arXiv subjects

Scott T Kay

Publications and source records attributed to Scott T Kay.

3 recordsLinked to original sources

arXiv2003

The power spectrum amplitude from clusters revisited: σ_8 using simulations with preheating and cooling

The amplitude of density perturbations, for the currently-favoured LambdaCDM cosmology, is constrained using the observed properties of galaxy clusters. The catalogue used is that of Ikebe et al. (2002). The cluster temperature to mass relation is obtained via N-body/hydrodynamical simulations including radiative cooling and preheating of cluster gas, which we have previously shown to reproduce well the observed temperature--mass relation in the innermost parts of clusters (Thomas et al. 2002). We generate and compare mock catalogues via a Monte Carlo method, which allows us to constrain the relation between X-ray temperature and luminosity, including its scatter, simultaneously with cosmological parameters. We find a luminosity-temperature relation in good agreement with the results of Ikebe et al. (2002), while for the matter power spectrum normalization, we find $σ_8 = 0.78_{-0.06}^{+0.30}$ at 95 per cent confidence for $Ω_0 = 0.35$. Scaling to WMAP's central value of $Ω_0 = 0.27$ would give a best-fit value of $σ_8 \simeq 0.9$.

astro-ph↗

arXiv2001

The impact of cooling and pre-heating on the Sunyaev-Zel'dovich effect

We use hydrodynamical simulations to assess the impact of radiative cooling and `pre-heating' on predictions for the Sunyaev--Zel'dovich (SZ) effect. Cooling significantly reduces both the mean SZ signal and its angular power spectrum, while pre-heating can give a higher mean distortion while leaving the angular power spectrum below that found in a simulation without heating or cooling. We study the relative contribution from high and low density gas, and find that in the cooling model about 60 per cent of the mean thermal distortion arises from low overdensity gas. We find that haloes dominate the thermal SZ power spectrum in all models, while in the cooling simulation the kinetic SZ power spectrum originates predominantly in lower overdensity gas.

astro-ph↗

arXiv2001

Sunyaev-Zel'dovich Predictions for the Planck Surveyor Satellite using the Hubble Volume Simulations

We use the billion-particle Hubble Volume simulations to make statistical predictions for the distribution of galaxy clusters that will be observed by the Planck Surveyor satellite through their effect on the cosmic microwave background -- the Sunyaev-Zel'dovich effect. We utilize the lightcone datasets for both critical density (tauCDM) and flat low-density (LambdaCDM) cosmologies: a `full-sky' survey out to $z \sim 0.5$, two `octant' datasets out to beyond $z=1$ and a 100 square degree dataset extending to $z \sim 4$. Making simple, but robust, assumptions regarding both the thermodynamic state of the gas and the detection of objects against an unresolved background, we present the expected number of SZ sources as a function of redshift and angular size, and also by flux (for both the thermal and kinetic effects) for 3 of the relevant HFI frequency channels. We confirm the expectation that Planck will detect around $5\times 10^4$ clusters, though the exact number is sensitive to the choice of several parameters including the baryon fraction, and also to the cluster density profile, so that either cosmology may predict more clusters. We also find that the majority of detected sources should be at $z<1.5$, and we estimate that around one per cent of clusters will be spatially resolved by Planck, though this has a large uncertainty.

astro-ph↗