Document Details Document Type : Article In Journal  Document Title : On the missing 2175 Å-bump in the Calzetti extinction curve On the missing 2175 Å-bump in the Calzetti extinction curve   Subject : Astronomyِ  Document Language : English  Abstract : 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 s.σp≈6.  ISSN : 0004-6361  Journal Name : Astronomy and Astrophysics  Volume : 533  Issue Number : 1  Publishing Year : 1432 AH 2011 AD  Article Type : Article  Added Date : Wednesday, April 25, 2012  Researchers Researcher Name (Arabic) Researcher Name (English) Researcher Type Dr Grade Email Jörg F Fischera Fischera, Jörg F Researcher Doctorate fischera@mso.anu.edu.au Michael A Dopita Dopita, Michael A Researcher Doctorate michael.dopita@anu.edu.au Files File Name Type Description  33028.pdf pdf Abstract Back To Researches Page