Bias of Damped Lyman-$\alpha$ systems from their cross-correlation with CMB lensing

TL;DR

This study measures the bias of damped Lyman-$ ext{α}$ systems by cross-correlating their positions with CMB lensing maps, providing insights into their large-scale structure and potential biases in observational data.

Contribution

First measurement of DLA bias using CMB lensing cross-correlation, offering a new method to study DLA distribution and large-scale structure.

Findings

DLA bias estimated as $b_{DLA}=2.6\\pm0.9$

Results consistent with previous Lyman-$\alpha$ forest studies

Current data limitations restrict measurement precision

Abstract

We cross-correlate the positions of damped Lyman-$\alpha$ systems (DLAs) and their parent quasar catalog with a convergence map derived from the Planck cosmic microwave background (CMB) temperature data. We make consistent measurements of the lensing signal of both samples in both Fourier and configuration space. By interpreting the excess signal present in the DLA catalog with respect to the parent quasar catalog as caused by the large scale structure traced by DLAs, we are able to infer the bias of these objects: $b_{\rm DLA}=2.6\pm0.9$. These results are consistent with previous measurements made in cross-correlation with the Lyman-$\alpha$ forest, although the current noise in the lensing data and the low number density of DLAs limits the constraining power of this measurement. We discuss the robustness of the analysis with respect to a number different systematic effects and forecast prospects of carrying out this measurement with data from future experiments.