Analyzing PAHs as a Tracer of Anomalous Microwave Emission Near the Galactic Plane Using the COSMOGLOBE DIRBE Reduction

TL;DR

This study investigates the correlation between anomalous microwave emission (AME) and PAH as well as far-infrared dust emissions near the Galactic Plane, finding a stronger correlation with far-infrared dust than PAHs, suggesting alternative emission mechanisms.

Contribution

It extends previous correlation analyses of AME with dust emissions into fainter, diffuse structures using COSMOGLOBE DIRBE data, providing new insights into the emission mechanisms.

Findings

AME correlates more strongly with far-infrared dust emission ($\rho\sim$0.9) than PAH emission ($\rho\sim$0.7).

Results suggest non-PAH dust grains or alternative mechanisms may dominate AME in the Galactic Plane.

Differences in excitation conditions could explain the weaker correlation with PAHs.

Abstract

The physical mechanism producing Anomalous Microwave Emission (AME) has been an unresolved puzzle for close to 30 years. 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 $\mu$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 data set. We find that the AME is better correlated with far-infrared dust emission ($\rho\sim$0.9) than the PAH emission ($\rho\sim$0.7) in the central $|b|\leq$ 10\degree\ 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.