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Probing cosmology with bright sirens from the CosmoDC2_BCO LSST synthetic catalog

Ranier Menote, Valerio Marra

TL;DR

This work forecasts cosmological constraints from bright sirens detected by current and next-generation gravitational-wave networks, supplemented by Roman-quality Type Ia supernovae. Using the CosmoDC2_BCO synthetic catalog, it quantifies how LVK, ET, and CE networks, alone and with Roman SNe, constrain $H_0$ and dynamical dark energy across ΛCDM, $w$CDM, and $w_0w_a$CDM, while exploring the impact of sky localization on follow-up. The results show sub-percent $H_0$ precision with third-generation detectors (∼0.2%–0.3% after a decade), and notable FoM improvements for dark-energy parameters when combined with Roman SN data (FoM ≈ 25 for ET+LVK and ≈ 76 for CE+ET+LVK). These findings position GW+EM observations as a leading pathway for next-decade precision cosmology, with practical guidance on ToO strategies and SN calibration. They also delineate limitations, such as shielding tidal effects and scheduling systematics, suggesting areas for further refinement as modeling and operations mature.

Abstract

Bright sirens, i.e. gravitational-wave detections of compact binary mergers with electromagnetic counterparts, provide a self-calibrated distance-redshift relation and are therefore powerful probes of cosmic expansion. Using the CosmoDC2_BCO catalog, we forecast cosmological constraints from current (LVK) and next-generation (ET, CE) detector networks, in combination with a Roman-like Type Ia supernova sample. We find that third-generation networks reach sub-percent precision on the Hubble constant within a few years, achieving 0.2% after a decade with CE+ET+LVK, while LVK remains limited to the 6% level. The LVK fifth observing run may shed light on the H_0 tension only if the inferred value falls outside the range spanned by the Planck and SH0ES determinations, which currently achieve far higher precisions. Supernovae do not directly tighten H_0 but stabilize its inference through parameter correlations and enable an absolute calibration of the supernova magnitude M_B. In dynamical dark-energy models, the joint analysis of Roman supernovae and bright sirens yields a Figure of Merit of 25 for ET+LVK and 76 for CE+ET+LVK, to be compared with the state-of-the-art DESI DR2 BAO plus DESY5 supernovae value of 56. Sky-localization thresholds of DeltaOmega < 50 deg^2, or even DeltaOmega < 10 deg^2, entail only mild penalties, suggesting efficient follow-up strategies. These results establish third-generation GW+EM observations, especially when combined with Roman supernovae, as a cornerstone for precision cosmology in the next decade.

Probing cosmology with bright sirens from the CosmoDC2_BCO LSST synthetic catalog

TL;DR

This work forecasts cosmological constraints from bright sirens detected by current and next-generation gravitational-wave networks, supplemented by Roman-quality Type Ia supernovae. Using the CosmoDC2_BCO synthetic catalog, it quantifies how LVK, ET, and CE networks, alone and with Roman SNe, constrain and dynamical dark energy across ΛCDM, CDM, and CDM, while exploring the impact of sky localization on follow-up. The results show sub-percent precision with third-generation detectors (∼0.2%–0.3% after a decade), and notable FoM improvements for dark-energy parameters when combined with Roman SN data (FoM ≈ 25 for ET+LVK and ≈ 76 for CE+ET+LVK). These findings position GW+EM observations as a leading pathway for next-decade precision cosmology, with practical guidance on ToO strategies and SN calibration. They also delineate limitations, such as shielding tidal effects and scheduling systematics, suggesting areas for further refinement as modeling and operations mature.

Abstract

Bright sirens, i.e. gravitational-wave detections of compact binary mergers with electromagnetic counterparts, provide a self-calibrated distance-redshift relation and are therefore powerful probes of cosmic expansion. Using the CosmoDC2_BCO catalog, we forecast cosmological constraints from current (LVK) and next-generation (ET, CE) detector networks, in combination with a Roman-like Type Ia supernova sample. We find that third-generation networks reach sub-percent precision on the Hubble constant within a few years, achieving 0.2% after a decade with CE+ET+LVK, while LVK remains limited to the 6% level. The LVK fifth observing run may shed light on the H_0 tension only if the inferred value falls outside the range spanned by the Planck and SH0ES determinations, which currently achieve far higher precisions. Supernovae do not directly tighten H_0 but stabilize its inference through parameter correlations and enable an absolute calibration of the supernova magnitude M_B. In dynamical dark-energy models, the joint analysis of Roman supernovae and bright sirens yields a Figure of Merit of 25 for ET+LVK and 76 for CE+ET+LVK, to be compared with the state-of-the-art DESI DR2 BAO plus DESY5 supernovae value of 56. Sky-localization thresholds of DeltaOmega < 50 deg^2, or even DeltaOmega < 10 deg^2, entail only mild penalties, suggesting efficient follow-up strategies. These results establish third-generation GW+EM observations, especially when combined with Roman supernovae, as a cornerstone for precision cosmology in the next decade.
Paper Structure (16 sections, 12 equations, 3 figures, 5 tables)

This paper contains 16 sections, 12 equations, 3 figures, 5 tables.

Table of Contents

  1. Introduction
  2. Synthetic data
  3. GW data
  4. Kilonova data
  5. Supernova data
  6. Methodology
  7. Cosmological models
  8. Time-evolution of constraints
  9. Likelihood Construction and Priors
  10. Bright sirens likelihood
  11. Supernovae likelihood
  12. Results
  13. Local measurement of $H_0$
  14. Cosmological parameter estimation
  15. Time evolution of constraints
  16. ...and 1 more sections

Figures (3)

  • Figure 1: Redshift distribution of GW detections (filled histograms) and those with kilonova counterparts (dashed lines) over a 10-year observation period, for different detector networks.
  • Figure 2: Comparison of cosmological constraints from BS only (left) and BS + SNe (right) for 3G detector networks. The analysis includes GW events with sky localization better than $100\,\mathrm{deg}^2$ over a total observation time of 10 years. The top row corresponds to $\Lambda$CDM, the second to the $w$CDM model, and the bottom row to the $w_0w_a$CDM model.
  • Figure 3: Time evolution of $\sigma_{H_0}$ for the $\Lambda$CDM model using BS only (top panel), and of the Figure of Merit on $w_0$ and $w_a$ for BS only (second panel) and BS + SNe (third panel), restricted to events with sky localization better than $100\,\mathrm{deg}^2$. The bottom three panels show the time evolution of $\sigma_{H_0}$ under different sky-localization thresholds.