Spin and structural halo properties at high redshift in a LCDM Universe

TL;DR

This study investigates how the spin parameter influences the structural properties of high redshift dark matter haloes in a LCDM universe, revealing correlations with clustering, shape, and velocity profiles.

Contribution

It provides detailed analysis of the relationship between halo spin and structural properties at high redshift using high-resolution cosmological simulations, including convergence tests.

Findings

High spin haloes are more strongly clustered at all masses and redshifts.

High spin haloes are more clustered and found in denser environments.

Circular velocity-based mass estimates can be off by up to 40% without considering spin.

Abstract

In this paper, we examine in detail the key structural properties of high redshift dark matter haloes as a function of their spin parameter. We perform and analyze high resolution cosmological simulations of the formation of structure in a LCDM Universe. We study the mass function, ellipticities, shapes, density profiles, rotation curves and virialization for a large sample of dark matter haloes from z = 15 - 6. We also present detailed convergence tests for individual haloes. We find that high spin haloes have stronger clustering strengths (up to 25%) at all mass and redshift ranges at these early epochs. High redshift spherical haloes are also up to 50% more clustered than aspherical haloes. High spin haloes at these redshifts are also preferentially found in high density environments, and have more neighbors than their low spin counterparts. We report a systematic offset in the peak of the circular velocity curves for high and low spin haloes of the same mass. Therefore, estimating halo masses without knowledge of the spin, using only the circular velocity can yield errors of up to 40%. The strong dependence of key structural properties on spin that we report here likely have important implications for studies of star formation and feedback from these galaxies.