The Hyper Suprime-Cam SSP Survey: Overview and Survey Design

TL;DR

The paper introduces the Hyper Suprime-Cam Subaru Strategic Program (HSC-SSP), detailing its motivation to address dark matter, dark energy, and high-redshift galaxy evolution through a three-tier imaging survey (Wide, Deep, UltraDeep) using the Hyper Suprime-Cam on the Subaru telescope. It describes the instrument's capabilities, the survey design, target fields, observing cadence, and pointing strategy, and outlines the data processing pipeline (hscPipe) and validation tools (SynPipe) that enable high-precision photometry, astrometry, and weak-lensing analyses. The work sets the stage for rich cosmological and astrophysical results, including photometric redshifts, galaxy shapes for weak lensing, and the discovery of high-z galaxies and supernovae, with data releases and planned spectroscopic follow-up under the SuMIRe framework. Overall, the paper establishes the technical foundation, survey architecture, and data-processing framework necessary for transformative wide-field cosmology with HSC.

Abstract

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 $r \approx 26$. 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.

Figures (7)

• Figure 1: The layout of 116 CCD chips, each of which has 2048$\times 4096$ pixels ($5.73^\prime \times 11.47^\prime$), on the focal plane. The CCD chips are arranged with two different gaps of approximately 12$^{\prime\prime}$ and $53^{\prime\prime}$ between the neighboring chips. The focal plane is approximately $1.5^\circ$ in diameter. There are 104 science chips (indicated in blue), 4 chips used for auto-guiding (in yellow) and 8 chips for monitoring the focus (in light red). Each chip is identified with a number from 0 to 115.
• Figure 2: The HSC bandpasses, including the reflectivity of all mirrors, transmission of all optics and filters as well as the atmosphere, and response of the CCDs, assuming an airmass of 1.2. Both the broad-band and narrow-band filters used in the survey are shown. The lower panel shows the spectrum of sky emission lines, demonstrating that the red narrow-band filters lie in relatively dark regions of the sky spectrum.
• Figure 3: The location of the HSC-Wide, Deep, and UltraDeep fields and the AEGIS field on the sky in equatorial coordinates. The color scale gives the level of Galactic dust extinction from SFD, as denoted by the color bar. See Figure \ref{['fig:deep_fields']} for the details of the Deep and UltraDeep fields.
• Figure 4: The blue and dark-green circles show locations of the fiducial pointings of the Deep and UltraDeep fields, respectively (see Table \ref{['tab:field_names']}). We have an additional five dithered pointings around each fiducial pointing, as described in the text.
• Figure 5: The spatial distribution of the number of visits in an example region of the Wide layer. The left and right panels show the coverage in the $g$ and $z$ bands, respectively. The solid circles show the fiducial pointings around which dithering is carried out (4 and 6 visits for $gr$ or $izy$, respectively). Full depth for the Wide layer corresponds to greenish regions in each panel.