A Chandra Study of the Rosette Star-Forming Complex. II. Clusters in the
  Rosette Molecular Cloud
  We explore here the young stellar populations in the Rosette Molecular Cloud
(RMC) region with high spatial resolution X-ray images from the Chandra X-ray
Observatory, which are effective in locating weak-lined T Tauri stars as well
as disk-bearing young stars. A total of 395 X-ray point sources are detected,
299 of which (76%) have an optical or near-infrared (NIR) counterpart
identified from deep FLAMINGOS images. From X-ray and mass sensitivity limits,
we infer a total population of about 1700 young stars in the survey region.
Based on smoothed stellar surface density maps, we investigate the spatial
distribution of the X-ray sources and define three distinctive structures and
substructures within them. Structures B and C are associated with previously
known embedded IR clusters, while structure A is a new X-ray-identified
unobscured cluster. A high mass protostar RMCX #89 = IRAS 06306+0437 and its
associated sparse cluster is studied. The different subregions are not coeval
but do not show a simple spatial-age pattern. Disk fractions vary between
subregions and are generally 20% of the total stellar population inferred from
the X-ray survey. The data are consistent with speculations that triggered star
formation around the HII region is present in the RMC, but do not support a
simple sequential triggering process through the cloud interior. While a
significant fraction of young stars are located in a distributed population
throughout the RMC region, it is not clear they originated in clustered
environments.
