Mathematics – Logic
Scientific paper
Jan 2012
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2012aas...21942601s&link_type=abstract
American Astronomical Society, AAS Meeting #219, #426.01
Mathematics
Logic
Scientific paper
Observations of He II Lyα Gunn-Peterson troughs have proved to be a valuable probe of the epoch of helium reionization at z ∼ 3. Since this optical depth can become unmeasurably large even for modest He II fractions, various alternate techniques have been proposed to push to higher redshift, and among the more promising is looking at higher order Lyman-series troughs. We here report four new observations of the He II Lyβ trough, including new data on the only sightline with a prior Lyβ observation. However, the effective optical depth ratio κeff,β/κeff,α is not simply predicted by fβλβ/fαλα = 0.16, and we analyze cosmological simulations to find that the correct ratio for helium at z ∼ 3 is 0.35. In one case we infer κeff,α > 8.8, strong evidence that helium was not fully reionized at z = 3.2-3.5, in agreement with previous measurements suggesting a later completion of reionization.
Support for HST Programs number 12178 and 12249 was provided by NASA through grants from the Space Telescope Science Institute.
Anderson Scott F.
Pieri Matthew M.
Smith Brett
Syphers David
Zheng Wei
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