The dust distribution in edge-on galaxies^*,**

Radiative transfer fits of V and K′-band images

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  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 (); the dust disk has a smaller vertical scalelength than the stellar (); the dust disk is almost transparent when seen face-on (central, face-on, optical depth ). 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.