Feedback in nearby dwarf starburst galaxies and giant extragalactic H II regions.

摘要

Giant extragalactic H II regions in nearby normal galaxies are similar to dwarf starburst galaxies in luminosity/star formation rate, physical size, and stellar population, although they differ in gravitational potential, star formation rate per unit area, and surrounding environment. This dissertation compares feedback processes in these two types of star-forming regions.; Feedback, the cycle which regulates the, relationship between star formation, the interstellar medium, and the intergalactic medium, is empirically measured via observations of interstellar gas in star-forming regions, where stellar winds and supernovae create galactic-scale outflows of interstellar gas and dust which in turn may heat and enrich the intergalactic medium. These kiloparsec-scale winds are most directly probed via the supernova-heated hot gas. However, the cold and photoionized warm interstellar gas from the disk is entrained in the flow and also traces large-scale motions of outflowing matter. I investigate this via optical and ultraviolet absorption-line spectroscopy of the cold neutral medium, as well as emission-line studies of the Halpha recombination in the warm ionized gas.; The H II regions in disks initially seem physically similar to dwarf starburst galaxies; shell fragments of ionized gas are found in both environments via high-resolution Halpha emission spectroscopy. However, while complex Na D absorption profiles trace outflowing cold, neutral gas accelerated to near the escape velocity, no such counterpart is detected in the H II regions in outer disks. The lack of large-scale outflows of cold, neutral gas from the H II regions indicates that while dwarf starburst galaxies and the giant H II regions in normal galaxies may have similar properties, yet the feedback cycle in these regions is different.