Scientists Releases Cosmic Census Data

The first massive data set of a “cosmic census” has been released using the largest digital camera on the Subaru Telescope.

With its beautiful images now available for the public at large, figuring out the fate of the Universe has come one step closer.

Data from the Hyper Suprime-Cam Subaru Strategic Program (HSC-SSP) was released to the public in February 2017.

HSC-SSP is a large survey being done using HSC, an optical imaging camera mounted at the prime focus of the Subaru Telescope. Since it is difficult to search such a huge dataset with standard tools, the National Astronomical Observatory of Japan (NAOJ) has developed a dedicated database and interface for ease of access and use of the data.

NAOJ embarked on the HSC-SSP survey in collaboration with the Kavli Institute for the Physics and Mathematics of the Universe (Kavli IPMU) in Japan, the Academia Sinica Institute of Astronomy and Astrophysics (ASIAA) in Taiwan, and Princeton University in the United States.

The project will survey 300 nights over 5 to 6 years. This survey consists of three layers: Wide, Deep, and UltraDeep, using optical and near infrared wavelengths in five broad bands (g, r, i, z, y) and four narrow-band filters.

This first public dataset already contains almost 100 million galaxies and stars. It demonstrates that HSC-SSP is making the most from the performance of the Subaru Telescope and HSC. In contrast, the US-based Sloan Digital Sky Survey (SDSS) — which is known for its wide area observation and equivalent data sets — took over 10 years to establish.

The total amount of data taken so far by the HSC-SSP, meanwhile, comprises 80 terabytes, which is comparable to the size of about 10 million images by a general digital camera.

This release includes data from the first 1.7 years (61.5 nights of observations beginning in 2014). The observed areas covered by the Wide, Deep, and UltraDeep layers are 108, 26, and 4 square degrees, respectively.

The limiting magnitudes, which refer to the depth of the observations, are 26.4, 26.6 and 27.3 mag in r-band (about 620 nm wavelength), respectively, allowing observations of some of the most distant galaxies in the Universe.

In multi-band images, the images are extremely sharp, with only 0.6 to 0.8 arcseconds across for point-like objects like stars. One arcsecond equals 3600th part of a degree. The high-quality data will allow an unprecedented view into the nature and evolution of galaxies and dark matter.