TY - JOUR
T1 - Evolution of the observed Ly α luminosity function from z = 6.5 to z = 7.7
T2 - Evidence for the epoch of reionization?
AU - Clément, B.
AU - Cuby, J. G.
AU - Courbin, F.
AU - Fontana, A.
AU - Freudling, W.
AU - Fynbo, J.
AU - Gallego, J.
AU - Hibon, P.
AU - Kneib, J. P.
AU - Le Fèvre, O.
AU - Lidman, C.
AU - McMahon, R.
AU - Milvang-Jensen, B.
AU - Moller, P.
AU - Moorwood, A.
AU - Nilsson, K. K.
AU - Pentericci, L.
AU - Venemans, B.
AU - Villar, V.
AU - Willis, J.
PY - 2012
Y1 - 2012
N2 - 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 × 10 4 Mpc 3 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.
AB - 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 × 10 4 Mpc 3 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.
KW - dark ages, reionization, first stars
KW - early Universe
KW - galaxies: high-redshift
KW - galaxies: luminosity function, mass function
KW - methods: observational
KW - techniques: image processing
UR - http://www.scopus.com/inward/record.url?scp=84856754670&partnerID=8YFLogxK
U2 - 10.1051/0004-6361/201117312
DO - 10.1051/0004-6361/201117312
M3 - Article
AN - SCOPUS:84856754670
SN - 0004-6361
VL - 538
JO - Astronomy and Astrophysics
JF - Astronomy and Astrophysics
M1 - A66
ER -