Astronomy and Astrophysics – Astrophysics
Scientific paper
May 2011
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2011aas...21822811p&link_type=abstract
American Astronomical Society, AAS Meeting #218, #228.11; Bulletin of the American Astronomical Society, Vol. 43, 2011
Astronomy and Astrophysics
Astrophysics
Scientific paper
The Chandra Carina Complex Project, coupled with complementary infrared observations, has revealed the young stellar population of the Great Nebula in Carina in unprecedented detail. Compared to previous studies of nearby, less massive clusters, these datasets provide a far richer sample of young, intermediate-mass (IM; 1.6--8 Msun) stars. In X-ray studies of young star clusters, two paradigms are currently favored by observation and theory: (1) IM stars occupy an X-ray-quiet "desert" between magnetically active low-mass stars and massive stars with strong stellar winds. (2) Among low-mass, pre-main-sequence (PMS) stars, X-ray luminosity is lower among classical T Tauri stars with circumstellar disks compared to weak-lined T Tauri stars. We have compiled a catalog of 1439 predominantly IM young stellar objects (YSOs) identified via infrared excess emission in the CCCP field, 410 of which were also detected by Chandra. In most cases, the X-ray emission is consistent with the presence of an unresolved, lower-mass companion to the infrared source, but we also find that X-ray emission correlates with cooler stellar photospheres and higher disk masses. This result appears to violate paradigm (1), while reversing paradigm (2) for the case of IM stars. X-ray emission appears to be intrinsic to IM stars during their early PMS evolution, perhaps driven by magnetic dynamo activity during the convective atmosphere phase, but this emission dies off as the stars approach the main sequence. Such a model predicts that the observed power-law slope of the X-ray luminosity function in a young star cluster steepens with age over timescales of a few Myr.
M.S.P. is supported by an NSF Astronomy and Astrophysics Postdoctoral Fellowship under award AST-0901646.
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