Origins of the 1/4 keV Soft X-Ray Background

Abstract

Snowden and coworkers have presented a model for the 1/4 keV soft X-ray diffuse background in which the observed flux is dominated by a ~ 10^6 K thermal plasma located in a 100-300 pc diameter bubble surrounding the Sun, but has significant contributions from a very patchy Galactic halo. Halo emission provides about 11% of the total observed flux and is responsible for half of the H I anticorrelation. The remainder of the anticorrelation is presumably produced by displacement of disk H I by the varying extent of the local hot bubble (LHB). The ROSAT R1 and R2 bands used for this work had the unique spatial resolution and statistical precision required for separating the halo and local components, but provide little spectral information. Some consistency checks had been made with older observations at lower X-ray energies, but we have made a careful investigation of the extent to which the model is supported by existing sounding rocket data in the Be (73-111 eV) and B bands (115-188 eV) where the sensitivities to the model are qualitatively different from the ROSAT bands. We conclude that the two-component model is well supported by the low-energy data. We find that these combined observations of the local component may be consistent with single-temperature thermal emission models in collisional ionization equilibrium if depleted abundances are assumed. However, different model implementations give significantly different results, offering little support for the conclusion that the astrophysical situation is so simple.

arXiv comment17 pages, 6 figures, accepted by the Astrophysical Journal

References in corpus (3)

• Maps of Dust IR Emission for Use in Estimation of Reddening and CMBR Foregrounds
• Collisional Plasma Models with APEC/APED: Emission Line Diagnostics of Hydrogen-like and Helium-like Ions
• A High Spectral Resolution Observation of the Soft X-ray Diffuse Background with Thermal Detectors

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• The Local Bubble and Interstellar Material Near the Sun
• A High Spectral Resolution Study of the Soft X-ray Background with the X-ray Quantum Calorimeter
• Solar Wind Charge Exchange contribution to the ROSAT All Sky Survey Maps
• Fermi bubbles: high latitude X-ray supersonic shell