English (United Kingdom)

https://curated-unify.zendy.io/wp-json/zendy-region/v1/featured_content/oa?rat=en

https://curated-unify.zendy.io/wp-json/zendy-region/v1/highlighted_journal/

Global: Zendy Tools annual

Presents the keyphrase highlighting as premium feature

Keyphrase Highlighting

Presents the summarisation as premium feature

Summarisation

Insights

Presents the pdf analysis as premium feature

PDF Analysis

Presents the zaia usage as premium feature

ZAIA

Global: Zendy Tools monthly

Global: Zendy Plus monthly

Presents the access of premium content as premium feature

Premium Content

Global: Zendy Plus annual

Global: Zendy Free Plan

We discuss the radiative transfer theory for translucent clouds illuminatedby an extended background source. First we derive a rigorous solution based onthe assumption that multiple scattering produce an isotropic flux. Then wederive a more manageable analytic approximation showing that it nicely matchesthe results of the rigorous approach. To validate our model, we compare ourpredictions with accurate laboratory measurements for various types of wellcharacterized grains, including purely dielectric and strongly absorbingmaterials representative of astronomical icy and metallic grains, respectively,finding excellent agreement without the need of adding free parameters. We useour model to explore the behavior of an astrophysical cloud illuminated by adiffuse source with dust grains having parameters typical of the classic ISMgrains of Draine & Lee (1984) and protoplanetary disks, with an application tothe dark silhouette disk 114-426 in Orion Nebula. We find that the scatteringterm modifies the transmitted radiation, both in terms of intensity(extinction) and shape (reddening) of the spectral distribution. In particular,for small optical thickness our results show that scattering makes reddeningalmost negligible at visible wavelengths. Once the optical thickness increasesenough and the probability of scattering events become close to or larger than1, reddening becomes present but appreciably modified with respect to thestandard expression for line-of-sight absorption. Moreover, variations of thegrain refractive index, in particular the amount of absorption, also play animportant role changing the shape of the spectral transmission curve, withdielectric grain showing the minimum amount of reddening.

Radiative Transfer in a Translucent Cloud Illuminated by an Extended Background Source