2021MNRAS.500..655D

We provide an empirical list of the Galactic dispersion measure (DM_Gal) contribution to the extragalactic fast radio bursts (FRBs) along 72 sightlines. It is independent of any model of the Galaxy, i.e. we do not assume the density of the disc or the halo, spatial extent of the halo, baryonic mass content, or any such external constraints to measure DM_Gal. We use 21-cm, UV, EUV, and X-ray data to account for different phases, and find that DM_Gal is dominated by the hot phase probed by X-ray absorption. We improve upon the measurements of N(O VII) and f_OVII compared to previous studies, thus providing a better estimate of the hot phase contribution. The median DM_Gal = 64⁺²⁰_–23 cm^–3 pc, with a 68 per cent (90 per cent) confidence interval of 33-172 (23-660) cm^–3 pc. The DM_Gal does not appear to follow any trend with the Galactic longitude or latitude, and there is a large scatter around the values predicted by simple disc + spherical halo models. Our measurements provide more complete and accurate estimates of DM_Gal independent from the previous studies. We provide a table and a code to retrieve DM_Gal for any FRB localized in the sky.