The dust distribution in edge-on galaxies. Radiative transfer fits of V and K'-band images

TL;DR

This study models dust distribution in seven edge-on galaxies using radiative transfer fits of V and K'-band images, revealing consistent dust properties and discussing model degeneracies and complex structures.

Contribution

It provides detailed radiative transfer modeling of dust in edge-on galaxies, including scattering effects, and compares results with simplified models and previous findings.

Findings

Dust radial scalelength is about 1.5 times the stellar one.

Dust disk has roughly one-third the vertical scaleheight of stars.

No evidence found for a second massive dust disk in K'-band images.

Abstract

Aims: I have analyzed a sample of seven nearby edge-on galaxies observed in the V and K'-band, in order to infer the properties of the dust distribution. Methods: A radiative transfer model, including scattering, have been used to decompose each image into a stellar disk, a bulge, and a dust disk. The parameters describing the distributions have been obtained through standard X^2 minimization techniques. Results: The dust disks fitted to the V-band images are consistent with previous work in literature: the radial scalelength of dust is larger than that for stars (h_d/h_s ~ 1.5); the dust disk has a smaller vertical scalelength than the stellar (z_d/z_s ~ 1/3); the dust disk is almost transparent when seen face-on (central, face-on, optical depth tau_0 =0.5-1.5). Faster radiative transfer models which neglect scattering can produce equivalent fits, with changes in the derived parameters within the accuracy of full fits including 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 for the large fitted dust scalelengths.