Cosmic magnification: nulling the intrinsic clustering signal

TL;DR

This paper presents a nulling technique to isolate the gravitational lensing magnification effect from galaxy clustering data, reducing bias from galaxy bias uncertainties, though with increased statistical errors.

Contribution

It introduces an effective nulling method that minimizes galaxy bias effects in clustering statistics, providing a robust alternative to cosmic shear analysis.

Findings

Nulling effectively isolates magnification signals.

Data becomes less sensitive to galaxy bias uncertainties.

Method offers unbiased cosmological parameter estimates.

Abstract

We investigate the extent to which the pure magnification effect of gravitational lensing can be extracted from galaxy clustering statistics, by a nulling method which aims to eliminate terms arising from the intrinsic clustering of galaxies. The aim is to leave statistics which are free from the uncertainties of galaxy bias. We find that nulling can be done effectively, leaving data which are relatively insensitive to uncertainties in galaxy bias and its evolution, leading to cosmological parameter estimation which is effectively unbiased. This advantage comes at the expense of increased statistical errors, which are in some cases large, but it offers a robust alternative analysis method to cosmic shear for cosmological imaging surveys designed for weak lensing studies, or to full modelling of the clustering signal including magnification effects.