tSZ Power Spectrum Research Articles

Retrieving cosmological information from small-scale CMB foregrounds

We propose a new analysis of small-scale cosmic microwave background (CMB) data by introducing the cosmological dependency of the foreground signals, focussing first on the thermal Sunyaev-Zel’dovich (tSZ) power spectrum, derived from the halo model. We analyse the latest observations by the South Pole Telescope (SPT) of the high-ℓ power (cross) spectra at 95, 150, and 220 GHz, as the sum of CMB and tSZ signals, both depending on cosmological parameters and remaining contaminants. In order to perform faster analyses, we propose a new tSZ modelling based on machine learning algorithms (namely Random Forest). We show that the additional information contained in the tSZ power spectrum tightens constraints on cosmological and tSZ scaling relation parameters. We combined for the first time the Planck tSZ data with SPT high-ℓ to derive new constraints. Finally, we show how the amplitude of the remaining kinetic SZ power spectrum varies depending on the assumptions made on both tSZ and cosmological parameters. These results show the importance of a thorough modelling of foregrounds in the cosmological analysis of small-scale CMB data. Reliable constraints on cosmological parameters can only be achieved once other significant foregrounds, such as the kinetic SZ and the cosmic infrared background (CIB), are also properly accounted for.

Assessing the Importance of Noise from Thermal Sunyaev–Zel′dovich Signals for CMB Cluster Surveys and Cluster Cosmology

Abstract We explore the significance of noise from thermal Sunyaev–Zel’dovich (tSZ) signals for cluster detection using cosmic microwave background (CMB) surveys. The noise arises both from neighboring objects and also from haloes below the detection limit. A wide range of surveys are considered: SPT-SZ, SPTpol, and SPT-3G from the South Pole Telescope; SO-Baseline and SO-Goal configurations for Simons Observatory; CMB-S4's wide-area (S4-Wide) and deep (S4-Ultra deep) surveys; and the futuristic CMB-HD experiment. We find that the noise from tSZ signals has a significant impact on CMB-HD and to some extent on S4-Ultra deep. For other experiments, the effect is negligible as the noise in the tSZ map is dominated by residual foregrounds or experimental noise. In the limit when the noise from tSZ signals is important, we find that removing the detected clusters and rerunning the cluster finder allows us to find a new set of less massive and distant clusters. Since the detected clusters are the dominant source of the tSZ power, removing them reduces the power at ℓ = 3000 by ×5 for CMB-HD; ×3.1 of S4-Ultra deep; ×2.4 for S4-Wide and SPT-3G; ×1.5 for SO-Goal and SPTpol; ×1.35 for SO-Baseline; and ×1.08 for SPT-SZ. We forecast the expected number of clusters and also derive parameter constraints by combining cluster counts with primary CMB and tSZ power spectra finding that the future surveys can reduce the error on the dark energy equation of state parameter to sub-percent levels and can also enable ≥3σ detection of the sum of neutrino masses.

CMB at small scales: Cosmology from tSZ power spectrum

Small scale CMB angular power spectrum contains not only primordial CMB information but also many contaminants coming from secondary anisotropies. Most of the latter depend on the cosmological model but are often marginalised over. We propose a new analysis of the SPT data focusing on the cosmological contribution of the thermal Sunyaev Zel’dovich (tSZ) effect. We model the tSZ angular spectrum with the halo model and train a random forest algorithm to speed up its computation. We show that using the cosmological information of the tSZ on top of the primordial CMB one contained in SPT data bring more constraints on cosmological parameters. We also combine for the first time Planck tSZ angular power spectrum with SPT ones to put further constraints. This proof of concept study shows how much a proper modelling of the foregrounds in the cosmological analyses is needed.

Breaking degeneracies with the Sunyaev-Zeldovich full bispectrum

Non-Gaussian (NG) statistics of the thermal Sunyaev-Zeldovich (tSZ) effect carry significant information which is not contained in the power spectrum. Here, we perform a joint Fisher analysis of the tSZ power spectrum and bispectrum to verify how much the full bispectrum can contribute to improve parameter constraints. We go beyond similar studies of this kind in several respects: first of all, we include the complete power spectrum and bispectrum (auto- and cross-) covariance in the analysis, computing all NG contributions; furthermore we consider a multi-component foreground scenario and model the effects of component separation in the forecasts; finally, we consider an extended set of both cosmological and intra-cluster medium parameters. We show that the tSZ bispectrum is very efficient at breaking parameter degeneracies, making it able to produce even stronger cosmological constraints than the tSZ power spectrum: e.g. the standard deviation on σ8 shrinks from σPS(σ8)=0.35 to σBS(σ8)=0.065 when we consider a multi-parameter analysis. We find that this is mostly due to the different response of separate triangle types (e.g. equilateral and squeezed) to changes in model parameters. While weak, this shape dependence is clearly non-negligible for cosmological parameters, and it is even stronger, as expected, for intra-cluster medium parameters.

Super sample covariance of the thermal Sunyaev-Zel’dovich effect

The thermal Sunyaev-Zel'dovich (tSZ) effect is a powerful probe of cosmology. The statistical errors in the tSZ power spectrum measurements are dominated by the presence of massive clusters in a survey volume that are easy to identify on individual cluster basis. First, we study the impact of super sample covariance (SSC) on the tSZ power spectrum measurements, and find that the sample variance is dominated by the connected non-Gaussian (cNG) covariance arising mainly from Poisson number fluctuations of massive clusters in the survey volume. Second, we find that removing such individually-detected, massive clusters from the analysis significantly reduces the cNG contribution, thereby leading the SSC to be a leading source of the sample variance. We then show, based on Fisher analysis, that the power spectrum measured from the remaining diffuse tSZ effects can be used to obtain tight constraints on cosmological parameters as well as the hydrostatic mass bias parameter. Our method offers complementary use of individual tSZ cluster counts and the power spectrum measurements of diffuse tSZ signals for cosmology and intracluster gas physics.

Including massive neutrinos in thermal Sunyaev Zeldovich power spectrum and cluster counts analyses

ABSTRACT We consistently include the effect of massive neutrinos in the thermal Sunyaev Zeldovich (SZ) power spectrum and cluster counts analyses, highlighting subtle dependencies on the total neutrino mass and data combination. In particular, we find that using the transfer functions for cold dark matter (CDM) + baryons in the computation of the halo mass function, instead of the transfer functions including neutrino perturbations, as prescribed in recent work, yields an ≈0.25 per cent downward shift of the σ8 constraint from tSZ power spectrum data, with a fiducial neutrino mass Σmν = 0.06 eV. In ΛCDM, with an X-ray mass bias corresponding to the expected hydrostatic mass bias, i.e. (1 − b) ≃ 0.8, our constraints from Planck SZ data are consistent with the latest results from SPT, DES-Y1, and KiDS+VIKING-450. In νΛCDM, our joint analyses of Planck SZ with Planck 2015 primary CMB yield a small improvement on the total neutrino mass bound compared to the Planck 2015 primary CMB constraint, as well as (1 − b) = 0.64 ± 0.04 (68 per cent CL). For forecasts, we find that competitive neutrino mass measurements using cosmic variance limited SZ power spectrum require masking the heaviest clusters and probing the small-scale SZ power spectrum up to ℓmax ≈ 104. Although this is challenging, we find that SZ power spectrum can realistically be used to tightly constrain intracluster medium properties: we forecast a 2 per cent determination of the X-ray mass bias by combining CMB-S4 and our mock SZ power spectrum with ℓmax = 103.

New constraints on the mass bias of galaxy clusters from the power spectra of the thermal Sunyaev–Zeldovich effect and cosmic shear

Abstract The thermal Sunyaev–Zeldovich (tSZ) power spectrum is a powerful probe of the present-day amplitude of matter density fluctuations, and has been measured up to $\ell \approx 10^3$ from the Planck data. The largest systematic uncertainty in the interpretation of this data is the so-called “mass bias” parameter B, which relates the true halo mass to the mass proxy used by the Planck team as $M\,_{\rm 500c}^{\rm Planck}=M\,_{\rm 500c}^{\rm true}/B$. Since the power spectrum of the cosmic weak lensing shear is also sensitive to the amplitude of matter density fluctuations via $S_8\equiv \sigma _8 \Omega _{\rm m}^{\alpha }$ with $\alpha \sim 0.5$, we can break the degeneracy between the mass bias and the cosmological parameters by combining the tSZ and cosmic shear power spectra. In this paper, we perform a joint likelihood analysis of the tSZ power spectrum from Planck and the cosmic shear power spectrum from Subaru Hyper Suprime-Cam. Our analysis does not use the primordial cosmic microwave background (CMB) information. We obtain a new constraint on the mass bias as $B = 1.37 ^{+0.15}_{-0.23}$ or $(1-b) = B^{-1}=0.73^{+0.08}_{-0.13}$ ($68\%$ confidence limit), for $\sigma _8 < 0.9$. This value of B is lower than that needed to reconcile the tSZ data with the primordial CMB and CMB lensing data, i.e., $B = 1.64 \pm 0.19$, but is consistent with the mass bias expected from hydrodynamical simulations, $B = 1.28 \pm 0.20$. Thus our results indicate that the mass bias is consistent with the non-thermal pressure support from mass accretion of galaxy clusters via the cosmic structure formation, and that the cosmologies inferred from the tSZ and the cosmic shear are consistent with each other.

Impact of the mean pressure profile of galaxy clusters on the cosmological constraints from the Planck tSZ power spectrum

ABSTRACTCosmological analyses based on surveys of galaxy clusters observed through the Sunyaev–Zel’dovich (SZ) effect strongly rely on the mean pressure profile of the cluster population. A tension is currently observed between the cosmological constraints obtained from the analyses of the CMB primary anisotropies and those from cluster abundance in SZ surveys. This discrepancy may be explained by a wrong estimate of the hydrostatic bias parameter that links the hydrostatic mass to the true mass of galaxy clusters. However, a variation of both the amplitude and the shape of the mean pressure profile could also explain part of this tension. We analyse the effects of a modification of this profile on the constraints of the σ8 and Ωm parameters through the analysis of the SZ power spectrum measured by the Planck collaboration. We choose two mean pressure profiles that are respectively lower and higher than the one obtained from the observation of nearby clusters by Planck. The selection of the parameters of these two profiles is based on the current estimates of the pressure and gas mass fraction profile distributions at low redshift. The cosmological parameters found for these two profiles are significantly different from the ones obtained with the Planck pressure profile. We conclude that an ${\sim }15{{\ \rm per\ cent}}$ decrease of the amplitude of the mean normalized pressure profile would alleviate the tension observed between the constraints of σ8 and Ωm from the CMB and cluster analyses without requiring extreme values of the mass bias parameter.

Can we neglect relativistic temperature corrections in thePlanckthermal SZ analysis?

Measurements of the thermal Sunyaev-Zel'dovich (tSZ) effect have long been recognized as a powerful cosmological probe. Here we assess the importance of relativistic temperature corrections to the tSZ signal on the power spectrum analysis of the Planck Compton-$y$ map, developing a novel formalism to account for the associated effects. The amplitude of the tSZ power spectrum is found to be sensitive to the effective electron temperature, $\bar{T}_e$, of the cluster sample. Omitting the corresponding modifications leads to an underestimation of the $yy$-power spectrum amplitude. Relativistic corrections thus add to the error budget of tSZ power spectrum observables such as $\sigma_8$. This could help alleviate the tension between various cosmological probes, with the correction scaling as $\Delta \sigma_8/\sigma_8 \simeq 0.019\,[k\bar{T}_e\,/\,5\,{\rm keV}]$ for Planck. At the current level of precision, this implies a systematic shift by $\simeq 1\sigma$, which can also be interpreted as an overestimation of the hydrostatic mass bias by $\Delta b \simeq 0.046\,(1-b)\,[k\bar{T}_e\,/\,5\,{\rm keV}]$, bringing it into better agreement with hydrodynamical simulations. It is thus time to consider relativistic temperature corrections in the processing of current and future tSZ data.

Constraints from thermal Sunyaev-Zel’dovich cluster counts and power spectrum combined with CMB

The thermal Sunyaev-Zel’dovich (tSZ) effect is one of the recent probes of cosmology and large-scale structures. We update constraints on cosmological parameters from galaxy clusters observed by thePlancksatellite in a first attempt to combine cluster number counts and the power spectrum of hot gas; we used a new value of the optical depth and, at the same time, sampling on cosmological and scaling-relation parameters. We find that in the ΛCDM model, the addition of a tSZ power spectrum provides small improvements with respect to number counts alone, leading to the 68% c.l. constraints Ωm= 0.32 ± 0.02,σ8= 0.76 ± 0.03, andσ8(Ωm/0.3)1/3= 0.78 ± 0.03 and lowering the discrepancy with results for cosmic microwave background (CMB) primary anisotropies (updated with the new value ofτ) to ≃1.8σonσ8. We analysed extensions to the standard model, considering the effect of massive neutrinos and varying the equation of state parameter for dark energy. In the first case, we find that the addition of the tSZ power spectrum helps in improving cosmological constraints with respect to number count alone results, leading to the 95% upper limit ∑mν< 1.88 eV. For the varying dark energy equation of state scenario, we find no important improvements when adding tSZ power spectrum, but still the combination of tSZ probes is able to provide constraints, producingw= −1.0 ± 0.2. In all cosmological scenarios, the mass bias to reconcile CMB and tSZ probes remains low at (1 −b) ≲ 0.67 as compared to estimates from weak lensing and X-ray mass estimate comparisons or numerical simulations.

Dark energy constraints from the thermal Sunyaev–Zeldovich power spectrum

We constrain the dark energy equation of state parameter, $w$, using the power spectrum of the thermal Sunyaev-Zeldovich (tSZ) effect. We improve upon previous analyses by taking into account the trispectrum in the covariance matrix and marginalising over the foreground parameters, the correlated noise, the mass bias $B$ in the Planck universal pressure profile, and all the relevant cosmological parameters (i.e., not just $\Omega_{\mathrm{m}}$ and $\sigma_8$). We find that the amplitude of the tSZ power spectrum at $\ell\lesssim 10^3$ depends primarily on $F\equiv \sigma_{8}(\Omega_{{\mathrm{m}}}/B)^{0.40}h^{-0.21}$, where $B$ is related to more commonly used variable $b$ by $B=(1-b)^{-1}$. We measure this parameter with 2.6\% precision, $F=0.460\pm 0.012$ (68% CL). By fixing the bias to $B=1.25$ and adding the local determination of the Hubble constant $H_0$ and the amplitude of the primordial power spectrum constrained by the Planck Cosmic Microwave Background (CMB) data, we find $w=-1.10\pm0.12$, $\sigma_{\mathrm{8}}=0.802\pm0.037$, and $\Omega_{{\mathrm{m}}}=0.265\pm0.022$ (68% CL). Our limit on $w$ is consistent with and is as tight as that from the distance-alone constraint from the CMB and $H_0$. Finally, by combining the tSZ power spectrum and the CMB data we find, in the $\Lambda$ Cold Dark Matter (CDM) model, the mass bias of $B=1.71\pm 0.17$, i.e., $1-b=0.58\pm 0.06$ (68% CL).

Investigating cluster astrophysics and cosmology with cross-correlation of the thermal Sunyaev–Zel'dovich effect and weak lensing

Recent detections of the cross-correlation of the thermal Sunyaev–Zel'dovich (tSZ) effect and weak gravitational lensing (WL) enable unique studies of cluster astrophysics and cosmology. In this work, we present constraints on the amplitude of the non-thermal pressure fraction in galaxy clusters, α0, and the amplitude of the matter power spectrum, σ8, using measurements of the tSZ power spectrum from Planck, and the tSZ–WL cross-correlation from Planck and the Red Cluster Sequence Lensing Survey. We fit the data to a semi-analytic model with the covariance matrix using N-body simulations. We find that the tSZ power spectrum alone prefers σ8 ∼ 0.85 and a large fraction of non-thermal pressure (α0 ∼ 0.2–0.3). The tSZ–WL cross-correlation on the other hand prefers a significantly lower σ8 ∼ 0.6 and low α0 ∼ 0.05. We show that this tension can be mitigated by allowing for a steep slope in the stellar mass–halo mass relation, which would cause a reduction of the gas in low-mass haloes. In such a model, the combined data prefer σ8 ∼ 0.7 and α0 ∼ 0.2, consistent with predictions from hydrodynamical simulations.

Combined analysis of galaxy cluster number count, thermal Sunyaev-Zel’dovich power spectrum, and bispectrum

The thermal Sunyaev-Zel’dovich (tSZ) effect is a powerful probe of the evolution of structures in the universe, and is thus highly sensitive to cosmological parameters σ8 and Ωm, though its power is hampered by the current uncertainties on the cluster mass calibration. In this analysis we revisit constraints on these cosmological parameters as well as the hydrostatic mass bias, by performing (i) a robust estimation of the tSZ power-spectrum, (ii) a complete modeling and analysis of the tSZ bispectrum, and (iii) a combined analysis of galaxy clusters number count, tSZ power spectrum, and tSZ bispectrum. From this analysis, we derive as final constraints σ8 = 0.79 ± 0.02, Ωm = 0.29 ± 0.02, and (1−b) = 0.71 ± 0.07. These results favor a high value for the hydrostatic mass bias compared to numerical simulations and weak-lensing based estimations. They are furthermore consistent with both previous tSZ analyses, CMB derived cosmological parameters, and ancillary estimations of the hydrostatic mass bias.

Cosmological constraints from thermal Sunyaev–Zeldovich power spectrum revisited

Thermal Sunyaev-Zeldovich (tSZ) power spectrum is one of the most sensitive methods to constrain cosmological parameters, scaling as the amplitude $\sigma_8^8$. It is determined by the integral over the halo mass function multiplied by the total pressure content of clusters, and further convolved by the cluster gas pressure profile. It has been shown that various feedback effects can change significantly the pressure profile, possibly even pushing the gas out to the virial radius and beyond, strongly affecting the tSZ power spectrum at high $l$. Energetics arguments and SZ-halo mass scaling relations suggest feedback is unlikely to significantly change the total pressure content, making low $l$ tSZ power spectrum more robust against feedback effects. Furthermore, the separation between the cosmic infrared background (CIB) and tSZ is more reliable at low $l$. Low $l$ modes are however probing very small volumes, giving rise to very large non-gaussian sampling variance errors. By computing the trispectrum contribution we identify $90<l<350$ as the minimum variance scale where the combined error is minimized. Using the measurement at this $l$ provides constraints that are almost as strong as using the entire power spectrum. We extend the work by the Planck collaboration by including a full trispectrum and feedback effects in the analysis. We perform a Markov-Chain Monte Carlo analysis over the two dimensional parameter space and find constraints on $\sigma_8$ by marginalizing over the feedback nuisance parameter.We obtain $\sigma_8 =0.820^{+0.021}_{-0.009}\left(\Omega_m/0.31\right)^{0.4}$, when fixing other parameters to Planck cosmology values. Our results suggest it is possible to obtain competitive cosmological constraints from tSZ without cluster redshift information, and that the current tSZ power spectrum shows no evidence for a low amplitude of $\sigma_8$.

Planck2015 results

We have constructed all-sky Compton parameters maps, y-maps, of the thermal Sunyaev-Zeldovich (tSZ) effect by applying specifically tailored component separation algorithms to the 30 to 857 GHz frequency channel maps from the Planck satellite. These reconstructed y-maps are delivered as part of the Planck 2015 release. The y-maps are characterized in terms of noise properties and residual foreground contamination, mainly thermal dust emission at large angular scales, and cosmic infrared background and extragalactic point sources at small angular scales. Specific masks are defined to minimize foreground residuals and systematics. Using these masks, we compute the y-map angular power spectrum and higher order statistics. From these we conclude that the y-map is dominated by tSZ signal in the multipole range, 20 <ℓ< 600. We compare the measured tSZ power spectrum and higher order statistics to various physically motivated models and discuss the implications of our results in terms of cluster physics and cosmology.

SZ effects in the Magneticum Pathfinder simulation: comparison with thePlanck, SPT, and ACT results

We calculate the one-point probability density distribution functions (PDF) and the power spectra of the thermal and kinetic Sunyaev-Zeldovich (tSZ and kSZ) effects and the mean Compton Y parameter using the Magneticum Pathfinder simulations, state-of-the-art cosmological hydrodynamical simulations of a large cosmological volume of (896 Mpc/h)^3. These simulations follow in detail the thermal and chemical evolution of the intracluster medium as well as the evolution of super-massive black holes and their associated feedback processes. We construct full-sky maps of tSZ and kSZ from the light-cones out to z=0.17, and one realization of 8.8x8.8 degree wide, deep light-cone out to z=5.2. The local universe at z<0.027 is simulated by a constrained realisation. The tail of the one-point PDF of tSZ from the deep light-cone follows a power-law shape with an index of -3.2. Once convolved with the effective beam of Planck, it agrees with the PDF measured by Planck. The predicted tSZ power spectrum agrees with that of the Planck data at all multipoles up to l~1000, once the calculations are scaled to the Planck 2015 cosmological parameters with \Omega_m=0.308 and \sigma_8=0.8149. Consistent with the results in the literature, however, we continue to find the tSZ power spectrum at l=3000 that is significantly larger than that estimated from the high-resolution ground-based data. The simulation predicts the mean fluctuating Compton Y value of <Y>=1.18x10^{-6} for \Omega_m=0.272 and \sigma_8=0.809. Nearly half (~ 5x10^{-7}) of the signal comes from halos below a virial mass of 10^{13}M_\odot/h. Scaling this to the Planck 2015 parameters, we find <Y>=1.57x10^{-6}. The PDF and the power spectrum of kSZ from our simulation agree broadly with the previous work.

Constraining the intracluster pressure profile from the thermal SZ power spectrum

The angular power spectrum of the thermal Sunyaev-Zel'dovich (tSZ) effect is highly sensitive to cosmological parameters such as sigma_8 and Omega_m, but its use as a precision cosmological probe is hindered by the astrophysical uncertainties in modeling the gas pressure profile in galaxy groups and clusters. In this paper we assume that the relevant cosmological parameters are accurately known and explore the ability of current and future tSZ power spectrum measurements to constrain the intracluster gas pressure or the evolution of the gas mass fraction, f_gas. We use the CMB bandpower measurements from the South Pole Telescope and a Bayesian Markov Chain Monte Carlo (MCMC) method to quantify deviations from the standard, universal gas pressure model. We explore analytical model extensions that bring the predictions for the tSZ power into agreement with experimental data. We find that a steeper pressure profile in the cluster outskirts or an evolving f_gas have mild-to-severe conflicts with experimental data or simulations. Varying more than one parameter in the pressure model leads to strong degeneracies that cannot be broken with current observational constraints. We use simulated bandpowers from future tSZ survey experiments, in particular a possible 2000 deg^2 CCAT survey, to show that future observations can provide almost an order of magnitude better precision on the same model parameters. This will allow us to break the current parameter degeneracies and place simultaneous constraints on the gas pressure profile and its redshift evolution, for example.

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

We have constructed the first all-sky map of the thermal Sunyaev-Zeldovich (tSZ) effect by applying specifically tailored component separation algorithms to the 100 to 857 GHz frequency channel maps from the Planck survey. These maps show an obvious galaxy cluster tSZ signal that is well matched with blindly detected clusters in the Planck SZ catalogue. To characterize the signal in the tSZ map we have computed its angular power spectrum. At large angular scales ($\ell < 60$), the major foreground contaminant is the diffuse thermal dust emission. At small angular scales ($\ell > 500$) the clustered Cosmic Infrared Background (CIB) and residual point sources are the major contaminants. These foregrounds are carefully modelled and subtracted. We measure the tSZ power spectrum in angular scales, $0.17^{\circ} \lesssim \theta \lesssim 3.0^{\circ}$, that were previously unexplored. The measured tSZ power spectrum is consistent with that expected from the Planck catalogue of SZ sources, with additional clear evidence of signal from unresolved clusters and, potentially, diffuse warm baryons. We use the tSZ power spectrum to obtain the following cosmological constraints: $\sigma_8(\Omega_{\mathrm{m}}/0.28)^{3.2/8.1}=0.784 \pm 0.016 (68% C.L.). Marginalized band-powers of the Planck tSZ power spectrum and the best-fit model are given. The non-Gaussianity of the Compton parameter map is further characterized by computing its 1D probability distribution function and its bispectrum. These are used to place additional independent constraints on $\sigma_{8}$.

The thermal Sunyaev–Zel'dovich effect power spectrum in light of Planck

(Abridged) The amplitude of the thermal Sunyaev Zel'dovich effect (tSZ) power spectrum is extremely sensitive to the abundance of galaxy clusters and therefore to fundamental cosmological parameters that control their growth, such as sigma_8 and Omega_m. Here we explore the sensitivity of the tSZ power spectrum to important non-gravitational ('sub-grid') physics by employing the cosmo-OWLS suite of large-volume cosmological hydrodynamical simulations, run in both the Planck and WMAP7 best-fit cosmologies. On intermediate and small angular scales (ell > ~1000, or theta < ~10 arcmin), accessible with the South Pole Telescope and the Atacama Cosmology Telescope, the predicted tSZ power spectrum is highly model dependent, with AGN feedback having a particularly large effect. However, at large scales, observable with the Planck telescope, the effects of sub-grid physics are minor. Comparing the simulations with observations, we find a significant amplitude offset on all measured angular scales (including large scales), if the Planck best-fit cosmology is assumed by the simulations. This is shown to be a generic result for all current tSZ models. By contrast, if the WMAP7 cosmology is adopted, there is full consistency with the Planck power spectrum measurements on large scales and agreement at the 2 sigma level with the SPT/ACT measurements at intermediate scales for our fiducial AGN model, which Le Brun et al. (2014) have shown reproduces the 'resolved' properties of the local cluster population remarkably well. These findings strongly suggest that there are significantly fewer massive galaxy clusters than expected for the Planck best-fit cosmology, which is consistent with recent measurements of the tSZ number counts. Our findings therefore pose a significant challenge to the cosmological parameter values preferred (and/or the model adopted) by the Planck primary CMB analyses.

A MEASUREMENT OF THE SECONDARY-CMB AND MILLIMETER-WAVE-FOREGROUND BISPECTRUM USING 800 deg2OF SOUTH POLE TELESCOPE DATA

We present a measurement of the angular bispectrum of the millimeter-wave sky in observing bands centered at roughly 95, 150, and 220 GHz, on angular scales of $1^\prime \lesssim \theta \lesssim 10^\prime$ (multipole number $1000 \lesssim l \lesssim 10000$). At these frequencies and angular scales, the main contributions to the bispectrum are expected to be the thermal Sunyaev-Zel'dovich (tSZ) effect and emission from extragalactic sources, predominantly dusty, star-forming galaxies (DSFGs) and active galactic nuclei. We measure the bispectrum in 800 $\mathrm{deg}^2$ of three-band South Pole Telescope data, and we use a multi-frequency fitting procedure to separate the bispectrum of the tSZ effect from the extragalactic source contribution. We simultaneously detect the bispectrum of the tSZ effect at $>$10$\sigma$, the unclustered component of the extragalactic source bispectrum at $>$5$\sigma$ in each frequency band, and the bispectrum due to the clustering of DSFGs---i.e., the clustered cosmic infrared background (CIB) bispectrum---at $>$5$\sigma$. This is the first reported detection of the clustered CIB bispectrum. We use the measured tSZ bispectrum amplitude, compared to model predictions, to constrain the normalization of the matter power spectrum to be $\sigma_8 = 0.787 \pm 0.031$ and to predict the amplitude of the tSZ power spectrum at $l = 3000$. This prediction improves our ability to separate the thermal and kinematic contributions to the total SZ power spectrum. The addition of bispectrum data improves our constraint on the tSZ power spectrum amplitude by a factor of two compared to power spectrum measurements alone and demonstrates a preference for a nonzero kinematic SZ (kSZ) power spectrum, with a derived constraint on the kSZ amplitude at $l=3000$ of A_kSZ $ = 2.9 \pm 1.6 \ \mu$K$^2$, or A_kSZ $ = 2.6 \pm 1.8 \ \mu$K$^2$ if the default A_kSZ > 0 prior is removed.