Jean P. Picat

Virmos-VLT deep survey (VVDS)

The Virmos-VLT deep survey (VVDS) is aimed to study the evolution of galaxies, large scale structure and AGNs over more than 90% of the current age of the Universe, based on a large number (more than 100.000) of spectra of galaxies. In a first step, the Vimos Spectrograph will be used to measure all galaxies from magnitude limited samples. In a second step, near IR spectroscopy will be obtained with the Nirmos spectrograph, to measure redshifts in the critical range 1.2AB = 22.5. At the center of one region a deep survey will be conducted for galaxies brighter than IAB = 24. This deep region has also been imaged at the VLA (1400 MHz) to a flux limit of 0.08 mJy and is being observed in X-Rays with XMM.

Probing unexplored territories with MUSE: a second generation instrument for the VLT

The Multi Unit Spectroscopic Explorer (MUSE) is a second-generation VLT panoramic integral-field spectrograph under preliminary design study. MUSE has a field of 1x1 arcmin2 sampled at 0.2x0.2 arcsec2 and is assisted by the VLT ground layer adaptive optics ESO facility using four laser guide stars. The simultaneous spectral range is 0.465-0.93 μm, at a resolution of R~3000. MUSE couples the discovery potential of a large imaging device to the measuring capabilities of a high-quality spectrograph, while taking advantage of the increased spatial resolution provided by adaptive optics. This makes MUSE a unique and tremendously powerful instrument for discovering and characterizing objects that lie beyond the reach of even the deepest imaging surveys. MUSE has also a high spatial resolution mode with 7.5x7.5 arcsec2 field of view sampled at 25 milli-arcsec. In this mode MUSE should be able to obtain diffraction limited data-cubes in the 0.6-0.93 μm wavelength range. Although the MUSE design has been optimized for the study of galaxy formation and evolution, it has a wide range of possible applications; e.g. monitoring of outer planets atmosphere, environment of young stellar objects, super massive black holes and active nuclei in nearby galaxies or massive spectroscopic surveys of stellar fields in the Milky Way and nearby galaxies.

VIMOS and NIRMOS multi-object spectrographs for the ESO VLT

The VIRMOS consortium of French and Italian Institutes is manufacturing 2 wide field imaging multi-object spectrographs for the European Southern Observatory Very Large Telescope, with emphasis on the ability to carry over spectroscopic surveys of large numbers of sources. The Visible Multi-Object Spectrograph, VIMOS, is covering the 0.37 to 1 micron wavelength domain, with a full field of view of 4 by 7 by 8 arcmin2 in imaging and MOS mode. The Near IR Multi-Object Spectrograph, NIRMOS, is covering the 0.9 to 1.8 microns wavelength range, with afield of view 4 by 6 by 8 arcmin2 in MOS mode. The spectral resolution for both instrument scan reach up to R equals 5000 for a 0.5 arcsec wide slit. Multi-slit masks are produced by a dedicated Mask Manufacturing Machine cutting through thin Invar sheets and capable of producing 4 slit masks approximately 300 by 300 mm each with approximately slits 5.7 mm long in less than one hour. Integral field spectroscopy is made possible in VIMOS by switching in the beam specially build masks fed by 6400 fibers coming form a 54 by 54 arcsec2 integral field head with a 80 by 80 array of silica micro-lenses. NIRMOS has a similar IFS unit with a field of 30 by 30 arcmin2. These instruments are designed to offer very large multiplexing capabilities. In MOS mode, about 1000 objects can be observed simultaneously with VIMOS, with a S/N equals 10 obtained on galaxies with I equals 24 in one hour, and approximately 200 objects can be observed simultaneously with NIRMOS, with a S/N equals 10 obtained don galaxies with J equals 22, H equals 20.6 in 1h at Req equals 200. We present here the status of VIMOS, currently under final integration, with expected first light in the summer 2000, together with the final design of NIRMOS presented at the Final Design Review. The VLT-VIRMOS deep redshift survey of more with the final design of NIRMOS presented at the Final Design Review. The VLT-VIRMOS deep redshift survey of more than 150000 galaxies over the redshift range 0 < z < 5 will be undertaken based on 120 guaranteed nights awarded to the project.

VIRMOS: visible and infrared multiobject spectrographs for the VLT

We present the current design of the VIsible Multi-Object Spectrograph (VIMOS) and the Near InfraRed Multi-Object Spectrograph (NIRMOS) for the European Southern Observatory Very Large Telescope. The basic scientific requirement is to conduct very deep redshift surveys of large quantities of objects, in a minimum number of nights. The technical specifications are to allow for a large multiplex gain over a wide field, and a high efficiency of the optical train, over the 0.37 to 1.8 micrometer domain. The baseline technical concept is built around 4 channels, covering 4 X 7 X 8 arcmin2 for VIMOS and 4 X 7 X 7 arcmin2 for NIRMOS. Each channel is an imaging spectrograph with a large field adaptation lens, a collimator, grisms or filters, and a F/1.8 camera, coupled to a 2048 X 4096 pixels CCD for VIMOS, and a 20482 HgCdTe Rockwell array for NIRMOS. The unique multiplex gain allows to obtain spectra of up to 840 object simultaneously with VIMOS, and up to 170 with NIRMOS (10 arcsec slits). An integral field spectroscopy mode with more than 6400 fibers coupled to micro-lenses will be available for VIMOS, covering a 1 X 1 arcmin2 field. The VLT-VIRMOS survey of more than 150,000 galaxies is planned down to magnitudes IAB equals 24, coupled to an ultra deep probe to IAB equals 26.

The VIRMOS very wide integral field unit for the VLT: integration and performances

We present the integration and performances of the VLT-VIMOS Integral Field spectroscopy Unit. This unit allows to observe a very large 54x54 arcsec2 field on the side of the VIMOS instrument multi-object field in the range 0.37 - 1μm. This unit contains 6400 sets of micro-lenses - fibers - micro-lenses, producing the equivalent of a 72 arcmin x 0.67 arcsec slit projected on the sky. Two spatial resolutions (0.67 arcsec and 0.33 arcsec) are offered, coupled with the low and high spectral resolution of VIMOS. After reviewing the design philosophy, we are presenting the main steps and challenges encountered during integration. Calibration tests conducted in France and at the Paranal observatory as well as the data reduction software that has been developed for IFU are discussed. The first sky images of this very wide Integral Field Unit have been obtained in the early 2002 commissioning periods at VLT.

EMIR, cryogenic NIR multi-object spectrograph for GTC

EMIR is a near-IR, multi-slit camera-spectrograph under development for the 10m GTC on La Palma. It will deliver up to 45 independent R equals 3500-4000 spectra of sources over a field of view of 6 feet by 3 feet, and allow NIR imaging over a 6 foot by 6 foot FOV, with spatial sampling of 0.175 inch/pixel. The prime science goal of the instrument is to open K-band, wide field multi-object spectroscopy on 10m class telescopes. Science applications range from the study of star-forming galaxies beyond z equals 2, to observations of substellar objects and dust-enshrouded star formation regions. Main technological challenges include the large optics, the mechanical and thermal stability and the need to implement a mask exchange mechanism that does not require warming up the spectrograph. EMIR is begin developed by the Instituto de Astrofisica de Canarias, the Instituto Nacional de Tecnica Aeroespacial, the Universidad Complutense de Madrid, the Observatoire Midi-Pyrennees, and the University of Durham. Currently in its Preliminary Design phase, EMIR is expected to start science operation in 2004.

Handling atmospheric dispersion and differential refraction effects in large-field multiobject spectroscopic observations

The atmospheric refraction affects the position of objects in the sky in two ways: a chromatic effect and a field differential effect. The former is about the same in the field and can be, in principle, corrected using an Atmospheric Dispersion Compensator (ADC). The latter is dependent of the field size and cannot be corrected. For spectroscopy in wide fields, both effects have to be carefully considered because they affect the spectrophotometry in terms of signal to noise ratio and spectral distortions. The present study aims to evaluate the atmospheric effects in the case of the VIMOS instrument for the ESO VLT. It is shown that provided a careful operational mode the distortion of spectra can be kept at a level less than 15% with reasonable constraints.

Neoclassic Cosmological Tests with QSOs

A new cosmological test has been devised, based on QSO samples. Its sensitivity to the parent cosmology (Ω and Λ) and to the various other parameters has been checked with numerical simulations. In particular it is found that increasing the upper redshift limit is largely as efficient as increasing the sample size.