Circumgalactic Dust as a Tracer of Baryon Cycling

Massive galaxies are surrounded by vast reservoirs of baryons that are enriched in mass and metals by energetic feedback processes. How these processes proceed and the amount of recycled material that they contribute to the circumgalactic medium remain important open questions. The circumgalactic medium contains dust grains formed in star-forming regions that were ejected from the galaxy by galactic fountains and winds, providing a powerful probe of baryon cycling. Here we conduct a search for UV reflection nebulae produced by extraplanar dust in 550 nearby (D < 100 Mpc), highly inclined galaxies with archival NUV and FUV imaging from GALEX. We demonstrate the ubiquity of spatially extended UV light at the disk-halo interface in stacks of galaxies binned by star-formation rate and morphology, and we discuss its likely origin in scattered light from circumgalactic dust. We conclude by estimating the amount of recycled material in the circumgalactic medium and the contribution of galactic fountains and winds to the X-ray halos seen around star-forming galaxies.