Investigation of the Origin of the Anomalous Microwave Emission in Lambda Orionis
Résumé
The anomalous microwave emission (AME) still lacks a conclusive explanation. This excess of emission, roughly between 10 and 50 GHz, tends to defy attempts to explain it as synchrotron or free-free emission. The overlap with frequencies important for cosmic microwave background explorations, combined with a strong correlation with interstellar dust, drive cross-disciplinary collaboration between interstellar medium and observational cosmology. The apparent relationship with dust has prompted a "spinning dust" hypothesis. The typical peak frequency range of the AME profile implicates spinning grains on the order of 1 nm. This points to polycyclic aromatic hydrocarbons (PAHs). We use data from the AKARI/Infrared Camera (IRC), due to its thorough PAH-band coverage, to compare AME from the Planck Collaboration astrophysical component separation product with infrared dust emission in the λ Orionis AME-prominent region. We look also at infrared dust emission from other mid IR and far-IR bands. The results and discussion contained here apply to an angular scale of approximately 1 •. We find that certainly dust mass correlates with AME, and that PAH-related emission in the AKARI/IRC 9 µm band correlates slightly more strongly. Using hierarchical Bayesian inference and full dust spectral energy distribution (SED) modeling we argue that AME in λ Orionis correlates more strongly with PAH mass than with total dust mass, lending support for a spinning PAH hypothesis within this region. We emphasize that future efforts to understand AME should focus on individual regions, and a detailed comparison of the PAH features with the variation of the AME SED.
Domaines
Astrophysique [astro-ph]
Origine : Fichiers produits par l'(les) auteur(s)
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