2000AJ....119..777L

We present deep BVRI CCD photometry of the stars in the dwarf irregular galaxy SagDIG. The color-magnitude diagrams of the measured stars in SagDIG show a blue plume that consists mostly of young stellar populations and a well-defined red giant branch (RGB). The foreground reddening of SagDIG is estimated to be E(B-V)=0.06. The tip of the RGB is found to be at I_TRGB=21.55±0.10 mag. From this the distance to this galaxy is estimated to be d=1.18±0.10 Mpc. This result, combined with its velocity information, shows that it is a member of the Local Group. The mean metallicity of the red giant branch is estimated to be [Fe/H]←2.2 dex. This shows that SagDIG is one of the most metal-poor galaxies. Total magnitudes of SagDIG [<r_H(=107")] are found to be B^T=13.99 mag, V^T=13.58 mag, R^T=13.19 mag, and I^T=12.88 mag, and the corresponding absolute magnitudes are M_B=-11.62 mag, M_V=-11.97 mag, M_R=-12.33 mag, and M_I=-12.60 mag. Surface brightness profiles of the central part of SagDIG are approximately fit by a King model with a core concentration parameter c=log(r_t/r_c)~0.6, and those of the outer part follow an exponential law with a scale length of 37". The central surface brightness is measured to be µ_B(0)=24.21 mag.arcsec^–2 and µ_V(0)=23.91 mag.arcsec^–2. The magnitudes and colors of the brightest blue and red stars in SagDIG (BSG and RSG) are measured to be, respectively, <V(3)>_BSG=19.89±0.13 mag, <(B-V)(3)>_BSG=0.08±0.07 mag, <V(3)>_RSG=20.39±0.10 mag, and <(B-V)(3)>_RSG=1.29±0.12 mag. The corresponding absolute magnitudes are derived to be <M_V(3)>_BSG=-5.66 mag and <M_V(3)>_RSG=-5.16 mag, which are about 1 mag fainter than those expected from conventional correlations with galaxy luminosity.