On the missing 2175 A-bump in the Calzetti extinction curve

Date

2011

Authors

Fischera, Joerg
Dopita, Michael

Journal Title

Journal ISSN

Volume Title

Publisher

Springer

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.

Description

Keywords

Keywords: A-density; Cold neutral mediums; Column density; Dust , extinction; Extinction curves; Inhomogeneities; ISM: structure; Log-normal; Turbulent medium; Distribution functions; Dust; Mach number; Probability density function; Turbulence; Ultraviolet radiatio Dust, extinction; ISM: structure; Turbulence

Citation

Source

Astronomy and Astrophysics

Type

Journal article

Book Title

Entity type

Access Statement

Open Access

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