Constraints on blue and red tilted primordial power spectra using dwarf galaxy properties

TL;DR

This paper investigates how deviations from the standard primordial power spectrum, specifically blue and red tilts, influence dwarf galaxy densities, providing new constraints on small-scale primordial fluctuations using galaxy observations.

Contribution

It introduces a method combining simulations and galaxy formation models to constrain small-scale primordial power spectrum tilts based on dwarf galaxy properties.

Findings

Constraints on small-scale tilt of the primordial power spectrum are improved.

Dwarf galaxy central densities effectively test deviations from the standard spectrum.

Method can be applied to analyze features in the power spectrum at small scales.

Abstract

Although the standard $\Lambda$+Cold Dark Matter ($\Lambda$CDM) model is well tested on large scales, the primordial power spectrum may deviate from the $\Lambda$CDM spectrum on small scales due to specific dark matter properties or alternative inflationary models. These deviations affect the formation of dark matter structure, which subsequently leads to different observable properties of galaxies. In this work, we study the impact of a blue and red tilted power spectrum on the central density of dwarf galaxies. To do this, we model densities of dwarf galaxies using a combination of high-resolution numerical simulations and galaxy formation model. The model galaxies in $\Lambda$CDM are consistent with observations of 41 faint dwarf satellite galaxies of the Milky Way. The deviations from the $\Lambda$CDM power spectrum are constrained by the central matter densities of dwarf galaxies, which set stringent constraints on the possible small-scale tilt of the primordial power spectrum, improving on the current limits. Moreover, similar analysis can be applied to test any feature in the power spectrum at small scales between $k\sim 10-100$~Mpc$^{-1}$.