A New Constraint on the Lyα\alpha Fraction of UV Very Bright Galaxies at Redshift 7

We study the extent to which very bright (-23.0 < MUV < -21.75) Lyman-break selected galaxies at redshifts z~7 display detectable Lya emission. To explore this issue, we have obtained follow-up optical spectroscopy of 9 z~7 galaxies from a parent sample of 24 z~7 galaxy candidates selected from the 1.65 sq.deg COSMOS-UltraVISTA and SXDS-UDS survey fields using the latest near-infrared public survey data, and new ultra-deep Subaru z'-band imaging (which we also present and describe in this paper). Our spectroscopy has yielded only one possible detection of Lya at z=7.168 with a rest-frame equivalent width EW_0 = 3.7 (+1.7/-1.1) Angstrom. The relative weakness of this line, combined with our failure to detect Lya emission from the other spectroscopic targets allows us to place a new upper limit on the prevalence of strong Lya emission at these redshifts. For conservative calculation and to facilitate comparison with previous studies at lower redshifts, we derive a 1-sigma upper limit on the fraction of UV bright galaxies at z~7 that display EW_0 > 50 Angstrom, which we estimate to be < 0.23. This result may indicate a weak trend where the fraction of strong Lya emitters ceases to rise, and possibly falls between z~6 and z~7. Our results also leave open the possibility that strong Lya may still be more prevalent in the brightest galaxies in the reionization era than their fainter counterparts. A larger spectroscopic sample of galaxies is required to derive a more reliable constraint on the neutral hydrogen fraction at z~7 based on the Lya fraction in the bright galaxies.Comment: 20 pages, 7 figures, accepted for publication in Ap

The Mass-Dependent Clustering History of K-selected Galaxies at z < 4 in the SXDS/UDS Field

We investigate mass-dependent galaxy evolution based on a large sample of (more than 50,000) K-band selected galaxies in a multi-wavelength catalog of the Subaru/XMM-Newton Deep Survey (SXDS) and the UKIRT Infrared Deep Sky Survey (UKIDSS)/Ultra Deep Survey (UDS). We employ the optical to near-infrared photometry to determine photometric redshifts of these galaxies. Then, we estimate the stellar mass of our sample galaxies using a standard fitting procedure. From the sample galaxies, we obtain the stellar mass function of galaxies and the cosmic stellar mass density up to z<4. Our results are consistent with previous studies and we find a considerable number of low-mass galaxies (M<10^{10.5}) at the redshift range 3<z<4. The stellar-mass dependent correlation functions of our sample galaxies show clear evolution and they connect to that in the local universe consistently. Also, the massive galaxies show strong clustering throughout our studied redshift range. The correlation length of massive galaxies rapidly decreases from z=4 to 2. We also find some high mass density regions of massive galaxies at 1.4<z<2.5 in our sample, which may be candidate progenitors of the present-day clusters of galaxies. At this redshift range, massive star-forming galaxies are the dominant population making up the structures and the passively evolving galaxies show stronger clustering and they may have formed earlier than those star-forming galaxies.Comment: 13 pages, 13 figures, 2 table

First Data Release of the Hyper Suprime-Cam Subaru Strategic Program

The Hyper Suprime-Cam Subaru Strategic Program (HSC-SSP) is a three-layered imaging survey aimed at addressing some of the most outstanding questions in astronomy today, including the nature of dark matter and dark energy. The survey has been awarded 300 nights of observing time at the Subaru Telescope and it started in March 2014. This paper presents the first public data release of HSC-SSP. This release includes data taken in the first 1.7 years of observations (61.5 nights) and each of the Wide, Deep, and UltraDeep layers covers about 108, 26, and 4 square degrees down to depths of i~26.4, ~26.5, and ~27.0 mag, respectively (5sigma for point sources). All the layers are observed in five broad bands (grizy), and the Deep and UltraDeep layers are observed in narrow bands as well. We achieve an impressive image quality of 0.6 arcsec in the i-band in the Wide layer. We show that we achieve 1-2 per cent PSF photometry (rms) both internally and externally (against Pan-STARRS1), and ~10 mas and 40 mas internal and external astrometric accuracy, respectively. Both the calibrated images and catalogs are made available to the community through dedicated user interfaces and database servers. In addition to the pipeline products, we also provide value-added products such as photometric redshifts and a collection of public spectroscopic redshifts. Detailed descriptions of all the data can be found online. The data release website is https://hsc-release.mtk.nao.ac.jp/.Comment: 34 pages, 20 figures, 7 tables, moderate revision, accepted for publication in PAS

The Hyper Suprime-Cam SSP survey: Overview and survey design

Hyper Suprime-Cam (HSC) is a wide-field imaging camera on the prime focus of the 8.2-m Subaru telescope on the summit of Mauna Kea in Hawaii. A team of scientists from Japan, Taiwan, and Princeton University is using HSC to carry out a 300-night multi-band imaging survey of the high-latitude sky. The survey includes three layers: the Wide layer will cover 1400 deg2 in five broad bands (grizy), with a 5 σ point-source depth of r ≈ 26. The Deep layer covers a total of 26 deg2 in four fields, going roughly a magnitude fainter, while the UltraDeep layer goes almost a magnitude fainter still in two pointings of HSC (a total of 3.5 deg2). Here we describe the instrument, the science goals of the survey, and the survey strategy and data processing. This paper serves as an introduction to a special issue of the Publications of the Astronomical Society of Japan, which includes a large number of technical and scientific papers describing results from the early phases of this survey

Students' experiences of the transition from bilingual to mainstream instruction

Master of Modern Languages in EducationThe benefits and effectiveness of bilingual programs (immersion programs) have been widely recognized world-wide. Accordingly, the number of bilingual programs has been increasing, particularly in recent years. Although a number of researchers have reported positive outcomes from bilingual programs based on measurable evidence, evaluation of bilingual programs from the students' point of view has been very limited. This study aimed to provide a greater understanding of how the Japanese-English bilingual school graduates from different cultural and language backgrounds perceive their bilingual school experience and their present mainstream secondary school program. By comparing and contrasting these two programs, the students described what they appreciated and the advantages and disadvantages of the bilingual program for them. Moreover, they also expressed their experience of transition to a mainstream secondary school. This study has identified that the different cultural and language backgrounds of the students are not a big issue for the students and they described a number of advantages of bilingual schools. However, they also identified that sometimes the varied levels of Japanese competency among the students in the bilingual programs caused a lower motivation for some students. Although none of the students had any difficulty adapting to the mainstream secondary school, they are frustrated by their present LOTE classes as the content is not at an appropriate level for them and they are often treated as a "special" person in class due to their high level of Japanese skill

The Clustering History of K-selected Galaxies at z<4 in the SXDS/UDS Field

　We investigate mass-dependent galaxy evolution based on a large sample of, about 50,000, K-band selected galaxies in a multi-wavelength catalog of the Subaru/XMM- Newton Deep Survey (SXDS) and the UKIRT Infrared Deep Sky Survey (UKIDSS), Ultra Deep Survey (UDS). After we discriminate galaxies from stars and various false objects, we employ the optical to near-infrared photometry to determine photometric redshifts of these galaxies. Then, we estimate the stellar mass of our sample galaxies using the same standard fitting procedure as used for estimate the photometric redshift (photo-z). Since we employ exactly the same SED models both in the photo-z determination and mass estimation, stellar masses of galaxies thus obtained are internally consistent with the photo-z and other physical parameters of the best-fit SEDs, including age, metallicity, extinction due to the internal dust, etc. We compute the stellar mass function and the stellar mass density (SMD) up to redshift z=4. By combining a large number of stellar masses and spatial distributions of galaxies in one contiguous wide and deep field, we examine properties of the mass-dependent clustering of galaxies. Compared to previous studies, we are able to estimate stellar mass functions more accurately over the wider redshift range and, also, we can investigate properties of the K-selected galaxies to much lower-mass galaxies (M*~1010.5M&Theta;) at high-z (up to 3≦z　The clustering properties derived from our data are relatively free from the field-to-field variation with the aid of the wide survey area. This enables us to investigate not only the evolution of stellar mass of galaxies but also the clustering evolution of galaxies as a function of the stellar mass up to the redshift z = 4. 　In order to discuss the clustering properties of the galaxies quantitatively, we derive the two-point angular correlation functions (ACFs) w(θ), using the technique proposed by Landy & Szalay (1993). The ACF shows the clustering properties of galaxies projected on the sky. From a given angular clustering measurement, the correlation length r0 of galaxies for each mass range can be estimated by the Limber equation (Limber 1953) using the redshift distribution of galaxies and a choice of cosmology (e.g., Peebles 1980). Since the spatial correlation function (SCF) obtained from a combination of w(θ) and the redshift distribution of sample galaxies should reflect the intrinsic clustering in the space, r0 shows the spatial clustering strength of sample galaxies. An observed trend we found is in good agreement with the local scaling behavior of the clustering with stellar mass of galaxies. More massive galaxies have stronger clustering at z10.5M&Theta;10.9 M&Theta;) may also be hosted in somewhat lower-mass DHs at the various different redshifts. We find that the turning redshift point of changing the dark matter haloes hosting the intermediate-mass galaxies is at z~2. We also find several high mass density regions of massive galaxies at 1.4≦z1011.3 M&Theta; ). Thus, the massive galaxies at this epoch are dominated by the massive sBzK galaxies. These high mass-density regions may be the proto-clusters which evolve into the present-day massive clusters of galaxies. We also find that the average stellar mass of the pBzK galaxies at 1.4≦z10.8 M&Theta;. Although this average mass corresponds to that of the intermediate-mass galaxies, the clustering strength of the whole pBzK population is as high as that of the massive galaxies (M*≧1011 M&Theta;). This result may suggest that the clustering structure of pBzK galaxies formed earlier than that of the sBzK galaxies at 1.4≦z<2.5, and may imprint the large-scale structures of massive galaxies at the earlier epoch

Establishment of a monoclonal antibody PMab-233 for immunohistochemical analysis against Tasmanian devil podoplanin

Monoclonal antibodies (mAbs) against not only human, mouse, and rat but also rabbit, dog, cat, bovine, pig, and horse podoplanins (PDPNs) have been established in our previous studies. PDPN is used as a lymphatic endothelial cell marker in pathological diagnoses. However, mAbs against Tasmanian devil PDPN (tasPDPN), which are useful for immunohistochemical analysis, remain to be developed. Herein, mice were immunized with tasPDPN-overexpressing Chinese hamster ovary (CHO)-K1 (CHO/tasPDPN) cells, and hybridomas producing mAbs against tasPDPN were screened using flow cytometry. One of the mAbs, PMab-233 (IgG1, kappa), specifically detected CHO/tasPDPN cells by flow cytometry and recognized tasPDPN protein by western blotting. Furthermore, PMab-233 strongly detected CHO/tasPDPN cells by immunohistochemistry. These findings suggest that PMab-233 may be useful as a lymphatic endothelial cell marker of the Tasmanian devil. Keywords: Tasmanian devil podoplanin, PDPN, PMab-23