Searching for the Culprit of Anomalous Microwave Emission: An AKARI PAH-range Analysis of Probable Electric Dipole Emitting Regions

TL;DR

This study investigates the potential link between PAH molecules and anomalous microwave emission (AME) using AKARI infrared data, aiming to clarify the emission's origin and the role of interstellar dust species.

Contribution

It provides new PAH abundance maps in regions with strong AME, exploring their possible contribution to microwave anomalies and highlighting the need for further environmental studies.

Findings

Part of AME may be due to thermal dust emission.

Star formation activity could mask PAH vibrational modes.

Further investigation needed across different galactic environments.

Abstract

In the evolutionary path of interstellar medium inquiry, many new species of interstellar dust have been modeled and discovered. The modes by which these species interact and evolve are beginning to be understood, but in recent years a peculiar new feature has appeared in microwave surveys. Anomalous microwave emission (AME), appearing between 10 and 90 GHz, has been correlated with thermal dust emission, leading to the popular suggestion that this anomaly is electric dipole emission from spinning dust. The observed frequencies suggest that spinning grains should be on the order of 1 nm in size, hinting at poly-cyclic aromatic hydrocarbon molecules. We present data from AKARI/Infrared Camera (IRC), due to the effective PAH/Unidentified Infrared Band (UIR) coverage of its 9 micron survey to investigate their role within a few regions showing strong AME in the Planck low frequency data. We include the well studied Perseus and rho Ophiuchi clouds . We use the IRAS/IRIS 100 micron data to account for the overall dust temperature. We present our results as abundance maps for dust emitting around 9 micron, and 100 micron. Part of the AME in these regions may actually be attributed to thermal dust emission, or the star forming nature of these targets is masking the vibrational modes of PAHs which should be present there, suggesting further investigation for various galactic environments.