Using the highest-resolution X-ray observation of the Trumpler 15 star cluster taken by the Chandra X-ray Observatory , we estimate the total size of its stellar population by comparing the X-ray luminosity function of the detected sources to a calibrator cluster , and identify for the first time a significant fraction ( \sim 14 % ) of its individual members .
The highest-resolution near-IR observation of Trumpler 15 ( taken by the HAWK-I instrument on the VLT ) was found to detect most of our X-ray selected sample of cluster members , with a K -excess disk frequency of 3.8 \pm 0.7 \% .
The near-IR data , X-ray luminosity function , and published spectral types of the brightest members support a cluster age estimate ( 5–10 Myr ) that is older than those for the nearby Trumpler 14 and Trumpler 16 clusters , and suggest that high-mass members may have already exploded as supernovae .
The morphology of the inner { \sim } 0.7 pc core of the cluster is found to be spherical .
However , the outer regions ( beyond { \sim } 2 pc ) are elongated , forming an “ envelope ” of stars that , in projection , appears to connect Trumpler 15 to Trumpler 14 ; this morphology supports the view that these clusters are physically associated .
Clear evidence of mass segregation is seen .
This study appears in a Special Issue of the ApJS devoted to the Chandra Carina Complex Project ( CCCP ) , a 1.42 square degree Chandra X-ray survey of the Great Nebula in Carina .