An unusual high-redshift object discovered with the Hubble Space Telescope: peculiar starburst galaxy or new gravitational lens?

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Abstract
We report the discovery of an object with a very peculiar structure, using observations from the refurbished Hubble Space Telescope (HST) as part of the Medium-Deep Survey project. The object includes four compact blue components arranged around an extended red component, with mutual separations of < 1 arcsec. Using a ground-based spectrum as an additional constraint, we consider the plausibility of two solutions to the structural problem. First, the blue components could be individual supergiant H II regions sitting in a host spiral or irregular galaxy which they dominate. Secondly, the system could be gravitationally lensed, where the blue components are all images of a single background source. In this case, a severe limit can be placed on the size of the emitting region, and the system has considerable potential for studies of H0 because of the short time-delay. A high mass-to-light ratio, compared with those known for low-redshift galaxies, however, would be required to produce the observed image separation.

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