Luminous arcs in clusters of galaxies

Abstract

We report observations of what appears to be a new class of spatially coherent extragalactic features having, in the two most compelling known examples, the following joint properties: location in clusters of galaxies, narrow arclike shape, enormous apparent length, and situation of center of curvature toward both a cD galaxy and the apparent center of gravity of the cluster. We present the principal available facts concerning the arcs and briefly discuss a variety of interpretations. The weight of evidence seems to favor the interpretation that these features are images of more distant objects produced by the gravitational field of the intervening clusters.