Statistical properties of a complete carbon star sample based on 2MASS infrared photometry

In the 2MASS All Sky Catalog of Point Sources 6620 carbon stars (hereafter called as sample stars) have been identified. The distribution of their color indices was investigated and compared with M-type stars. It is concluded that in the interval (J - K)₀ < 1.7 mag the color indices of carbon stars overlap with G-, K- and M-type stars but stars with (J - K)₀ > 2.2 mag almost all are carbon stars. Taking a fixed absolute magnitude of M(K) = -8.1 mag for N-type stars and of M (K) -2 mag for warmer carbon stars, interstellar reddenings and distances have been determined. The distribution of carbon stars in the Galactic plane mark the two nearest spiral arms in correspondence with their positions known from young stars and open clusters. However, in the global scale the distribution is asymmetrical due to the influence of local dust clouds on limiting magnitudes of various carbon star surveys. The scale height ZQ for N-type stars and for warm carbon stars is found to be 0.39 and 1.2 kpc, respectively. The periods of carbon variables with P < 400 days show approximately a linear increase with color index.