Probing the anisotropy of the Milky Way gaseous halo: Sight-lines toward
  Mrk 421 and PKS2155-304
  (Abridged) We recently found that the halo of the Milky Way contains a large
reservoir of warm-hot gas that contains a large fraction of the missing baryons
from the Galaxy. The average physical properties of this circumgalactic medium
(CGM) are determined by combining average absorption and emission measurements
along several extragalactic sightlines. However, there is a wide distribution
of both, the halo emission measure and the \ovii column density, suggesting
that the Galactic warm-hot gaseous halo is anisotropic. We present {\it Suzaku}
observations of fields close to two sightlines along which we have precise
\ovii absorption measurements with \chandran. The column densities along these
two sightlines are similar within errors, but we find that the emission
measures are different. Therefore the densities and pathlengths in the two
directions must be different, providing a suggestive evidence that the warm-hot
gas in the CGM of the Milky Way is not distributed uniformly. However, the
formal errors on derived parameters are too large to make such a claim. The
average density and pathlength of the two sightlines are similar to the global
averages, so the halo mass is still huge, over 10 billion solar masses. With
more such studies, we will be able to better characterize the CGM anisotropy
and measure its mass more accurately. We also show that the Galactic disk makes
insignificant contribution to the observed \ovii absorption; a similar
conclusion was also reached independently about the emission measure. We
further argue that any density inhomogeneity in the warm-hot gas, be it from
clumping, from the disk, or from a non-constant density gradient, would
strengthen our result in that the Galactic halo path-length and the mass would
become larger than what we estimate here. As such, our results are conservative
and robust.
