Stellar contents of the galactic giant H II region NGC 3603

Abstract

We present CCD UBVRI and Hα photometry for the starburst cluster associated with the galactic giant H II 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 digrams (CMDs) yields 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 τ ∼ 4.6 Myr.