Impact of Cluster Physics on the Sunyaev-Zel'dovich Power Spectrum

Abstract

We use an analytic model to investigate the theoretical uncertainty on the thermal Sunyaev-Zel'dovich (SZ) power spectrum due to astrophysical uncertainties in the thermal structure of the intracluster medium. Our model accounts for star formation and energy feedback (from supernovae and active galactic nuclei) as well as radially dependent non-thermal pressure support due to random gas motions, the latter calibrated by recent hydrodynamical simulations. We compare the model against X-ray observations of low-redshift clusters, finding excellent agreement with observed pressure profiles. Varying the levels of feedback and non-thermal pressure support can significantly change both the amplitude and shape of the thermal SZ power spectrum. Increasing the feedback suppresses power at small angular scales, shifting the peak of the power spectrum to lower . On the other hand, increasing the nonthermal pressure support has the opposite effect, significantly reducing power at large angular scales. In general, including non-thermal pressure at the level measured in simulations has a large effect on the power spectrum, reducing the amplitude by 50% at angular scales of a few arcminutes compared to a model without a non-thermal component. Our results demonstrate that measurements of the shape of the power spectrum can reveal useful information on important physical processes in groups and clusters, especially at high redshift where there exists little observational data. Comparing with the recent South Pole Telescope measurements of the small-scale cosmic microwave background power spectrum, we find our model reduces the tension between the values of σ 8 measured from the SZ power spectrum and from cluster abundances.

Little evidence for entropy and energy excess beyond r500 - An end to ICM preheating?

“…Since the "actual" total mass is also partially supported by non-thermal pressure, we model the non-thermal pressure fraction using the form given in Shaw et al (2010),…”

“…where Ptot is total gas pressure, f (r, z) = a(z) r r 500 nnt , a(z) = a0(1 + z) β with a0 = 0.18 ± 0.06, β = 0.5 and nnt = 0.8 ± 0.25 (Shaw et al 2010). We also study the effect of different non-thermal pressure fraction by varying a0.…”

“…The effect of clumping and nonthermal pressure, especially at large radii, has been shown to be important (Eckert et al 2015;Battaglia et al 2015;Shaw et al 2010;Shi et al 2015) and we incorporate both in our analysis.…”

Planck2013 results. XXI. Power spectrum and high-order statistics of thePlanckall-sky Compton parameter map

“…One advantage of using the tSZ angular power spectrum over cluster counts is that no explicit measurement of cluster masses is required. Also, lower mass, and therefore fainter, clusters, which may not be detected as individual objects, contribute to this statistical signal (Battaglia et al 2010;Shaw et al 2010). However, significant drawbacks of using the tSZ angular power spectrum include potential contamination from point sources (Rubiño-Martín & Sunyaev 2003;Taburet et al 2010) and other foregrounds.…”

“…Moreover, the scales probed are particularly sensitive to the uncertainties in modelling the intracluster medium (ICM) over a broad range of masses and redshifts, and at large clustercentric radii (Battaglia et al 2010). Recent work, using hydrodynamical simulations (Battaglia et al 2010(Battaglia et al , 2012) N-body simulations plus semi-analytic gas models (Trac et al 2011) and purely analytic models (Shaw et al 2010), have significantly reduced the tension between the observed and predicted values. However the distribution of amplitudes between different mod- els and simulations is still significantly larger than the measurement errors, degrading the constraints that can be placed on cosmological parameters with these methods (Dunkley et al 2013;Reichardt et al 2013).…”