2005AJ....129.1523F

We present high angular resolution, near-infrared images of the obscured Galactic giant H II region G333.1-0.4, in which we detect an OB star cluster. For G333.1-0.4 we find OB stars and other massive objects in very early evolutionary stages, possibly still accreting. We obtained K-band spectra of three stars; two show O-type photospheric features, while the third has no photospheric features but does show CO 2.3 µm band-head emission. This object is at least as hot as an early B-type star, based on its intrinsic luminosity, and is surrounded by a circumstellar disk or envelope that produces near-infrared excess emission. A number of other relatively bright cluster members also display excess emission in the K band, indicative of disks or envelopes around young massive stars. Based on the O star photometry and spectroscopy, the distance to the cluster is 2.6±0.4 kpc, similar to a recently derived kinematic (near side) value. The slope of the K-band luminosity function is similar to those found in other young clusters. The mass function slope is more uncertain, and we find -1.3±0.2<Γ←1.1±0.2 for stars with M>5 M_☉, where the upper and lower limits are calculated independently for different assumptions regarding the excess emission of the individual massive stars. The number of Lyman continuum photons derived from the contribution of all massive stars in the cluster is 0.2x10⁵⁰/s < N_Lyc< 1.9x10⁵⁰/s. The integrated cluster mass is 1.0x10³ M_☉ < M_cluster< 1.3x10³ M_☉.