Evolution of Supernova Remnant Bubbles in a Warm Diffuse Medium: Survey of Results from One-dimensional Models and Their Impact on Estimates of Interstellar Porosity

Abstract

With straightforward modeling of the late evolution of supernova remnants, including a modest nonthermal contribution to the pressure in the preshock (ambient) gas, we demonstrate that in the solar neighborhood: <P />1.the porosity induced by the remnant population in a warm intercloud medium (n ∼0.15 cm<SUP>-3</SUP>) would not be large (q ≲ 0.2), and <P />2.the slowly cooling supernova remnant bubbles harbor large populations of the high-stage ions (O VI, N V, and C IV at least), sufficient to explain their mean densities in the galactic plane (though a comparable contribution may derive from OB association bubbles). <P />With these results it is no longer clear that there is any need for a pervasive phase of hot gas in the interstellar medium, beyond that found within localized disturbances.