Limits on the Gunn-Peterson Effect at z = 5

Abstract

We report new limits on the Gunn-Peterson effect at a redshift near 5 using spectroscopic observations of the z = 5 Sloan Digital Sky Survey quasar, J033829.31+002156.3, made with the LRIS and HIRES spectrographs on the Keck telescopes. Lower resolution spectrophotometrically calibrated observations made with LRIS over the wavelength region 4500-9600 angstroms were used to obtain a continuum shape and to flux calibrate much higher resolution (R = 36,000) observations made with HIRES. The LRIS data show an Oke D_A index of 0.75. Portions of the HIRES spectrum return to near the extrapolated continuum level. Including both statistical and systematic errors we place an upper limit of tau = 0.1 on the regions of minimum opacity. We argue that, even if this opacity arises in underdense regions of the intergalactic gas, we require a high value of the metagalactic ionizing flux at these redshifts ($J_{\nu }\gg 4\times 10^{-23}\mathrm{ergsc}{\mathrm{m}}^{-2}{\mathrm{s}}^{-1}\mathrm{H}{\mathrm{z}}^{-1}\mathrm{s}{\mathrm{r}}^{-1}$ at $z\sim 4.72$) to produce a solution which is consistent with even minimum nucleosynthesis estimates of the baryon density. We also report the presence of a Mg II absorption system of extremely high equivalent width ($W_{\lambda ,rest}(2796)=1.73$ Å) at z=2.304.

15 pages including 2 figures. Also available at http://www.ifa.hawaii.edu/~acowie/gp_5.html To be published in Astrophysical Journal Letters

References in corpus (1)

• High-Redshift Quasars Found in Sloan Digital Sky Survey Commissioning Data

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