Physics
Scientific paper
May 2010
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2010aas...21642408w&link_type=abstract
American Astronomical Society, AAS Meeting #216, #424.08; Bulletin of the American Astronomical Society, Vol. 41, p.837
Physics
Scientific paper
Emission from interstellar dust grains is typically modeled assuming that grains are homogeneous solid particles. Recent work has shown that this may not be the case in the ISM, and that grains may be composed of more than one type of material and/or contain some fraction of their volume occupied by vacuum. Porous grains absorb and re-radiate energy differently than solid grains, and virtually all previous studies of porous grains have focused on radiative heating and absorption properties in the optical/UV. Here, we examine the effects of collisional heating of porous grains, in the context of the hot post-shock region behind supernova remnant (SNR) shocks. Modeling IR emission from warm grains, particularly when combined with X-ray spectroscopy of the hot plasma, is a powerful diagnostic on SNR conditions, such as gas density, ambient dust-to-gas mass ratio, and total dust mass present, but these numbers all have significant dependence on grain properties. For a grain porosity of 50%, the gas density required for heating is a factor of 3 higher than that needed for solid grains. However, porous grains are more efficient radiators per unit mass, and less mass is required to produce observed IR luminosities. Degeneracies in model spectra are present over the limited wavelength range of Spitzer, but additional long-wavelength observations with Herschel could significantly constrain models further. Sputtering rates for porous grains are different as well, and we show implications for liberation of refractory elements into the gaseous phase behind a range of shock speeds and conditions. Collisional heating studies in the IR complement radiative optical and UV studies, and provide new constraints on dust physics in the ISM.
Borkowski Kazimierz J.
Reynolds Stephen P.
Williams Brian J.
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