Intrinsic size correlations in weak lensing

TL;DR

This paper introduces a halo model-based approach to intrinsic galaxy size correlations, highlighting their significance as a systematic in weak lensing size magnification measurements and their impact on cosmological parameter estimation.

Contribution

The paper develops a simple halo model for intrinsic size correlations and assesses their contamination effect on weak lensing convergence measurements.

Findings

Intrinsic size correlations can significantly contaminate lensing measurements.

Cross-correlation of sizes with convergence is an important systematic.

Neglecting these correlations can bias cosmological inferences.

Abstract

We present a simple model for describing intrinsic correlations for galaxy sizes based on the halo model. Studying these correlations is important both to improve our understanding of galaxy properties and because it is an important potential systematic for weak lensing size magnification measurements. Our model assumes that the density field drives these intrinsic correlations and we also model the distribution of satellite galaxies. We calculate the possible contamination to measurements of lensing convergence power spectrum from galaxy sizes, and show that the cross-correlation of intrinsic sizes with convergence is potentially an important systematic. We also explore how these intrinsic size correlations may affect surveys with different redshift depth. We find that, in this simple approach, intrinsic size correlations cannot be neglected in order to estimate lensing convergence power spectrum for constraining cosmological parameters.