Astronomy and Astrophysics – Astrophysics
Scientific paper
1999-12-17
Astrophys.J.Suppl.128:511-548,2000
Astronomy and Astrophysics
Astrophysics
Accepted to ApJS. 37 pages, 14 figures, including 12 jpeg files. Uses emulateapj Latex style file. Single PS file preprint ava
Scientific paper
10.1086/313396
We present a detailed comparison of optical H II region spectra to photoionization models based on modern stellar atmosphere models. We examine both spatially resolved and integrated emission-line spectra of the HII regions DEM L323, DEM L243, DEM L199, and DEM L301 in the Large Magellanic Cloud. The published spectral classifications of the dominant stars range from O7 to WN3, and morphologies range from Stromgren sphere to shell structure. Two of the objects include SNR contamination. The overall agreement with the predictions is generally within 0.2 dex for major diagnostic line ratios. An apparent pattern in the remaining discrepancies is that the predicted T_e is ~1000 K hotter than observed. (Abridged) Our analysis of the complex DEM L199 allows a nebular emission-line test of unprecedented detail for WR atmospheres. Surprisingly, we find no nebular He II 4686 emission, despite the fact that both of the dominant WN3 stars should be hot enough to fully ionize He I in their atmospheres. We confirm that the \eta-prime emission-line parameter is not as useful as hoped for determining the ionizing stellar effective temperature, T*. Both empirically and theoretically, we find that it is insensitive for T* >40 kK, and that it also varies spatially. The shock-contaminated objects show that \eta-prime will also yield a spuriously high T* in the presence of shocks. It is furthermore sensitive to shell morphology. We suggest [Ne III]/Hb as an additional probe of T*. Although it is abundance-dependent, [Ne III]/Hb has higher sensitivity to T*, is independent of morphology, and is insensitive to shocks in our objects. We attempt a first empirical calibration of these nebular diagnostics of T*.
Dopita Mike A.
Oey Sally M.
Shields Joseph C.
Smith Christopher R.
No associations
LandOfFree
Calibration of Nebular Emission-Line Diagnostics: I. Stellar Effective Temperatures does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.
If you have personal experience with Calibration of Nebular Emission-Line Diagnostics: I. Stellar Effective Temperatures, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Calibration of Nebular Emission-Line Diagnostics: I. Stellar Effective Temperatures will most certainly appreciate the feedback.
Profile ID: LFWR-SCP-O-244434