IONIZED GAS IN THE HALOS OF EDGE-ON STARBURST GALAXIES: EVIDENCE FOR SUPERNOVA-DRIVEN SUPERWINDS

摘要

Supernova-driven galactic winds ("superwinds") have been invoked to explain many aspects of galaxy formation and evolution. Such winds should arise when the supernova rate is high enough to create a cavity of very hot shock-heated gas within a galaxy. This gas can then expand outward as a high-speed wind that can accelerate and heat ambient interstellar or circum-galactic gas causing it to emit optical line radiation and/or thermal X-rays. Theory suggests that such winds should be common in starburst galaxies and that the nature of the winds should depend on the star formation rate and distribution. In order to systematize our observational understanding of superwinds (determine their incidence rate and the dependence of their properties on the star formation that drives them) and to make quantitative comparisons with the theory of superwinds, we have analyzed data from an optical spectroscopic and narrow-band imaging survey of an infrared flux-limited (S_(60 μm) ≥ 5.4 Jy) sample of about 50 IR-warm (S_(60 μm) /S_(100 μm) > 0.4), starburst galaxies whose stellar disks are viewed nearly edge-on (b/a approx > 2). This sample contains galaxies with infrared luminosities from ≈ 10~(10)-10~(12) solar luminosity and allows us to determine the properties of superwinds over a wide range of star formation rates. We have found that extraplanar emission-line gas is a very common feature of these edge-on, IR-bright galaxies and the properties of the extended emission-line gas are qualitatively and quantitatively consistent with the superwind theory. We can summarize these properties as morphological, ionization, dynamical, and physical.