Rings and Bent Chain Galaxies in the GEMS and GOODS Fields

Twenty-four galaxies with rings or partial rings were studied in the GEMS andGOODS fields out to z~1.4. Most resemble local collisional ring galaxies inmorphology, size, and clumpy star formation. Clump ages range from 10^8 to 10^9yr and clump masses go up to several x10^8 Msun, based on color evolutionmodels. The clump ages are consistent with the expected lifetimes of ringstructures if they are formed by collisions. Fifteen other galaxies thatresemble the arcs in partial ring galaxies but have no evident disk emissionwere also studied. Their clumps have bluer colors at all redshifts compared tothe clumps in the ring and partial ring sample, and their clump ages areyounger than in rings and partial rings by a factor of ~10. In most respects,they resemble chain galaxies except for their curvature; we refer to them as``bent chains.'' Several rings are symmetric with centered nuclei and noobvious companions. They could be outer Lindblad resonance rings, although somehave no obvious bars or spirals to drive them. If these symmetric cases areresonance rings, then they could be the precursors of modern resonance rings,which are only ~30% larger on average. This similarity in radius suggests thatthe driving pattern speed has not slowed by more by ~30% during the last ~7 Gy.Those without bars could be examples of dissolved bars.Comment: 17 pages, 13 figures, to appear in ApJ, 651, November 10, 200