Fig. 1. Color-magnitude diagrams of four fields in and near the Sculptor dSph galaxy. Chip 4 is centered on the galaxy core. Note the complex main-sequence morphology and prominent red horizontal branch (HB) component apparent in the SW field. The NW and SE fields show only the oldest main-sequence component and no clear sign of the red HB stars. The NE field is mostly devoid of Sculptor stars, a surprising result given the isopleth maps of Irwin and Hatzidimitriou (1995)

Fig. 2. A chart showing the locations of the Sgr fields observed to trace out its tidal extension. The open squares denote target fields along the Sgr major axis, while the open circles are the controls. The other symbols denote the original known size of Sgr at the time of its discovery (small ellipse; Ibata et al. 1994), and in 1997 (large dashed ellipse; Mateo et al. 1996; Alard 1996; Fahlman et al. 1996; Ibata et al. 1997). The regions where the Macho project (Alcock et al. 1997) and Alard (1996) detected Sgr RR Lyr stars are also denoted

Fig. 3. A plot of the net star counts along the Sgr major axis (see Figure 2) as a function of angular distance from the galaxy center (taken to coincide with the globular cluster M 54). The short, bold lines above and below each point show the systematic effect of decreasing and increasing the reddening by 0.03 mag, respectively; the standard error bars denote the Poisson uncertainties of the counts. The righthand axis shows the equivalent V-band surface brightness of Sgr at each point. This axis was calibrated using the prior results of Mateo et al. (1996). The horizontal dotted line denotes the count level at which a `kink' in the profile is observed; the corresponding location on the sky is shown with a short dashed line in Figure 2

Fig. 4. Mass-to-light ratios of a number of dSph galaxies as a function of total luminosity. Recent results for Leo I (Mateo et al. 1998b) and LGS 3 (Cook et al. 1998; the very large error bars for this galaxy are plotted) are included. The dashed line is the equation given in the text for (M/L)_s = 1.5 and M_dark = 2.0·10⁷M_sun