COSMOLOGICAL CONSTRAINTS FROM SUNYAEV-ZEL'DOVICH-SELECTED CLUSTERS WITH X-RAY OBSERVATIONS IN THE FIRST 178 deg[superscript 2] OF THE SOUTH POLE TELESCOPE SURVEY

• Main Authors: Andersson, Karl (Contributor), Bautz, Marshall W. (Contributor), McDonald, Michael A. (Contributor)
• Other Authors: MIT Kavli Institute for Astrophysics and Space Research (Contributor)
• Format: Article
• Language: English
• Published: IOP Publishing, 2015-02-17T14:22:52Z.
• Subjects: Article
• Online Access: Get fulltext

We use measurements from the South Pole Telescope (SPT) Sunyaev-Zel'dovich (SZ) cluster survey in combination with X-ray measurements to constrain cosmological parameters. We present a statistical method that fits for the scaling relations of the SZ and X-ray cluster observables with mass while jointly fitting for cosmology. The method is generalizable to multiple cluster observables, and self-consistently accounts for the effects of the cluster selection and uncertainties in cluster mass calibration on the derived cosmological constraints. We apply this method to a data set consisting of an SZ-selected catalog of 18 galaxy clusters at z > 0.3 from the first 178 deg[superscript 2] of the 2500 deg[superscript 2] SPT-SZ survey, with 14 clusters having X-ray observations from either Chandra or XMM-Newton. Assuming a spatially flat ΛCDM cosmological model, we find the SPT cluster sample constrains σ[subscript 8](Ω [subscript m] /0.25)[superscript 0.30] = 0.785 ± 0.037. In combination with measurements of the cosmic microwave background (CMB) power spectrum from the SPT and the seven-year Wilkinson Microwave Anisotropy Probe data, the SPT cluster sample constrains σ[subscript 8] = 0.795 ± 0.016 and Ω [subscript m] = 0.255 ± 0.016, a factor of 1.5 improvement on each parameter over the CMB data alone. We consider several extensions beyond the ΛCDM model by including the following as free parameters: the dark energy equation of state (w), the sum of the neutrino masses (Σm [subscript ν]), the effective number of relativistic species (N [subscript eff]), and a primordial non-Gaussianity (f [subscript NL]). We find that adding the SPT cluster data significantly improves the constraints on w and Σm [subscript ν] beyond those found when using measurements of the CMB, supernovae, baryon acoustic oscillations, and the Hubble constant. Considering each extension independently, we best constrain w = -0.973 ± 0.063 and the sum of neutrino masses Σm [subscript ν] < 0.28 eV at 95% confidence, a factor of 1.25 and 1.4 improvement, respectively, over the constraints without clusters. Assuming a ΛCDM model with a free N [subscript eff] and Σm [subscript ν], we measure N [subscript eff] = 3.91 ± 0.42 and constrain Σm [subscript ν] < 0.63 eV at 95% confidence. We also use the SPT cluster sample to constrain f [subscript NL] = -220 ± 317, consistent with zero primordial non-Gaussianity. Finally, we discuss the current systematic limitations due to the cluster mass calibration, and future improvements for the recently completed 2500 deg[superscript 2] SPT-SZ survey. The survey has detected ~500 clusters with a median redshift of ~0.5 and a median mass of ~2.3 × 10[superscript 14] M [subscript ☉] h[superscript -1] and, when combined with an improved cluster mass calibration and existing external cosmological data sets will significantly improve constraints on w.
University of Pennsylvania (Contract 2834-MIT-SAO-4018)