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arXiv · 1106.6055

Searching for z~7.7 Lyman Alpha Emitters in the COSMOS Field with NEWFIRM

Hannah Krug·Sylvain Veilleux·Vithal Tilvi·Sangeeta Malhotra·James Rhoads·Pascale Hibon·Rob Swaters·Ron Probst·Arjun Dey·Mark Dickinson·Buell T. Jannuzi
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Abstract

The study of Ly-alpha emission in the high-redshift universe is a useful probe of the epoch of reionization, as the Ly-alpha line should be attenuated by the intergalactic medium (IGM) at low to moderate neutral hydrogen fractions. Here we present the results of a deep and wide imaging search for Ly-alpha emitters in the COSMOS field. We have used two ultra-narrowband filters (filter width of ~8-9 °A) on the NEWFIRM camera, installed on the Mayall 4m telescope at Kitt Peak National Observatory, in order to isolate Ly-alpha emitters at z = 7.7; such ultra-narrowband imaging searches have proved to be excellent at detecting Ly-alpha emitters. We found 5-sigma detections of four candidate Ly-alpha emitters in a survey volume of 2.8 x 10^4 Mpc^3 (total survey area ~760 arcmin^2). Each candidate has a line flux greater than 8 x 10^-18 erg s^-1 cm^-2. Using these results to construct a luminosity function and comparing to previously established Ly-alpha luminosity functions at z = 5.7 and z = 6.5, we find no conclusive evidence for evolution of the luminosity function between z = 5.7 and z = 7.7. Statistical Monte Carlo simulations suggest that half of these candidates are real z = 7.7 targets, and spectroscopic follow-up will be required to verify the redshift of these candidates. However, our results are consistent with no strong evolution in the neutral hydrogen fraction of the IGM between z = 5.7 and z = 7.7, even if only one or two of the z = 7.7 candidates are spectroscopically confirmed.

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Hannah Krug, Sylvain Veilleux, Vithal Tilvi, Sangeeta Malhotra, James Rhoads, Pascale Hibon, Rob Swaters, Ron Probst, Arjun Dey, Mark Dickinson, Buell T. Jannuzi. 2011-12-06. Searching for z~7.7 Lyman Alpha Emitters in the COSMOS Field with NEWFIRM. https://doi.org/10.1088/0004-637x%2F745%2F2%2F122

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