Stellar contents of the galactic giant HII region NGC 3603

Abstract

We present CCD UBVRI and Hа photometry for the starburst cluster associated with the galactic giant HII region NGC 3603. The mean reddening of the cluster members comes out to be (E(B-V)) = 1.48±0.21 (s.d.). The surface distribution of the reddening shows a radial variation with a minimum near to the cluster center and two local maxima at radii ~ 30" and ~ 70". Our photometric data indicate an anomalous reddening law for the dust inside the cluster region, and the ratio of the total to the selective extinction, R, is found to be ~ 4.3. A comparison of the observational and intrinsic colour-magnitude diagrams (CMDs) yield a mean distance modulus of (m-M)₀ = 14.0, which corresponds to a distance of 6.3 ± 0.6 kpc. This distance is smaller than those obtained in earlier works (e.g., 7.2 kpc, Melnick et al. 1989, AAA 49.132.013) but is in good agreement with the kinematic distance (6.1±0.6 kpc) recently reported by De Pree et al. (1999. AAA 71.132.041). The cluster shows a large age spread, containing stars as old as up to several Myr. However, the mean age of the cluster is found to be ≤ 1 Myr. We estimate a minimum star formation efficiency of ~ 25% and a gas removal time of Ƭ~ 4.6 Myr.