Structure formation with suppressed small-scale perturbations

Abstract

All commonly considered dark matter scenarios are based on hypothetical particles with small but non-zero thermal velocities and tiny interaction cross-sections. A generic consequence of these attributes is the suppression of small-scale matter perturbations either due to free-streaming or due to interactions with the primordial plasma. The suppression scale can vary over many orders of magnitude depending on particle candidate and production mechanism in the early Universe.While nonlinear structure formation has been explored in great detail well above the suppression scale, the range around suppressed perturbations is still poorly understood. In this paper we study structure formation in the regime of suppressed perturbations using both analytical techniques and numerical simulations. We develop simple and theoretically motivated recipes for the halo mass function, the expected number of satellites, and the halo concentrations, which are designed to work for power spectra with suppression at arbitrary scale and of arbitrary shape. As case studies, we explore warm and mixed dark matter scenarios where effects are most distinctive. Additionally, we examine the standard dark matter scenario based on weakly interacting massive particles (WIMP) and compare it to pure cold dark matter with zero primordial temperature. We find that our analytically motivated recipes are in good agreement with simulations for all investigated dark matter scenarios, and we therefore conclude that they can be used for generic cases with arbitrarily suppressed small-scale perturbations.

Constraining the Nature of Dark Matter with the Star-formation History of the Faintest Local Group Dwarf Galaxy Satellites

“…This would still match the constraints from the Wolf et al procedure and would have c∼25 based on simulations (Schneider 2015), which would then yield a collapse redshift z=10 for the 4% criterion (Zhao et al 2009). This is clearly early enough to accommodate any of the SF histories of UFDs.…”

“…D(z) can be inverted to find the collapse redshift. Schneider (2015) showed that the slope of the curves z c -M fits results from CDM simulations up to a normalization. We use here the Bolshoi simulation results as quoted by van den Bosch et al (2013), where two criteria are presented: the collapse redshift by when the halo accreted into 4% and half of its final mass.…”

“…Schneider (2015) showed that it can be improved with an extended Press-Schechter formalism and by requiring the average collapse redshift of halos that survive until today. z c is defined as the time when the halo has accreted a fraction F of its final mass M. The average growth factor of all the progenitors can be straightforwardly derived:…”

Lyman- α constraints on ultralight scalar dark matter: Implications for the early and late universe

“…which was introduced in [57,58] based on the conditional mass function normalized to the N -body simulation results. 6 Here R sub , M sub and S sub are radius, mass and variance of a given subhalo, while M halo and S halo are the mass and the variance of the main halo, defined as follows:…”

The mass–concentration–redshift relation of cold and warm dark matter haloes

“…Interest in such models has been revitalized by recent claims of detection of an ∼ 3.5 keV X-ray line, which is in principle consistent with the decay of a WDM particle (e.g. Bulbul et al 2014;Boyarsky et al 2014, 2015, but see, Malyshev, Neronov & Eckert 2014Anderson, Churazov & Bregman 2015). These results have motivated observations of DM-dominated dwarf galaxies of the Local Group (Lovell et al 2015) which, to date, have not provided compelling evidence for DM decay (Jeltema & Profumo 2016).…”