Worms or froth? Fine-scale structure in the far-infrared Milky Way

Abstract

Mosaics of the inner Galaxy have been constructed from selected IRAS data products. Through median‐filtration techniques, we have been able to eliminate the strong gradient in brightness towards the Galactic midplane thus revealing peaks and valleys in the residual FIR emission that span several degrees. Some of the negative residuals are coincident with known ‘‘windows’’ in the otherwise opaque screen of dust near the Galactic plane. The processing also reveals diaphanous fine structure in the FIR emission with size scales as small as the 4’×4’ resolution of the images. This cirrus‐like structure brightens towards the Galactic midplane just like the smoothly varying background, thus indicating it ubiquity throughout the inner Galaxy. Although we had expected to find morphological evidence for supernova‐driven ‘‘chimneys’’ or ‘‘worms’’ rooted in the Galactic plane, the far‐infrared fine structure appears more complex (e.g., less coherent and less rooted) as viewed in projection. This may be due to the varying distances and sizes of the emitting features. Evidence for a froth‐like superposition of nearby and distant filaments and shells is presented.Mosaics of the inner Galaxy have been constructed from selected IRAS data products. Through median‐filtration techniques, we have been able to eliminate the strong gradient in brightness towards the Galactic midplane thus revealing peaks and valleys in the residual FIR emission that span several degrees. Some of the negative residuals are coincident with known ‘‘windows’’ in the otherwise opaque screen of dust near the Galactic plane. The processing also reveals diaphanous fine structure in the FIR emission with size scales as small as the 4’×4’ resolution of the images. This cirrus‐like structure brightens towards the Galactic midplane just like the smoothly varying background, thus indicating it ubiquity throughout the inner Galaxy. Although we had expected to find morphological evidence for supernova‐driven ‘‘chimneys’’ or ‘‘worms’’ rooted in the Galactic plane, the far‐infrared fine structure appears more complex (e.g., less coherent and less rooted) as viewed in projection. This may be due to the var...