Abstract

WEAVE is the next-generation wide-field survey facility for the William Herschel Telescope (WHT). WEAVE will provide the instrument required for full scientific exploitation of the Gaia, LOFAR , and APERTIF surveys in the Northern Hemisphere. WEAVE is a multi-object and multi-integral-field-unit (IFU) facility utilizing a large, new 2-degree-diameter prime focus corrector at the WHT with a pick-and-place fibre positioner system hosting nearly 1000 multi-object fibres or 20 mini-IFUs for each observation, or a single wide-field IFU . The fibres are fed into a dual-beam spectrograph located in the GHRIL enclosure on the WHT ’s Nasmyth platform. The spectrograph records nearly 1000 spectra simultaneously at a resolution of R _{5000 over an instantaneous wavelength range of 366-959 nm or at a resolution of R} 20000 over two more-limited wavelength ranges. WEAVE has been on sky since late 2022. The WEAVE Survey will provide complete phase-space coordinates of roughly 3 million stars in the northern sky selected with ESO ’s Gaia satellite, chemical analysis of more than 1 million stars from Gaia, half a million massive stars in the Galactic Plane, distances and properties of galaxies selected from the low-frequency radio-wave surveys being conducted with LOFAR , “three-dimensional” spectroscopy of galaxies selected from surveys using the new Apertif focal plane array at WSRT , and deep surveys of galaxy clusters and moderate-redshift galaxies. In this talk I will discuss the motivation, design, construction, and commissioning of WEAVE and the impressive “first-light” and Science Verification data we’ve already collected with it.