AAS 205th Meeting, 9-13 January 2005
Session 64 Extragalactic Star Clusters
Poster, Tuesday, January 11, 2005, 9:20am-6:30pm, Exhibit Hall

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[64.01] Luminous X-ray Sources and Emission-Line Clusters in the Antennae

A.M. Gilbert (MPE), J.R. Graham (UC Berkeley)

About half of the super-Eddington CXO sources in the dusty overlap region of the Antennae Galaxies have IR super star cluster (SSC) counterparts within 100 pc. These CXO sources may be coincident with or recently ejected from SSCs. High-resolution spectra of the youngest SSCs (ages of 3-7 Myr) reveal broad Brg emission due to cluster outflows that are powered by the combined stellar winds of the ionizing stars and the ejecta of supernovae. A simple population synthesis model for the X-ray emission from the massive stellar populations of a 106 Msun cluster predicts X-ray luminosities from L(X) = 6 x 1037 erg/s during its wind-dominated phase (at ages < 3.7 Myr) up to super-Eddington luminosities > 1039 erg/s when high-mass X-ray binaries are present. Comparing the model with the ratio of observed X-ray and IR luminosities circumvents the problem of poorly known, variable extinction since the two wavebands probe similar absorption columns. Normal stellar populations can explain the observed X-ray luminosities of some of the Antennae sources, but an additional source of X-ray emission is required for a ULX. Multiwavelength observations, extinction measurements, and the ages and stellar populations of X-ray counterparts are essential to differentiate between normal X-ray populations and more exotic ones (e.g. relativistically beamed XRBs or intermediate-mass black holes), thus determining the demographics of truly superluminous X-ray sources.

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© 2004. The American Astronomical Society.