paper

Ly alpha emissters at z=6.5 in the SSA22 field: An area more neutral or void at the end of the reionization epoch

arXiv:1011.5313 · doi:10.1111/j.1365-2966.2010.18077.x

Abstract

We present results of a survey of Lyman emitters (LAEs) at which is thought to be the final epoch of the cosmic reionization. In a arcmin deep image of the SSA22 field taken through a narrowband filter NB912 installed in the Subaru/Suprime-Cam, we have found only 14 LAE candidates with $L_{\rm Lyα}\ga3\times10^{42}$ erg s. Even applying the same colour selection criteria, the number density of the LAE candidates is a factor of 3 smaller than that found at the same redshift in the Subaru Deep field (SDF). Assuming the number density in the SDF is a cosmic average, the probability to have a number density equal to or smaller than that found in the SSA22 field is only 7% if we consider fluctuation by the large-scale structure (i.e. cosmic variance) and Poisson error. Therefore, the SSA22 field may be a rare void at . On the other hand, we have found that the number density of -drop galaxies with in the SSA22 field agrees well with that in the SDF. If we consider a scenario that a larger neutral fraction of intergalactic hydrogen, , in the SSA22 field obscures a part of Ly emission, in the SSA22 field should be about 2 times larger than that in the SDF. This can be translated into at in the SSA22 field. A much larger survey area than previous ones is required to overcome a large fluctuation reported here and to obtain a robust constraint on at the end of the reionization from LAEs.

MNRAS accepted

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