Processing of polycyclic aromatic hydrocarbons in molecular-loop regions near the Galactic center revealed by AKARI

Abstract

We present the AKARI mid-infrared diffuse map of an area of about 4 deg x 3 deg near the Galactic center in the 9 um band. The band intensity is mostly attributed to the aromatic hydrocarbon infrared emissions of carbonaceous grains at wavelengths of 6.2, 7,7, 8.6, and 11.3 um. We detect the 9 um emission structures extending from the Galactic plane up to the latitude of about 2.5 deg, which have spatial correspondence to the molecular loops revealed by the NANTEN 12CO (J=1-0) observations. We find that the surface brightness at 9 um is suppressed near the foot points of the CO loops. The ratios of the 9 um to the IRAS 100 um brightness show significant depression near such bright regions in the CO emission. With the AKARI near-IR 2.5--5 um spectroscopy, we find that the 3.3 um aromatic hydrocarbon emission is absent in the region associated with the loop. These suggest the processing and destruction of carbonaceous grains in the CO molecular loops.

18 pages, 9 figures, accepted for publication in PASJ

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Cited by in corpus (7)

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• AKARI near-infrared spectroscopy of the aromatic and aliphatic hydrocarbon emission features in the galactic superwind of M 82
• Observational studies on the Near-Infrared Unidentified Emission Bands in Galactic HII regions
• The Central Region of the Barred Spiral Galaxy NGC1097 Probed by AKARI Near-Infrared Spectroscopy
• The foot points of the Giant Molecular Loops in the Galactic center region
• A Method to Extract Spatially Resolved Polycyclic Aromatic Hydrocarbon Emission from Spitzer Spectra: Application to M51
• Large-scale mapping of the massive star-forming region RCW38 in the [CII] and PAH emission