Constraining gravity at large scales with X-ray galaxy cluster studies

¹ KIPAC at Stanford University, 452 Lomita Mall, Stanford CA, 94305-4085, USA, and SLAC National Accelerator Laboratory, 2575 Sand Hill Road, Menlo Park, CA 94025, USA
² Institute for Astronomy, 2680 Woodlawn Drive, Honolulu, HI 96822, USA
³ Astronomisches Rechen-Institut, Zentrum für Astronomie der Universität Heidelberg, Mönchhofstrasse 12-14, 69120 Heidelberg, Germany
⁴ Institute of Astronomy, Madingley Road, Cambridge CB3 0HA, UK

Abstract

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, f_gas, 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 the ΛCDM paradigm.