2002/09/04 by Joshua G. Nollenberg, Evan D. Skillman, Donald R. Garnett +1 · 2 citations
Physics and Astronomy · #Astronomy and Astrophysical Research #Galaxies: Formation, Evolution, Phenomena #Stellar, planetary, and galactic studies #astro-ph
paper · pdf · doi:10.1086/344299
published as Astrophys.J. 581 (2002) 1002-1012 · 32 Pages total, including 6 encapsulated postscript figures (one with two parts). Accepted for Publication in the 20 Dec 2002 ApJ
arxiv created 2002/09/04 · openalex publication_date 2002/12/16 · arxiv updated 2009/12/01 · openalex created_date 2016/06/24 · openalex updated_date 2026/08/01
We report Infrared Space Observatory ( ISO ) Short Wavelength Spectrometer infrared spectroscopy of the H II region Hubble V in NGC 6822 and the blue compact dwarf galaxy I Zw 36. Observations of Brα, [S III] at 18.7 and 33.5 μm, and [S IV] at 10.5 μm are used to determine ionic sulfur abundances in these H II regions. There is relatively good agreement between our observations and predictions of S +3 abundances based on photoionization calculations, although there is an offset in the sense that the models overpredict the S +3 abundances. We emphasize a need for more observations of this type in order to place nebular sulfur abundance determinations on firmer ground. The S/O ratios derived using the ISO observations in combination with optical data are consistent with values of S/O, derived from optical measurements of other metal-poor galaxies. We present a new formalism for the simultaneous determination of the temperature, temperature fluctuations, and abundances in a nebula, given a mix of optical and infrared observed line ratios. The uncertainties in our ISO measurements and the lack of observations of [S III] λ9532 or λ9069 do not allow an accurate determination of the amplitude of temperature fluctuations for Hubble V and I Zw 36. Finally, using synthetic data, we illustrate the diagnostic power and limitations of our new method.