Protostars and Planets VI, Heidelberg, July 15-20, 2013
Scattering in molecular clouds: Constraining the dust grain size distribution through near-infrared cloudshine and mid-infrared coreshine
Andersen, Morten (UJF-Grenoble 1/CNRS-INSU, Institut de Planetologie et d\'Astrophysique de Grenoble)
Steinacker, Juergen (UJF-Grenoble 1/CNRS-INSU, Institut de Planetologie et d\'Astrophysique de Grenoble, Max-Planck-Institut fur Astronomie (MPIA), Konigstuhl 17, 69117, Heidelberg, Germany)
Thi, Wing-Fai (UJF-Grenoble 1/CNRS-INSU, Institut de Planetologie et d\'Astrophysique de Grenoble)
Pagani, Laurent (LERMA, UMR 8112 du CNRS, Observatoire de Paris UMR 5274)
Bacmann, Aurore (UJF-Grenoble 1/CNRS-INSU, Institut de Planetologie et d\'Astrophysique de Grenoble)
Paladini, Roberta (IPAC, Pasadena, USA)
Recently, scattering off dust grains within molecular cores was observed in Spitzer observations at 3.6 micron and was coined coreshine. The scattering means there is a population of large (more than 0.25 micron) grains within molecular core and that the properties of the large grains can be studied through scattered light.
We combine Spitzer IRAC and ground-based near-infrared observations to characterize the cloudshine and coreshine that appear in the core L260 to place constraints on the dust size distribution of the large grains. Using a spatially simple one dimensional model core, we perform radiative transfer calculations to study the impact of various dust size distributions on the intensity profiles across the core.
The observed scattered light patterns in the Ks and 3.6 micron bands are found to be similar. By comparison with the radiative transfer models a comparison of the two profiles places constraints on the relative abundance of small and large (more than 0.25 micron) dust grains. The scattered light profiles are found to be inconsistent with an interstellar silicate grain distribution extending to 0.25 micron and large grains are needed to reach the observed fluxes and the flux ratios. In addition to observing coreshine in the Spitzer IRAC channels, the combination with ground-based near-infrared observations are suited to constrain the properties of large grains in cores.
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