X-Ray Detection of Warm Ionized Matter in the Galactic Halo
  We report on a systematic investigation of the cold and mildly ionized
gaseous baryonic metal components of our Galaxy, through the analysis of high
resolution Chandra and XMM-Newton spectra of two samples of Galactic and
extragalactic sources. The comparison between lines of sight towards sources
located in the disk of our Galaxy and extragalactic sources, allows us for the
first time to clearly distinguish between gaseous metal components in the disk
and halo of our Galaxy. We find that a Warm Ionized Metal Medium (WIMM)
permeates a large volume above and below the Galaxy's disk, perhaps up to the
Circum-Galactic space (CGM). This halo-WIMM imprints virtually the totality of
the OI and OII absorption seen in the spectra of our extragalactic targets, has
a temperature of T(Halo-WIMM)=2900 +/- 900 K, a density <n_H>(Halo-WIMM) =
0.023 +/- 0.009 cm-3 and a metallicity Z(Halo-WIMM) = (0.4 +/- 0.1) Z_Solar.
Consistently with previous works, we also confirm that the disk of the Galaxy
contains at least two distinct gaseous metal components, one cold and neutral
(the CNMM: Cold Neutral Metal Medium) and one warm and mildly ionized, with the
same temperature of the Halo-WIMM, but higher density (<n_H>(Disk-WIMM) = 0.09
+/- 0.03 cm-3) and metallicity (Z(Disk-WIMM) = 0.8 +/- 0.1$ Z_Solar). By
adopting a simple disk+sphere geometry for the Galaxy, we estimates masses of
the CNMM and the total (disk + halo) WIMM of M(CNMM) <~ 8e8 Solar masses and
M(WIMM) ~ 8.2e9 Solar masses.
