Reconstructing the Fraction of Baryons in the Intergalactic Medium with Fast Radio Bursts via Gaussian Processes

Abstract

Nowadays, fast radio bursts (FRBs) are promising new probe for astronomy and cosmology. Due to their extragalactic and cosmological origin, FRBs could be used to study the intergalactic medium (IGM) and the cosmic expansion. It is expected that numerous FRBs with identified redshifts will be available in the future. \(\rm DM_{IGM}\), the contribution from IGM to the observed dispersion measure (DM) of FRB, carries the key information about IGM and the cosmic expansion history. We can study the evolution of the universe by using FRBs with identified redshifts. In the present work, we are interested in the fraction of baryon mass in IGM, \(f_{\rm IGM}\), which is useful to study the cosmic expansion and the problem of "missing baryons". We propose to reconstruct the evolution of \(f_{\rm IGM}\) as a function of redshift \(z\) with FRBs via a completely model-independent method, namely Gaussian processes. Since there is no a large sample of FRBs with identified redshifts by now, we use the simulated FRBs instead. Through various simulations, we show that this methodology works well.