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Probing Interacting Dark Sectors with upcoming Post-Reionization and Galaxy Surveys

Rahul Shah, Antara Dey, Purba Mukherjee, Supratik Pal

Abstract

We investigate the constraining power of future post-reionization and galaxy surveys on possible interactions between dynamical dark energy and dark matter. The analysis focuses on the interaction strength and the dark energy equation of state parameters, in addition to the six standard cosmological parameters. Using fiducial values obtained from the current observational bounds (Planck 2018 + DESI DR2 + Pantheon+), mock datasets for upcoming 21-cm intensity mapping, galaxy clustering and cosmic shear observations from the SKA-mid, and for the upcoming large-scale survey from the Euclid mission, were generated. Subsequently, Markov chain Monte Carlo analyses combining current cosmological data with these mock datasets were performed to forecast parameter constraints. The results indicate that both SKA-mid and Euclid observations can significantly improve constraints on interacting dark sector parameters. In particular, the interaction strength and dark energy equation of state parameters can be constrained considerably tighter than current combined constraints from Planck 2018, DESI DR2 and Pantheon+. Comparing different probe combinations and survey configurations, it is found that SKA2 provides the tightest projected constraints, particularly on the interaction strength, while Euclid achieves a precision broadly comparable to that of SKA1. The results highlight the potential of these upcoming surveys to probe interactions within the dark sector.

Probing Interacting Dark Sectors with upcoming Post-Reionization and Galaxy Surveys

Abstract

We investigate the constraining power of future post-reionization and galaxy surveys on possible interactions between dynamical dark energy and dark matter. The analysis focuses on the interaction strength and the dark energy equation of state parameters, in addition to the six standard cosmological parameters. Using fiducial values obtained from the current observational bounds (Planck 2018 + DESI DR2 + Pantheon+), mock datasets for upcoming 21-cm intensity mapping, galaxy clustering and cosmic shear observations from the SKA-mid, and for the upcoming large-scale survey from the Euclid mission, were generated. Subsequently, Markov chain Monte Carlo analyses combining current cosmological data with these mock datasets were performed to forecast parameter constraints. The results indicate that both SKA-mid and Euclid observations can significantly improve constraints on interacting dark sector parameters. In particular, the interaction strength and dark energy equation of state parameters can be constrained considerably tighter than current combined constraints from Planck 2018, DESI DR2 and Pantheon+. Comparing different probe combinations and survey configurations, it is found that SKA2 provides the tightest projected constraints, particularly on the interaction strength, while Euclid achieves a precision broadly comparable to that of SKA1. The results highlight the potential of these upcoming surveys to probe interactions within the dark sector.

Paper Structure

This paper contains 15 sections, 26 equations, 6 figures, 11 tables.

Table of Contents

  1. Introduction
  2. Interacting Two-Fluid Set-Up with CDM and Dynamical DE
  3. Datasets and Forecast Methodology
  4. Fiducial Cosmology and Mock Data Generation
  5. Forecast Methodology
  6. Forecasting with Future Surveys
  7. 21-cm intensity mapping in the Post-Reionization Epoch
  8. Galaxy Clustering
  9. Cosmic Shear
  10. Conservative and Realistic Prescriptions
  11. Results and Discussion
  12. The Non-Phantom Regime
  13. Effect of the Dark Energy Sound Speed
  14. Alternative Dark Energy Parametrization: JBP
  15. Conclusions

Figures (6)

  • Figure 1: Projected $1\sigma$ errors for SKA intensity mapping, galaxy clustering and cosmic shear observations for the i-CPL phantom model. Results are shown for SKA1 and SKA2 surveys under both conservative and realistic treatments of non-linear scales, and for Euclid.
  • Figure 2: Projected constraints for SKA1 intensity mapping observations for the i-CPL phantom model. The figure compares the constraints from current CMB+BAO+SNIa data with (left panel) the projected SKA1 Band 1 forecasts under the conservative and realistic treatments of non-linear scales, and (right panel) from SKA1 intensity mapping observations in Band 1 and Band 2 under the conservative prescription.
  • Figure 3: Projected constraints for SKA-mid galaxy clustering and cosmic shear observations for the i-CPL phantom model. The figure compares the constraints from current CMB+BAO+SNIa data with (left panel) the projected SKA1 forecasts, under the conservative and realistic treatments of non-linear scales, and Euclid, and (right panel) from SKA1 and SKA2 under the conservative prescription.
  • Figure 4: Projected constraints for SKA1 galaxy clustering and cosmic shear observations for the i-CPL non-phantom model ($w>-1$). The figure compares the constraints from current CMB+BAO+SNIa data with the projected SKA1 forecasts under the realistic treatment of non-linear scales.
  • Figure 5: Projected constraints for SKA1 galaxy clustering and cosmic shear observations for the i-CPL phantom model with the sound speed of dark energy perturbations $c_s^2$ free, compared with $c_s^2=1$, under the realistic treatment of non-linear scales.
  • ...and 1 more figures