Cosmology using galaxy cluster peculiar velocities

Future multi-frequency microwave background experiments with arcminute resolution and micro-Kelvin temperature sensitivity will be able to detect the kinetic Sunyaev-Zeldovich effect, providing a way to measure radial (line-of-sight) peculiar velocities of massive galaxy clusters. We show that measurement of cluster peculiar velocities have the potential to constrain several dark energy parameters. We also compare cluster peculiar velocities with other dark energy probes: the eventual constraints from radial peculiar velocity measurements on the dark energy parameters are comparable to constraints from supernovae measurements, and better than cluster counts and baryon acoustic oscillations; adding radial peculiar velocity to other dark energy probes improves constraints on the figure of merit by more than a factor of two.;We also study the impact of the mass-observable relation (i.e the relation between the observed Sunyaev-Zeldovich flux and the mass of the galaxy cluster) and other systematic errors on cluster radial peculiar velocities. We find that cluster radial peculiar velocities closely trace the large-scale peculiar velocity field independent of cluster mass. On the other hand, cluster radial peculiar velocity determinations are complicated by microwave emission from dusty galaxies and radio sources, which may be correlated with clusters. Systematic errors due to these factors can give substantial biases in determination of dark energy parameters, although radial peculiar velocity surveys will contain enough information that the errors can be modeled using the data itself, with little degradation in cosmological constraints.;An alternative to using the galaxy cluster radial peculiar velocity field directly is the cluster momentum distribution. Dark-matter cosmological simulations can provide the total cluster momentum distribution, while the Sunyaev-Zeldovich effect gives the baryon momentum. Thus, to better understand the cluster momentum distribution, we study the effect of quasar feedback on the baryon fraction in galaxy groups using high-resolution numerical simulations. For a sample of ten galaxy group-sized dark matter halos, the total gas fraction in the two simulations generally differs by less than 10%. We conclude that the quasar feedback do not add any significant systematic errors to the cluster momentum.;keywords: Cosmology: theory, Cosmology: Sunyaev-Zeldovich effect, cosmological parameters, galaxies: clusters, velocity, statistics.