On the Possible Sources of D/H Dispersion at High Redshift

Recent observations suggest the existence of a white dwarf population in theGalactic halo, while others suggest that deuterium has been astrated in systemsat high redshift and low metallicity. We propose that these observations couldbe signatures of an early population of intermediate-mass stars. Such apopulation requires a Population III initial mass function different from thatof the solar neighborhood, as perhaps also suggested by the observed cosmicinfrared background. Also, to avoid overproduction of C and N, it is requiredthat the Z=0 yields of these stars have low ($\sim 10^{-3}$ solar) abundancesas suggested by some recent calculations. Under these assumptions, we present amodel which reproduces the observed D vs Si trend, and predicts a high cosmicType Ia supernova rate, while producing a white dwarf population that accountsfor only $\sim$ 1.5% of the dark halo. This scenario can be tested byobservations of the cosmic supernova rate, and by confirmation and furtherstudies of the putative white dwarf halo population.Comment: AASTeX, 17 pages, 3 embedded eps fig