Soft X-Ray Observations of the Galactic halo

We propose an XMMNewton observation of the hot gas in the Galactic halo. The bright emission lines and complexes recorded by XMMNewton will reveal the ionization history of the gas and tightly constrain halo models.Furthermore, the XMMNewton spectrum will be combined with the O VI intensity recorded in an existing FUSE observation of the same direction. The combination will reveal the three dominant ionization levels of oxygen in hot plasma, and so enable the first measurement of the abundance of oxygen in the hot phase of the interstellar medium. truncated!, Please see actual data for full text [truncated!, Please see actual data for full text]