Empirical estimates of the Galactic halo contribution to the dispersion
  measures of extragalactic fast radio bursts using X-ray absorption
  We provide an empirical list of the Galactic dispersion measure ($DM_{Gal}$)
contribution to the extragalactic fast radio bursts along 72 sightlines. It is
independent of any model of the Galaxy, i.e., we do not assume the density of
the disk 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(\oviin) 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\% (90\%) 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 disk+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.
