Isabelle Guinouard

Proceedings of the SPIE

Wide-field multi-object spectroscopy is a high priority for European astronomy over the next decade. Most 8-10m telescopes have a small field of view, making 4-m class telescopes a particularly attractive option for wide-field instruments. We present a science case and design drivers for a wide-field multi-object spectrograph (MOS) with integral field units for the 4.2-m William Herschel Telescope (WHT) on La Palma. The instrument intends to take advantage of a future prime-focus corrector and atmospheric-dispersion corrector (Agocs et al, this conf.) that will deliver a field of view 2 deg in diameter, with good throughput from 370 to 1,000 nm. The science programs cluster into three groups needing three different resolving powers R: (1) high-precision radial-velocities for Gaia-related Milky Way dynamics, cosmological redshift surveys, and galaxy evolution studies (R = 5,000), (2) galaxy disk velocity dispersions (R = 10,000) and (3) high-precision stellar element abundances for Milky Way archaeology (R = 20,000). The multiplex requirements of the different science cases range from a few hundred to a few thousand, and a range of fibre-positioner technologies are considered. Several options for the spectrograph are discussed, building in part on published design studies for E-ELT spectrographs. Indeed, a WHT MOS will not only efficiently deliver data for exploitation of important imaging surveys planned for the coming decade, but will also serve as a test-bed to optimize the design of MOS instruments for the future E-ELT.

WEAVE: the next generation wide-field spectroscopy facility for the William Herschel Telescope

We present the preliminary design of the WEAVE next generation spectroscopy facility for the William Herschel Telescope (WHT), principally targeting optical ground-based follow up of upcoming ground-based (LOFAR) and spacebased (Gaia) surveys. WEAVE is a multi-object and multi-IFU facility utilizing a new 2 degree prime focus field of view at the WHT, with a buffered pick and place positioner system hosting 1000 multi-object (MOS) fibres or up to 30 integral field units for each observation. The fibres are fed to a single spectrograph, with a pair of 8k(spectral) x 6k (spatial) pixel cameras, located within the WHT GHRIL enclosure on the telescope Nasmyth platform, supporting observations at R~5000 over the full 370-1000nm wavelength range in a single exposure, or a high resolution mode with limited coverage in each arm at R~20000.

The FALCON Concept: Multi-Object Spectroscopy Combined with MCAO in Near-IR

A large fraction of the present-day stellar mass was formed between z = 0.5 and z ~ 3 and our understanding of the formation mechanisms at work at these epochs requires both high spatial and high spectral resolution: one shall simultaneously obtain images of objects with typical sizes as small as 1–2 kpc (~ 0″.1), while achieving 20–50 km/s (R≥ 5000) spectral resolution. In addition, the redshift range to be considered implies that most important spectral features are redshifted in the near-infrared. The obvious instrumental solution to adopt in order to tackle the science goal is therefore a combination of multi-object 3D spectrograph with multi-conjugate adaptive optics in large fields. A very promising way to achieve such a technically challenging goal is to relax the conditions of the traditional full adaptive optics correction. A partial, but still competitive correction shall be prefered, over a much wider field of view. This can be done by estimating the turbulent volume from sets of natural guide stars, by optimizing the correction to several and discrete small areas of few arcsec 2 selected in a large field (Nasmyth field of 25 arcmin) and by correcting up to the 6th, and eventually, up to the 60th Zernike modes. Simulations on real extragalactic fields, show that for most sources (> 80%), the recovered resolution could reach 0″. 15–0″.25 in the J and H bands. Detection of point-like objects is improved by factors from 3 to ≥10, when compared with an instrument without adaptive correction. The proposed instrument concept, FALCON, is equipped with deployable mini-integral field units (IFUs), achieving spectral resolutions between R=5000 and 20000. Its multiplex capability, combined with high spatial and spectral resolution characteristics, is a natural ground based complement to the next generation of space telescopes. Galaxy formation in the early Universe is certainly a main science driver. We describe here how FALCON shall allow to answer puzzling questions in this area, although the science cases naturally accessible to the instrument concept makes it of interest for most areas of astrophysics.

Project overview of OPTIMOS-EVE: the fibre-fed multi-object spectrograph for the E-ELT

OPTIMOS-EVE (OPTical Infrared Multi Object Spectrograph - Extreme Visual Explorer) is the fibre fed multi object spectrograph proposed for the European Extremely Large Telescope (E-ELT), planned to be operational in 2018 at Cerro Armazones (Chile). It is designed to provide a spectral resolution of 6000, 18000 or 30000, at wavelengths from 370 nm to 1.7 μm, combined with a high multiplex (>200) and a large spectral coverage. Additionally medium and large IFUs are available. The system consists of three main modules: a fibre positioning system, fibres and a spectrograph. The recently finished OPTIMOS-EVE Phase-A study, carried out within the framework of the ESO E-ELT instrumentation studies, has been performed by an international consortium consisting of institutes from France, Netherlands, United Kingdom and Italy. All three main science themes of the E-ELT are covered by this instrument: Planets and Stars; Stars and Galaxies; Galaxies and Cosmology. This paper gives an overview of the OPTIMOS-EVE project, describing the science cases, top level requirements, the overall technical concept and the project management approach. It includes a description of the consortium, highlights of the science drivers and resulting science requirements, an overview of the instrument design and telescope interfaces, the operational concept, expected performance, work breakdown and management structure for the construction of the instrument, cost and schedule.

X-Shooter: A Medium-resolution, Wide-Band Spectrograph for the VLT

X-shooter is the first second-generation instrument for the ESO Very Large Telescope, and will be installed in 2008. It is intended to become the most powerful optical & near-infrared medium-resolution spectrograph in the world, with a unique spectral coverage from 300 to 2500 nm in one shot. The X-shooter consortium members are from Denmark, France, Italy, The Netherlands and ESO.

Final design and progress of WEAVE: the next generation wide-field spectroscopy facility for the William Herschel Telescope

We present the Final Design of the WEAVE next-generation spectroscopy facility for the William Herschel Telescope (WHT), together with a status update on the details of manufacturing, integration and the overall project schedule now that all the major fabrication contracts are in place. We also present a summary of the current planning behind the 5-year initial phase of survey operations. WEAVE will provide optical ground-based follow up of ground-based (LOFAR) and space-based (Gaia) surveys. WEAVE is a multi-object and multi-IFU facility utilizing a new 2-degree prime focus field of view at the WHT, with a buffered pick-and-place positioner system hosting 1000 multi-object (MOS) fibres, 20 integral field units, or a single large IFU for each observation. The fibres are fed to a single (dual-beam) spectrograph, with total of 16k spectral pixels, located within the WHT GHRIL enclosure on the telescope Nasmyth platform, supporting observations at R~5000 over the full 370-1000nm wavelength range in a single exposure, or a high resolution mode with limited coverage in each arm at R~20000. The project is now in the manufacturing and integration phase with first light expected for early of 2018.

On-sky tests of sky-subtraction methods for fiber-fed spectrographs

We present preliminary results on on-sky test of sky subtraction methods for fiber-fed spectrograph. Using dedicated observation with FLAMES/VLT in I-band, we have tested the accuracy of the sky subtraction for 4 sky subtraction methods: mean sky, closest sky, dual stare and cross-beam switching. The cross beam-switching and dual stare method reach accuracy and precision of the sky subtraction under 1%. In contrast to the commonly held view in the literature, this result points out that fiber-fed spectrographs are adapted for the observations of faint targets.

Overview of the GYES instrument: a multifibre high-resolution spectrograph for the prime focus of the Canada-France-Hawaii Telescope

ESAs cornerstone mission Gaia will construct a billion-star catalogue down to magnitude 20 but will only provide detailed chemical information for the brighter stars and will be lacking radial velocity at the faint end due to insufficient Signal-to-Noise Ratios (SNR). This calls for the deployment of a ground spectrograph under time scales coherent with those of Gaia for a complementary survey. The GYES instrument is a high resolution (~ 20,000) spectrometer proposed for installation on the Canada- France-Hawaii Telescope (CFHT) to perform this survey in the northern hemisphere. It exploits the large Field of View (FoV) available at the prime focus together with a high multiplex (~ 500 fibres) to achieve a SNR of 30 in two hours at magnitude 16 and render the survey possible on the order of 300 nights. The on-going feasibility study aims at jointly optimising all components of the system: the field corrector, the positioner, the fibres and the spectrograph. The key challenges consist in accommodating the components in the highly constrained environment of the primary focus, as well as in achieving maximum efficiency thanks to high transmission and minimum reconfiguration delays. Meanwhile, for GYES to have its first light at the time of Gaias initial data release (2014-2015), it is mandatory to keep its complexity down by designing a predominantly passive instrument.

Performances of X-shooter, the new wide-band intermediate resolution spectrograph at the VLT

X-shooter is the first second-generation instrument newly commissioned a the VLT. It is a high efficiency single target intermediate resolution spectrograph covering the range 300 - 2500 nm in a single shot. We summarize the main characteristics of the instrument and present its performances as measured during commissioning and the first months of science operations.

Updated optical design and trade-off study for MOONS, the Multi-Object Optical and Near Infrared spectrometer for the VLT

This paper presents the latest optical design for the MOONS triple-arm spectrographs. MOONS will be a Multi-Object Optical and Near-infrared Spectrograph and will be installed on one of the European Southern Observatory (ESO) Very Large Telescopes (VLT). Included in this paper is a trade-off analysis of different types of collimators, cameras, dichroics and filters.