| Abstract |
Many important spectral features are included in the near-IR wavelength region, which enable us to investigate the interstellar environments of galaxies. In particular, the spectral absorption features due to interstellar ices, especially H2O and CO2 ices, provide us crucial information on present and past interstellar environments, and thus the evolutionary histories of galaxies. More specifically, we can derive information on the temperature, chemical condition, and radiation history of the ISM from ices. Before AKARI, however, few detections of the ices were reported for nearby galaxies. The AKARI's unique capability of near-infrared spectroscopy with high sensitivity enables us to systematically study ices in nearby galaxies.
We explored many near-IR spectra (2.5 - 5 microns) of the 211 pointed observations, which were carried out within the framework of the AKARI mission program, "ISM in our Galaxy and Nearby galaxies (ISMGN)". As a result, out of 122 nearby galaxies, we have significantly detected the H2O ices from 36 galaxies and the CO2 ices from 9 galaxies. It is notable that the ices are detected not only in late-type galaxies but also in early-type galaxies. We find that the CO2 ice is more compactly distributed near the galactic center than the H2O ice. In this presentation, I show the results of our systematic study on the ices in nearby galaxies, and discuss their physical implications for the interstellar environments of the galaxies. |
