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S. D. Stokes, M. S. Oey (University of Wyoming)
H II regions are a probe into the composition patterns of galaxies. It has been known for a long time that in most disk galaxies the abundances decrease as a function of galactocentric radius (Rg). However, a systematic increase with Rg in the ionizing stellar effective temperature (T*) could partially mimic the nebular excitation patterns that have been attributed exclusively to abundance variations. Thus, many abundance gradients may have been overestimated, and it is necessary to evaluate any existing gradients in T* in order to more accurately determine the abundance gradients. In this paper, we analyze the intensities of [Ne III]\lambda 3869/H\beta as a parameter that is sensitive to T* in 19 spiral galaxies taken from literature. We examined the ratio of [Ne III]/H\beta vs. \lambda5007[OIII]/\lambda3727[OII] as a function of Rg to look for any gradients. Our preliminary results seem to show an increasing gradient in T* with respect to Rg in some galaxies.
The author(s) of this abstract have provided an email address for comments about the abstract: saxy@uwyo.edu