Carbon stars and C/M ratio in the WLM dwarf irregular galaxy

Valcheva, A.; Ivanov, V. D.; Ovcharov, E.; Nedialkov, P.

doi:10.1051/0004-6361:20054536

Cited by 16 publications

(23 citation statements)

References 37 publications

(78 reference statements)

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“…The mean distance from the V and I magnitudes is (m − M) P0 = 24.93 ± 0.03. (Valcheva et al 2007) is in statistical agreement with the present value, which is perfectly matched by the value of 24.95 ± 0.10 from four Cepheids with 3.6 and 4.5 μm mag (Ngeow et al 2009). …”

Section: Wlmsupporting

confidence: 91%

New period-luminosity and period-color relations of classical Cepheids

Tammann

Reindl

Sandage

2011

A&A

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The metal-poor, fundamental-mode (P0) and first-overtone (P1) Cepheids in the dwarf galaxies IC 1613, WLM, Pegasus, Sextans A, Sextans B, and Leo A are compared with the about equally metal-poor Cepheids of the Small Magellanic Cloud (SMC). The period-color (P-C) and period-luminosity (P-L) relations of the seven galaxies are indistinguishable, but differ distinctly from those in the Large Magellanic Cloud (LMC) and the solar neighborhood. Adopting (m − M) 0 SMC = 18.93 from independent evidence, one can determine reliable distance moduli for the other dwarf galaxies of (m − M) 0 = 24.34 ± 0.03, 24.95 ± 0.03, 24.87 ± 0.06, 25.60 ± 0.03 (mean for Sextans A & B), and 24.59 ± 0.03, respectively.

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Section: Wlmsupporting

confidence: 91%

New period-luminosity and period-color relations of classical Cepheids

Tammann

Reindl

Sandage

2011

A&A

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“…Stars with (CN − TiO) smaller than ≈−0.3 have (J − K s ) 0 and (H − K s ) 0 colors typical of late dwarfs (see Bessell & Brett, 1988) that are seen here along the line of sight and mimic AGB stars. The dashed line is the Valcheva et al (2007) limit to select C stars from the AGB stars found in their WLM study. They called AGB stars all the objects brighter than the TRGB.…”

Section: Discussionmentioning

confidence: 99%

“…From the investigation of Dolphin (2000), we adopt (m − M) 0 = 24.90 for its distance and a metallicity for its intermediate-age population of [Fe/H] = -1.4. WLM has been the target of a recent NIR study by Valcheva et al (2007) who identified numerous C and M AGB stars. They determined a C/M ratio for WLM that is quite different from the one calculated by from the (CN -TiO) criterion.…”

Section: The Target Galaxiesmentioning

confidence: 99%

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The assessment of the near infrared identification of carbon stars

Battinelli¹,

Demers²,

Mannucci³

2007

A&A

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Context. The selection of AGB C and M stars from NIR colours has been done in recent years using adjustable criteria that are in needs of standardization if one wants to compare, in a coherent manner, properties of various populations. Aims. We intend to assess the NIR colour technique to identify C and M stars. Methods. We compare the NIR colours of several C stars previously identified from spectroscopy or narrow band techniques in WLM, IC 10 and NGC 6822. Results. We demonstrate that very few M stars have (J − K) 0 > 1.4 but a non negligible number of C stars are bluer than this limit. Thus, counts of M and C stars based on such limit do not produce pure samples. Conclusions. C/M ratios determined from NIR colours must be regarded as underestimates mainly because the M numbers include many warm C stars and also K stars if no blue limit is considered.Key words. galaxies: individual: IC 10 -galaxies: individual: WLM -galaxies: individual: NGC 6822 -stars: carbonstars: AGB and post-AGB -galaxies: dwarf IntroductionCarbon stars were initially identified in large numbers by objective prism surveys, first in the Milky Way (Blanco 1965;Westerlund 1965) then a decade later similar surveys toward the Magellanic Clouds (Blanco et al. 1978) yielded hundreds of C stars. To reach fainter magnitudes, thus larger distances, a photometric technique based on two narrow band filters was introduced in the nineteen eighties (Richer et al. 1984;Cook et al. 1986). This approach, based on the (CN -TiO) index along with a colour, such as (V −I) or (R−I) has been successfully exploited to survey most of the Local Group galaxies (see for example: Battinelli & Demers 2005a;Brewer et al. 1995;Nowotny et al. 2003;Rowe et al. 2005). The narrow band technique presents, however, some serious drawbacks, the required filters are expensive to acquire and more importantly they are not available on major telescopes.With the evolution of the near infrared (NIR) instrumentation Asymptotic Giant Branch (AGB) stars became the subjects of a number of observations in the Galaxy and beyond. Mould & Aaronson (1980) demonstrated that AGB stars in the SMC have slightly bluer NIR colours that their cousins in the LMC. Spectroscopically confirmed C stars were found to fall on an extend red tail in the (J−K) vs. K plane, thus easily distinguishable Based on observations obtained at the Italian Telescopio Nazionale Galileo.Full Tables 2 and 3 It is well know that the NIR colours of the RGB are function of the metallicity of the stellar population (Ferraro et al. 2000). The mean colours of O-rich or C-rich AGB stars brighter than the tip could similarly be metallicity dependent. There is at the present time no observational evidence for this effect. The NIR Article published by EDP Sciences and available at

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“…6, that this limit corresponds essentially to the red border of the M stars but certainly not to the blue border of C stars. Various authors (Davidge 2003;Cioni & Habing 2003;Cioni & Habing 2005;Valcheva et al 2007) have shifted the blue limit of C stars to take into account the metallicity of the galaxy under consideration. The metallicity of the intermediate-age populations of Local Group galaxies is in general rather poorly known.…”

Section: Colour Distribution Of C Starsmentioning

confidence: 99%

Assessment of the near infrared identification of carbon stars

Battinelli¹,

Demers²

2008

A&A

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Context. Thousands of C stars have been identified in Local Group galaxies using narrow band photometry. To survey C stars at larger distances and alternative to the narrow-band approach is needed. Aims. We obtain, from ESO Archive data, NIR magnitudes and colours of previously known C stars in two dwarf irregular Local Group galaxies, namely IC 1613 and NGC 3109. Methods. We compare the NIR magnitudes and colours of the C star populations, previously identified from narrow band techniques to estimate the star formation history of their intermediate-age populations. Results. We demonstrate that the photometric properties of C stars show a wider range in the NIR than in the optical. As confirmed by models we see, among the four galaxies investigated with a 0.7 dex metallicity range, little if any metallicity effect in the C star colour distribution.

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Carbon stars and C/M ratio in the WLM dwarf irregular galaxy

Cited by 16 publications

References 37 publications

New period-luminosity and period-color relations of classical Cepheids

New period-luminosity and period-color relations of classical Cepheids

The assessment of the near infrared identification of carbon stars

Assessment of the near infrared identification of carbon stars

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