Analyzing Polycyclic Aromatic Hydrocarbons as a Tracer of Anomalous Microwave Emission near the Galactic Plane Using the COSMOGLOBE DIRBE Reduction

Abstract The physical mechanism producing anomalous microwave emission (AME) has been an unresolved puzzle for close to 30 yr. One candidate mechanism is rotational emission from polycyclic aromatic hydrocarbons (PAHs), which can have the necessary electric dipole moment and size distribution to account for the AME in representative interstellar environments. However, previous investigations have found that AME is better correlated with the far-infrared dust emission rather than the PAH emission. In this work, we analyze the correlations between the AME and the PAH and far-infrared dust emission using the 3.3 μ m PAH emission feature as observed by band 3 of the Diffuse Infrared Background Experiment (DIRBE). This analysis builds on previous work conducted in individual molecular clouds and extends it into fainter, more diffuse structures. In addition, we utilize the COSMOGLOBE DIRBE reduction for this work, building on previous studies that used the original DIRBE dataset. We find that the AME is better correlated with far-infrared dust emission ( ρ ∼ 0.9) than the PAH emission ( ρ ∼ 0.7) in the central ∣ b ∣ ≤ 10° region of the sky. This could indicate either that non-PAH dust grains or an alternative physical emission mechanism is primarily responsible for the AME in the Galactic plane or that the excitation conditions for mid-infrared emission and for AME from PAHs differ substantially.