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Kinematic lensing with high-resolution spectroscopic surveys. A unique opportunity for transformative cosmology at high redshifts in the 2040s

Stefano Camera, Martin Kilbinger, Jean-Paul Kneib, Ofer Lahav, Giovanni Aricò, Sofia Contarini, Giulia Degni, Antonio Farina, Massimo Guidi, Vanshika Kansal, Federico Marulli, Alejandra Melo, Simone Sartori

Abstract

We present a science case to perform high-redshift cosmic shear surveys for cosmology with next-generation spectroscopic instruments, such as the proposed MegaMapper and Wide-field Spectroscopic Telescope. We argue that by using the novel technique called 'kinematic lensing' (KL) it will be possible to obtain shear catalogues at redshifts between 2 and 5. We show that the signal-to-noise ratio of KL at such high redshifts is on average twice as much that expected from current weak lensing (WL) surveys such as Euclid or LSST, and several times that of the previous generation of WL surveys like DES and KiDS, even with very conservative assumptions about the fraction of spectroscopically-detected sources for which KL shear estimates will be available. This will allow cosmologists to perform joint galaxy clustering-cosmic shear analyses over unprecedented cosmic volumes and to probe the growth of structures deep in the matter-dominated era and across the onset of dark-energy domination, offering a unique opportunity to unveil the mystery of cosmic acceleration.

Kinematic lensing with high-resolution spectroscopic surveys. A unique opportunity for transformative cosmology at high redshifts in the 2040s

Abstract

We present a science case to perform high-redshift cosmic shear surveys for cosmology with next-generation spectroscopic instruments, such as the proposed MegaMapper and Wide-field Spectroscopic Telescope. We argue that by using the novel technique called 'kinematic lensing' (KL) it will be possible to obtain shear catalogues at redshifts between 2 and 5. We show that the signal-to-noise ratio of KL at such high redshifts is on average twice as much that expected from current weak lensing (WL) surveys such as Euclid or LSST, and several times that of the previous generation of WL surveys like DES and KiDS, even with very conservative assumptions about the fraction of spectroscopically-detected sources for which KL shear estimates will be available. This will allow cosmologists to perform joint galaxy clustering-cosmic shear analyses over unprecedented cosmic volumes and to probe the growth of structures deep in the matter-dominated era and across the onset of dark-energy domination, offering a unique opportunity to unveil the mystery of cosmic acceleration.
Paper Structure (5 sections, 1 figure)

This paper contains 5 sections, 1 figure.

Table of Contents

  1. The large-scale structure: the next frontier of cosmology.
  2. The state of the art: galaxy clustering and cosmic shear.
  3. A science case for future spectroscopic galaxy surveys: kinematic lensing.
  4. Our proposal: cosmology with a high-redshift kinematic lensing survey.
  5. The road ahead: technological challenges and scientific opportunities.

Figures (1)

  • Figure 1: Left panel: Galaxy angular densities for cosmic shear studies as a function of redshift. Black curves show analytical models for the redshift distribution of galaxies from photometric surveys of the previous generation (S3, dotted) or of the current one (S4, dashed), whereas coloured curves illustrate the expectation for S5 spectroscopic surveys (for more conservative to more optimistic magnitude thresholds). Middle panel: Expected cosmic shear power spectrum as a function of angular multipole for the surveys of the right panel. Right panel: Signal-to-noise ratio of the cosmic shear power spectrum, cumulative over the angular multipole $l$, for the galaxy samples under consideration. The coloured areas span the cases where only $0.5\%$ to $5\%$ (from lighter to darker) of the galaxies in the left panel will be suitable for KL shear estimates. The different extension of the non-transparent curves/areas marks the range of multipoles corresponding to strictly linear scales.