PREIBISCH T., FLAISCHLEN S., GACZKOWSKI B., TOWNSLEY L. and BROOS P.
Abstract (from CDS):
Context. NGC 3293 is a young stellar cluster at the northwestern periphery of the Carina Nebula Complex that has remained poorly explored until now. Aims. We characterize the stellar population of NGC 3293 in order to evaluate key parameters of the cluster population such as the age and the mass function, and to test claims of an abnormal IMF and a deficit of M≤2.5M☉ stars. Methods. We performed a deep (70ks) X-ray observation of NGC 3293 with Chandra and detected 1026 individual X-ray point sources. These X-ray data directly probe the low-mass (M≤2M☉) stellar population by means of the strong X-ray emission of young low-mass stars. We identify counterparts for 74% of the X-ray sources in our deep near-infrared images. Results. Our data clearly show that NGC 3293 hosts a large population of ~=solar-mass stars, refuting claims of a lack of M≤2.5M☉ stars. The analysis of the color magnitude diagram suggests an age of ∼8-10Myr for the low-mass population of the cluster. There are at least 511 X-ray detected stars with color magnitude positions that are consistent with young stellar members within 7 arcmin of the cluster center. The number ratio of X-ray detected stars in the [1-2]M☉ range versus the M≥5M☉ stars (known from optical spectroscopy) is consistent with the expectation from a normal field initial mass function. Most of the early B-type stars and ~=20% of the later B-type stars are detected as X-ray sources. Conclusions. Our data shows that NGC 3293 is one of the most populous stellar clusters in the entire Carina Nebula Complex (very similar to Tr 16 and Tr 15; only Tr 14 is more populous). The cluster probably harbored several O-type stars, whose supernova explosions may have had an important impact on the early evolution of the Carina Nebula Complex.