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Centro de Astrofísica da Universidade do Porto

The cluster abundance in cosmic string models for structure formation

P. P. Avelino, J. H. P. Wu, E. P. S. Shellard

Abstract
We use the present observed number density of large X-ray clusters to constrain the amplitude of matter density perturbations induced by cosmic strings on the scale of 8h-1Mpc (σ8), in both open cosmologies and flat models with a non-zero cosmological constant. We find a slightly lower value of σ8 than that obtained in the context of primordial Gaussian fluctuations generated during inflation. This lower normalization of σ8 results from the mild non-Gaussianity on cluster scales, where the one-point probability distribution function is well approximated by a χ2 distribution and thus has a longer tail than a Gaussian distribution. We also show that σ8 normalized using cluster abundance is consistent with the COBE normalization.

Monthly Notices of the Royal Astronomical Society
Volume 318, Page 329
October 2000

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Institute of Astrophysics and Space Sciences

Institute of Astrophysics and Space Sciences (IA) is a new but long anticipated research infrastructure with a national dimension. It embodies a bold but feasible vision for the development of Astronomy, Astrophysics and Space Sciences in Portugal, taking full advantage and fully realizing the potential created by the national membership of the European Space Agency (ESA) and the European Southern Observatory (ESO). IA resulted from the merging the two most prominent research units in the field in Portugal: the Centre for Astrophysics of the University of Porto (CAUP) and the Center for Astronomy and Astrophysics of the University of Lisbon (CAAUL). It currently hosts more than two-thirds of all active researchers working in Space Sciences in Portugal, and is responsible for an even greater fraction of the national productivity in international ISI journals in the area of Space Sciences. This is the scientific area with the highest relative impact factor (1.65 times above the international average) and the field with the highest average number of citations per article for Portugal.

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