Euclid Wide Spectroscopic SurveyLIGER light conespower spectrum multipolesrelativistic redshift-space distortionsweak gravitational lensing
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Abstract (AI)
Measurements of galaxy clustering are affected by redshift-space distortions (RSDs). Peculiar velocities, gravitational lensing, and other light-cone projection effects modify the observed redshifts, fluxes, and sky positions of distant light sources. We determined which of these effects leave a detectable imprint on several two-point clustering statistics to be extracted from the Euclid wide spectroscopic survey (EWSS) on large scales. We generated 140 mock galaxy catalogues with the survey geometry and selection function of the EWSS and made use of the LIGER (LIght cones with GEneral Relativity) method to account for a variable number of relativistic RSDs to linear order in the cosmological perturbations. We estimated different two-point clustering statistics from the mocks and used the likelihood-ratio test to calculate the statistical significance with which the EWSS could reject the null hypothesis that certain relativistic projection effects can be neglected in the theoretical models. We find that the combined effects of lensing magnification and convergence imprint characteristic signatures on several clustering observables. Their signal-to-noise ratio (S/N) ranges between 2.5 and 6 (depending on the adopted summary statistic) for the highest-redshift galaxies in the EWSS. The corresponding feature due to the peculiar velocity of the Sun is measured with a S/N of order one or two. The multipoles of the power spectrum from the catalogues that include all relativistic effects reject the null hypothesis that RSDs are only generated by the variation in the peculiar velocity along the line of sight with a significance of 2.9 standard deviations. As a by-product of our study, we demonstrate that the mixing-matrix formalism to model finite-volume effects in the multipole moments of the power spectrum can be robustly applied to surveys made of several disconnected patches. Our results indicate that relativistic RSDs, in particular the contribution from weak gravitational lensing, cannot be disregarded when modelling two-point clustering statistics extracted from the EWSS.
Key Findings
1
Lensing magnification and convergence produce characteristic signatures in multiple two-point clustering statistics, with signal-to-noise ratios of 2.5–6 for the highest-redshift galaxies.
2
Power-spectrum multipoles including all relativistic effects reject the hypothesis that redshift-space distortions arise solely from line-of-sight peculiar-velocity variation at 2.9 standard deviations.
3
Relativistic projection effects were assessed using 140 Euclid wide spectroscopic survey mock catalogues generated with realistic geometry and selection functions.
4
The mixing-matrix formalism robustly models finite-volume effects in power-spectrum multipoles for surveys comprising several disconnected patches.
5
The peculiar velocity of the Sun contributes a detectable clustering feature with a signal-to-noise ratio of approximately 1–2.
Research Object
Euclid Wide Spectroscopic Survey galaxy clustering observables on large scales
Research Subject
Detectable signatures and statistical significance of relativistic redshift-space distortion and light-cone projection effects, including lensing magnification, convergence, and solar peculiar velocity
Publication Details
Publication Date
2025-03-14
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