Excess of high-$z$ galaxies as a test for bumpy power spectrum of density perturbations

TL;DR

This study explores how Gaussian bump features in the matter power spectrum influence early galaxy formation, revealing potential observational signatures at high redshift that differ from standard cosmology.

Contribution

It demonstrates that bumpy power spectra lead to earlier halo formation and predicts observable differences in high-redshift galaxy counts, testable by JWST.

Findings

Dark matter halos form earlier than in $\\Lambda$CDM

Halo mass functions at $z=0$ are similar to standard models

Excess of bright high-$z$ sources could indicate bumpy spectra

Abstract

Modified matter power spectra with approximately Gaussian bump on sub-Mpc scales can be a result of a complex inflation. We consider five spectra with different Gaussian amplitudes $A$ and locations $k_0$ and run N-body simulations in a cube $(5 Mpc/h)^3$ at $z>8$ to reveal the halo mass functions and their evolution with redshift. We have found that the Sheth-Tormen formula provides a good approximation to a such kind of halo mass functions. In the considered models the dark matter halo formation starts much more earlier than in $\Lambda$CDM, which in turn can result in an earlier star formation and a nuclear activity in galaxies and can be detected and tested by, e.g., JWST. At $z=0$ the halo mass functions are hardly distinguishable from the standard $\Lambda$CDM, therefore the models with the bumpy spectra can be identified in observations by their excess in number of bright sources at high redshift only.