Cosmology-insensitive estimate of IGM baryon mass fraction from five localized fast radio bursts

Abstract

Five fast radio bursts (FRBs), including three apparently non-repeating ones FRB 180924, FRB 181112, and FRB 190523, and two repeaters, FRB 121102 and FRB 180916.J0158+65, have already been localized so far. We apply a method developed recently by us (Li et al. 2019) to these five localized FRBs to give a cosmology-insensitive estimate of the fraction of baryon mass in the IGM, \(f_{\rm IGM}\). Using the measured dispersion measure (DM) and luminosity distance \(d_{\rm L}\) data (inferred from the FRB redshifts and \(d_{\rm L}\) of type Ia supernovae at the same redshifts) of the five FRBs, we constrain the local \(f_{\rm IGM} = 0.84^{+0.16}_{-0.22}\) with no evidence of redshift dependence. This cosmology-insensitive estimate of \(f_{\rm IGM}\) from FRB observations is in excellent agreement with previous constraints using other probes. Moreover, using the three apparently non-repeating FRBs only we get a little looser but consistent result \(f_{\rm IGM} = 0.74^{+0.24}_{-0.18}\). In these two cases, reasonable estimations for the host galaxy DM contribution (\({\rm DM_{host}}\)) can be achieved by modelling it as a function of star formation rate. The constraints on both \(f_{\rm IGM}\) and \({\rm DM_{host}}\) are expected to be significantly improved with the rapid progress in localizing FRBs.