Effects of Neutrino Masses and Asymmetries on Dark Matter Halo Assembly

Abstract

Massive cosmological neutrinos suppress the Large-Scale Structure (LSS) in the Universe by smoothing the cosmic over-densities, and hence structure formation is delayed relative to that in the standard Lambda-Cold Dark Matter ($\Lambda$CDM) model. We characterize the merger and mass accretion history of dark matter halos with the halo formation time $a_{1/2}$, tree entropy $s$ and halo leaf function $\ell (X)$ and measure them using neutrino-involved N-body simulations. We show that a non-zero sum of neutrino masses $M_{\nu }$ delays the $a_{1/2}$ for halos with virial mass between $10^{13}{M}_{\odot }$ and $3\times 10^{13}{M}_{\odot }$, whereas a non-zero neutrino asymmetry parameter ${\eta }^2$ has the opposite effect. While the mean tree entropy $\bar{s}$ does not depend significantly on either $M_{\nu }$ or ${\eta }^2$, the halo leaf function does. Furthermore, the dependencies of $\ell$ on $M_{\nu }$ and ${\eta }^2$ have significant evolution in redshift $z$, with the relative contributions of $M_{\nu }$ and ${\eta }^2$ showing a sigmoid-like transition as a function of $z$ around $z\approx 0.6$. Together with the matter power spectrum, these halo parameters allow us to break the parameter degeneracy between $M_{\nu }$ and ${\eta }^2$ so that they can both be constrained in principle.

22 pages, 9 figures

References in corpus (6)

• Concentrations of Dark Haloes Emerge from Their Merger Histories
• One line to run them all: SuperEasy massive neutrino linear response in $N$-body simulations
• The cosmic neutrino background as a collection of fluids in large-scale structure simulations
• Characterising the Structure of Halo Merger Trees Using a Single Parameter: The Tree Entropy
• The impact of massive neutrinos on halo assembly bias
• Relic Neutrino Degeneracies and Their Impact on Cosmological Parameters

Cited by in corpus (3)

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• Signature of Massive Neutrinos from the Clustering of Critical Points. I. Density-threshold-based Analysis in Configuration Space
• Measuring neutrino mass and asymmetry with matter pairwise velocities