The Fe/Ni ratio in ionized nebulae: clues on dust depletion patterns

Abstract

We perform a homogeneous analysis of the Fe/Ni abundance ratio in eight Galactic planetary nebulae (PNe) and three Galactic H II regions that include the Orion nebula, where we study four nebular zones and one shocked region. We use [Fe ii], [Fe iii], and [Ni iii] lines, and ionization correction factors (ICFs) that account for the unobserved ions. We derive an ICF for nickel from an extensive grid of photoionization models. We compare our results with those derived by other authors for 16 neutral clouds in the solar neighbourhood with available Fe/Ni ratios in the literature. We find an excellent agreement between the ionized nebulae and the diffuse clouds, with both types of regions showing a clear correlation between the Fe/Ni ratios and the iron and nickel depletion factors. The trend shows that the objects with a relatively low depletion have near solar Fe/Ni ratios whereas at higher depletions the Fe/Ni ratio increases with the depletion. Our results confirm that, compared to iron atoms, nickel ones are more efficiently stuck to the dust grains in ambients where dust formation or growth have been more efficient.

Accepted for publication in MNRAS. 11 pages, 7 Figures, 7 tables

References in corpus (6)

• A Unified Representation of Gas-Phase Element Depletions in the Interstellar Medium
• PyNeb: a new tool for analyzing emission lines. I. Code description and validation of results
• Properties of the ionized gas in HH202. II: Results from echelle spectrophotometry with UVES
• Oxygen enrichment in carbon-rich planetary nebulae
• A morpho-kinematic and spectroscopic study of the bipolar nebulae: M 2-9, Mz 3, and Hen 2-104
• The radial abundance gradient of chlorine in the Milky Way

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