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NGC 6822 is an irregular dwarf galaxy and part of the Local Group. Its closeproximity and apparent isolation provide a unique opportunity to study galacticevolution without any obvious strong external influences. This paper aims tostudy the spatial distribution of the asymptotic giant branch (AGB) populationand metallicity in NGC 6822. Using deep, high quality JHK photometry, takenwith WFCAM on UKIRT, carbon- and oxygen-rich AGB stars have been isolated. Theratio between their number, the C/M ratio, has then been used to derive the[Fe/H] abundance across the galaxy. The tip of the red giant branch is locatedat K0 = 17.41 \pm 0.11 mag and the colour separation between carbon- andoxygen-rich AGB stars is at (J - K)0 = 1.20 \pm 0.03 mag (i.e. (J - K)2MAS S{\guillemotright} 1.28 mag). A C/M ratio of 0.62 \pm 0.03 has been derived inthe inner 4 kpc of the galaxy, which translates into an iron abundance of[Fe/H] = -1.29\pm0.07 dex. Variations of these parameters were investigated asa function of distance from the galaxy centre and azimuthal angle. The AGBpopulation of NGC 6822 has been detected out to a radius of 4 kpc giving adiameter of 56 arcmin. It is metal-poor, but there is no obvious gradient inmetallicity with either radial distance from the centre or azimuthal angle. Thedetected spread in the TRGB magnitude is consistent with that of a galaxysurrounded by a halo of old stars. The C/M ratio has the potential to be a veryuseful tool for the determination of metallicity in resolved galaxies but abetter calibration of the C/M vs. [Fe/H] relation and a better understanding ofthe sensitivities of the C/M ratio to stellar selection criteria is firstrequired.

The AGB population of NGC 6822: distribution and the C/M ratio from JHK photometry