Size Bias in Galaxy Surveys

TL;DR

This paper investigates how size bias, caused by gravitational lensing, affects galaxy survey data, revealing it can significantly distort galaxy statistics beyond the impact of magnification bias.

Contribution

It introduces the concept of size bias in galaxy surveys and analyzes its combined effect with magnification bias on galaxy statistical properties.

Findings

Size bias can significantly alter galaxy catalog statistics.

Size bias may have a greater impact than magnification bias in current surveys.

Photometric samples are particularly susceptible to size bias effects.

Abstract

Only certain galaxies are included in surveys: those bright and large enough to be detectable as extended sources. Because gravitational lensing can make galaxies appear both brighter and larger, the presence of foreground inhomogeneities can scatter galaxies across not only magnitude cuts but also size cuts, changing the statistical properties of the resulting catalog. Here we explore this size bias, and how it combines with magnification bias to affect galaxy statistics. We demonstrate that photometric galaxy samples from current and upcoming surveys can be even more affected by size bias than by magnification bias.