Mapping [O III] Emission in Diffuse Ionized Gas

Type Conference Paper
Names Rex C. Beaber, L. M. Haffner, R. J. Reynolds, G. J. Madsen
Conference Name Bulletin of the American Astronomical Society
Volume 38
Pages 922
Date December 1, 2006
Library Catalog NASA ADS
Abstract Doubly-ionized oxygen continues to be an intriguing tracer of physical conditions in diffuse ionized gas. Although [O III] emission is strong in many classical H II and PNe photoionized environments, [O III]/H-alpha has been consistently measured to be very low in the Warm Ionized Medium (WIM) of the Milky Way. Understanding how this ratio varies throughout the Galaxy is important for investigating changes in the dominant ionizing mechanism in a low-density medium. In some edge-on spiral galaxies, studies have found this line ratio to increase with height above the galactic plane, which could be explained by an increase in temperature as well as a shift in the dominant ionization mechanism for doubly-ionized oxygen with height. The Wisconsin H-Alpha Mapper (WHAM) provides unprecedented spectral resolution and sensitivity for studying the diffuse interstellar environments of our Galaxy. We present three new WHAM maps of [O III] emission towards directions of known ionizing sources. These regions give us new insight into the physical conditions of low-density, photoionized gas and deliver unique measurements of the ionizing continuum from the sources. WHAM is supported by NSF grant AST 02-04973.
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