Images of the six galaxies with detected inflows, detected by the Keck I telescope. Credit: NASA/STScI
Images of the six galaxies with detected inflows, detected by the Keck I telescope. Most of these galaxies have a disk-like, spiral structure, similar to that of the Milky Way. Star formation activity occurring in small knots is evident in several of the galaxies’ spiral arms. Because the spirals appear tilted in the images, Rubin et al. concluded that we are viewing them from the side, rather than face-on. This orientation meshes well with a scenario of ‘galactic recycling’ in which gas is blown out of a galaxy perpendicular to its disk, and then falls back at different locations along the edge of the disk. These images were taken with the Advanced Camera for Surveys on the Hubble Space Telescope. Credit: NASA/STScI