DESI

Five thousand robotic fibre positionersmulti-object spectroscopyTaking spectra of many chosen targets in one field at once, through fibres placed by robotic positioners (DESI, SDSS-V) or through programmable slits and shutters (JWST NIRSpec). The basis of redshift surveys. across a 3° field on the Mayall 4 m feed ten spectrographs covering 360–980 nm at R ≈ 2000–5500. Its redshiftredshiftz = λ_observed/λ_emitted − 1, the stretching of light by cosmic expansion (or by recession). For distant sources it stands in for distance and look-back time: z ≈ 1 is about 8 Gyr ago, z ≈ 10 about 13.3 Gyr. survey of bright galaxies, luminous red galaxies, emission-line galaxies, quasars and the Lyman-α forest measures baryon acoustic oscillationsbaryon acoustic oscillationsA preferred separation of about 150 Mpc (comoving) in the galaxy distribution, imprinted by sound waves in the early Universe. Measuring it at many redshifts traces the expansion history like a standard ruler. and redshift-space distortionsredshift-space distortionsAnisotropy in the clustering of galaxies mapped by redshift, caused by their peculiar velocities falling into structures. Measures the growth rate of structure. from z ≈ 0.1 to beyond 3.

Operator

DOE

Site

Kitt Peak, Arizona (Mayall 4 m)

Aperture

4 m

Passband

360 nm – 980 nm

Survey start

14 May 2021