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 present the properties of Lyα emitters (LAEs) at z = 5.7 in the Subaru Deep Field. A photometric sample of 89 LAE candidates is constructed from narrow-band (NB816) data down to N B816 = 26.0 (AB) in a continuous 725 arcmin 2 area. Spectra of 39 objects satisfying the photometric selection criteria for LAEs were obtained with Subaru and Keck II Telescopes, among which 28 were confirmed LAEs, one was a nearby galaxy, and eight were unclassified. We also obtained spectra of another 24 NB816-excess objects in the field, identifying six additional LAEs. We find that the Lyα luminosity function derived from the photometric sample is reproduced well by a Schechter function with L ⋆ = 7.9 +3.0 −2.2 × 10 42 erg s −1 and φ ⋆ = 6.3 +3.0 −2.0 × 10 −4 Mpc −3 for α = −1.5 (fixed) over the whole luminosity range of L ≃ 3 × 10 42 -3 × 10 43 erg s −1 . We then measure rest-frame Lyα equivalent widths (EWs) for the confirmed LAEs, to find that the median among the 28 objects satisfying the photometric selection criteria is W i 0 = 233 Å. We infer that 30% -40% of LAEs at z = 5.7 exceed W i 0 = 240 Å. These large-EW objects probably cannot be accounted for by ordinary star-forming populations with a Salpeter IMF. We also find that LAEs with fainter far-UV luminosities have larger EWs. Finally, we derive the far-UV luminosity function of LAEs down to M UV ≃ −19.6 using the photometric sample, and compare it with that of Lyman-break galaxies (LBGs). We find that as high as about 80% of LBGs at z ∼ 6 have W i 0 ≥ 100 Å, in sharp contrast to lower-z counterparts.

We report the results of a wide-field narrowband survey for redshift z $ 5.7 Ly emitters carried out with the 34 0 Â 27 0 field-of-view SuprimeCam mosaic CCD camera on the Subaru 8.3 m telescope. Deep narrowband imaging of the SSA22 field through a 120 Å bandpass filter centered at a nominal wavelength of 8150 Å was combined with deep multicolor RIz 0 broadband imaging with SuprimeCam, then supplemented with BVRZ imaging taken with the 42 0 Â 28 0 field-of-view CFH12K camera on the Canada-France-Hawaii 3.6 m telescope to select high-redshift galaxy candidates. Spectroscopic observations were made using the new wide-field multiobject DEIMOS spectrograph on the 10 m Keck II telescope for 22 of the 26 candidate objects. Eighteen of these objects were identified as z $ 5.7 Ly emitters, and a further nineteenth object from the candidate list was identified based on an LRIS spectrum. At the 3.3 Å resolution of the DEIMOS observations the asymmetric profile for Ly emission with its steep blue falloff can be clearly seen in the spectra of the identified galaxies. This is by far the largest spectroscopic sample of galaxies at these redshifts, and we use it to describe the distribution of equivalent widths and continuum color break properties for identified Ly galaxies compared with the foreground population. The large majority (at least 75%) of the lines have rest-frame Ly equivalent widths substantially less than 240 Å and can be understood in terms of young star-forming galaxies with a Salpeter initial mass function for the stars. With the narrowband selection criteria of IÀN > 0.7 and N < 25.05 (AB magnitudes) we find a surface density of Ly emitters of 0.03 arcmin À2 in the filter bandpass (Áz = 0.1) down to a limiting flux of just under 2 Â 10 À17 ergs cm À2 s À1 . The luminosity function of the Ly emitters is similar to that at lower redshifts to the lowest measurable luminosity of 10 43 ergs s À1 as is the universal star formation rate based on their continuum properties. However, we note that the objects are highly structured in both their spatial and spectral properties on the angular scale of the fields (%60 Mpc), and that multiple fields will have to be averaged to accurately measure their ensemble properties.

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.

Knowing the amount of ionizing photons from young star-forming galaxies is of particular importance to understanding the reionization process. Here we report initial results of Subaru/Suprime-Cam deep imaging observation of the SSA22 proto-cluster region at z = 3.09, using a special narrow-band filter to optimally trace ionizing radiation from galaxies at z ∼ 3. The unique wide field-of-view of Suprime-Cam enabled us to search for ionizing photons from 198 galaxies (73 Lyman break galaxies (LBGs) and 125 Ly-α emitters (LAEs)) with spectroscopically measured redshifts z ≃ 3.1. We detected ionizing radiation from 7 LBGs, as well as from 10 LAE candidates. Some of the detected galaxies show significant spatial offsets of ionizing radiation from non-ionizing UV emission. For some LBGs the observed non-ionizing UV to Lyman continuum flux density ratios are smaller than values expected from population synthesis models with a standard Salpeter initial mass function (IMF) with moderate dust attenuation (which is suggested from the observed UV slopes), even if we assume very transparent IGM along the sightlines of these objects. This implies an intrinsically bluer spectral energy distribution, e.g, that produced by a top-heavy IMF, for these LBGs. The observed flux desity ratios of non-ionizing UV to ionizing radiation of 7 detected LBGs range from 2.4 to 23.8 and the median is 6.6. The observed flux density ratios of the detected LAEs are even smaller than LBGs, if they are truly at z ≃ 3.1. We find that the median value of the flux density ratio for the deteced LBGs suggest that their escape fractions is likely to be higher than 4%, if the Lyman continuum escape is isotropic. The results imply that some of the LBGs in the proto-cluster at z ∼ 3 have the escape fraction significantly higher than that of galaxies (in a general field) at z ∼ 1 studied previously.