mountain profile Institute for Astronomy University of Hawaii

Interstellar Medium

Maintained by WW

Dust and Ice

Only one percent of the mass of the interstellar medium is composed of dust, but this refractory material plays key roles in star, planet, and complex molecule formation. The dust grains absorb light, accrete gas phase atoms that form icy mantles, and they coagulate to larger grains, and eventually pebbles, and larger bodies.  Adwin Boogert and collaborators study the dust and ices using infrared spectroscopy at the Keck, IRTF, Spitzer, and future James Webb Space Telescope. Toward dense clouds, they found an enhancement in the reddening at 2 micron, indicative of grain growth by coagulation. This is correlated with ice mantle growth, which makes the grains stickier. The icy mantles were found to have a rich composition quite similar to cometary ices, but the identification of several observed spectroscopic features is still debated. As a co-princiipal investigator of the approved program ‘Ice Age’ at the JWST telescope, Boogert is preparing for observations that will spectroscopically map the dust and ice properties in dense clouds and investigate the link with solar system ices.

Infrared spectrum of a highly reddened star tracing silicate and carbon dust with icy mantles in a dense molecular cloud (black lines). It was observed with the Keck II telescope on Maunakea (λ < 4μm) and the Spitzer Space Telescope (λ > 5μm). The red and green lines are models used to extract the dust and ice signatures. By observing many of such background stars we are able measure dust and ice mantle evolution from quiescent dense clouds to star formating regions.