Carbon star survey of Local Group galaxies - X. Wolf-Lundmark-Melotte a galaxy with an extreme C/M ratio

We used the CFH12K wide field camera to survey the carbon star population of the Wolf-Lundmark-Melotte system using the CN-TiO technique. 149 C stars are identified with a mean (I) = 20.28, corresponding to [M-I) = -4.65, a mean luminosity similar to what we found in other irregular galaxies. Star counts in and around the main body of WLM reveal that its stellar distribution is quite elliptical (epsilon = 0.58) with major and minor axes of 26' and 11'. Comparison of the density profile of C stars and old red giants shows that their scale lengths differ by only 15% pointing to mixed populations. WLM is found to be unique among dwarf irregular galaxies by having essentially a handful of early-type AGB M stars thus leading to an extreme C/M ratio. We conclude that like NGC 3109, WLM is a disk shaped galaxy, seen at an inclination of similar to69degrees and devoid of an extended spherical stellar halo.