G287.84--0.82: An Infrared Star Cluster in the Carina Nebula

We have studied the properties of an infrared cluster embedded in the gas and dust of the southern part of the Carina Nebula (NGC 3372), where the probable existence of current star formation has already been predicted. We used mid-infrared (A & C bands) and near-infrared (JHKs) images from the MSX and the 2MASS surveys respectively, combined with an optical Hα narrow-band filter image obtained at the CTIO. The infrared star cluster has at least 17 members, and its parameters, radius and stellar density are in very good agreement with high- to intermediate-mass star formation scenarios. The detected IR sources have roughly the same intrinsic infrared excess determined from their position in colour-colour and colour-magnitude diagrams, suggesting that these objects could be related to pre-main sequence stars of high to intermediate mass. Furthermore, we present a low-dispersion spectrum of LS 1883 (O9.5V) star located near the centre of the IR cluster. The position of this object in the colour-colour and colour-magnitude IR diagrams lies close to the reddening vector of an ZAMS O9V spectral type star, and it seems to be the first star of this cluster to emerge. All these facts are consistent with the current star-forming scenarios associated with highly embedded star clusters.