Galaxies with substantial star formation rates often exhibit large-scale winds composed of material flowing out of the galaxy. The galactic fountain model posits that some fraction of this material reaches a large distance from the galaxy, cools, and then recondenses and falls back onto the galaxy. However, details of the condensing materials density, ionization state, and temperature are not known. M82 exhibits an archetypal multi-phase galactic wind comprising a mixture of hot plasma, dust, and neutral gas. Far-infrared spectral observations of the wind and cooling region around the galaxy can elucidate the physical characteristics and time scales of the fountain mechanism. Here we calculate the expected intensity of this signal, and demonstrate that a suitably designed sub-orbital experiment could search for direct emission from the cooling material comprising the galactic fountain in M82. We also study notional instrument designs for a sounding rocket and for a balloon payload, and determine their relative performance in the presence of realistic photon loading.
Zemcov et al. (Thu,) studied this question.