Clustering dark energy and halo abundances

Abstract

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 channels -has 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 ΛCDM 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 SunyaevZel'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 energy -a dark energy fluid with negligible sound speed -with 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.

Skewness of matter distribution in clustering dark energy cosmologies

“…In some approaches the DE speed of sound can evade the canonical value c 2 s DE = 1 (see examples in Refs. [2][3][4][5][6][7]) and therefore leaving imprints on structure formation [8][9][10][11][12][13][14][15][16][17][18][19][20].…”

Structure formation in clustering DBI dark energy model with constant sound speed

“…Thus studying the large-scale structure provides valuable information about the nature of DE (or MG) (Tegmark 2004;Tegmark et al 2006). So far, the issue of structure formation in the context of DE models has been extensively considered in the literature (Linder & Jenkins 2003;Abramo et al 2007;Sefusatti & Vernizzi 2011;Batista & Pace 2013;Roupas et al 2014;Malekjani et al 2015;Naderi et al 2015;Nazari-Pooya et al 2016;Batista & Marra 2017;. Also, this subject has been widely studied in the framework of MG theories (Koyama 2006;Brax & Valageas 2012;Nesseris 2013;Asadzadeh et al 2016;Nunes 2018).…”

Tidal virialization of dark matter haloes with clustering dark energy

“…In this case, the virialization time is defined when the moment of inertia of a sphere I = 2M tot R 2 /5 of non-relativistic particles is in a steady state, i.e. d 2 I/dt 2 = 0, yielding [14,36]…”