Leveraging protohalos and scale-dependent bias to calibrate the BAO scale in real space

TL;DR

This paper improves the calibration of the BAO scale in real space by modeling scale-dependent bias in protohalo correlation functions, significantly enhancing measurement precision without shifting the BAO feature.

Contribution

It introduces a novel bias model incorporating scale dependence in protohalo analysis, leading to more accurate and precise BAO scale measurements.

Findings

Scale-dependent bias improves BAO scale measurement precision by up to 47%.

The linear combination of protohalo and matter fields yields the highest precision.

No shift in the BAO feature is caused by including scale dependence.

Abstract

The location of the baryon acoustic oscillation (BAO) feature in the two-point correlation function (2PCF) of matter produces a standard ruler that is useful for the measurement of the expansion history of the Universe. Inspired by the possibility of reconstructing the positions of protohalos in the initial density field with a novel method rooted in optimal transport theory, we revisit the BAO signal in the protohalo correlation function. Our work examines the performance of a template 2PCF built on a tracer bias relation that includes scale dependence -- a term that can be motivated by peaks theory or a general bias expansion. Working in protohalos, halos, and the linear combination of the protohalo and matter fields that is motivated by the continuity equation, we demonstrate that this model accurately captures the shape of the BAO feature and improves the precision of the BAO scale measurement relative to a model that does not include scale-dependent bias by 47% in protohalos, 15% in halos, and 14% in the linear combination of the protohalo and matter fields. Allowing for scale dependence does not appear to introduce any shift in the BAO feature. The precision of the BAO distance scale estimate is highest with the linear combination of the protohalo and matter fields, which offers a factor of 3.5 improvement over Eulerian-space measurements and a factor of 4-8 improvement over the estimate made with protohalos alone.