When do cosmic peaks, filaments or walls merge? A theory of critical events in a multi-scale landscape

Abstract

The merging rate of cosmic structures is computed, relying on the Ansatz that they can be predicted in the initial linear density field from the coalescence of critical points with increasing smoothing scale, used here as a proxy for cosmic time. Beyond the mergers of peaks with saddle points (a proxy for halo mergers), we consider the coalescence and nucleation of all sets of critical points, including wall-saddle to filament-saddle and wall-saddle to minima (a proxy for filament and void mergers respectively), as they impact the geometry of galactic infall, and in particular filament disconnection. Analytical predictions of the one-point statistics are validated against multiscale measurements in 2D and 3D realisations of Gaussian random fields (the corresponding code being available upon request) and compared qualitatively to cosmological $N$-body simulations at early times ($z\ge 10$) and large scales ($\ge 5\mathrm{Mpc}/h$). The rate of filament coalescence is compared to the merger rate of haloes and the two-point clustering of these events is computed, along with their cross-correlations with critical points. These correlations are qualitatively consistent with the preservation of the connectivity of dark matter haloes, and the impact of the large scale structures on assembly bias. The destruction rate of haloes and voids as a function of mass and redshift is quantified down to $z=0$ for a $\Lambda$CDM cosmology. The one-point statistics in higher dimensions are also presented, together with consistency relations between critical point and critical event counts.

22 pages, 19 figures. Accepted for publication in MNRAS

References in corpus (5)

• Multiple minor mergers: formation of elliptical galaxies and constraints for the growth of spiral disks
• Initial Conditions for Large Cosmological Simulations
• The impact of the connectivity of the cosmic web on the physical properties of galaxies at its nodes
• Excursion set peaks: the role of shear
• Dynamical flows through Dark Matter Haloes II: one and two points statistics at the virial radius

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• Non-perturbative halo clustering from cosmological density peaks
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• Getting in shape with minimal energy. A variational principle for protohaloes
• Probing cosmology via the clustering of critical points
• Signature of Massive Neutrinos from the Clustering of Critical Points. I. Density-threshold-based Analysis in Configuration Space
• Mass assembly history of dark matter halos in the light of $H_0$ tension
• Estimating major merger rates and spin parameters ab initio via the clustering of critical events