Multi-wavelength spectroscopic probes: biases from neglecting light-cone effects

TL;DR

This paper evaluates how ignoring light-cone effects like lensing magnification in spectroscopic surveys biases estimates of primordial non-Gaussianity and cosmological parameters, emphasizing the importance of including these effects in models.

Contribution

It quantifies the bias introduced by neglecting light-cone effects in upcoming cosmological surveys, highlighting the necessity to incorporate lensing magnification in analyses.

Findings

Neglecting lensing magnification causes biases >1σ in parameter estimates.

Including light-cone effects is crucial for accurate cosmological inference.

Biases affect both primordial non-Gaussianity and standard cosmological parameters.

Abstract

Next-generation cosmological surveys will observe larger cosmic volumes than ever before, enabling us to access information on the primordial Universe, as well as on relativistic effects. In a companion paper, we applied a Fisher analysis to forecast the expected precision on $f_{\rm NL}$ and the detectability of the lensing magnification and Doppler contributions to the power spectrum. Here we assess the bias on the best-fit values of $f_{\rm NL}$ and other parameters, from neglecting these light-cone effects. We consider forthcoming 21cm intensity mapping surveys (SKAO) and optical galaxy surveys (DESI and Euclid), both individually and combined together. We conclude that lensing magnification at higher redshifts must be included in the modelling of spectroscopic surveys. If lensing is neglected in the analysis, this produces a bias of more than 1$\sigma$ - not only on $f_{\rm NL}$, but also on the standard cosmological parameters.