HUBBLE SPACE TELESCOPE SPECTRAL OBSERVATIONS NEAR THE He II Ly{alpha} BREAK: IMPLICATIONS FOR He II REIONIZATION

Quasars that allow the study of intergalactic medium (IGM) He II are very rare, since they must be at high redshift along sightlines free of substantial hydrogen absorption, but recent work has dramatically expanded the number of such quasars known. We analyze two dozen higher-redshift (z = 3.1-3.9)...

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