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arXiv · 1010.2754

The lack of intense Lyman~alpha in ultradeep spectra of z=7 candidates in GOODS-S: imprint of reionization?

A. Fontana·E. Vanzella·L. Pentericci·M. Castellano·M. Giavalisco·A. Grazian·K. Boutsia·S. Cristiani·M. Dickinson·E. Giallongo·M. Maiolino·A. Moorwood·P. Santini
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Abstract

We present ultradeep optical spectroscopy obtained with FORS2 on VLT of seven Lyman-break galaxy (LBG) candidates at z>6.5 selected in the GOODS-S field from Hawk-I/VLT and WFC3/HST imaging. For one galaxy we detect a low significance emission line (S/N< 7), located at 9691.5 +/- 0.5A and with flux 3.4 x 10^(-18)erg/cm^2/s. If identified as Lyman alpha, it places the LBG at redshift z=6.972+/- 0.002, with a rest-frame equivalent width EW}=13A. Using Monte Carlo simulations and conservative EW distribution functions at 2 10 is ~ 2%, and that of observing only one galaxy out of seven with S/N=5 is ~4%, but these can be as small as ~1E-3, depending on the details of the EW distribution. We conclude that either a significant fraction of the candidates is not at high redshift or that some physical mechanism quenches the Lyman alpha emission emerging from the galaxies at z>6.5, abruptly reversing the trend of the increasing fraction of strong emitters with increasing redshift observed up to z~ 6.5. We discuss the possibility that an increasingly neutral intergalactic medium is responsible for such quenching.

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A. Fontana, E. Vanzella, L. Pentericci, M. Castellano, M. Giavalisco, A. Grazian, K. Boutsia, S. Cristiani, M. Dickinson, E. Giallongo, M. Maiolino, A. Moorwood, P. Santini. 2010-10-13. The lack of intense Lyman~alpha in ultradeep spectra of z=7 candidates in GOODS-S: imprint of reionization?. https://doi.org/10.1088/2041-8205%2F725%2F2%2Fl205

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