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Title: Polycyclic Aromatic Hydrocarbons, Anomalous Microwave Emission, and their Connection to the Cold Neutral Medium
Abstract

Using new large-area maps of the cold neutral medium (CNM) fraction,fCNM, we investigate the relationship between the CNM, the abundance of polycyclic aromatic hydrocarbons (PAHs), and the anomalous microwave emission (AME). We first present ourfCNMmap based on full-sky HI4PI data, using a convolutional neural network to convert the spectroscopic Hidata tofCNM. We demonstrate thatfCNMis strongly correlated with the fraction of dust in PAHs as estimated from mid- and far-infrared dust emission. In contrast, we find no correlation betweenfCNMand the amount of AME per dust emission and no to weakly negative correlation betweenfCNMand the AME peak frequency. These results suggest PAHs preferentially reside in cold, relatively dense gas, perhaps owing to enhanced destruction in more diffuse media. The lack of positive correlation betweenfCNMand AME peak frequency is in tension with expectations from theoretical models positing different spectral energy distributions of AME in the cold versus warm neutral medium. We suggest that different PAH abundances and emission physics in different interstellar environments may explain the weaker-than-expected correlation between 12μm PAH emission and AME even if PAHs are the AME carriers.

 
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NSF-PAR ID:
10366320
Author(s) / Creator(s):
; ;
Publisher / Repository:
DOI PREFIX: 10.3847
Date Published:
Journal Name:
The Astrophysical Journal
Volume:
929
Issue:
1
ISSN:
0004-637X
Format(s):
Medium: X Size: Article No. 23
Size(s):
["Article No. 23"]
Sponsoring Org:
National Science Foundation
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