A Chandra ACIS Study of the Young Star Cluster Trumpler 15 in Carina and Correlation with Near-infrared Sources

TL;DR

This study uses high-resolution X-ray and near-infrared observations to analyze the stellar population, structure, and age of the Trumpler 15 cluster, revealing its size, composition, and relation to nearby clusters.

Contribution

It provides the first estimate of Trumpler 15's total stellar population, its age, morphology, and evidence of mass segregation using combined X-ray and near-IR data.

Findings

Estimated the cluster's total size and member fraction (~14%).

Detected a K-excess disk frequency of 3.8+-0.7%.

Supported an age estimate of 5-10 Myr and found morphological features indicating physical association with Trumpler 14.

Abstract

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 (~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+-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 ~0.7 pc core of the cluster is found to be spherical. However, the outer regions (beyond 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.