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Clustering dark energy and halo abundances

Clustering dark energy and halo abundances Within the standard paradigm, dark energy is taken as a homogeneous fluid that drives the accelerated expansion of the universe and does not contribute to the mass of collapsed objects such as galaxies and galaxy clusters. The abundance of galaxy clustersmeasured through a variety of channelshas been extensively used to constrain the normalization of the power spectrum: it is an important probe as it allows us to test if the standard CDM model can indeed accurately describe the evolution of structures across billions of years. It is then quite significant that the Planck satellite has detected, via the Sunyaev-Zel'dovich effect, less clusters than expected according to the primary CMB anisotropies. One of the simplest generalizations that could reconcile these observations is to consider models in which dark energy is allowed to cluster, i.e., allowing its sound speed to vary. In this case, however, the standard methods to compute the abundance of galaxy clusters need to be adapted to account for the contributions of dark energy. In particular, we examine the case of clustering dark energya dark energy fluid with negligible sound speedwith a redshift-dependent equation of state. We carefully study how the halo mass function is modified in this scenario, highlighting corrections that have not been considered before in the literature. We address modifications in the growth function, collapse threshold, virialization densities and also changes in the comoving scale of collapse and mass function normalization. Our results show that clustering dark energy can impact halo abundances at the level of 10%30%, depending on the halo mass, and that cluster counts are modified by about 30% at a redshift of unity. http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Journal of Cosmology and Astroparticle Physics IOP Publishing

Clustering dark energy and halo abundances

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Copyright
Copyright © 2017 IOP Publishing Ltd and Sissa Medialab
eISSN
1475-7516
DOI
10.1088/1475-7516/2017/11/048
Publisher site
See Article on Publisher Site

Abstract

Within the standard paradigm, dark energy is taken as a homogeneous fluid that drives the accelerated expansion of the universe and does not contribute to the mass of collapsed objects such as galaxies and galaxy clusters. The abundance of galaxy clustersmeasured through a variety of channelshas been extensively used to constrain the normalization of the power spectrum: it is an important probe as it allows us to test if the standard CDM model can indeed accurately describe the evolution of structures across billions of years. It is then quite significant that the Planck satellite has detected, via the Sunyaev-Zel'dovich effect, less clusters than expected according to the primary CMB anisotropies. One of the simplest generalizations that could reconcile these observations is to consider models in which dark energy is allowed to cluster, i.e., allowing its sound speed to vary. In this case, however, the standard methods to compute the abundance of galaxy clusters need to be adapted to account for the contributions of dark energy. In particular, we examine the case of clustering dark energya dark energy fluid with negligible sound speedwith a redshift-dependent equation of state. We carefully study how the halo mass function is modified in this scenario, highlighting corrections that have not been considered before in the literature. We address modifications in the growth function, collapse threshold, virialization densities and also changes in the comoving scale of collapse and mass function normalization. Our results show that clustering dark energy can impact halo abundances at the level of 10%30%, depending on the halo mass, and that cluster counts are modified by about 30% at a redshift of unity.

Journal

Journal of Cosmology and Astroparticle PhysicsIOP Publishing

Published: Nov 1, 2017

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