Using ISM Structure to Constrain the Origin of Anomalous Microwave Emission

Understanding the structures present in the interstellar medium is an important step for determining how energy and material flow through our galaxy. The [CII] emission line is an ideal tool for studying structure, as carbon has a relatively low ionization potential, and therefore traces the interface between the ionized gas and the atomic gas. Spectrally resolved maps of the [CII] emission across the Perseus Molecular Cloud and the HII region RCW175 created by the GREAT instrument provide detailed information about the structure and kinematics of the gas in these two regions. Combining this data with archival IRS spectral maps of the PAH emission across these regions would provide for comparisons between the gas and the small dust grains in both an HII region and a molecular cloud.

In addition to providing detailed maps of the gas in these two regions, this data provides an exciting resource for studying the anomalous microwave emission (AME). AME has been detected in a variety of Galactic sources and even some extragalactic targets. Observations of the microwave emission by COBE and PLANCK both show more emission than predicted by models of thermal vibrational dust. Current theories suggest the AME is caused by spinning dust grains, although there is still some speculation about the true source. Characterizing the ISM conditions in which the AME is enhanced could provide key insights into what generates this emission, and allow for better constraints to be placed on the removal of the emission from measurements of the Cosmic Microwave Background (CMB). As there have been strong detections of AME in both the Perseus Molecular Cloud and RCW175, these [CII] maps provide resources for constraining the gas and dust conditions in regions producing AME.

All corresponding data are publicly available from the IRSA SOFIA Archive (projects 04_0028, 06_0198).

(Left) The GREAT [CII] map of RCW175 with contours from the WISE3 11.3 micron map overlaid. (Right): The [CII] spectra for one of the pixels at the edge of the HII Region.