[Paper Review] Gamma-Ray Bursts, Supernovae Ia and Baryon Acoustic Oscillations: a binned cosmological analysis

Maria Giovanna Dainotti, Giuseppe Sarracino+1 more|arXiv (Cornell University)|Jun 15, 2022

Gamma-ray bursts and supernovae127 references50 citations

TL;DR

This study combines Gamma-Ray Bursts (GRBs) via the fundamental plane correlation, Supernovae Ia, and Baryon Acoustic Oscillations (BAOs) in a binned redshift analysis to extend the cosmic distance ladder to z ≈ 5. By correcting for selection biases and redshift evolution, the authors show that GRBs significantly improve H₀ and ΩM precision when combined with SNe Ia and BAOs, reducing tension with Planck measurements by up to 40% in the highest redshift bin.

ABSTRACT

Cosmological probes at any redshift are necessary to reconstruct consistently the cosmic history. Studying properly the tension on the Hubble constant, $H_0$, obtained by Supernovae Type Ia (SNe Ia) and the Planck measurements of the Cosmic Microwave Background Radiation would require complete samples of distance indicators at any epoch. Gamma-Ray Bursts (GRBs) are necessary for the aforementioned task because of their huge luminosity that allows us to extend the cosmic ladder at very high redshifts. However, using GRBs alone as standard candles is challenging because their luminosity varies widely. To this end, we choose a reliable correlation for GRBs with a very small intrinsic scatter: the so-called fundamental plane correlation for GRB afterglows corrected for selection biases and redshift evolution. We choose a well-defined sample: the platinum sample, composed of 50 Long GRBs. To further constrain cosmological parameters, we use Baryon Acoustic Oscillations (BAOs) given their reliability as standard rulers. Thus, we have applied GRBs, SNe Ia, and BAOs in a binned analysis in redshifts so that GRBs' contribution is fully included in the last redshift bin, which reaches $z=5$. We use the fundamental plane correlation together with SNe Ia and BAOs, to constrain $H_0$ and the density matter today, $\Omega_{M}$. This methodology allows us to assess the role of GRBs combined with SNe Ia and BAOs. We have obtained results for $H_0$ and $\Omega_{M}$ using GRBs+ SNe Ia+BAOs with better precision than the SNe Ia alone for every bin, thus confirming the beneficial role of BAOs and GRBs added together. In addition, consistent results between GRBs+ SNe Ia +BAOs are obtained when compared with the SNe Ia +BAOs, showing the importance of GRBs since the distance ladder is extended up to $z=5$ with a similar precision obtained with other probes without including the GRBs.

Motivation & Objective

• To extend the cosmic distance ladder to high redshifts (z ≈ 5) using GRBs as standard candles.
• To assess the cosmological utility of GRBs by combining them with SNe Ia and BAOs in a binned redshift analysis.
• To reduce the H₀ tension between local SNe Ia/Cepheid measurements and Planck CMB data by incorporating high-redshift GRB data.
• To evaluate the impact of GRBs on cosmological parameter constraints (H₀ and ΩM) when corrected for selection biases and redshift evolution.
• To demonstrate that GRBs can provide precision comparable to SNe Ia when combined with BAOs, enabling high-redshift cosmology.

Proposed method

• Uses the platinum sample of 50 long GRBs with the fundamental plane correlation for afterglow luminosity, corrected for selection biases and redshift evolution.
• Applies a binned cosmological analysis across redshift bins, with GRBs contributing exclusively to the highest bin (z ≈ 5).
• Combines GRB data with SNe Ia and BAO measurements to constrain H₀ and ΩM using a joint likelihood analysis.
• Corrects GRB luminosities using the Dainotti relation (T*ₐₗₗ vs. Lₓ) to reduce intrinsic scatter.
• Performs simulations with 1000 synthetic GRBs on the platinum fundamental plane to assess future precision potential.
• Computes tension metrics (xᵢ) between local H₀ estimates and Planck CMB results using the formula: xᵢ = (H₀,ᵢ − H₀,𝐶𝑀𝐵)/√(σ²_H₀,ᵢ + σ²_H₀,𝐶𝑀𝐵).

Experimental results

Research questions

• RQ1 Can GRBs, when calibrated via the fundamental plane, serve as reliable cosmological distance indicators at z ≈ 5?
• RQ2 How does adding GRBs to SNe Ia and BAOs affect the precision of H₀ and ΩM constraints in a binned redshift analysis?
• RQ3 To what extent does including GRBs reduce the H₀ tension with Planck CMB measurements?
• RQ4 Does the inclusion of GRBs improve cosmological parameter constraints compared to SNe Ia and BAOs alone, especially in high-redshift bins?
• RQ5 What is the expected precision of GRBs as cosmological probes with future data, given current uncertainties?

Key findings

• Adding GRBs to SNe Ia and BAOs reduces the uncertainty on H₀ and ΩM in every redshift bin, with the largest improvements in bin 5 (z ≈ 5).
• For bin 5, the H₀ tension with Planck decreases by 40.0% when GRBs are included (x = 2.14 vs. 3.57 for SNe Ia alone), indicating a significant reduction in discrepancy.
• The inclusion of GRBs reduces the H₀ tension by 16.7% when H₀ is varied alone (x = 4.14 vs. 4.97 for SNe Ia only), and by 1.4% when both H₀ and ΩM are varied.
• Simulations with 1000 synthetic GRBs on the platinum fundamental plane yield ΩM precision of σ(ΩM) = 0.077, matching the precision of some SNe Ia-only bins.
• GRBs allow cosmological parameter inference up to z = 5 with similar precision to SNe Ia and BAOs, confirming their role in extending the cosmic distance ladder.
• Despite higher uncertainties and smaller sample size (4× smaller than SNe Ia), GRBs significantly enhance high-redshift cosmological constraints when combined with other probes.