Simon Fraser University
SFU Cosmology Seminars

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Thursday, 12 April 2007, 13:00 in P8445B

Dr. David Rapetti (KIPAC/Stanford)

X-ray galaxy clusters as cosmological probes

Late-time cosmic acceleration is currently one of the most intriguing questions in cosmology. The standard cosmological model now consists of a present-day Universe filled with approximately 4 per cent of normal baryonic matter, 23 per cent of cold dark matter (CDM) and 73 per cent of quantum vacuum energy (the cosmological constant, Λ) that provides the late-time cosmic acceleration. However, any departure from this standard ΛCDM model would suggest either a new energy component of the Universe, so-called dark energy, or a modified gravity theory, so-called dark gravity. Using X-ray galaxy clusters we have developed two independent and complementary experiments to constrain cosmic acceleration. Our first experiment measures distances to the largest and most relaxed X-ray galaxy clusters using their gas mass fraction fgas. This allows us to reconstruct cosmic expansion up to z ~ 1. This experiment also provides one of the most precise measurements of the mean matter density of the Universe. Combining this experiment with supernovae type Ia and cosmic microwave background data we obtain tight constraints on departures around the concordance ΛCDM paradigm. Furthermore we use two different and complementary theoretical frameworks to explore departures from ΛCDM. We find that ΛCDM is still a robust description of current data at about the 1σ level. Our second experiment measures the growth of structure which is a strong function of cosmological parameters. We count X-ray galaxy clusters above both a flux and a luminosity threshold at different redshifts (z < 0.7) and compare this with precise theoretical predictions of the mass function. We obtain the tightest constraints to date for a single experiment on the equation of state of dark energy.

Seminars in 2006:

2006-10-04 12:45 in P8445A - Serge Winitzki (Ludwig Maximilians University, Munich): Predictions in eternally inflating universe
2006-11-22 12:45 in P8445B - Ingrid Stairs (UBC): Relativistic binary pulsars
2006-11-23 14:00 in P8445B - Veselin Filev (University of Southern California): Adding flavors in AdS/CFT correspondence
2006-11-30 14:00 in P8445B - Marco Peloso (University of Minnesota): The role of SUSY flat directions in reheating
2006-12-05 13:00 in P8445B - Jasper Wall (UBC): Submillimetre galaxies and star-formation in the early Universe
2007-01-11 13:00 in P8445B - Krzysztof Sliwa (Tufts University): Supersymmetry for particle physicists
2007-01-16 14:00 in SSB7109 - Bojan Losic (University of Alberta): Aspects of nonlinear perturbation theory in cosmology
2007-02-01 13:00 in P8445B - Adam Moss (UBC): Dark energy and the rubber band
2007-03-08 13:00 in P8445B - Catherine Heymans (UBC): Probing dark matter and dark energy with weak gravitational lensing
2007-03-22 13:00 in P8445B - Ira Wasserman (Cornell): The neutron star in 1930 -- and today (special colloquium)
2007-03-23 12:30 in P8445B - Ira Wasserman (Cornell): Dynamics of the r mode instability of neutron stars
2007-03-27 14:00 in SSB7109 - Shinji Mukohyama (University of Tokyo): Cosmology with warped flux compactification
2007-04-03 14:00 in SSB7109 - Christian Armendariz-Picon (Syracuse): Do quantum excitations of the inflaton decay?
2007-04-12 13:00 in P8445B - David Rapetti (KIPAC/Stanford): X-ray galaxy clusters as cosmological probes
2007-04-19 13:00 in P8445B - Eric Peng (HIA/DAO, Victoria): Globular cluster systems and the early evolution of galaxies
2007-04-24 14:00 in P8445B - Evgeny Sorkin (UBC): The pinching black strings
2007-05-03 13:00 in P8445B - Tanmay Vachaspati (Case Western Reserve University): Formation of black holes

[ See complete seminar archives | iCal feed ]

Modified by Andrei Frolov <frolov@sfu.ca> on 2023-11-01