An Accurate Physical Model for Halo Concentrations

Abstract

The relation between halo mass, M , and concentration, c, is a critical component in our understanding of the structure of dark matter halos. While numerous models for this relation have been proposed, almost none of them attempt to derive the evolution of the relation analytically. We build on previous efforts to model the c-M relation as a function of physical parameters such as the peak height, ν, and the effective power spectrum slope, n eff , which capture the dependence of c on halo mass, redshift, and cosmology. We present three major improvements over previous models. First, we derive an analytical expression for the c-M relation that is valid under the assumption of pseudo-evolution, i.e., assuming that the density profiles of halos are static in physical coordinates while the definition of their boundary evolves. We find that this ansatz is highly successful in describing the evolution of the low-mass end of the c-M relation. Second, we employ a new physical variable, the effective exponent of linear growth, α eff , to parameterize deviations from an Einstein-de Sitter expansion history. Third, we combine an updated definition of n eff with the additional dependence on α eff and propose a phenomenological extension of our analytical framework to include all halo masses. This semianalytical model matches simulated concentrations in both scale-free models and ΛCDM to 5% accuracy with very few exceptions and differs significantly from all previously proposed models. We present a publicly available code to compute the predictions of our model in the python toolkit Colossus, including updated parameters for the model of Diemer and Kravtsov.

Warm dark matter chills out: constraints on the halo mass function and the free-streaming length of dark matter with eight quadruple-image strong gravitational lenses

“…with β (z) = 0.026z − 0.04, using the CDM massconcentration model of Diemer & Joyce (2019) and a scatter of 0.1 dex (Dutton & Macciò 2014). The WDM suppression factor for the mass-concentration relation we use was calibrated for halos on mass scales below M200 ∼ 10 9 M , and is accurate in the redshift range z = 0 − 3.…”

The abundance and structure of subhaloes near the free streaming scale and their impact on indirect dark matter searches

“…We selected all haloes and subhaloes that contain more than 1,000 particles. The mass-concentration relation for field haloes has been refined until today (e.g., Prada et al 2012;Correa et al 2015;Klypin et al 2016;Okoli & Afshordi 2016;Pilipenko et al 2017;Child et al 2018;Diemer & Joyce 2019) and that for less massive field haloes has been studied down to ∼ 10 7 M to date (e.g., Pilipenko et al 2017). It is also studied for near the free streaming scale (≤∼ 10 −3 M , Ishiyama 2014).…”

Breaking a dark degeneracy: The gamma-ray signature of early matter domination

“…We exclude EMDE-boosted microhalos (as hosts) by only considering halos down to the mass scale associated with the reheating wave number k RH . We associate a concentration c = R vir /R s to each halo mass using the median concentration-mass relation c(M ) from Ref [108],. and we define R vir as the radius enclosing 200 times the critical density to match that work.…”