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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Bibliographic Details
Published in:The Astrophysical journal 2011-01, Vol.726 (2)
Main Authors: Syphers, David, Anderson, Scott F., Haggard, Daryl, Zheng Wei, Meiksin, Avery, Schneider, Donald P., York, Donald G.
Format: Article
Language:English
Subjects:
ASTROPHYSICS, COSMOLOGY AND ASTRONOMY
COSMIC RADIO SOURCES
ELEMENTS
FLUIDS
GALAXIES
GASES
HELIUM
INTERGALACTIC SPACE
NONMETALS
OPACITY
OPTICAL PROPERTIES
PHYSICAL PROPERTIES
QUASARS
RARE GASES
RED SHIFT
SPACE
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Summary: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) low-resolution He II quasar spectra from the Hubble Space Telescope and find that their He II Gunn-Peterson troughs suggest exclusion of very early and very late reionization models, favoring a reionization redshift of z {approx} 3. Although the data quality is not sufficient to reveal details such as the expected redshift evolution of helium opacity, we obtain the first ensemble measure of helium opacity at high redshift averaged over many sightlines: {tau} = 4.90 at z {approx} 3.3. We also find that it would be very difficult to observe the IGM red wing of absorption from the beginning of He II reionization, but depending on the redshift of reionization and the size of ionization zones, it might be possible to do so in some objects with the current generation of UV spectrographs.
ISSN:0004-637X
1538-4357
DOI:10.1088/0004-637X/726/2/111