Revisiting constraints on the photon rest mass with cosmological fast radio bursts

Abstract

Fast radio bursts (FRBs) have been suggested as an excellent celestial laboratory for testing the zero-mass hypothesis of the photon. In this work, we use the dispersion measure (DM)–redshift measurements of 23 localized FRBs to revisit the photon rest mass mγ . As an improvement over previous studies, here we take into account the more realistic probability distributions of DMs contributed by the FRB host galaxy and intergalactic medium (IGM) from the IllustrisTNG simulation. To better account for the systematic uncertainty induced by the choices of priors of cosmological parameters, we also combine the FRB data with the cosmic microwave background data, the baryon acoustic oscillation data, and type Ia supernova data to constrain the cosmological parameters and mγ simultaneously. We derive a new upper limit of mγ ≤ 3.8 × 10-51 kg, or equivalently mγ ≤ 2.1 × 10-15 eV/c2 (mγ ≤ 7.2 × 10-51 kg, or equivalently mγ ≤ 4.0 × 10-15 eV/c2) at 1σ (2σ) confidence level. Meanwhile, our analysis can also lead to a reasonable estimation for the IGM baryon fraction f IGM = 0.873+0.061 -0.050. With the number increment of localized FRBs, the constraints on both mγ and f IGM will be further improved. A caveat of constraining mγ within the context of the standard ΛCDM cosmological model is also discussed.

Cosmology-Independent Photon Mass Limits from Localized Fast Radio Bursts by Using Artificial Neural Networks

“…Ref. [27] obtained 𝑚𝛾 ≤ 3.8 × 10 −51 kg (1𝜎) for flat ΛCDM using a sample of 23 localized FRBs. Despite not assuming a specific cosmological model, the precision of our constraint from 32 localized FRBs is comparable to these previous results.…”

“…Expanding upon the sample of 23 localized FRBs utilized in Ref. [27], we incorporate 9 new localized FRBs recently detected by the 110-antenna Deep Synoptic Array. [78] Note that two new FRBs with redshift measurements, FRB 20220319D and FRB 20220914A, are not included in our sample.…”

“…Based on the vacuum dispersion method, several studies have used FRBs to put stringent upper limits on the photon mass. [18][19][20][21][22][23][24][25][26][27][28] Since FRBs originate at cosmological distances, the cosmic expansion rate 𝐻(𝑧) has to be considered in constraining the photon mass 𝑚𝛾. In all previous studies, the required 𝐻(𝑧) information is calculated within the standard ΛCDM cosmological model.…”

“…[33,34] Here, we conservatively adopt a Gaussian prior of DM MW halo = 65 ± 15 pc•cm −3 . [27,35] The DM due to the IGM, i.e., DMIGM, depends on the cosmological model and is largely influenced by the number of halos intersected along the propagation path. Due to density perturbations on large-scale structures, it is challenging to calculate the precise value of DMIGM for individual FRBs.…”

“…( 6) and ( 11)], to be determined. In previous works, [18][19][20][21][22][23][24][25][26][27] the conventional approach is to adopt the flat ΛCDM cosmological model and to replace the denominator 𝐻(𝑧) with 𝐻0[𝛺𝑚(1 + 𝑧) 3 + 𝛺Λ] 1/2 . Subsequently, 𝐻𝛾(𝑧) and 𝐻e(𝑧) are calculated by treating the cosmological parameters 𝛺𝑚 and 𝛺Λ as fixed values.…”