On the Cosmic Web Elongation in Fuzzy Dark Matter Cosmologies

Kavli Affiliate: George Efstathiou

| First 5 Authors: Tibor Dome, Anastasia Fialkov, Philip Mocz, Björn Malte Schäfer, Michael Boylan-Kolchin

| Summary:

The fuzzy dark matter (FDM) scenario has received increased attention in
recent years due to the small-scale challenges of the vanilla Lambda cold dark
matter ($Lambda$CDM) cosmological model and the lack of robust experimental
evidence for any constituent particle. In this study, we use cosmological
$N$-body simulations to investigate the high-redshift cosmic web and its
responsiveness to an FDM-like power spectrum cutoff in the primordial density
perturbations by looking at three distinct properties of virialised FDM dark
matter halos as a function of the particle mass $m$. First, compared to
$Lambda$CDM the concentrations of their mass density profiles are lower,
peaking at an $m$-dependent halo mass and thus breaking the approximate
universality of density profiles in $Lambda$CDM even further. The halo
profiles of the intermediate-to-major and minor-to-major shape parameters are
monotonically increasing with ellipsoidal radius in $N$-body simulations of
$Lambda$CDM, yet become non-monotonic owing to baryonic physics at lower
redshifts and an FDM-like power spectrum cutoff at higher redshifts. Finally,
intrinsic alignment correlations, stemming from the deformation of initially
spherically collapsing halos in an ambient gravitational tidal field, become
stronger with decreasing FDM particle mass. At $zsim 4$, we find a $6.4
sigma$-significance in the fractional differences between the inferred
isotropised linear alignment magnitudes $D_{text{iso}}$ in $Lambda$CDM and
the rather extreme $m=10^{-22}$ eV FDM model. Such FDM-like imprints on the
internal properties of virialised halos are strikingly visible in the pristine
high-$z$ cosmic web whose evolution is governed largely by linear structure
formation physics.

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