UA Science

You are here

BASS Project

The Beijing-Arizona Sky Survey (BASS) is an ambitious wide-field multicolor survey of 5000 deg2 of the Northern Galactic Cap using the 90prime imager on the 2.3m Bok Telescope at Kitt Peak, as a three to four-year collaboration between the Chinese team led by NAOC and the US team led by Steward ObservatoryUniversity of Arizona. The survey will use approximately 240 nights, covering SDSS g and r bands, reaching limiting AB magnitudes of 24.0 and 23.4 (5σ compact extended source), respectively. This is roughly 1.5 magnitudes deeper than the corresponding SDSS imaging in this part of they sky, and will provide substantial legacy value for exploring the sky visible from the Northern hemisphere. The survey will follow the successful SCUSS mode with strong participation and support from teams in both China and the US to produce high level science products for the general astronomical community. Primary science objectives include investigating Galactic structure, the evolution of quasars, the clustering of galaxies, and transient events. 

The survey data will allow effective target selection for the DESI (Dark Energy Spectroscopic Instrument) survey project over the survey area. The BASS imaging in the optical g and r bands will be joined with z band imaging from the Kitt Peak 4-meter telescope (Mayall) located just up the ridge from the Bok, as part of the Mosaic z-band Legacy Survey (MzLS). Furthermore, the DECam Legacy Survey (DECaLS) is filling in the extragalactic sky below a declination of 30 degrees using the CTIO 4-meter (Blanco). The three DESI imaging surveys will be combined to enable target selection of faint galaxies and quasars over 14,000 square degrees of extragalactic sky with the 5000-fiber DESI spectrographs, providing exciting new constraints on the expansion history of the Universe and the nature of dark energy (for further details about DESI see the brochure here). 

Raw BASS data are provided to the community almost immediately after they are obtained, through the NOAO Science Archive (select "Bok 2.3m + 90Prime imager" for the "Telescope & Instrument"). Catalogs associated with a preliminary data release from 2015 observations can be queried through the Chinese Astronomical Data Center (CAsDC). Further public data releases will occur roughly annually. 

This plot shows the first-year coverage in the g and r bands. The survey is divided into three passes in each band, with each pass at roughly one-third the final depth. Field centers for the 90Prime pointings comprising BASS (tiles) are shown with gray crosses. Tiles that have been observed are shown in blue boxes, with the shade increasing based on the number of completed passes.

This photo shows a small section of a color image made from Bok g and r and NOAO Mosaic z-band.

You can get more information by talking to Ian McGreer or Xiaohui Fan.