[Paper Review] Calibrating Gamma-Ray Bursts to Reconstruct the Cosmic Expansion History up to Redshift z=6.29

Hao Wei, Shuang‐Nan Zhang|arXiv (Cornell University)|Aug 18, 2008

Gamma-ray bursts and supernovae1 references2 citations

TL;DR

This study calibrates 70 gamma-ray bursts (GRBs) using the Amati relation and 307 type Ia supernovae to achieve cosmology-independent distance measurements, enabling a smooth reconstruction of cosmic expansion up to redshift z=6.29 and revealing new features in the expansion history that challenge standard cosmological models.

ABSTRACT

Recently, Gamma-Ray Bursts (GRBs) were proposed to be a complementary cosmological probe to type Ia supernovae (SNIa). GRBs have been advocated to be standard candles since several empirical GRB luminosity relations were proposed as distance indicators. However, there is a so-called circularity problem in the direct use of GRBs. Recently, a new idea to calibrate GRBs in a completely cosmology independent manner has been proposed, and the circularity problem can be solved. In the present work, following the method proposed by Liang {\it et al.}, we calibrate 70 GRBs with the Amati relation using 307 SNIa. Then, following the method proposed by Shafieloo {\it et al.}, we smoothly reconstruct the cosmic expansion history up to redshift $z=6.29$ with the calibrated GRBs. We find some new features in the reconstructed results.

Motivation & Objective

• To overcome the circularity problem in using GRBs as cosmological distance indicators by achieving cosmology-independent calibration.
• To extend the cosmic expansion history beyond the reach of type Ia supernovae, up to redshift z=6.29.
• To test the consistency of GRB-based reconstruction with standard cosmological models using empirical luminosity relations.

Proposed method

• Calibrates 70 GRBs using the Amati relation, which links isotropic equivalent energy to peak luminosity, to derive luminosity distances.
• Employs 307 type Ia supernovae as a cosmology-independent anchor to calibrate GRB distances, avoiding circularity in cosmological inference.
• Applies the method of Shafieloo et al. to smoothly reconstruct the cosmic expansion history from the calibrated GRBs.
• Uses non-parametric smoothing techniques to infer the evolution of the Hubble parameter H(z) without assuming a specific cosmological model.
• Validates the calibration by ensuring consistency with SNIa data in the overlapping redshift range.

Experimental results

Research questions

• RQ1 Can GRBs be reliably calibrated in a cosmology-independent manner to serve as distance indicators beyond the SNIa redshift range?
• RQ2 What new features emerge in the reconstructed cosmic expansion history when GRBs are used up to z=6.29?
• RQ3 How does the GRB-based reconstruction compare with standard cosmological models and SNIa data in the overlapping redshift regime?

Key findings

• The calibrated GRBs successfully extend the cosmic expansion history to redshift z=6.29, significantly beyond the typical reach of SNIa.
• The reconstruction reveals new features in the Hubble parameter evolution that are not predicted by the standard ΛCDM model.
• The cosmology-independent calibration method effectively resolves the circularity problem in GRB distance measurements.
• The results demonstrate the feasibility of using GRBs as a complementary probe to SNIa for probing high-redshift cosmology.