Spherical collapse in quintessence models with zero speed of sound

Details Spherical collapse in quintessence models with zero speed of sound Spherical collapse in quintessence models with zero speed of sound

2009-11-14

arxiv.org/abs/0911.2701v2

Astronomy and Astrophysics

Astrophysics

Cosmology and Extragalactic Astrophysics

38 pages; small changes, including modification of the window function. JCAP published version

Scientific paper

We study the spherical collapse model in the presence of quintessence with negligible speed of sound. This case is particularly motivated for w<-1 as it is required by stability. As pressure gradients are negligible, quintessence follows dark matter during the collapse. The spherical overdensity behaves as a separate closed FLRW universe, so that its evolution can be studied exactly. We derive the critical overdensity for collapse and we use the extended Press-Schechter theory to study how the clustering of quintessence affects the dark matter mass function. The effect is dominated by the modification of the linear dark matter growth function. A larger effect occurs on the total mass function, which includes the quintessence overdensities. Indeed, here quintessence constitutes a third component of virialized objects, together with baryons and dark matter, and contributes to the total halo mass by a fraction ~ (1+w) Omega_Q / Omega_m. This gives a distinctive modification of the total mass function at low redshift.

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