Hyper Suprime-Cam Subaru Strategic Survey in a Nutshell
The HSC-SSP a three-layered, multi-band (grizy plus 4 narrow-band filters) imaging survey with the Hyper Suprime-Cam (HSC) on the 8.2m Subaru Telescope. HSC has 104 science CCDs covering a 1.5 degree diameter field of view with a 0.168 arcsec pixel scale. The delivered image quality is excellent across the field of view; the median seeing in the i-band is about 0.6 arcsec. Each of the Wide, Deep, and UltraDeep layer covers 1400 deg2 (r~26), 27 deg2 (r~27), and 3.5 deg2 (r~28), respectively. By combining data from these layers, we address some of the most pressing problems in modern cosmology and astrophysics with a particular focus on gravitational weak lensing, galaxy evolution, supernovae, and galactic structure. The survey is uniquely designed to enable various science cases, with particular attention to controlling systematic errors. The survey is awarded 300 nights over 5-6 years and it started in March 2014.
|Layer||Area (deg2)||# of 1.8deg2 HSC fields||Filters & Depth|
|Wide||1400||916||grizy (r ~ 26)|
|Deep||27||15||grizy+3NBs (r ~ 27)|
|Ultradeep||3.5||2||grizy+3NBs (r ~ 28)|
Filters and Depths
The nature, depth, and solid angle of each filter for the HSC survey are carefully determined to meet the main science requirements. The following table summarizes the filters and depths for each survey layer. The exposure here is the total exposure time (e.g., g-band in the Wide layer is 2.5 min x 4 exposures = 10 min). The limiting magnitudes are 5 sigma limits within 2 arcsec diameter apertures and they include effects of source confusion. For point sources under FWHM=0.9 seeing, the depths are 0.3 mag deeper. The filter response functions are described in detail in Kawanomoto et al. (2018). The total responses shown in the figure above are available here. For the atmosphere, we assumed airmass=1.2 (which is close to the median airmass of the survey) and PWV=1.5mm. You can find some more information on the camera responses in the observatory’s page.
|Layer||Filter||Exptime (# of exposures)||Total nights||Lim. mag.||Moon phase|
|Wide||g,r||10min (4)||53||26.5, 26,1||dark|
|Wide||z,y||20min (6)||108||25.1, 24.4||gray|
|Deep||g,r||1.4hrs (10)||7.3||27.5, 27.1||dark|
|UD||g,r||7hrs (20)||4.8||28.1, 27.7||dark|
|UD||z,y||18.9hrs (20)||13||26.8, 26.3||gray|
|Wide||Spring and autumn equatorial stripes, Hectomap|
|Deep||XMM-LSS, E-COSMOS, ELAIS-N1, DEEP2-F3|
The fields are chosen to satisfy the following conditions:
- The fields overlap with other multi-wavelength data sets to maximize scientific potential when combined with the HSC data. The major data sets which offer unique synergy with HSC data are the arcminute-resolution, high-sensitivity CMB survey by ACT in Chile, and its polarization extension ACTPol; X-ray surveys from XMM and eROSITA; near-/mid-infrared imaging surveys (e.g., VIKING/VIDEO and UKIDSS); and deep spectroscopic surveys (e.g., VIPERS, GAMA, COSMOS, HectoMAP).
- The Ultradeep regions are included in the Deep fields, and the Deep fields are included in the Wide fields. ELAIS-N1 is an exception here.
- The fields are chosen to be low in Galactic dust extinction.