Post-inflationary Contamination of Local Primordial Non-Gaussianity in Galaxy Power Spectra

Understand

The scale-dependent bias of galaxy density contrasts is an important signal to be extracted in constraining local primordial non-Gaussianity ($f_{\rm NL}^{\text{local}}$) from observations of large-scale structure.

• Constraints so obtained rely on the assumption that horizon-scale features in the galaxy power spectrum are exclusively due to primordial physical mechanisms.
• Yet, post-inflationary effects can induce modulations to the galaxy number density that appear as horizon-scale, scale-dependent bias.
• We investigate the effect of two such sources of scale-dependent bias - the free-streaming of light relics and fluctuations in the background of ionising radiation - on precision measurements of local primordial non-Gaussianity $f_{\rm NL}^{\text{local}}$ from galaxy power spectrum measurements.