Dust Content, Galaxy Orientations, and Shape Noise in Imaging Surveys

Abstract

We show that dust absorption in disk galaxies leads to a color- and orientation-dependent centroid shift which is expected to be observable in multi-band imaging surveys. This centroid shift is an interesting new probe which contains astrophysically and cosmologically relevant information: it can be used to probe the dust content of a large sample of galaxies, and to reduce the shape noise due to inclination of disk galaxies for weak lensing shear. Specifically, we find that data sets comparable to CFHTLenS, the Dark Energy Survey (DES) or the Hyper Suprime-Cam (HSC) survey should provide a dust measurement for several hundred galaxies per square degree. Conversely, given knowledge of the dust optical depth, this technique will significantly lower the shape noise for the brightest galaxies in the sample (signal-to-noise greater than a few hundred), thereby increasing their relative importance for the weak lensing shear measurement.