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Published online by Cambridge University Press: 30 May 2009
Using two complementary X-ray galaxy cluster studies we present new cosmological constraints on dark energy. Using Chandra measurements of the X-ray gas mass fraction, fgas, we obtain a detection of the effects of dark energy comparable in significance to recent type Ia supernovae (SNIa) studies. Using X-ray luminosity function (XLF) data from galaxy cluster surveys, we obtain the first interesting determination of the dark energy equation of state from measurements of the growth of cosmic structure in clusters. Both of our experiments provide strong, independent support to theΛCDM paradigm.