Hyper Suprime-Cam (HSC) is a wide-field imaging camera on the prime focus of the 8.2m Subaru telescope on the summit of Maunakea 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 deg 2 in five broad bands (grizy), with a 5 σ point-source depth of r ≈ 26. The Deep layer covers a total of 26 deg 2 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 deg 2). 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.

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.

We present luminosity functions (LFs) and various properties of Ly emitters (LAEs) at z ¼ 3:1, 3.7, and 5.7, in a 1 deg 2 sky of the Subaru /XMMÀNewton Deep Survey (SXDS) Field. We obtain a photometric sample of 858 LAE candidates based on deep Subaru Suprime-Cam imaging data and a spectroscopic sample of 84 confirmed LAEs from Subaru FOCAS and VLT VIMOS spectroscopy in a survey volume of $106 Mpc 3 with a limiting Ly luminosity of $3 ; 10 42 ergs s À1. We derive the LFs of the Ly and UV continuum ('1500 8) for each redshift, taking into account the statistical error and the field-to-field variation. We find that the apparent Ly LF shows no significant evolution between z ¼ 3:1 and 5.7 within factors of 1.8 and 2.7 in L à and à , respectively. On the other hand, the UV LF of LAEs increases from z ¼ 3:1 to 5.7, indicating that galaxies with Ly emission are more common at earlier epochs. We identify six LAEs with AGN activities from our spectra combined with VLA, Spitzer, and XMM-Newton data. Among the photometrically selected LAEs at z ¼ 3:1 and 3.7, only '1% show AGN activities, while the brightest LAEs with log L(Ly) k 43:4 43:6 ergs s À1 appear to always host AGNs. Our LAEs are bluer in UV-continuum color than dropout galaxies, suggesting lower extinction and/or younger stellar populations. Our stacking analyses provide upper limits to the radio luminosity and the f He ii /f Ly line fraction and constrain the hidden star formation (+low-luminosity AGN ) and the primordial population in LAEs.

In this paper, we describe the optical imaging data processing pipeline developed for the Subaru Telescope's Hyper Suprime-Cam (HSC) instrument. The HSC Pipeline builds on the prototype pipeline being developed by the Large Synoptic Survey Telescope's Data Management system, adding customizations for HSC, large-scale processing capabilities, and novel algorithms that have since been reincorporated into the LSST codebase. While designed primarily to reduce HSC Subaru Strategic Program (SSP) data, it is also the recommended pipeline for reducing general-observer HSC data. The HSC pipeline includes high level processing steps that generate coadded images and science-ready catalogs as well as low-level detrending and image characterizations.