Simulations of Supernova Remnants in Diffuse Media III. The Population of Buoyant Remnants Above the Milky Way's Disk

Abstract

We model SNRs at a variety of heights above the disk. Our detailed numerical simulations include non-equilibrium ionization and recombination and follow the remnants' evolution until their hot bubbles have cooled. We analytically calculate the bubbles' buoyant acceleration. From the results, we estimate the time and space average O VI, N V, and C IV column densities and emission intensities, 1/4 keV soft X-ray surface brightness, area coverage, and volume occupation of the population of isolated SNRs above the Galaxy's HI layer. Irrespective of assumed supernova explosion energy, ambient nonthermal pressure, or frictional drag coefficient, the predicted O VI column density matches the observed distribution between 130 pc and 2000 pc. The SNRs' O VI intensity is a significant fraction of the average observed intensity. Within the range of uncertainty in the SN rate, such SNRs can explain all of the observed 1/4 keV surface brightness attributed to the extraplanar gas beyond the H I layer in the southern hemisphere (~400 x 10^-6 counts/s/arcmin^2). Thus, extraplanar SNRs could be the most important source of hot gas between the Local Bubble and z ~ 2000 pc in the relatively quiescent southern hemisphere. These results stand whether the remnants are assumed to be buoyant or not. The population of old extraplanar SNRs should cover most of the high latitude sky, but bright young extraplanar SNRs should cover less than 1% of the sky. Perhaps the l=247, b=-64 crescent in the 1/4 keV X-ray maps could be a young remnant.

arXiv commentAccepted by ApJ for publication on February 10, 2006 (Volume 638). 44 pages, including 6 figures, 10 tables (and 1 blank page)

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Cited by in corpus (11)

• The Far Ultraviolet Spectroscopic Explorer Survey of OVI Absorption in the Disk of the Milky Way
• An XMM-Newton Survey of the Soft X-ray Background. III. The Galactic Halo X-ray Emission
• The Extension of the Transition Temperature Plasma into the Lower Galactic Halo
• The Origin of the Hot Gas in the Galactic Halo: Confronting Models with XMM-Newton Observations
• Impact of supernova and cosmic-ray driving on the surface brightness of the galactic halo in soft X-rays
• Si iv Column Densities Predicted from Non-Equilibrium Ionization Simulations of Turbulent Mixing Layers and High-Velocity Clouds
• Determining The Galactic Halo's Emission Measure from UV and X-ray Observations
• Astrophysics in 2006
• A Study of the Vertical Motion of Supernova Remnant Bubbles in the Interstellar Medium Drawn from the Results of Three-Dimensional MHD Simulations
• A Possible Supernova Remnant high above the Galactic Disk
• Hot Gas in the Galactic Thick Disk and Halo Near the Draco Cloud