STUDY OF CO2/H2O ICE ABUNDANCE RATIOS IN NEARBY GALAXIES WITH THE AKARI NEAR-INFRARED SPECTROSCOPY
Publications of The Korean Astronomical Society
We study CO 2 /H 2 O ice abundance ratios in nearby galaxies using AKARI near-infrared slit spectroscopy. Past studies of the ices intensively examined CO 2 /H 2 O ratios mainly in our Galaxy, and found that there were considerable variations in the CO 2 /H 2 O ratios from object to object. The cause of the variations is, however, still under debate. As a result of the analysis of our sample that includes 1031 regions in 158 galaxies, the CO 2 /H 2 O ratios are in a range of 0.05-0.30. In the
... 0.05-0.30. In the dataset, we find that the CO 2 /H 2 O ratios positively correlate with the Brα/PAH 3.3 µm ratios which reflect the massive star formation activity. Furthermore, we find that the CO 2 /H 2 O ratios positively correlate with the specific star formation rates of the galaxies where the ices are detected, that reflect the evolutionary stage of a galaxy. These results suggest that the CO 2 /H 2 O ratios are enhanced in active star-forming regions and young galaxies.