The Extent of NGC 6822 Revealed by Its C Star Population

Using the CFH12K camera, we apply the four band photometric technique toidentify 904 carbon stars in an area 28' x 42' centered on NGC 6822. A few Cstars, outside of this area were also discovered with the Las Campanas SwopeTelescope. The NGC 6822 C star population has an average I of 19.26 mag leadingto an average absolute I magnitude of -4.70 mag, a value essentially identical to the mean magnitude obtained forthe C stars in IC 1613. Contrary to stars highlighting the optical image of NGC6822, C stars are seen at large radial distances and trace a huge slightlyelliptical halo which do not coincide with the huge HI cloud surroundingNGC6822. The previously unknown stellar component of NGC 6822 has a exponentialscale length of 3.0' +/- 0.1' and can be traced to five scale lengths. The C/Mratio of NGC 6822 is evaluated to br 1.0 +/- 0.2.Comment: accepted, to be published in A