: Spatial Distributions Of the C And M-giant Stars C/m Ratiomentioning

confidence: 95%

“…We have studied the near-infrared photometric properties of AGB stars in three dwarf elliptical galaxies: NGC 185, NGC 147, and NGC 205 (Kang et al 2005;Sohn et al 2006;Jung et al 2012), and in one dwarf irregular galaxy: NGC 6822 . Section 2 introduces the near-infrared JHK s observation of IC 1613, the data reduction, and the photometry.…”

Section: Introductionmentioning

confidence: 99%

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Near-infrared photometric properties of asymptotic giant branch stars in the dwarf irregular galaxy IC 1613

Chun

Jung

Kang

et al. 2015

A&A

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Aims. We investigated the photometric properties of asymptotic giant branch (AGB) stars of the dwarf irregular galaxy IC 1613 and its metallicity. Methods. We used near-infrared JHK s photometric data obtained with the WIRCam array on Canada-France-Hawaii Telescope (CFHT). The optical gi imaging data of a previous study were cross-matched with ours to distinguish the stellar populations in the galaxy and to select the AGB stars. We also separated the C stars from the M-giant stars in the JHK s color−color diagram. Results. We identified 140 C stars and 306 M-giant stars in IC 1613. The (J − K s ) color histogram of AGB stars shows the main peak of M-giant stars and the red tail of C stars. The broad color distribution of M-giant stars and the isochrones in the color magnitude diagram indicate that IC 1613 has a wide range of intermediate-age stars. We also know that most C stars were formed over the past 2−8 Gyr according the M bol -age relation. The C/M ratio of 0.46 ± 0.05 was estimated and [Fe/H] abundance of −1.23 ± 0.06 was derived from the C/M ratio. Radial distributions of C/M ratio and metallicity show the shallow trend of the negative metallicity gradient from the center. The local C/M ratio also indicates that the HI cavity has higher C/M values than the bright HI spot and HI gas region. However, the low [Fe/H] value near the central region of the galaxy is likely to be caused by the change in age of the dominant stellar population according to the radial distance, not the real metallicity variation. It might also be that relatively younger and metal-rich C stars are concentrated in the center of the galaxy, while the M-giant stars were homogeneously distributed from the center to the borders of the galaxy.

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Section: Color Distribution and Luminosity Function Of The Agb Starssupporting

confidence: 81%

Section: Color Distribution and Luminosity Function Of The Agb Starsmentioning

confidence: 57%

Section: Color Distribution and Luminosity Function Of The Agb Starsmentioning

confidence: 88%

Section: Spatial Distributions Of the C And M-giant Stars C/m Ratiomentioning

confidence: 95%

Section: Introductionmentioning

confidence: 99%

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Near-infrared photometric properties of asymptotic giant branch stars in the dwarf irregular galaxy IC 1613

Chun

Jung

Kang

et al. 2015

A&A

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Near-infrared spectroscopy of AGB star candidates in Fornax, Sculptor, and NGC 6822

Groenewegen¹,

Lançon

Marescaux

2009

A&A

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Context. The asymptotic giant branch (AGB) phase is characterised by substantial mass loss that is accompanied by the formation of dust. In extreme cases this will make the star no longer visible in the optical. For a better understanding of AGB evolution it is important to identify and characterise these very red AGB stars. Aims. The first aim of this article is to improve the census of red AGB stars in three Local Group galaxies, based on near-IR spectroscopic observations of new candidates with red 2MASS (J − K) colours. The opportunity is taken to compare the near-IR spectra with those of Milky Way stars. Methods. We used ISAAC on the ESO VLT to take J and H-band spectra of 36 targets in Fornax, Sculptor and NGC 6822. Results. Twelve new C-stars are found in Fornax, and one is confirmed in Sculptor. All C-stars have (J − K) > 1.6, and are brighter than −3.55 in bolometric magnitude. Ten new oxygen-rich late-type giant stars are identified in Fornax, but none is extremely red or very luminous. Five luminous O-rich AGB stars are identified in NGC 6822, of which 3 show water absorption, indicative of spectral type M. Again, none is as red as Milky Way OH/IR stars, but in this galaxy the list of candidate AGB stars is biased against very red objects. In some C-stars with (J − K) > 2 an extremely strong 1.53 μm absorption band is found. These stars are probably all Mira variables and the feature is related to the low temperature, high density chemistry that is a first step towards dust formation and mass loss.

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Long-period variables in NGC 147 and NGC 185

Lorenz

Lebzelter

Nowotny

et al. 2011

A&A

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Context. Previous studies on the stellar content of the two nearby dwarf galaxies NGC 147 and NGC 185 reveal a rich population of late-type giants in both systems, including a large number of carbon-rich objects. These stars are known to show pronounced photometric variability, which can be used for a more detailed characterisation of these highly evolved stars. Owing to their well-studied parameters, these Local Group members are ideal candidates for comparative studies. Aims. Through photometric monitoring, we attempt to provide a catalogue of long-period variables (LPVs), including Mira variables, semi-regular variables, and even irregular variables in NGC 147 and NGC 185. We investigate the light variations and compare the characteristics of these two LPV populations with the results found for other galaxies, such as the LMC. Methods. We carried out time-series photometry in the i-band of the two target galaxies with the Nordic Optical Telescope (NOT), covering a time span of ≈2.5 years. More than 30 epochs were available for a period search. These data were then combined with single-epoch K-band photometry, also obtained with the NOT. Narrow-band photometry data from the literature was used to distinguish between O-rich and C-rich stars. Results. We report the detection of 513 LPVs in NGC 185 and 213 LPVs in NGC 147, showing amplitudes Δi of up to ≈2 mag and periods ranging between 90 and 800 days. The period-luminosity diagram for each of our target galaxies exhibits a well populated sequence of fundamental mode pulsators. The resulting period-luminosity relations we obtained are compared to relations from the literature. We discuss the universality of those relations because of which, as a side result, a correction of the distance modulus of NGC 185 may be necessary. A value of (m − M) = 24. m 30 seems to be more appropriate to match the observed data. Only one of our two galaxies, namely NGC 185, has a significant fraction of possibly first overtone pulsators. An interpretation of this finding in terms of differences in the star-formation histories is suggested.

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

Cited by 23 publications

References 44 publications

Near-infrared photometric properties of asymptotic giant branch stars in the dwarf irregular galaxy IC 1613

Near-infrared photometric properties of asymptotic giant branch stars in the dwarf irregular galaxy IC 1613

Near-infrared spectroscopy of AGB star candidates in Fornax, Sculptor, and NGC 6822

Long-period variables in NGC 147 and NGC 185

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