2009/09/02 by C. R. O'Dell, W. M. Goss · 10 citations
Physics and Astronomy · #Astronomy and Astrophysical Research #Astrophysics and Star Formation Studies #Electrical and Electromagnetic Research #Electron density #Emission nebula #Emission spectrum #Light curve #Line (geometry) #Nebula #Orion Nebula #Spectroscopy #Wavelength #astro-ph.GA
paper · pdf · doi:10.1088/0004-6256/138/5/1235
published in The Astronomical Journal 138(5), 1235-1242 (Institute of Physics)
arxiv created 2009/09/02 · openalex publication_date 2009/09/17 · arxiv updated 2015/05/14 · openalex created_date 2016/06/24 · openalex updated_date 2026/08/05
We have combined 327.5 MHz radio observations and optical spectroscopy to study conditions in the Extended Orion Nebula (EON). We see a steady progression of characteristics with increasing distance from the dominant photoionizing star θ 1 Ori C. This progression includes a decrease in the F (Hα)/ F (Hβ) ratio, an increase in the relative strength of scattered stellar continuum, decrease in electron density determined from the [S ii ] doublet, and increase in the ratio of emission measures derived from the Hβ line and the 327.5 MHz radio continuum. We conclude that beyond about 5' south of θ 1 Ori C that scattered light from the much brighter central Huygens region of the nebula significantly contaminates local emission. This strengthens earlier arguments that wavelength and model-dependent scattering of emission-line radiation imposes a fundamental limit on our ability to determine the physical conditions and abundances in this and arguably other similar Galactic Nebulae. The implications for the study of extragalactic H ii regions are even more severe. We confirm the result of an earlier study that at least the eastern boundary of the EON is dominated by scattered light from the Huygens region.