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We report the ultraviolet luminosity function (UVLF) of Lyman break galaxies at z∼ 5 derived from a deep and wide survey using the prime focus camera of the 8.2 m Subaru telescope (Suprime‐Cam). Target fields consist of two blank regions of the sky, namely, the region including the Hubble Deep Field‐North and the J0053+1234 region, and the total effective surveyed area is 1290 arcmin2. Applications of carefully determined colour selection criteria in V−Ic and Ic−z′ yield a detection of 853 z∼ 5 candidates with z′AB < 26.5 mag. The UVLF at z∼ 5 based on this sample shows no significant change in the number density of bright (L≳L*z=3) LBGs from that at z∼ 3, while there is a significant decline in the LF's faint end with increasing look‐back time. This result means that the evolution of the number densities is differential with UV luminosity: the number density of UV luminous objects remains almost constant from z∼ 5 to 3 (the cosmic age is about 1.2 to 2.1 Gyr) while the number density of fainter objects gradually increases with cosmic time. This trend becomes apparent thanks to the small uncertainties in number densities both in the bright and faint parts of LFs at different epochs that are made possible by the deep and wide surveys we use. We discuss the origins of this differential evolution of the UVLF along the cosmic time and suggest that our observational findings are consistent with the biased galaxy evolution scenario: a galaxy population hosted by massive dark haloes starts active star formation preferentially at early cosmic time, while less massive galaxies increase their number density later. We also calculated the UV luminosity density by integrating the UVLF and at z∼ 5 found it to be 38.8+6.7−4.1 per cent of that at z∼ 3 for the luminosity range L > 0.1L*z=3. By combining our results with those from the literature, we find that the cosmic UV luminosity density marks its peak at and then slowly declines towards higher redshift.

Summary Intermediate‐period seismograms of shear waves from deep earthquakes are examined for shear‐wave splitting diagnostic of seismic velocity anisotropy in the upper‐mantle wedge between the subducting Tonga slab and stations in the Fiji Islands. Earthquakes with near‐vertical incidence angles are selected to minimize complications of converted phases and the free surface. Horizontal‐component seismograms for 25 deep earthquakes recorded at station LAK on the Lau Ridge show splitting of up to 0.9 s with an average of 0.45 ± 0.25 s between fast and slow S‐wave components. Anisotropy in the upper mantle is the most likely cause of the splitting. The ESE orientation of the fast velocity direction at station LAK corresponds to an axis of symmetry of the anisotropic mantle and is approximately perpendicular to magnetic lineations in the Lau Basin and the northeastern portion of the South Fiji Basin. The observations are consistent with a model of flow alignment of olivine (100) and orthopyroxene (001) axes parallel to the direction of basin extension. Seismograms for eight deep earthquakes at station SVA on Viti Levu show up to 1.0 s splitting with an average of 0.65 ± 0.29 s and a weak NNE preferred orientation of fast velocity. Polarizations of shear‐wave particle motions corrected for anisotropy are within 36°± 26° of polarizations predicted for nine moment tensor solutions. The magnitude of shear‐wave splitting and estimates of the thickness of the lithosphere in the Fiji region imply that the anisotropy cannot be contained in the lithosphere alone. Either the anisotropy is distributed in both the lithosphere and asthenosphere, or the asthenosphere alone is anisotropic.

We report a deficiency of luminous Lyman break galaxies (LBGs) with a large rest-frame equivalent width (EW rest ) of Lya emission at . Combining our spectroscopic sample of LBGs at and those from the z ∼ 5-6 z ∼ 5 literature, we found that luminous LBGs at generally show weak Lya emissions, while faint LBGs show z ∼ 5-6 a wide range of Lya EW rest and tend to have strong ( ) Lya emissions; i.e., there is a deficiencẙ EW տ 20 A rest of strong Lya emission in luminous LBGs. There seems to be a threshold UV luminosity for the deficiency; it is M 1400 p Ϫ21.5 to Ϫ21.0 mag, which is close to or somewhat brighter than the of the UV luminosity M * function at and 6. Since the large EW rest of Lya emission can be seen among the faint LBGs, the ratio of z ∼ 5 Lya emitters to LBGs may change rather abruptly with the UV luminosity. If the weakness of Lya emission is due to dust absorption, the deficiency suggests that luminous LBGs at tend to be in dusty and more z p 5-6 chemically evolved environments and that they begin star formation earlier than faint LBGs, although other causes cannot be ruled out.

Shear wave polarization anisotropy in the wedge portion of the upper mantle between a subducting plate and the earth's surface is investigated using three‐component seismograms of intermediate depth and deep earthquakes recorded at 14 local stations in Honshu, Japan. Eighty nine high‐quality seismograms were selected from a period of 3 years. The data used in this study are restricted such that incidence angles are smaller than the critical angle of 30° to the earth's surface in order to avoid phase shifts in the shear wave train. To find directions of the maximum and minimum velocities in split shear waves, where shear waves are resolved into two phases with the maximum time separation, each set of the two horizontal component seismograms is rotated in the horizontal plane. The split shear waves thus obtained are again recombined after the correction of anisotropy, and the anisotropy‐corrected particle motion is compared with the focal mechanism for a cross‐check of the observed anisotropy. Directions of the maximum axes are plotted on azimuthincidence angle stereograms at each station. The stereograms and the cross sections of seismic ray paths show that (1) the anisotropic material is distributed at intermediate location between earthquake sources and receiving stations, and (2) the anisotropic region is separated into two parts: one in the north of the present study area with the polarization of the maximum velocity shear wave trending 0° to 30° from the north (north anisotropy) and the other in the south with it trending 90° to 120° (south anisotropy). The maximum time delays between the two shear waves along a vertical seismic ray is about l s for both the anisotropic regions. The horizontal extent of the anisotropic area in the north is 50 km at depths of 50 to 150 km. perhaps prevalent in west Honshu. However, the depth of anisotropic material is not well constrained because of insufficient coverage of seismic ray paths and angles. If we assume the vertical extent of the anisotropic material to be 100 km, the maximum velocity contrast would be 4%. If we adopt a crack alignment model, for the observed anisotropy, cracks are inferred to be distributed vertically trending 0° to 30° in the north and 90° to 120° in the south. If we assume an olivine alignment model, olivine crystals are inferred to be aligned in the north with the a axis of the slip direction trending 0° to 30° and the slip plane normal to the b axis being vertical and in the south anisotropy with the axis trending 90° to 120° and the slip plane being horizontal.