Observations of interstellar and circumstellar ice

Aikawa, Y.; Noble, J. A.; Sakon, I.; Kamuro, D.; Irimichi, N.; Pontoppidan, K.M.; Fraser, H.; Tamura, M.; Terada, H. and Ueno, M. (2009). Observations of interstellar and circumstellar ice. In: Onaka, Takashi; White, Glenn J.; Nakagawa, Takao and Yamamura, Issei eds. AKARI, a Light to Illuminate the Misty Universe. Astronomical Society of the Pacific Conference Series (418). San Francisco, CA: Astronomical Society of the Pacific, pp. 47–55.


We observed ice absorption bands at NIR (2.5 μm–5.0 μm) towards field stars behind molecular clouds and low-mass YSOs with edge-on disk. We developed and tested a procedure to reduce the slitless spectroscopy data of extended object and the data with multiple objects in one field of view. Absorption bands of H2O, CO2 and CO are clearly detected towards field stars and YSOs. The spectral type and visual extinction of each field star are estimated using color-color diagram. The visual extinction of our field stars ranges from 15 mag to 25 mag. The column density of H2O ice towards our target stars ranges from 3×1017 cm-2 to 1×1019 cm-2, while the CO2 ice column density is (1–7)×1017 cm-2. These ice column densities are found to be roughly proportional to visual extinction.

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