Small scale clustering of late forming dark matter

TL;DR

This study investigates the nonlinear clustering of late-forming dark matter (LFDM) using high-resolution simulations, revealing suppressed low-mass halo abundance and better alignment with observed low-velocity galaxy counts compared to standard models.

Contribution

It provides the first detailed nonlinear analysis of LFDM, demonstrating its compatibility with high-redshift data and its distinctive impact on small-scale structure formation.

Findings

LFDM predicts fewer low-mass halos than $\\Lambda$CDM.

LFDM halos are less dense at smaller masses.

LFDM aligns better with low-velocity galaxy observations.

Abstract

We perform a study of the nonlinear clustering of matter in the late-forming dark matter (LFDM) scenario in which dark matter results from the transition of a nonminimally coupled scalar field from radiation to collisionless matter. A distinct feature of this model is the presence of a damped oscillatory cutoff in the linear matter power spectrum at small scales. We use a suite of high-resolution N-body simulations to study the imprints of LFDM on the nonlinear matter power spectrum, the halo mass and velocity functions and the halo density profiles. The model largely satisfies high-redshift matter power spectrum constraints from Lyman-$\alpha$ forest measurements, while it predicts suppressed abundance of low-mass halos ($\sim 10^{9}-10^{10}$ h$^{-1}$ M$_\odot$) at all redshifts compared to a vanilla $\Lambda$CDM model. The analysis of the LFDM halo velocity function shows a better agreement than the $\Lambda$CDM prediction with the observed abundance of low-velocity galaxies in the local volume. Halos with mass $M\gtrsim 10^{11}$ h$^{-1}$ M$_\odot$ show minor departures of the density profiles from $\Lambda$CDM expectations, while smaller-mass halos are less dense, consistent with the fact that they form later than their $\Lambda$CDM counterparts.