Nonnuclear Hyper/Ultraluminous X-Ray Sources in the Starbursting Cartwheel Ring Galaxy

We report the Chandra/ACIS-S detection of more than 20 ultraluminous X-raysources (ULXs, L_{0.5-10 keV} >~ 3 x 10^{39} ergs/sec) in the Cartwheelcollisional ring galaxy system, of which over a dozen are located in the outeractive star-forming ring. A remarkable hyperluminous X-ray source (HLX,L_{0.5-10 keV} >~ 10^{41} ergs/sec assuming isotropic radiation), whichdominates the X-ray emission from the Cartwheel ring, is located in the samesegment of the ring as most ULXs. These powerful H/ULXs appear to be coincidentwith giant HII region complexes, young star clusters, and radio andmid-infrared hot-spots: all strong indicators of recent massive star formation.The X-ray spectra show that H/ULXs have similar properties as those of the {\itmost luminous} ULXs found in the nearest starbursts and galaxy mergers such asthe Antennae galaxies and M82. The close association between the X-ray sourcesand the starbursting ring strongly suggests that the H/ULXs are intimatelyassociated with the production and rapid evolution of short-lived massivestars. The observations represent the most extreme X-ray luminositiesdiscovered to date associated with star-forming regions--rivaling the X-rayluminosities usually associated with active galactic nuclei.