A search for cosmological anisotropy using the Lyman alpha forest from SDSS quasar spectra

TL;DR

This study tests the cosmological isotropy assumption using the Lyman alpha forest in SDSS quasar spectra, finding results consistent with isotropy after accounting for systematic effects, thus supporting the standard cosmological model.

Contribution

It introduces a novel large-scale anisotropy test using the Lyman alpha forest from SDSS quasar data over high redshifts, extending previous methods.

Findings

Data are consistent with isotropy after systematics correction.

Probes initial conditions beyond post-inflation causality scales.

Supports the cosmological principle with independent data.

Abstract

The Cosmological Principle, the combined assumptions of cosmological isotropy and homogeneity, underpins the standard model of Big Bang cosmology with which we interpret astronomical observations. A new test of isotropy over the redshift range $2<z<4$ and across large angular scales on the sky is presented. We use the cosmological distribution of neutral hydrogen, as probed by the Ly$\alpha$ forest seen towards distant quasars. The Sloan Digital Sky Survey provides the largest dataset of quasar spectra available to date. We use combined information from Data Releases 12 and 14 to select a sample of 142,661 quasars most suitable for this purpose. The scales covered by the data extend beyond post-inflation causality scales, thus probing initial conditions in the early universe. We identify significant spatially correlated systematic effects that can emulate cosmological anisotropy. Once these systematics have been accounted for, the data are found to be consistent with isotropy, providing an important independent check on the standard model, consistent with results from cosmic microwave background data.