WEAVE-StePS: A stellar population survey using WEAVE at WHT

¹ INAF – Osservatorio Astronomico di Brera, Via Brera 28, 20121 Milano, Italy
e-mail: angela.iovino@inaf.it
² INAF – Osservatorio Astronomico di Padova, Vicolo dell’Osservatorio 5, 35122 Padova, Italy
³ INAF – Osservatorio Astronomico di Capodimonte, Via Moiariello 16, 80131 Napoli, Italy
⁴ Dipartimento di Fisica ‘E.R. Caianiello’, Università degli studi di Salerno, Via Giovanni Paolo II 132, 84084 Fisciano, (SA), Italy
⁵ INAF – Osservatorio di Astrofisica e Scienza dello Spazio, Via P. Gobetti 93/3, 40129 Bologna, Italy
⁶ Instituto de Astronomía y Ciencias Planetarias de Atacama (INCT), Universidad de Atacama, Copayapu 485, Copiapó, Chile
⁷ INAF – Osservatorio Astrofisico di Arcetri, Largo Enrico Fermi 5, 50125 Firenze, Italy
⁸ Centro de Astrobiología (CSIC-INTA), Ctra de Ajalvir km 4, Torrejón de Ardoz, 28850 Madrid, Spain
⁹ Università degli studi di Milano-Bicocca, Piazza della Scienza, 20125 Milano, Italy
¹⁰ Isaac Newton Group of Telescopes, ING, 38700 La Palma, (SC Tenerife), Spain
¹¹ Instituto de Astrofísica de Canarias, IAC, Vía Láctea s/n, 38205 La Laguna, (SC Tenerife), Spain
¹² Departamento de Astrofísica, Universidad de La Laguna, 38206 La Laguna, (SC Tenerife), Spain
¹³ School of Physics and Astronomy, University of Birmingham, Birmingham, B15 2TT UK
¹⁴ INAF – IASF Milano, Via Bassini 15, 20133 Milano, Italy
¹⁵ Dipartimento di Fisica e Astronomia “G. Galilei”, Università di Padova, Vicolo dell’Osservatorio 3, 35122 Padova, Italy
¹⁶ Dept. Physics, University of Oxford, Keble Road, Oxford, OX1 3RH UK
¹⁷ RAL, Space, Science and Technology Facilities Council, Harwell, Didcot, OX11 0QX UK
¹⁸ Instituto de Astrofísica de Andalucía (CSIC), PO Box 3004 18080 Granada, Spain
¹⁹ Kapteyn Astronomical Institute, Rijksuniversiteit Groningen, Landleven 12, 9747 AD Groningen, The Netherlands
²⁰ SRON – Netherlands Institute for Space Research, Landleven 12, 9747 AD Groningen, The Netherlands
²¹ Institute of Astronomy, University of Cambridge, Madingley Road, Cambridge, CB3 0HA UK
²² Departamento de Física de la Tierra y Astrofísica, Universidad Complutense de Madrid, 28040 Madrid, Spain
²³ Instituto de Física de Partículas y del Cosmos (IPARCOS), Universidad Complutense de Madrid, 28040 Madrid, Spain
²⁴ Università di Bologna – Department of Physics and Astronomy, Via Gobetti 93/2, 40129 Bologna, Italy

Received: 27 October 2022
Accepted: 18 January 2023

Abstract

Context. The upcoming new generation of optical spectrographs on four-meter-class telescopes will provide valuable opportunities for forthcoming galaxy surveys through their huge multiplexing capabilities, excellent spectral resolution, and unprecedented wavelength coverage.

Aims. WEAVE is a new wide-field spectroscopic facility mounted on the 4.2 m William Herschel Telescope in La Palma. WEAVE-StePS is one of the five extragalactic surveys that will use WEAVE during its first five years of operations. It will observe galaxies using WEAVE MOS (∼950 fibres distributed across a field of view of ∼3 square degrees on the sky) in low-resolution mode (R ∼ 5000, spanning the wavelength range 3660 − 9590 Å).

Methods. WEAVE-StePS will obtain high-quality spectra (S/N ∼ 10 Å⁻¹ at R ∼ 5000) for a magnitude-limited (I_AB = 20.5) sample of ∼25 000 galaxies, the majority selected at z ≥ 0.3. The survey goal is to provide precise spectral measurements in the crucial interval that bridges the gap between LEGA-C and SDSS data. The wide area coverage of ∼25 square degrees will enable us to observe galaxies in a variety of environments. The ancillary data available in each of the observed fields (including X-ray coverage, multi-narrow-band photometry and spectroscopic redshift information) will provide an environmental characterisation for each observed galaxy.

Results. This paper presents the science case of WEAVE-StePS, the fields to be observed, the parent catalogues used to define the target sample, and the observing strategy that was chosen after a forecast of the expected performance of the instrument for our typical targets.

Conclusions. WEAVE-StePS will go back further in cosmic time than SDSS, extending its reach to encompass more than ∼6 Gyr. This is nearly half of the age of the Universe. The spectral and redshift range covered by WEAVE-StePS will open a new observational window by continuously tracing the evolutionary path of galaxies in the largely unexplored intermediate-redshift range.