Article

A new signature of primordial non-Gaussianities from the abundance of galaxy clusters

Monthly Notices of the Royal Astronomical Society (Impact Factor: 5.52). 09/2011; DOI: 10.1111/j.1365-2966.2012.21331.x
Source: arXiv

ABSTRACT The evolution with time of the abundance of galaxy clusters is very sensitive
to the statistical properties of the primordial density perturbations. It can
thus be used to probe small deviations from Gaussianity in the initial
conditions. The characterization of such deviations would help distinguish
between different inflationary scenarios, and provide us with information on
physical processes which took place in the early Universe. We have found that
when the information contained in the galaxy cluster counts is used to
reconstruct the dark energy equation of state as a function of redshift,
assuming erroneously that no primordial non-Gaussianities exist, an apparent
evolution with time in the effective dark energy equation of state
arises,characterized by the appearance of a clear discontinuity.

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    ABSTRACT: The redshift dependence of the abundance of galaxy clusters is very sensitive to the statistical properties of primordial density perturbations. It can thus be used to probe small deviations from Gaussian initial conditions. Such deviations constitute a very important signature of many inflationary scenarios, and are thus expected to provide crucial information on physical processes which took place in the very early Universe. We have determined the biases which may be introduced in the estimation of cosmological parameters by wrongly assuming the absence of primordial non-Gaussianities. Although we find that the estimation of the present-day dark energy density using cluster counts is not very sensitive to the non-Gaussian properties of the density field, we show that the biases can be considerably larger in the estimation of the dark energy equation of state parameter $w$ and of the amplitude of the primordial density perturbations. Our results suggest that a significant level of non-Gaussianity at cluster scales may be able to reconcile the constraint on the amplitude of the primordial perturbations obtained using galaxy cluster number counts from the Planck Sunyaev-Zeldovich Catalog with that obtained from the primary Cosmic Microwave Background anisotropies measured by the Planck satellite.
    Monthly Notices of the Royal Astronomical Society 04/2013; 435(1). · 5.52 Impact Factor

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