The dust distribution in edge-on galaxies

Free access article

Issue		A&A Volume 471, Number 3, September I 2007


Page(s)		765 - 773
Section		Extragalactic astronomy
DOI		http://dx.doi.org/10.1051/0004-6361:20077649

A&A 471, 765-773 (2007)
DOI: 10.1051/0004-6361:20077649

Radiative transfer fits of V and K $^\prime$ -band images

S. Bianchi

INAF - Istituto di Radioastronomia, Sezione di Firenze, Largo Enrico Fermi 5, 50125 Firenze, Italy
e-mail: sbianchi@arcetri.astro.it

(Received 15 April 2007 / Accepted 3 May 2007)

Abstract
Aims.I have analyzed a sample of seven nearby edge-on galaxies observed in the V and K'-bands, in order to infer the properties of the dust distribution.
Methods.A radiative transfer model, including scattering, was used to decompose each image into a stellar disk, a bulge, and a dust disk. The parameters describing the distributions were obtained through standard $\chi^2$ minimization techniques.
Results.The dust disks fitted to the V-band images are consistent with previous work in the literature: the radial scalelength of dust is larger than for stars ( $h_\mathrm{d}/h_\mathrm{s} \sim 1.5$ ); the dust disk has a smaller vertical scalelength than the stellar ( $z_\mathrm{d}/z_\mathrm{s} \sim 1/3$ ); the dust disk is almost transparent when seen face-on (central, face-on, optical depth $\tau_0 =0.5{-}1.5$ ). Equivalent fits can be produced using faster radiative transfer models that neglect scattering. In the K'-band, no trace is found of a second, massive, dust disk, which has been invoked to explain observations of dust emission in the submillimeter. I discuss the model degeneracies and the effect of complex structures on the fitted distributions. In particular, most bulges in the sample show a box/peanuts morphology with large residuals; two lower-inclination galaxies show a dust ring distribution, which could be the cause of the large, fitted, dust scalelengths.

Key words: dust, extinction -- galaxies: ISM -- galaxies: stellar content -- galaxies: spiral

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