Infrared carbon stars: new identifications and their space distribution in the Galaxy

We present JHKL photometry of a sample of 150 IRAS stars in the third and fourth galactic quadrant with | b | <2(deg) 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. Based on observations obtained at the European Southern Observatory, Chile