Signatures of First Stars in Galaxy Surveys: Multi-Tracer Analysis of the Supersonic Relative Velocity Effect and the Constraints from the BOSS Power Spectrum Measurements

TL;DR

This paper investigates how the primordial supersonic relative velocity between dark matter and baryons influences large-scale galaxy clustering, using BOSS data to constrain the effect and proposing multi-tracer methods for future improvements.

Contribution

It provides the first constraint on the relative velocity bias parameter from galaxy survey data and introduces a multi-tracer analysis approach to enhance detection sensitivity.

Findings

Upper limit on star fraction sensitive to relative velocity: <3.3% at 95% CL

Multi-tracer analysis can reduce sample variance and improve constraints

Future surveys could achieve 0.1% precision in measuring the effect

Abstract

We study the effect of the supersonic relative velocity between dark matter and baryons on large-scale galaxy clustering and derive the constraint on the relative velocity bias parameter from the Baryonic Oscillation Spectroscopic Survey (BOSS) power spectrum measurements. Recent work has shown that the relative velocity effect may have a dramatic impact on the star formation at high redshifts, if first stars are formed in minihalos around z~20, or if the effect propagates through secondary effects to stars formed at later redshifts. The relative velocity effect has particularly strong signatures in the large scale clustering of these sources, including the BAO position. Assuming that a small fraction of stars in low-redshift massive galaxies retain the memory of the primordial relative velocity effect, galaxy clustering measurements can be used to constrain the signatures of the first stars. Luminous red galaxies contain some of the oldest stars in the Universe and are ideally suited to search for this effect. Using the BOSS power spectrum measurements from the Sloan Data Release 9, in combination with Planck, we derive the upper limit on the fraction of the stars sensitive to relative velocity effect f_star<3.3% at the 95% confidence level in the CMASS galaxy sample. If additional galaxy sample not sensitive to the effect is available in a given survey, a joint multi-tracer analysis can be applied to construct a sample-variance cancelling combination, providing a model-independent way to verify the presence of the relative velocity effect in the galaxy power spectrum on large scales. Such a multi-tracer analysis in future galaxy surveys can greatly improve the current constraint, achieving a 0.1% level in f_star.