Abstract
The excessive dispersion measure (DM) of fast radio bursts (FRBs) has been proposed to be a powerful tool to study intergalactic medium (IGM) and to perform cosmography. One issue is that the fraction of baryons in the IGM, f IGM, is not properly constrained. Here, we propose a method of estimating f IGM using a putative sample of FRBs with the measurements of both DM and luminosity distance d L. The latter can be obtained if the FRB is associated with a distance indicator (e.g., a gamma-ray burst or a gravitational-wave event), or the redshift z of the FRB is measured and d L at the corresponding z is available from other distance indicators (e.g., SNe Ia) at the same redshift. As d L/DM essentially does not depend on cosmological parameters, our method can determine f IGM independent of cosmological parameters. We parameterize f IGM as a function of redshift and model the DM contribution from a host galaxy as a function of star formation rate. Assuming f IGM has a mild evolution with redshift with a functional form and by means of Monte Carlo simulations, we show that an unbiased and cosmology-independent estimate of the present value of f IGM with a ∼12% uncertainty can be obtained with 50 joint measurements of d L and DM. In addition, such a method can also lead to a measurement of the mean value of DM contributed from the local host galaxy.
- Publication:
-
The Astrophysical Journal, Volume 876, Issue 2, article id. 146,
6 pp. (2019). - Pub Date:
- May 2019
- DOI:
- 10.3847/1538-4357/ab18fe
- arXiv:
- arXiv:1904.08927
- Bibcode:
- 2019ApJ...876..146L
- Keywords:
-
- cosmology: observations;
- intergalactic medium;
- Astrophysics - Cosmology and Nongalactic Astrophysics;
- Astrophysics - High Energy Astrophysical Phenomena;
- General Relativity and Quantum Cosmology
- E-Print Comments:
- 6 pages, 5 figures, to appear in ApJ; doi:10.3847/1538-4357/ab18fe