STELLAR POPULATIONS IN THE DWARF ELLIPTIC GALAXY NGC 185

BVRI CCD photometry of approximately 5300 stars in the central (2.'2 X 3.'5) area of the dwarf elliptical galaxy NGC 185 in the Local Group is presented. The color-magnitude diagrams of NGC 185 show three distinct stellar populations: (1) a strong red giant branch (RGB) population, the tip of which found to be at I(TRGB) = 20.3 +/- 0.2 mag, and (V-1)TRGB = 1.95 +/- 0.05, (2) an asymptotic giant branch (AGB) located above the tip of the RGB, and (3) a small number of young stars having blue to yellow colors. The reddening of the bright foreground stars has been determined using the (B-V) - (V-I) diagram to be E(B-V) =0.19 +/- 0.03 mag. The distance has been estimated from the I magnitude of the tip of the RGB, giving (m-M)0 = 23.96 +/- 0.21 mag for A(I) = 0.38 mag, corresponding to 620 +/- 60 kpc. The mean metallicity of the RGB stars has been determined using the median color of the RGB stars at M(I) = -3.5 mag, (V-I)-3.5,0 = 1.727 mag: giving a mean metallicity of [Fe/H] = -1.23 +/- 0.16 dex. The dispersion in color at M(I) = -3.5 mag is DELTA(V-I)-3.5 = 0.12 mag, implying a metallicity dispersion of -1.6 < [Fe/H] < -0.9 dex. Surface photometry of the area within R = 50'' is also presented, showing that colors get rapidly bluer inside R almost-equal-to 10''. A V luminosity function for the blue stars has been derived, the slope of which is very similar to that for other nearby galaxies. The AGB stars extend to M(bol) almost-equal-to -5.0 mag, and most of the AGB stars above the tip of the RGB are likely to belong to an intermediate-age population. The bolometric luminosity function of the red giant stars in NGC 185 is found to be very similar to that of M32.