The highly ionized regions of NGC 6302 and NGC 6537

Abstract

view Abstract Citations (22) References (39) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS The Highly Ionized Regions of NGC 6302 and NGC 6537 Rowlands, N. ; Houck, J. R. ; Herter, T. Abstract We present (Ne V) 24.32 micrometer and 3426 A emission-line fluxes for NGC 6302 and NGC 6537. These fluxes along with those of (Ne V) 14.3 micrometer allow us to determine the physical conditions within the highly ionized regions of these nebulae. The electron densities found via the (Ne V) line ratios are similar to those found in studies of the low-ionization regions. However, the electron temperatures determined from the (Ne V) line ratios are much greater than those in the low-ionization regions. However, the electron temperatures determined from the (Ne V) line ratios are much greater than those in the low-ionization regions. We use photoionization models to show that these high derived electron temperatures are inconsistent with the assumption that the nebular ionization is produced solely by radiation from the central star. Much of the intense (Ne V) 3426 A emission from these objects must arise from highly ionized shocked material; a conclusion which is in accord with other evidence. The fact that the (Ne V) infrared lines are less affected by the shock means that we can estimate the relative volumes of the shocked and radiatively excited portions of these nebulae. In the most likely scenario, the volume of the highly ionized shocked region is less than 10% that of the highly ionized region formed by photoionization. We note that under such conditions, infrared emission lines are more useful than optical or UV emission lines for abundance studies because they are less affected by shocks. With appropiate corrections to the optical and UV emission-line fluxes, these nebulae can still be described by photoionization models. Publication: The Astrophysical Journal Pub Date: June 1994 DOI: 10.1086/174192 Bibcode: 1994ApJ...427..867R Keywords: Abundance; Emission Spectra; High Temperature Gases; Infrared Astronomy; Photoionization; Planetary Nebulae; Shock Fronts; Ultraviolet Astronomy; Electron Density Profiles; Electron Energy; Excitation; Infrared Astronomy Satellite; Interstellar Extinction; Ion Recombination; Ionized Gases; Astrophysics full text sources ADS | data products SIMBAD (2)