Volume 533, September 2011
|Number of page(s)||8|
|Section||Interstellar and circumstellar matter|
|Published online||12 September 2011|
On the missing 2175 Å-bump in the Calzetti extinction curve
Research School of Astronomy & Astrophysics, Mount Stromlo
2 Astronomy Department, Faculty of Science, King Abdulaziz University, PO Box 80203, Jeddah, Saudi Arabia
Accepted: 13 July 2011
Aims. The aim of the paper is to give a physical explanation of the absence of the feature in the Calzetti extinction curve.
Methods. We analyze the dust attenuation of a homogeneous source seen through a distant inhomogeneous distant screen. The inhomogeneities are described through an idealized isothermal turbulent medium where the probability distribution function (PDF) of the column density is log-normal. In addition it is assumed that below a certain critical column density the carriers of the extinction bump at 2175 Å are being destroyed by the ambient UV radiation field.
Results. Turbulence is found to be a natural explanation not only of the flatter curvature of the Calzetti extinction curve but also of the missing bump provided the critical column density is NH ≥ 1021 cm-2. The density contrast needed to explain both characteristics is well consistent with the Mach number of the cold neutral medium of our own Galaxy which suggests a density contrast σρ/ ⟨ ρ ⟩ ≈ 6.
Key words: turbulence / dust, extinction / ISM: structure
© ESO, 2011
Current usage metrics show cumulative count of Article Views (full-text article views including HTML views, PDF and ePub downloads, according to the available data) and Abstracts Views on Vision4Press platform.
Data correspond to usage on the plateform after 2015. The current usage metrics is available 48-96 hours after online publication and is updated daily on week days.
Initial download of the metrics may take a while.