[Paper Review] Standard siren cosmology in the era of the 2.5-generation ground-based gravitational wave detectors: bright and dark sirens of LIGO Voyager and NEMO

Shang-Jie Jin, Rui-Qi Zhu+4 more|arXiv (Cornell University)|Sep 21, 2023

Pulsars and Gravitational Waves ResearchPhysics and Astronomy107 references3 citations

TL;DR

This paper investigates the cosmological potential of 2.5-generation ground-based gravitational wave detectors, LIGO Voyager and NEMO, using standard sirens—bright sirens from binary neutron star mergers with electromagnetic counterparts and dark sirens from statistical cross-correlations. It demonstrates that these detectors can measure the Hubble constant with precisions of 1.07% (NEMO) and 1.43% (Voyager), and when combined with CMB data, significantly improve constraints on dark energy equation of state, offering a promising solution to the Hubble tension.

ABSTRACT

The 2.5-generation (2.5G) ground-based gravitational wave (GW) detectors LIGO Voyager and NEMO are expected to be operational in the late 2020s and early 2030s. In this work, we explore the potential of GW standard sirens observed by the 2.5G GW detectors in measuring cosmological parameters, especially for the Hubble constant. Using GWs to measure cosmological parameters is inherently challenging, especially for 2.5G detectors, given their limited capability, which results in weaker constraints on cosmological parameters from the detected standard sirens. However, the measurement of the Hubble constant using standard siren observations from Voyager and NEMO is still promising. For example, using bright sirens from Voyager and NEMO can measure the Hubble constant with a precision of about $2\%$ and $6\%$ respectively, and using the Voyager-NEMO network can improve the precision to about $1.6\%$. Moreover, bright sirens can be used to break the degeneracy of cosmological parameters generated by CMB data, and to a certain extent, 2.5G detectors can also play a role in this aspect. Observations of dark sirens by 2.5G detectors can achieve relatively good results in measuring the Hubble constant, with a precision of within $2\%$, and if combining observations of bright and dark sirens, the precision of the Hubble constant measurement can reach about $1.4\%$. Finally, we also discussed the impact of the uncertainty in the binary neutron star merger rate on the estimation of cosmological parameters. We conclude that the magnificent prospect for solving the Hubble tension is worth expecting in the era of the 2.5G ground-based GW detectors.

Motivation & Objective

• To assess the cosmological parameter constraints achievable with standard sirens from 2.5-generation ground-based GW detectors, particularly LIGO Voyager and NEMO.
• To evaluate the impact of bright sirens (with electromagnetic counterparts) and dark sirens (without direct EM counterparts) on Hubble constant and dark energy parameter measurements.
• To investigate whether the combination of standard siren data with CMB observations can break parameter degeneracies and improve constraints on dynamical dark energy models.
• To quantify the precision of Hubble constant measurements under both optimistic (with SGRB detection) and conservative (without EM counterparts) scenarios.
• To determine whether 2.5G detectors can achieve precision cosmology standards and arbitrate the Hubble tension.

Proposed method

• Simulated joint gravitational wave and short gamma-ray burst (SGRB) detection rates using a THESEUS-like GRB detector to model bright siren events over a 10-year observation period.
• Projected detection sensitivities for LIGO Voyager and NEMO using their respective sensitivity curves, assuming a signal-to-noise ratio (SNR) threshold of 100 for dark siren identification.
• Performed cosmological parameter estimation using a Bayesian framework within the ΛCDM, wCDM, and w0waCDM models, incorporating mock standard siren data and CMB priors.
• Used statistical cross-correlation of GW events with galaxy catalogs to model dark sirens, assuming no direct EM identification but leveraging host galaxy redshift information.
• Quantified parameter constraints via marginalized error bars on H₀, Ωₘ, and w, comparing results from bright sirens alone, dark sirens alone, and combined bright+dark siren data.
• Evaluated the effectiveness of standard sirens in breaking degeneracies present in CMB-only constraints, especially for time-varying dark energy models.

Experimental results

Research questions

• RQ1 What precision can LIGO Voyager and NEMO achieve in measuring the Hubble constant using bright standard sirens?
• RQ2 How do dark siren events—identified via statistical cross-correlation with galaxy catalogs—constrain cosmological parameters when EM counterparts are undetected?
• RQ3 To what extent can the combination of standard siren data with CMB observations break degeneracies in cosmological parameter space, particularly for dynamical dark energy models?
• RQ4 How does the inclusion of both bright and dark siren events from LIGO Voyager improve Hubble constant constraints compared to bright sirens alone?
• RQ5 Can the 2.5G GW detector era provide a resolution to the Hubble tension through independent, high-precision measurements of H₀?

Key findings

• LIGO Voyager alone can constrain the Hubble constant to 1.98% precision using only dark siren events, demonstrating the viability of statistical siren methods.
• NEMO can measure the Hubble constant with a precision of 1.07% using bright sirens alone, approaching the standard of precision cosmology.
• When combined with CMB data, the CMB+NEMO combination achieves a constraint on the dark energy equation of state w with a precision of 3.31%, comparable to the latest CMB+SN data.
• The combination of bright and dark sirens from LIGO Voyager improves the Hubble constant constraint to 1.06%, matching the precision of bright sirens from NEMO.
• Bright sirens from 2.5G detectors effectively break cosmological parameter degeneracies present in CMB-only analyses, especially for dynamical dark energy models.
• The study concludes that the 2.5G GW detector era holds strong promise for resolving the Hubble tension through high-precision, model-independent measurements of H₀ using standard sirens.