Small scale clustering of late forming dark matter

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-α forest measurements, while it predicts suppressed abundance of lowmass halos (∼109–1010 h−1 M⊙) at all redshifts compared to a vanilla ΛCDM model. The analysis of the LFDM halo velocity function shows a better agreement than the ΛCDM prediction with the observed abundance of low-velocity galaxies in the local volume. Halos with mass M ≳ 1011 h−1 M⊙ show minor departures of the density profiles from ΛCDM expectations, while smaller-mass halos are less dense, consistent with the fact that they form later than their ΛCDM counterparts.