We study CO2/H2O ice abundance ratios in nearby galaxies using AKARI near-infrared slit spec- troscopy. Past studies of the ices intensively examined CO2/H2O ratios mainly in our Galaxy, and found that there were considerable variations in the CO2/H2O 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 CO2/H2O ratios are in a range of 0.05-0.30. In the dataset, we nd that the CO2/H2O ratios positively correlate with the Brα/PAH 3.3 μm ratios which re ect the massive star formation activity. Furthermore, we find that the CO2/H2O ratios positively correlate with the specific star formation rates of the galaxies where the ices are detected, that re ect the evolutionary stage of a galaxy. These results suggest that the CO2/H2O ratios are enhanced in active star-forming regions and young galaxies.

ABSTRACT
1. INTRODUCTION
2. OBSERVATION AND DATA ANALYSIS
3. RESULTS
4. Discussion
    4.1. Variations in CO2/H2O Ratios in M82
    4.2. Variations in CO2/H2O Ratios in all the Sample Galaxies
5. SUMMARY
REFERENCES

• Mitsuyoshi Yamagishi(Graduate School of Science, Nagoya University)
• Hidehiro Kaneda(Graduate School of Science, Nagoya University)
• Shinki Oyabu(Graduate School of Science, Nagoya University)
• Daisuke Ishihara(Graduate School of Science, Nagoya University)
• Takashi Onaka(Graduate School of Science, The University of Tokyo)
• Takashi Shimonishi(Graduate School of Science, Kobe University)
• Toyoaki Suzuki(SRON Netherlands Institute for Space Research)