[Normal Galaxies, Clusters of Galaxies -- Oral ]
Constraints on Cosmology and X-ray Scaling Relations from the
Growth of Massive Galaxy Clusters
Adam Mantz, Stanford/SLAC
Steve Allen(1), David Rapetti(1), Harald Ebeling(2), Alex Drlica-Wagner(1); (1) Stanford/SLAC, (2) University of Hawaii
I will present simultaneous constraints on galaxy cluster
X-ray scaling relations and cosmology obtained from observations of the
growth of massive clusters. The data set consists of 238 flux-selected
clusters at redshifts $z \leq 0.5$ drawn from the ROSAT All-Sky Survey,
and incorporates extensive Chandra follow-up observations. Our results
on the scaling relations are consistent with excess heating of the
intracluster medium; however, this heating appears to be limited to the
central regions of clusters. The evolution of the scaling relations is
consistent with the predictions of simple gravitational collapse models,
indicating that the effects of excess heating on cluster properties do
not evolve significantly within redshift 0.5. Clusters with cooling
cores make up a significant fraction of our sample at all redshifts,
consistent with most previous observations and with recent simulations.
For spatially flat, constant-$w$ cosmological models, the cluster data
yield $\Omega_m = 0.23 \pm 0.04$, $\sigma_8 = 0.82 \pm 0.05$, and $w =
-1.01 \pm 0.20$, including conservative allowances for systematic
uncertainties. Our results are consistent and competitive with a variety
of independent cosmological data. In evolving-$w$ models, marginalizing
over transition redshifts in the range 0.05--1, the combination of the
growth of structure data with the cosmic microwave background, supernovae,
cluster gas mass fractions and baryon acoustic oscillations constrains
the dark energy equation of state at late and early times to be respectively
$w_0 = -0.88 \pm 0.21$ and $w_{et} = -1.05 \^{+0.20}_{-0.36}$. While our
results on dark energy from the growth of structure alone are statistically
limited at present, constraints from the combination with other cosmological
data could be tightened by incorporating gravitational lensing observations
and/or improved simulations of baryonic physics in clusters.