AAS 207th Meeting, 8-12 January 2006
Session 16 Example Constellation-X Science
Poster, Monday, 9:20am-7:00pm, January 9, 2006, Exhibit Hall

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[16.03] Probing dark energy with Constellation-X

D.A. Rapetti, S.W. Allen (KIPAC at Stanford/SLAC), Con-X Facility Science Team

Con-X will carry out two powerful and independent sets of tests of dark energy based on X-ray observations of galaxy clusters. The first group of tests will measure the absolute distances to clusters, primarily using measurements of the X-ray gas mass fraction in the largest, dynamically relaxed clusters, but with additional constraining power provided by follow-up observations of the Sunyaev-Zel'dovich (SZ) effect. As with supernovae studies, such data determine the transformation between redshift and true distance, d(z), allowing cosmic acceleration to be measured directly. The second, independent group of tests will use the spectroscopic capabilities of Con-X to determine scaling relations between X-ray observables and mass. Together with theoretical models for the mass function and X-ray and SZ cluster surveys, these data will help to constrain the growth of structure, which is also a strong function of cosmological parameters.

Con-X data will constrain dark energy with comparable accuracy and in a beautifully complementary manner to the best other techniques available circa 2018. For example, with a modest ~10-15% (10-15Ms) investment of the available observing time over the first 5 years of the Con-X mission, we will be able to measure the X-ray gas mass fraction (or predict the Compton y-parameter) to 5% or 3.5% accuracy for 500 or 250 clusters, respectively, with a median redshift z~. When combined with CMB data, the predicted dark energy constraints from Con-X X-ray gas mass fraction data are comparable to those projected by the SNAP collaboration for CMB+SNAP data as well as the predictions for future galaxy redshift surveys. Only by combining such independent and complementary methods can a precise understanding of the nature of dark energy be expected to be achieved.

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