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 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 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.

Core-collapse supernovae (CC-SNe) are the explosions that announce the death of massive stars. Some CC-SNe are linked to long-duration gamma-ray bursts (GRBs) and are highly aspherical. One important question is to what extent asphericity is common to all CC-SNe. Here we present late-time spectra for a number of CC-SNe from stripped-envelope stars and use them to explore any asphericity generated in the inner part of the exploding star, near the site of collapse. A range of oxygen emission-line profiles is observed, including a high incidence of double-peaked profiles, a distinct signature of an aspherical explosion. Our results suggest that all CC-SNe from stripped-envelope stars are aspherical explosions and that SNe accompanied by GRBs exhibit the highest degree of asphericity.

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We report angular correlation function (ACF) of Lyman Break Galaxies (LBGs) with unprecedented statistical quality on the basis of 16,920 LBGs at z = 4 detected in the 1 deg 2 sky of the Subaru/XMM-Newton Deep Field. The ACF significantly departs from a power law, and shows an excess on small scale. Particularly, the ACF of LBGs with i ′ < 27.5 have a clear break between the small and large-scale regimes at the angular separation of ≃ 7 ′′ whose projected length corresponds to the virial radius of dark halos with a mass of 10 11−12 M ⊙ , indicating multiple LBGs residing in a single dark halo. Both on small (2 ′′ < θ < 3 ′′ ) and large (40 ′′ < θ < 400 ′′ ) scales, clustering amplitudes monotonically increase with luminosity for the magnitude range of i ′ = 24.5 − 27.5, and the small-scale clustering shows a stronger luminosity dependence than the large-scale clustering. The small-scale bias reaches b ≃ 10 − 50, and the outskirts of small-scale excess extend to a larger angular separation for brighter LBGs. The ACF and number density of LBGs can be explained by the cold dark matter model.

The Faint Object Camera and Spectrograph (FOCAS) is a Cassegrain optical instrument for the Subaru Telescope. Its capabilities include $6^\prime \phi$ FOV direct imaging, low-resolution spectroscopy ($R=250 \hbox{--} 2000$ with ${0\rlap {.}{}^{\mathrm {\prime \prime }}4}$ slitwidth), multi-slit spectroscopy and polarimetry. We describe the overall design of FOCAS, its observing functions, and the performance verification procedures that have been carried out.

Abstract.We have performed a detailed analysis of 3 optically normal galaxies extracted from the XMM Bright Serendipitous Source Sample. Thanks to the good statistics of the XMM-Newton data, we have unveiled the presence of an AGN in all of them. In particular, we detect both X-ray obscured (N H > 10 22 cm −2 ) and unobscured (N H < 10 22 cm −2 ) AGNs with intrinsic 2-10 keV luminosities in the range between 10 42 -10 43 erg s −1 . We find that the X-ray and optical properties of the sources discussed here could be explained assuming a standard AGN hosted by galaxies with magnitudes M R < M * , taking properly into account the absorption associated with the AGN, the optical faintness of the nuclear emission with respect to the host galaxy, and the inadequate set-up and atmospheric conditions during the optical spectroscopic observations. Our new spectroscopic observations have revealed the expected AGN features also in the optical band. These results clearly show that optical spectroscopy sometimes can be inefficient in revealing the presence of an AGN, which instead is clearly found from an X-ray spectroscopic investigation. This remarks the importance of being careful in proposing the identification of X-ray sources (especially at faint fluxes) when only low quality optical spectra are in hand. This is particularly important for faint surveys (such as those with XMM-Newton and Chandra), in which optically dull but X-ray active objects are being found in sizeable numbers.