We present Lyα luminosity function (LF), clustering measurements, and Lyα line profiles based on the largest sample, to date, of 207 Lyα emitters (LAEs) at z = 6.6 on the 1-deg 2 sky of Subaru/XMM-Newton Deep Survey (SXDS) field. Our z = 6.6 Lyα LF including cosmic variance estimates yields the best-fit Schechter parameters of φ * = 8.5 +3.0 −2.2 × 10 −4 Mpc −3 and L * Lyα = 4.4 +0.6 −0.6 × 10 42 erg s −1 with a fixed α = −1.5, and indicates a decrease from z = 5.7 at the 90% confidence level. However, this decrease is not large, only ≃ 30% in Lyα luminosity, which is too small to be identified in the previous studies. A clustering signal of z = 6.6 LAEs is detected for the first time. We obtain the correlation length of r 0 = 2 − 5 h −1 100 Mpc and bias of b = 3 − 6, and find no significant boost of clustering amplitude by reionization at z = 6.6. The average hosting dark halo mass inferred from clustering is 10 10 − 10 11 M ⊙ , and duty cycle of LAE population is roughly ∼ 1% albeit with large uncertainties. The average of our high-quality Keck/DEIMOS spectra shows an FWHM velocity width of 251 ± 16km s −1 . We find no large evolution of Lyα line profile from z = 5.7 to 6.6, and no anti-correlation between Lyα luminosity and line width at z = 6.6. The combination of various reionization models and our observational results about the LF, clustering, and line profile indicates that there would exist a small decrease of IGM's Lyα transmission owing to reionization, but that the hydrogen IGM is not highly neutral at z = 6.6. Our neutral-hydrogen fraction constraint implies that the major reionization process took place at z 7.

We report the properties of the 35 robust candidates of Lyα blobs (LABs), which are larger than 16 arcsec 2 in isophotal area and brighter than 0.7 × 10 −16 ergs s −1 cm −2 , searched in and around the proto-cluster region at redshift z = 3.1 discovered by Steidel et al. in the SSA22 field, based on wide-field (31 ′ × 23 ′ ) and deep narrow-band (NB497; 4977/77) and broad-band (B,V , and R) images taken with the prime-focus camera on the Subaru telescope. The two previously known giant LABs are the most luminous and the largest ones in our survey volume of 1.3 × 10 5 Mpc 3 . We revealed the internal structures of the two giant LABs and discovered some bubble-like features, which suggest that intensive starburst and galactic superwind phenomena occurred in these objects in the past. The rest 33 LABs have isophotal area of ∼16-78 arcsec 2 and flux of 0.7-7 ×10 −16 ergs s −1 cm −2 . These 35 LABs show a continuous distribution of isophotal area and emission line flux. The distributions of average surface brightness and morphology are widespread from relatively compact high surface 1 Based on data collected at Subaru Telescope and in part obtained from data archive at Astronomical Data Analysis Center, which are operated by the National Astronomical Observatory of Japan.

We report the discovery of primeval large-scale structures (LSSs) including two protoclusters in a forming phase at . We carried out extensive deep narrowband imaging in the 1 deg 2 sky of the Subaru/XMM-Newton Deep z p 5.7 Field and obtained a cosmic map of 515 Lya emitters (LAEs) in a volume with a transverse dimension of and a depth of ∼40 Mpc in comoving units. This cosmic map shows filamentary LSSs, including 180 Mpc # 180 Mpc clusters and surrounding 10-40 Mpc scale voids, similar to the present-day LSSs. Our spectroscopic follow-up observations identify overdense regions in which two dense clumps of LAEs with a sphere of 1 Mpc diameter in physical units are included. These clumps show about 130 times higher star formation rate density, mainly due to a large overdensity, ∼80, of LAEs. These clumps would be clusters in a formation phase involving a burst of galaxy formation.

The gamma-ray burst (GRB) 050904 at z = 6.3 provides the first opportunity of probing the intergalactic medium (IGM) by GRBs at the epoch of the reionization. Here we present a spectral modeling analysis of the optical afterglow spectrum taken by the Subaru Telescope, aiming to constrain the reionization history. The spectrum shows a clear damping wing at wavelengths redward of the Lyman break, and the wing shape can be fit either by a damped Lyα system with a column density of log(N HI /cm −2 ) ∼ 21.6 at a redshift close to the detected metal absorption lines (z metal = 6.295), or by almost neutral IGM extending to a slightly higher redshift of z IGM,u ∼ 6.36. In the latter case, the difference from z metal may be explained by acceleration of metal absorbing shells by the activities of the GRB or its progenitor. However, we exclude this possibility by using the light transmission feature around the Lyβ resonance, leading to a firm upper limit of z IGM,u ≤ 6.314. We then show an evidence that the IGM was largely ionized already at z = 6.3, with the best-fit neutral fraction of IGM, x HI = 0.00, and upper limits of x HI < 0.17 and 0.60 at 68 and 95% C.L., respectively. This is the first direct and quantitative upper limit on x HI at z > 6. Various systematic uncertainties are examined, but none of them appears large enough to change this conclusion. To get further information on the reionization, it is important to increase the sample size of z > ∼ 6 GRBs, in order to find GRBs with low column densities (log N HI < ∼ 20) within their host galaxies, and for statistical studies of Lyα line emission from host galaxies.

We obtained a deep wide-field (32 0 ; 24 0 ) narrowband (k c ¼ 49778; Ák ¼ 778) image of a field including the protocluster at z ¼ 3:1 in the SSA22a field studied by Steidel et al. using the Subaru Telescope. The field we observed is about 10 times as large as that studied by Steidel et al. We detected 283 highly confident strong Ly emitter candidates at z $ 3:1 down to 25.8 AB mag with the observed equivalent width larger than 154 8. These strong Ly emitter candidates show a highly nonuniform distribution with the beltlike region of high surface density, which is found to extend over $60 Mpc in comoving scale. The average number density of the strong Ly emitter candidates in this high-density region is 3 times as high as that of a blank field. The probability of finding such a large-scale high-density peak is as small as 0.1% in the context of the CDM structure formation scenario, if we assume a linear bias parameter b $ 4. In addition to these strong Ly emitters, we also detected 49 Ly absorbers, which show significant deficit in the narrowband image. We further detected 74 extended emitters, which have significant fluxes over the areas of 18 arcsec 2 or more. Interestingly, both these absorbers and extended emitters show sky distributions very similar to that of the strong Ly emitters. This supports the reality of the large-scale structure at z ¼ 3:1 and suggests that galaxy formation preferentially occurs in the high-density region of strong Ly emitters.