'Missing Mass' Found in Recycled Dwarf Galaxies

Left: Composite radio/optical/ultraviolet image of NGC 5291 and its surroundings, including the debris propelled outward by collision with another galaxy. Blue is atomic Hydrogen observed with the VLA; white is optical; red is ultraviolet (Galex satellite). Red labels mark the dwarf galaxies studied in this research. Right: Detail of image produced by computer simulation of the galactic collision, showing debris ring and condensations that became star-forming dwarf galaxies. CREDIT: P-A Duc, CEA-CNRS/NRAO/AUI/NSF/NASA