Speaker
Description
Stars form mainly in filamentary molecular clouds. This makes it important to determine, how these cloud filaments form, accrete matter, and fragment into pre-stellar cores. Accretion will continue even in later stages, associated with the protostars that are born in the cores. During the star formation, also the properties of the interstellar gas and dust evolve. This affects the cloud physics and give direct evidence on the star-formation timescales.
We have studied Taurus and Orion molecular clouds that are, respectively, prototypical regions of low-mass and high-mass star formation. Far-infrared data are analysed to quantify and compare the density structures of Taurus and Orion filaments. Measurements with the Herschel satellite indicate clear evolution of the dust, with average grain sizes 0.1 µm or even larger. This is associated with changes in the dust extinction curve and result in increased dust opacity especially at sub-millimetre wavelengths. In the Orion Molecular Cloud 3 the grains may have reached sizes up to 0.3-0.5 µm. This upper limit is set partly by the fact that the colour excesses of background stars do still trace the cloud structure.
In addition to the main results on the filament structure and dust properties, I will discuss how radiative transfer modelling is used to interpret the data from near-infrared to millimetre wavelengths. I will conclude by describing plans for future studies with the James Webb Space Telescope.