Carbon stars in the outer spheroid of NGC 6822

Context: .From a 2°× 2° of NGC 6822 survey we have previously established that this Local Group dwarf irregular galaxy possesses a huge spheroid having more than one degree in length. This spheroid is in rotation but its rotation curve is known only within ~ 15' from the center. It is therefore critical to identify bright stars belonging to the spheroid to characterize, as far as possible, its outer kinematics.
Aims: .We use the new wide field near infrared imager CPAPIR, operated by the SMARTS consortium, to acquire J, K_s images of two 34.8'× 34.8' areas in the outer spheroid to search for C stars.
Methods: .The colour diagram of the fields allows the identification of 192 C stars candidates but a study of the FWHM of the images permits the rejection of numerous non-stellar objects with colours similar to C stars.
Results: . We are left with 75 new C stars, their mean K_s magnitude and mean colour are similar to the bulk of known NGC 6822 C stars.
Conclusions: .This outer spheroid survey confirms that the intermediate-age AGB stars are a major contributor to the stellar populations of the spheroid. The discovery of some 50 C stars well beyond the limit of the previously known rotation curve calls for a promising spectroscopic follow-up to a major axis distance of 40'.