Metallicities of Extraplanar H II Regions in Edge-on Spiral Galaxies

Type Conference Paper
Names Katherine M. Rueff, J. C. Howk, C. Wotta, K. V. Croxall, B. D. Savage, J. O'Meara
Proceedings Title American Astronomical Society
Conference Name AAS Meeting #223, #246.19
Date January 1, 2014
URL http://adsabs.org/2014AAS.22324619R
Library Catalog labs.adsabs.harvard.edu
Abstract We present spectroscopy of thick disk H II regions in the edge-on spiral galaxies NGC 891 and NGC 4013 using MODS on the LBT and LRIS on KECK. These star forming regions, located at large z-heights from the galactic plane, provide a direct probe of the origins of thick disk interstellar material. In NGC 891, the derived H II region metallicity is consistent with the metallicity found in the plane but is located at a distance of z ~ 650 pc beyond the plane. This region was likely formed from material that was expelled from the plane in energetic processes consistent with a galactic fountain model. Whereas, in NGC 4013, the H II region, located at z ~ 850 pc beyond the plane, has a much lower derived metallicity compared to the galactic plane. This lower metallicity H II region implies that the original interstellar material that formed these stars contained a mixture of both solar metallicity material and some fraction of lower metallicity material, characteristic of a galactic fountain in combination with infalling lower-metal material described by galactic accretion.
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