uri physics colloquium

Dark Matter and Galactic Dust at Megaparsec Scales

Jacqueline McCleary, NASA

abstract

Though it comprises 80% of gravitationally interacting matter, the exact nature of dark matter is still unknown. As the largest virialized objects in the universe, clusters of galaxies lie at the nexus of cosmology and astrophysics and make excellent test beds for theories of dark matter. In this talk, I will discuss our survey of substructures in the dark matter of massive, nearby, clusters of galaxies. We reconstruct these clusters’ mass distributions through their weak gravitational lensing signal, the small but coherent distortion they induce on the shapes of galaxies in their backgrounds.

Cluster cosmology studies like our own require accurate galaxy colors, and in this context I will also present evidence for an anomalous, extended, halo of dust around galaxies. By correlating the reddening of light from background galaxies with the locations of foreground objects, we find evidence of dust extending out to 10 Mpc. This potentially major systematic error is not currently accounted for in cluster cosmology studies.