A quality check of the $AKARI$ mid-infrared all-sky diffuse map toward the massive star-forming regions NGC 6334 and NGC 6357

TL;DR

This study compares CO and PAH emissions in star-forming regions NGC 6334 and NGC 6357 to assess the calibration accuracy of the AKARI mid-infrared map, revealing good overall correlation but local variations due to UV radiation effects.

Contribution

It provides a calibration check of AKARI 9 μm data using CO emission and analyzes spatial correlations in star-forming regions, highlighting UV influence on PAH emission.

Findings

Good spatial correlation between CO and PAH emissions.

Calibration accuracy of AKARI 9 μm map confirmed.

Higher ionization and PAH excitation in NGC 6357.

Abstract

We present a comparative study of CO and polycyclic aromatic hydrocarbon (PAH) emission toward a region including the massive star-forming regions of NGC 6334 and NGC 6357. We use the NANTEN $^{12}$CO($J$ = 1--0) data and the $AKARI$ 9 $\mu$m All-Sky diffuse map in order to evaluate the calibration accuracy of the $AKARI$ data. We confirm that the overall CO distribution shows a good spatial correspondence with the PAH emission, and their intensities exhibit a good power-law correlation with a spatial resolution down to 4$'$ over the region of 10$^\circ$$\times$10$^\circ$. We also reveal poorer correlation for small scale structures between the two quantities toward NGC 6357, due to strong UV radiation from local sources. Larger scatter in the correlation toward NGC 6357 indicates higher ionization degree and/or PAH excitation than that of NGC 6334.