We present accurate photometric redshifts in the 2-deg 2 COSMOS field. The redshifts are computed with 30 broad, intermediate, and narrow bands covering the UV (GALEX), Visible-NIR (Subaru, CFHT, UKIRT and NOAO) and mid-IR (Spitzer/IRAC). A χ 2 template-fitting method (Le Phare) was used and calibrated with large spectroscopic samples from VLT-VIMOS and Keck-DEIMOS. We develop and implement a new method which accounts for the contributions from emission lines ([O II], Hβ, Hα and Lyα) to the spectral energy distributions (SEDs). The treatment of emission lines improves the photo-z accuracy by a factor of 2.5. Comparison of the derived photo-z with 4148 spectroscopic redshifts (i.e. ∆z = z s − z p ) indicates a dispersion of σ ∆z/(1+zs) = 0.007 at i + AB < 22.5, a factor of 2 − 6 times more accurate than earlier photo-z in the COSMOS, CFHTLS and COMBO-17 survey fields. At fainter magnitudes i + AB < 24 and z < 1.25, the accuracy is σ ∆z/(1+zs) = 0.012. The deep NIR and IRAC coverage enables the photo-z to be extended to z ∼ 2 albeit with a lower accuracy (σ ∆z/(1+zs) = 0.06 at i + AB ∼ 24). The redshift distribution of large magnitude-selected samples is derived and the median redshift is found to range from z m = 0.66 at 22 < i + AB < 22.5 to z m = 1.06 at 24.5 < i + AB < 25. At i + AB < 26.0, the multi-wavelength COSMOS catalog includes approximately 607,617 objects. The COSMOS-30 photo-z enable the full exploitation of this survey for studies of galaxy and large scale structure evolution at high redshift.

We report an extensive search for Ly emitters (LAEs) at z ¼ 6:5 in the Subaru Deep Field. Subsequent spectroscopy with Subaru and Keck identified eight more LAEs, giving a total of 17 spectroscopically confirmed LAEs at z ¼ 6:5. Based on this spectroscopic sample of 17, complemented by a photometric sample of 58 LAEs, we have derived a more accurate Ly luminosity function of LAEs at z ¼ 6:5, which reveals an apparent deficit at the bright end of $0.75 mag fainter L Ã , compared with that observed at z ¼ 5:7. The difference in the LAE luminosity functions between z ¼ 5:7 and 6.5 is significant at the 3 level, which is reduced to 2 when cosmic variance is taken into account. This result may imply that the reionization of the universe has not been completed at z ¼ 6:5. We found that the spatial distribution of LAEs at z ¼ 6:5 was homogeneous over the field. We discuss the implications of these results for the reionization of the universe.

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.