Abstract
Context. The relationship between the dispersion measures (DMs) and redshifts of fast radio bursts (FRBs) is of scientific interest. Upcoming commensal surveys may detect and localise many FRBs to the sub-arcsecond angular resolutions required for accurate redshift determination. Meanwhile, it is important to exploit sources accumulated with more limited localisation to their maximum scientific potential. Aims. We present techniques for the DM-redshift analysis of large numbers of unlocalised FRBs, accounting for uncertainties due to their extragalactic DM components, redshift dependences, and progenitor scenarios. Methods. We reviewed the components comprising observed FRB DMs. We built redshift-scalable probability distribution functions for these components, which we combined in cases of multiple progenitor scenarios. Accounting for prior FRB redshift distributions we inverted these models, enabling FRB redshifts to be constrained. Results. We illustrate the influence of FRB progenitors on their observed DMs, which may remain significant to redshift z ~ 3. We identify the FRB sample sizes required to distinguish between multiple progenitor scenarios. We place new, physically motivated redshift constraints on all catalogued FRBs to date and use these to reject potential host galaxies in the localisation area of an FRB according to various models. We identify further uses for DM-redshift analysis using many FRBs. We provide our code so that these techniques may be employed using increasingly realistic models as our understanding of FRBs evolves.
Highlights
Many fast radio bursts (FRBs) have unconstrained redshifts
Concluding remarks We present in this paper a statistical framework for the exploration of the FRB dispersion measures (DMs)-redshift relationship, which provides the basis for several analyses
It facilitates the assessment of host galaxy contributions to FRB DMs using physically motivated models
Summary
Many fast radio bursts (FRBs) have unconstrained redshifts. Since their discovery in 2007 (Lorimer et al 2007), tens of these short-duration (∼0.1–10 ms), dispersed radio bursts have been catalogued (Petroff et al 2016). Save for the repeating FRB 121102 (Spitler et al 2014, 2016), their extragalactic origins have been inferred via their dispersion measures (DMs) These DMs, related to the frequency-dependent index of refraction and resulting arrival time delays experienced by radio waves which propagate through ionised electrons, are proportional to the integrated electron densities along their propagation paths. This, along with sightline variance in IGM electrons within collapsed structures results in a redshift-dependent potential DM distribution for FRBs (Ioka 2003; McQuinn 2014; Macquart et al 2015) This distribution is intrinsically linked to the locations of FRBs within their host galaxies and to their progenitors
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