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S. Sadeh

Publications and source records attributed to S. Sadeh.

9 recordsLinked to original sources

Neutrino Mass Inference from SZ Surveys

The growth of structure in the universe begins at the time of radiation-matter equality, which corresponds to energy scales of $\sim 0.4 eV$. All tracers of dark matter evolution are expected to be sensitive to neutrino masses on this and smaller scales. Here we explore the possibility of using cluster number counts and power spectrum obtained from ongoing SZ surveys to constrain neutrino masses. Specifically, we forecast the capability of ongoing measurements with the PLANCK satellite and the ground-based SPT experiment, as well as measurements with the proposed EPIC satellite, to set interesting bounds on neutrino masses from their respective SZ surveys. We also consider an ACT-like CMB experiment that covers only a few hundred ${\rm deg^{2}}$ also to explore the tradeoff between the survey area and sensitivity and what effect this may have on inferred neutrino masses. We find that for such an experiment a shallow survey is preferable over a deep and low-noise scanning scheme. We also find that projected results from the PLANCK SZ survey can, in principle, be used to determine the total neutrino mass with a ($1σ$) uncertainty of $0.28 eV$, if the detection limit of a cluster is set at the $5σ$ significance level. This is twice as large as the limits expected from PLANCK CMB lensing measurements. The corresponding limits from the SPT and EPIC surveys are $\sim 0.44 eV$ and $\sim 0.12 eV$, respectively. Mapping an area of 200 deg$^{2}$, ACT measurements are predicted to attain a $1σ$ uncertainty of 0.61 eV; expanding the observed area to 4,000 deg$^{2}$ will decrease the uncertainty to 0.36 eV.

astro-ph.CO

Power Spectra of CMB Polarization by Scattering in Clusters

Mapping CMB polarization is an essential ingredient of current cosmological research. Particularly challenging is the measurement of an extremely weak B-mode polarization that can potentially yield unique insight on inflation. Achieving this objective requires very precise measurements of the secondary polarization components on both large and small angular scales. Scattering of the CMB in galaxy clusters induces several polarization effects whose measurements can probe cluster properties. Perhaps more important are levels of the statistical polarization signals from the population of clusters. Power spectra of five of these polarization components are calculated and compared with the primary polarization spectra. These spectra peak at multipoles $\ell \geq 3000$, and attain levels that are unlikely to appreciably contaminate the primordial polarization signals.

astro-ph.CO

The probability distribution of cluster formation times and implied Einstein Radii

We provide a quantitative assessment of the probability distribution function of the concentration parameter of galaxy clusters. We do so by using the probability distribution function of halo formation times, calculated by means of the excursion set formalism, and a formation redshift-concentration scaling derived from results of N-body simulations. Our results suggest that the observed high concentrations of several clusters are quite unlikely in the standard Lambda CDM cosmological model, but that due to various inherent uncertainties, the statistical range of the predicted distribution may be significantly wider than commonly acknowledged. In addition, the probability distribution function of the Einstein radius of A1689 is evaluated, confirming that the observed value of ~45" +/- 5" is very improbable in the currently favoured cosmological model. If, however, a variance of ~20% in the theoretically predicted value of the virial radius is assumed, than the discrepancy is much weaker. The measurement of similarly large Einstein radii in several other clusters would pose a difficulty to the standard model. If so, earlier formation of the large scale structure would be required, in accord with predictions of some quintessence models. We have indeed verified that in a viable early dark energy model large Einstein radii are predicted in as many as a few tens of high-mass clusters.

astro-ph

Cluster abundances and S-Z power spectra: effects of non-Gaussianity and early dark energy

In the standard Lambda CDM cosmological model with a Gaussian primordial density fluctuation field, the relatively low value of the mass variance parameter (sigma_8=0.74{+0.05}{-0.06}, obtained from the WMAP 3-year data) results in a reduced likelihood that the measured level of CMB anisotropy on the scales of clusters is due to the Sunyaev-Zeldovich (S-Z) effect. To assess the feasibility of producing higher levels of S-Z power, we explore two alternative models which predict higher cluster abundance. In the first model the primordial density field has a chi^2_1 distribution, whereas in the second an early dark energy component gives rise to the desired higher cluster abundance. We carry out the necessary detailed calculations of the levels of S-Z power spectra, cluster number counts, and angular 2-point correlation function of clusters, and compare (in a self-consistent way) their predicted redshift distributions. Our results provide a sufficient basis upon which the viability of the three models may be tested by future high quality measurements.

astro-ph

Modeling Integrated Properties and the Polarization of the Sunyaev-Zeldovich Effect

Two little explored aspects of Compton scattering of the CMB in clusters are discussed: The statistical properties of the Sunyaev-Zeldovich (S-Z) effect in the context of a non-Gaussian density fluctuation field, and the polarization patterns in a hydrodynamcially-simulated cluster. We have calculated and compared the power spectrum and cluster number counts predicted within the framework of two density fields that yield different cluster mass functions at high redshifts. This is done for the usual Press & Schechter mass function, which is based on a Gaussian density fluctuation field, and for a mass function based on a chi^2-distributed density field. We quantify the significant differences in the respective integrated S-Z observables in these two models. S-Z polarization levels and patterns strongly depend on the non-uniform distributions of intracluster gas and on peculiar and internal velocities. We have therefore calculated the patterns of two polarization components that are produced when the CMB is doubly scattered in a simulated cluster. These are found to be very different than the patterns calculated based on spherical clusters with uniform structure and simplified gas distribution.

astro-ph

Impact of a non-Gaussian density field on Sunyaev-Zeldovich observables

The main statistical properties of the Sunyaev-Zeldovich (S-Z) effect - the power spectrum, cluster number counts, and angular correlation function - are calculated and compared within the framework of two density fields which differ in their predictions of the cluster mass function at high redshifts. We do so for the usual Press and Schechter mass function, which is derived on the basis of a Gaussian density fluctuation field, and for a mass function based on a chi^2 distributed density field. These three S-Z observables are found to be very significantly dependent on the choice of the mass function. The different predictions of the Gaussian and non-Gaussian density fields are probed in detail by investigating the behaviour of the three S-Z observables in terms of cluster mass and redshift. The formation time distribution of clusters is also demonstrated to be sensitive to the underlying mass function. A semi-quantitative assessment is given of its impact on the concentration parameter and the temperature of intracluster gas.

astro-ph

The Sunyaev-Zeldovich Effect

This brief, general review the Sunyaev-Zeldovich (S-Z) effect includes a description of the calculation of the total intensity change and polarization components, a discussion of the basic properties of the S-Z power spectrum and cluster number counts, and a summary of the main observational results.

astro-ph

Sunyaev-Zeldovich Cluster Counts as a Probe of Intra-Supercluster Gas

X-ray background surveys indicate the likely presence of diffuse warm gas in the Local Super Cluster (LSC), in accord with expectations from hydrodynamical simulations. We assess several other manifestations of warm LSC gas; these include anisotropy in the spatial pattern of cluster Sunyaev-Zeldovich (S-Z) counts, its impact on the CMB temperature power spectrum at the lowest multipoles, and implications on measurements of the S-Z effect in and around the Virgo cluster.

astro-ph

S-Z Anisotropy & Cluster Counts: Consistent Selection of sigma_8 and the Temperature-Mass Relation

The strong dependence of the mass variance parameter, sigma_8, on the adopted cluster mass-temperature relation is explored. A recently compiled X-ray cluster catalog and various mass-temperature relations are used to derive the corresponding values of sigma_8. Calculations of the power spectrum of the CMB anisotropy induced by the Sunyaev-Zeldovich effect and cluster number counts are carried out in order to assess the need for a consistent choice of the mass-temperature scaling and the parameter sigma_8. We find that the consequences of inconsistent choice of the mass-temperature relation and sigma_8 could be quite substantial, including a considerable mis-estimation of the magnitude of the power spectrum and cluster number counts. Our results can partly explain the large scatter between published estimates of the power spectrum and number counts. We also show that the range of values of the power-law index in the scaling C_l ~ sigma_8^[6-7] deduced in previous studies is likely overestimated; we obtain a more moderate dependence, C_l ~ sigma_8^[4].

astro-ph