Physical conditions in low-ionization regions of the Orion Nebula

J. A. Baldwin, A. Crotts, R. J. Dufour, G. J. Ferland, S. Heathcote, J. J. Hester, K. T. Korista, P. G. Martin, C. R. O'Dell, R. H. Rubin, A. G.G.M. Tielens, D. A. Verner, E. M. Verner, D. K. Walter, Z. Wen

Research output: Contribution to journalArticlepeer-review

46 Scopus citations


We reexamine the spectroscopic underpinnings of recent suggestions that [O I] and [Fe II] lines from the Orion H II region are produced in gas where the iron-carrying grains have been destroyed and the electron density is surprisingly high. Our new observations show that previous detections of [O I] 5577 were dominated by telluric emission. Our limits are consistent with a moderate density (≈104 cm-3) photoionized gas. We show that a previously proposed model of the Orion H II region reproduces the observed [O I] and [Fe II] spectrum. These lines are fully consistent with formation in a dusty region of moderate density.

Original languageEnglish
Pages (from-to)L115-L118
JournalAstrophysical Journal
Issue number2 PART II
StatePublished - Sep 10 1996

Bibliographical note

Funding Information:
We thank STScI for its support through grants GO-4385, GO-5748, GO-6056, GO-6093, and AR-06403.01-95A. R. J. D. and G. J. F. acknowledge NASA/Ames Research Center Interchange Grants NCC2-5008 and NCC2-5028, respectively. Research in Nebular Astrophysics at the University of Kentucky is supported by the National Science Foundation through award AST 93-19034. We are grateful to D. Oster-brock, L. Lucy, A. Pradhan, and M. Bautista for useful discussions.


  • ISM: H II regions
  • ISM: abundances
  • ISM: atoms
  • ISM: individual (Orion Nebula)

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science


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