| Abstract | We present VRI CCD photometry of ~490 stars in the dwarf galaxy LGS 3 in the Local Group. The color-magnitude diagrams of LGS 3 show a well defined red giant branch (RGB), a small number of asymptotic giant branch stars, and several blue stars which are possibly young main-sequence stars. The tip of the RGB is found to be at I_TRGB_ =20.6+/-0.2 mag and (V - I)_TRGB_ = 1.31+/-0.05 mag. From the I magnitude of the tip of the RGB, we estimate the distance modulus of LGS 3 to be (m - M)_0_ =24.54+/- 0.21 mag for an adopted extinction of A_V_ = 0.08 mag, corresponding to a distance of 810 +/- 80 kpc. This result shows that LGS 3 may be a satellite of M31 or M33 which are close to LGS 3 in the sky. We measure the mean color of the RGB at M_I_ = -3.5 mag (~0.5 mag fainter than the tip of the RGB) to be (V - I)_-3.5_ = 1.28+/-0.05 mag. From these values we estimate the mean metallicity of the RGB stars to be [Fe/H]= -2.10+/- 0.22 dex. The integrated magnitudes of LGS 3 within the aperture radius r = 106" are measured to be V= 14.26 mag, R = 13.84 mag, and I = 13.26 mag. The absolute integrated magnitude of LGS 3 is derived to be M_V_ = - 10.35 mag. The central surface brightness is measured to be μ_V_(0) = 24.81+/-0.07 mag arcsec^-2^. Surface brightness profiles and star number density profiles based on star counts are well fitted by a King model with a core concentration parameter c =log(r_t_/r_c_) = 1.25+/-0.13, where r_t_ and r_c_ represents the tidal radius and the core radius, respectively. The core radius is measured to be r_c_ = 49"+/-3", corresponding to 190+/-10 pc. The metallicity and the absolute magnitude of LGS 3 are consistent with the metallicity-luminosity relation for the dwarf spheroidal galaxies in the Local Group. |
