Suzaku Observations of the Local and Distant Hot ISM
Abstract
Suzaku observed the molecular cloud MBM12 and a nearby "blank" field in order to measure both the ``local'' and ``distant'' components of the diffuse soft X-ray background. Towards MBM12, a "local" O VII emission line was clearly detected with surface brightness in the range 2.3-3.5 ph/cm^2/s/sr (line units, LU), depending upon the analysis method used. The origin of this emission could be either the Local Hot Bubble (LHB) or charge exchange with oxygen ions in the solar wind. If entirely from the LHB, the emission could be explained by a region with 100 pc radius, an electron density of 0.0087 cm^-3, and a temperature of 1.2 MK, although the implied emission measure is significantly larger than typically used in modeling the 1/4 keV band emission. The solar wind proton flux during these observations was moderate with unexceptional oxygen ion ratios, suggesting that flaring emission due to charge exchange would not be large, although there remains the possibility of a slowly-varying component.
In the off-cloud observation, O VII and O VIII emission from a distant plasma component was detected with surface brightnesses of 2.34± 0.33 and 0.77 ± 0.16 LU respectively. If this oxygen emission is from a thermal plasma in collisional equilibrium, the O VIII/O VII ratio suggests it has a temperature of ∼ 2 MK.- Publication:
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AAS/High Energy Astrophysics Division #9
- Pub Date:
- September 2006
- Bibcode:
- 2006HEAD....9.0117S