Using the CFH12K camera, we apply the four band photometric technique to identify 904 carbon stars in an area 28 ′ × 42 ′ centered on NGC 6822. A few C stars, outside of this area, were also discovered with the Las Campanas Swope Telescope. The NGC 6822 C star population has < I > = 19.26 leading to a < M I > = -4.70, a value essentially identical to the mean magnitude obtained for the C stars in IC 1613. Contrary to stars highlighting the optical image of NGC 6822, C stars are seen at large radial distances and trace a huge slightly elliptical halo which does not coincide with the huge HI cloud surrounding NGC 6822. The previously unknown stellar component of NGC 6822 has a exponential scale length of 3.0 ′ ± 0.1 ′ and can be traced to five scale lengths. The C/M ratio of NGC 6822 is evaluated to be 1.0 ±0.2.

We have begun a survey of the structure of the Milky Way halo, as well as the halos of other Local Group galaxies, as traced by their constituent giant stars. These giant stars are identiÐed via large-area, CCD photometric campaigns. Here we present the basis for our photometric search method, which relies on the gravity sensitivity of the Mg I triplet]MgH features near 5150 in FÈK stars, and which A is sensed by the Ñux in the intermediate-band DDO51 Ðlter. Our technique is a simpliÐed variant of the combined Washington/DDO51 four-Ðlter technique described by Geisler, which we modify for the speciÐc purpose of efficiently identifying distant giant stars for follow-up spectroscopic study : We show here that for most stars the Washington color is correlated monotonically with the Washington By combining the data on stars from di †erent clusters, and by taking advantage of the wide abundance spread within u Centauri, we verify the primary dependence of the M[DDO51 color on luminosity and demonstrate the secondary sensitivity to metallicity among giant stars. Our empirical results are found to be generally consistent with those from analysis of synthetic spectra by Paltoglou & Bell.Finally, we provide conversion formulae from the (M, system to the (V , V [I) system, corre-M[T 2 ) sponding reddening laws, as well as empirical red giant branch curves from u Centauri stars for use in deriving photometric parallaxes for giant stars of various metallicities (but equivalent ages) to those of u Centauri giants.