Candidate List of Edge-on Galaxies with Substantial Extraplanar Dust

Abstract

We present a list of edge-on galaxies that might have substantial extraplanar dust. Twenty-three edge-on galaxies were selected as target galaxies from an edge-on galaxy catalog, and their Galaxy Evolution Explorer far-ultraviolet images were fitted with a three-dimensional radiative transfer galaxy model. The galaxy model is described by two disks: one for the light source and the other for the dust. The best-fit parameters were found by employing a global optimization method called differential evolution. To find the galaxies with substantial extraplanar dust using the best-fit parameters, we plotted the ratio of scale height to galactic diameter: z s / D 25,ph (light source) versus z d / D 25,ph (dust). We found that 17 and 6 galaxies fall on the region of ( z s / D 25,ph  × 100) >0.2 and ( z s / D 25,ph  × 100) < 0.2, respectively. The former is labeled “high-group” and the latter is labeled “low-group.” We conclude that “high-group” galaxies likely have substantial extraplanar dust, while “low-group” galaxies likely have little extraplanar dust, i.e., typical galactic thin disks, based on the following points: (1) the relative positions of “high-group” and “low-group” on the plot z s / D 25,ph versus z d / D 25,ph with respect to the reference values from optical radiative transfer studies; (2) the lower scale height of the young stellar population than the old stellar population; and (3) a test result that shows the existence of extraplanar dust causes z s and z d to be overestimated in the fitting results. We also examined the dependence of the group separation on the surface density of far-ultraviolet luminosity ( ), but found no strong dependence.