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Evolution of the observed Lyα luminosity function from z=6.5 to z=7.7: evidence for the epoch of reionization?

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Clément, B. and Cuby, J. G. and Courbin, F. and Fontana, A. and Freudling, W. and Fynbo, J. and Gallego Maestro, Jesús and Hibon, P. and Kneib, J. P. and Le Fèvre, O. and Lidman, C. and McMahon, R. and Milvang-Jensen, B. and Moller, P. and Moorwood, A. and Nilsson, K. K. and Pentericci, L. and Venemans, B. and Villar, V. and Willis, J. (2012) Evolution of the observed Lyα luminosity function from z=6.5 to z=7.7: evidence for the epoch of reionization? Astronomy and astrophysics, 538 . ISSN 0004-6361

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Official URL: http://dx.doi.org/10.1051/0004-6361/201117312




Abstract

Aims. Lyα emitters (LAEs) can be detected out to very high redshifts during the epoch of reionization. The evolution of the LAE luminosity function with redshift is a direct probe of the Lyα transmission of the intergalactic medium (IGM), and therefore of the IGM neutral-hydrogen fraction. Measuring the Lyα luminosity function (LF) of Lyα emitters at redshift z = 7.7 therefore allows us to constrain the ionizing state of the Universe at this redshift. Methods. We observed three 7. 5 × 7. 5 fields with the HAWK-I instrument at the VLT with a narrow band filter centred at 1.06 μm and targeting Lyα emitters at redshift z ∼ 7.7. The fields were chosen for the availability of multiwavelength data. One field is a galaxy cluster, the Bullet Cluster, which allowed us to use gravitational amplification to probe luminosities that are fainter than in the field. The two other fields are subareas of the GOODS Chandra Deep Field South and CFHTLS-D4 deep field. We selected z = 7.7 LAE candidates from a variety of colour criteria, in particular from the absence of detection in the optical bands. Results. We do not find any LAE candidates at z = 7.7 in ∼2.4 × 104 Mpc3 down to a narrow band AB magnitude of ∼26, which allows us to infer robust constraints on the Lyα LAE luminosity function at this redshift.
Conclusions. The predicted mean number of objects at z = 6.5, derived from somewhat different luminosity functions of Hu et al. (2010, ApJ, 725, 394), Ouchi et al. (2010, ApJ, 723, 869), and Kashikawa et al. (2011, ApJ, 734, 119) are 2.5, 13.7, and 11.6, respectively. Depending on which of these luminosity functions we refer to, we exclude a scenario with no evolution from z = 6.5 to z = 7.7 at 85% confidence without requiring a strong change in the IGM Lyα transmission, or at 99% confidence with a significant quenching of the IGM Lyα transmission, possibly from a strong increase in the high neutral-hydrogen fraction between these two redshifts.


Item Type:Article
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© ESO 2012. We acknowledge financial support from Agence Nationale de la Recherche (grant ANR-09-BLAN-0234-01). F. C. is supported by the Swiss National Science Foundation (SNSF). The Dark Cosmology Centre is funded by the Danish National Research Foundation.

Uncontrolled Keywords:Lyman-break galaxies; Origins deep survey; Goods-south field; J-band search; Redshift 6; Cosmic variance; 1st galaxies; Emitters; Emission; Z-similar-to-9
Subjects:Sciences > Physics > Astrophysics
Sciences > Physics > Astronomy
ID Code:33690
Deposited On:21 Oct 2015 13:44
Last Modified:10 Dec 2018 15:05

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