PI: J. Christopher Howk, Univ. of Notre Dame, firstname.lastname@example.org
Address: Dept. of Physics, 225 Nieuwland Science Hall, Notre Dame, IN 46544, USA
CoI: Katherine Rueff, Univ. of Notre Dame
CoI: Nicolas Lehner, Univ. of Notre Dame
CoI: John O'Meara, St. Michael's College
Title: Probing Star Formation and Primordial Infall in the Thick Disks of Spiral Galaxies
Abstract: The interstellar thick disks of most spiral galaxies contain all of the phases found in their thin disks, including a cold, dense phase of the ISM. In the course of studying the multiphase thick disks of spirals, we have discovered evidence for in situ star formation based on our detection of thick disk \HII regions with faint, blue stellar continuum emission. These nebulae lie at heights 0.5 < z < 2.7 kpc and are found in several edge-on spiral galaxies in the local universe. These nebulae can be used to study the star formation process in the low pressure environments of the thick disk and to probe the vertical distribution of metals in galaxies, the latter fixed by the expulsion of metals from the thin disk and the infall of material from the surrounding intergalactic medium. We propose to obtain Keck-I LRIS spectroscopy of a complete sample of thick disk \HII regions in the canonical spiral galaxy NGC 891. We will use these observations with previous ground- and space-based imaging to study the underlying massive stellar content of the regions and determine the gas-phase abundances of the \HII regions. Our measurements will provide the first metallicity measurements of thick disk material in a spiral beyond the Milky Way and provide one of the few observational constraints on the amount of matter being actively accreted by a spiral galaxy.
National Optical Astronomy Observatory, 950 North Cherry Avenue, P.O. Box 26732, Tucson, Arizona 85726, Phone: (520) 318-8000, Fax: (520) 318-8360