Galaxy Zoo: A Catalog of Overlapping Galaxy Pairs for Dust Studies

Abstract

Analysis of galaxies with overlapping images offers a direct way to probe the\ndistribution of dust extinction and its effects on the background light. We\npresent a catalog of 1990 such galaxy pairs selected from the Sloan Digital Sky\nSurvey (SDSS) by volunteers of the Galaxy Zoo project. We highlight subsamples\nwhich are particularly useful for retrieving such properties of the dust\ndistribution as UV extinction, the extent perpendicular to the disk plane, and\nextinction in the inner parts of disks. The sample spans wide ranges of\nmorphology and surface brightness, opening up the possibility of using this\ntechnique to address systematic changes in dust extinction or distribution with\ngalaxy type. This sample will form the basis for forthcoming work on the ranges\nof dust distributions in local disk galaxies, both for their astrophysical\nimplications and as the low-redshift part of a study of the evolution of dust\nproperties. Separate lists and figures show deep overlaps, where the inner\nregions of the foreground galaxy are backlit, and the relatively small number\nof previously-known overlapping pairs outside the SDSS DR7 sky coverage.\n