Halo mass functions at high redshift

Abstract

Recent JWST observations of very early galaxies, at $\mathrm{z}\gtrsim 10$, have led to claims that tension exists between the sizes and luminosities of high-redshift galaxies and what is predicted by standard $\hat{I}›$CDM models. Here we use the adaptive mesh refinement code $\text{Enzo}$ and the N-body smoothed particle hydrodynamics code $\text{SWIFT}$ to compare (semi-)analytic halo mass functions against the results of direct N-body models at high redshift. In particular, our goal is to investigate the variance between standard halo mass functions derived from (semi-)analytic formulations and N-body calculations and to determine what role any discrepancy may play in driving tensions between observations and theory. We find that the difference between direct N-body calculations and (semi-) analytic halo mass function fits is less than a factor of 2 (at $\mathrm{z}\sim 10$) within the mass range of galaxies currently being observed by JWST, and is therefore not a dominant source of error when comparing theory and observation at high redshift.

Accepted for publication in the Open Journal of Astrophysics, 11 pages, 9 figures. Acknowledgements updated