Speaker
Marta Alves
(Institut d'Astrophysique Spatiale (IAS))
Description
The Planck all-sky survey has opened a new window in our understanding of interstellar dust emission in extending to sub-millimetre wavelengths and microwave frequencies the detailed mapping of dust emission provided by past infrared missions. Such a wide frequency coverage allows us to probe the spectral energy distribution (SED) of large and cold dust grains, which are the bulk of the dust mass. Therefore, it can help us disentangle the effects of dust column density, radiation field and grain properties, which contribute to the dust brightness.
Early results from Planck revealed variations of the high-latitude dust temperature and emission cross-section, showing evolution of dust grains. The analysis of nearby molecular clouds also showed the cooling of the dust particles from diffuse regions to the densest parts, accompanied by an increase in the dust emissivity, which can be associated with grain growth through coagulation.
I will present the all-sky model of dust emission based on Planck and IRAS data, from 353 to 3000 GHz, which delivers maps of dust temperature, optical depth and opacity spectral index, used to produce an all-sky map of the dust reddening. The challenges of using the dust opacity at 353 GHz as a tracer of the dust column density will be discussed. I will also show the results of detailed studies of the cirrus and the Galactic plane, where we are able to extend the analysis to frequencies below 353 GHz. A change in the shape of the dust spectrum relative to that extrapolated from far-infrared wavelengths is detected, which requires a description by alternative emission mechanisms.
Author
Marta Alves
(Institut d'Astrophysique Spatiale (IAS))