AAS 205th Meeting, 9-13 January 2005
Session 139 The Ionized ISM: Observations and Theory
Poster, Thursday, January 13, 2005, 9:20am-4:00pm, Exhibit Hall

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[139.06] A Complete Model Helium Atom: Theoretical Emissivities, the Case B Approximation, and the Primordial Helium Abundance

R. L. Porter, R. P. Bauman, K. B. MacAdam, G. J. Ferland (University of Kentucky, Department of Physic and Astronomy)

We have completed the development of a new model helium atom for the spectra simulation code Cloudy. All relevant astrophysically significant processes are included, and the spectrum is solved self-consistently with the thermal and ionization structure of the simulated system. We present here an overview of the differences that distinguish our model from those by previous authors. We also compare predicted case B emissivities with those from previous works. The differences will have significant consequences for the interpretation of spectra of a wide variety of systems. We also explore deviations from the case B approximation and present an estimate of the primordial helium abundance.

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The author(s) of this abstract have provided an email address for comments about the abstract: rporter@pa.uky.edu

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© 2004. The American Astronomical Society.