An XMM-Newton Survey of the Soft X-ray Background. I. The O VII and O
  VIII Lines Between l=120 and l=240
  We present measurements of the soft X-ray background (SXRB) O VII and O VIII
intensity between $l = 120\degr$ and $l = 240\degr$, the first results of a
survey of the SXRB using archival XMM-Newton observations. We do not restrict
ourselves to blank-sky observations, but instead use as many observations as
possible, removing bright or extended sources by hand if necessary. The oxygen
intensities are typically ~0.5-10 photons/cm^2/s/sr (line units, L.U.) for O
VII and ~0-5 L.U. for O VIII. Our dataset includes 69 directions with multiple
observations, whose oxygen intensity variations can be used to constrain SWCX
models. One observation exhibits an O VII enhancement of ~25 L.U. over 2 other
observations of the same direction, although most SWCX enhancements are $\la 4$
L.U. for O VII and $\la 2$ L.U. for O VIII. We find no clear tendency for the O
VII centroid to shift toward the forbidden line energy in observations with
bright SWCX enhancements. There is also no universal association between
enhanced SWCX emission and increased solar wind flux or the closeness of the
sightline to the sub-solar region of the magnetosheath. After removing
observations likely to be contaminated by heliospheric SWCX emission, we use
our results to examine the Galactic halo. There is some scatter in the halo
intensity about the predictions of a simple plane-parallel model, indicating a
patchiness to the halo emission. The O VII/O VIII intensity ratio implies a
halo temperature of ~2.0-2.5 MK, in good agreement with previous studies.
(Abridged)
