Astron. Astrophys. 334, 609-617 (1998)

Infrared carbon stars: new identifications and their space distribution in the Galaxy ^{*, **}

F. Guglielmo ¹, T. Le Bertre ² and N. Epchtein <sup>1, 3

1</sup> Observatoire de Paris, Département de Recherche Spatiale, CNRS URA 264, F-92195 Meudon Principal Cedex, France
² Observatoire de Paris, Département de Radioastronomie Millimétrique, CNRS URA 336, F-75014 Paris, France
³ Observatoire de la Côte d'Azur, Département Fresnel, BP 4229, F-06304 Nice Cedex 4, France

Received 20 March 1997 / Accepted 11 February 1998

Abstract

We present JHKL photometry of a sample of 150 IRAS stars in the third and fourth galactic quadrant with b selected according to their IRAS colour (0.160 [12-25] 1.156). We identify 27 carbon star candidates using the [12-25] vs. K-L two-colour diagram method. Among them, 10 are listed in the Stephenson's catalogue of carbon stars and 17 are new infrared carbon stars (IRCS) candidates. Their distances are found to be larger than 3 kpc. These data are combined with previous data to study the space distribution of IRCS. The number density seems to be independent of the galactocentric distance (R) toward the Galactic Center and to decrease exponentially toward the anticenter. At the present stage, it is not possible to disentangle effects such as incompleteness of the sample, different space distribution law and dependence of the luminosity on metallicity. In particular, we suggest that the apparent scarcity of IRCS in the central direction of the Galaxy (R 5 kpc) might be due to a selection effect. From the available data, we have found no IRCS within 1 kpc of the Galactic Center.

Key words: stars: carbon stars: circumstellar matter stars: late-type stars: AGB and post-AGB Galaxy: stellar content infrared: stars

* Based on observations obtained at the European Southern Observatory, Chile
** Tables 3 and 4 are only available in electronic form at CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsweb.u-strasbg.fr/Abstract.html

Send offprint requests to: TL, (lebertre@obspm.fr)

Contents

• 1. Introduction
• 2. Observation and results
• 3. Discussion
  • 3.1. Infrared carbon stars in the sample
  • 3.2. Revisiting the space distribution of infrared carbon stars
    • 3.2.1. Center, inner and intermediate directions
    • 3.2.2. Anticenter direction
• 4. Conclusion
• Acknowledgements
• References

© European Southern Observatory (ESO) 1998

Online publication: May 15, 1998

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