Speaker:		Tony Cowie

Affiliation:	IfA

Title:		EARLY METAL FORMATION AND THE INTERGALACTIC MEDIUM

Abstract:	
The Lyman alpha forest of neutral hydrogen lines seen in the
spectra of quasars gives us a map of the density structure in the
diffuse intergalactic gas out to z = 5.  The discovery that this
material is enriched with heavy elements was one of the surprises
which HIRES on Keck provided.  The ionization balance in the
metals is a powerful diagnostic of the intergalactic gas and the
background ionizing radiation field at these redshifts, while the
measured universal metal density provides an estimate of the
amount of massive star formation that must have taken place in
the `dark ages' at z > 5, and makes one of the key predictions
justifying the Next Generation Space Telescope.