UBVI CCD Photometry of the Remote Old Open Cluster AM-2

We present UBVI CCD photometry of 1,276 stars in the remote old open cluster AM-2. The color-magnitude diagrams show a main sequence turn-off at (B-V)~ 1.05 and V~ 19.5 mag, and a group of red giant clump stars at (B-V)~ 1.5 and V~ 17.4 mag. A prominent gap in the main sequence is seen at V=20.1 mag (M_V=3.5 mag). The reddening has been estimated using three methods, to be E(B-V)=0.57+/-0.03 (m.e.). The ultraviolet excess has been measured to be delta (U-B)_{0.6}=0.102 +/- 0.018 (m.e.), which yields a metallicity estimate of [Fe/H] = -0.51 +/- 0.12 (m.e.) dex. The distance to AM-2 has been determined from the zero-age-main-sequence fitting and the luminosity of the red giant clump, to be d= 8.87+/- 0.65 kpc. The corresponding galactocentric distance of AM-2 is R_GC=14.50 kpc. The age of AM-2 is estimated to be 5+/-1 Gyrs using the isochrone fitting and the morphological age indicators. The luminosity function of the main sequence stars is found to be similar to that of the old open cluster NGC 2243. Starcounts show that AM-2 extends out to R ~ 80'' (=3.4 pc) with a half mass radius of R_h ~ 50'' ( = 2.3 pc).