Galaxies at z ≈4 and the Formation of Population II

摘要

We report the discovery of four high-redshift objects (3.3 < z < 4) observed behind the rich cluster CL 0939+4713 (Abell 851). One object (DG 433) has a redshift of z = 3.3453; the other three objects have redshifts of z ≈4: A0 at z = 3.9819, DG 353 and P1/P2 at z = 3.9822. It is possible that all four objects are being lensed in some way by the cluster, DG 433 being weakly sheared, A0 being strongly sheared, and DG 353 and P1/P2 being an image pair of a common source object; detailed modeling of the cluster potential will be necessary to confirm this hypothesis. The weakness of common stellar wind features like N V and especially C IV in the spectra of these objects argues for subsolar metallicities, at least as low as the SMC.