Abstracts: Poster Contributions

ESO Workshop on Scientific Drivers for ESO Future VLT/VLTI Instrumentation



Molecular Environment of the AGN in NGC1068 from H2 line emission observed with ANTU/ISAAC

E. Galliano & D. Alloin, ESO Santiago (Chile)

We discuss the distribution and kinematics of the molecular environment of the AGN in NGC1068 over the 1.5"x3.5" region around the central engine, derived from the H2 2.12 um line emission observed with ANTU/ISAAC. The H2 line profiles mapped over the region reveal a complex velocity field which can be modeled by the combination of keplerian motion plus wind component. At first order, the 140 km/s velocity jump observed between the eastern and western H2 emitting knots at a distance of around 70 pcs, indicates the presence of a massive object of 108 solar mass.


NEVEC: the NOVA ESO VLTI Expertise Centre

E.J. Bakker, I. Percheron, J. Meisner, J. de Jong, and L. Hartmann (NEVEC staff at the University of Leiden), A. Glindemann (ESO), W. Jaffe, R. Le Poole, G.K. Miley, H. Rottgering, and B. Heijligers (University of Leiden), L.B.F.M. Waters, R. van Boekel (University of Amsterdam), W. Cotton (NRAO), L. d'Arcio (SRON), W. Boland (NOVA)

The NOVA-ESO VLTI Expertise Centre (NEVEC) is a joint venture between the Netherlands Research school for Astronomy (NOVA) and the European Southern Observatory (ESO). NEVEC Headquarter (HQ) is located at Leiden Observatory with an additional office at the University of Amsterdam. NEVEC is funded by NOVA and formulated in a Memorandum of Understanding signed at the University of Amsterdam (UvA) on 31 May 1999, and inaugurated on May 26, 2000 in Leiden.

This paper gives an overview about the previous, current, and future activities of NEVEC. These include work on MIDI, PRIMA (including a pre-PRIMA survey), concepts for next generation VLTI instruments (e.g. homothetic mapping, nulling), VLTI calibration program, instrument models, data formats, VLTI commissioning, education in interferometry (e.g. Leiden summer school 2000), algorithm development, and scientific exploration of VLTI data.

Special attention will be give to the Dutch interest in the next generation VLTI instruments.


Satellite observations with ISAAC

A. Coustenis, E. Lellouch, B. Schmitt, J-G. Cuby, J-P. Maillard

We will observe Titan, Saturn's satellite with ISAAC at VLT/UT1 in November 2000. The aim is to record the satellite's spectrum in the 4.5-5 micron region in order to measure the CO abundance in the atmosphere, thus determining its origin and also to characterize the satellite's surface at 5 micron, and its possible variation with orbital longitude. In fine, these observations will further constrain the nature of bright and dark terrains at Titan's surface and help to maximize the scientific return of the Cassini mission.


Search for signatures of an exosphere around the extra-solar planet HD209458b

A. Coustenis (Paris), C. Moutou (ESO), J. Schneider (Paris), M. Mayor (Geneva), D. Queloz (Geneva), R. St Gilles (Paris)

The transit of the extra-solar planet orbiting HD209458 has been observed with UVES on the VLT. Faint absorption signatures are expected on top of the stellar spectrum, due to the extended envelope of gas possibly surrounding the planet - called exosphere. This challenging attempt of detecting chemical species in a distant and tenuous planetary atmosphere, is only possible with instruments such as UVES on the VLT. Indeed, the high spectral resolution, and high signal-to-noise ratio obtained with UVES are required to detect the faint absorption lines and to follow their time variability during the transit. Strong constraints could then be put on the atmospheric models of such objects.


Characterization of microlensing sources by multiple-beam phase-referenced interferometric imaging with the VLTI

F. Delplancke et al. (ESO)

Surveys such as MACHO and OGLE have revealed a wealth of photometric microlensing events. However, the interpretation of these events, and in particular the exact determination of the distance and mass of the lens, is subject to an underdetermination of observables with respect to the actual physical parameters at play in the phenomenon. Characterization of microlensing sources have been carried out so far only on a statistical basis. Interferometric imaging achieved by phase-referencing on simultaneous baselines can help to solve for all the physical parameters individually, including mass and distance of the lens. In practice, this will permit to make a 2-D image of the lensed star, to follow its evolution in time with sufficient resolution, and to measure astrometrically its parallax. The VLTI equipped with PRIMA will permit us a first approach to this problem, however an enhanced version capable of using simultaneously several baselines will be required for a full implementation of this method.


Zero noise CCD: a new readout technique for extremely low light level observations

J-L. Gach(1), D. Darson(2), C. Guillaume(3), C. Goillandeau(3), C. Cavadore(4), O. Boissin(1), J. Boulesteix(1).

(1)Observatoire de Marseille; (2)Ecole Normale Supérieure de Paris; (3)Observatoire de Haute-Provence; (4)ESO Optical Detector Team

Since the beginning of the CCDs, the only readout technique used up to now is the correlated double sampling scheme with bandwidth limitation. We developped a totally new technique based on the real time treatment of the output signal of the CCD by a digital signal processor: this allows complex filtering and better evaluation of the pixel charge. This technique is much more noiseless than the previous one and allows to read CCDs at a much lower readout noise, even without any noise in the near future. This is of prime importance for observations at very faint fluxes, dominated by detector noise and not shot noise. That kind of CCD systems could be used for medium to high resolution (both spatial and spectral) 3D spectroscopy of faint sources, and is unbeatable with scanning instruments such as FTS and Fabry Perot spectrographs. Since 8-10m class telescopes are pushing ground observations to fainter and fainter limits with higher and higher spatial resolution, noiseless detectors will become necessary to push even more away the limits.


FINITO: a fringe tracker for VLTI in two and three beam configuration

M. Gai(1), L. Corcione(1), D. Gardiol(1), A. Gennai(2), M.G. Lattanzi(1), D. Loreggia(1), G. Massone(1), S. Menardi(2)

(1) Osservatorio Astronomico di Torino (Italy) / (2) ESO

ESO and the Astronomical Observatory of Torino, Italy, are collaborating for development of a fringe sensor unit for VLTI, based on temporal modulation of the optical path and high sensitivity array detector, operating in H band.

The instrument will be used for set-up of the VLTI sub-systems, and it will stabilize the telescope beams for the first generation scientific instruments (AMBER, MIDI, VINCI), providing an improvement of up to 5 magnitudes in limiting sensitivity thanks to the extended integration time.

FINITO has dual feed capability over a 1 arcsecond field, on the UTs, so that significant regions around guide stars can be sampled. Moreover, it is able to operate either with two or three telescope beams, as required for closure phase measurements, to support future generation instruments.


The data reduction system of mid infrared instrument of the VLTI MIDI : software structures and algorithms

M. Nafati, G. Perin, Observatoire de Paris/Meudon (France)

This paper describes the structure design and algorithms of the data reduction system (DRS) of MIDI. The scientific purpose (first mode) of the DRS is to provide the visibility (modulus and phase if available) of the observed science sources. It can also provide facilities to reduce and analyze the data acquired with MIDI at an expert level (second mode). This capacity is mandatory for observation programs which will require the best performances of MIDI and also in case of trouble to understand the origins of the problems.

The Data Reduction System is an off-line process with respect to the global observation process. The first mode is called the scientific level and the modules associated to this level constitute the Scientific_Workbench software. The second mode is called the expert level with its associated Expert_Workbench software.

According to the MIDI (spatial filtering, spectral, chopping,·) modes of the instrument and their complexity, we expose our work in term of design and algorithms.

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CIRPASS - a near IR integral field and multi-object spectrograph

I.R. Parry (Institute of Astronomy, Cambridge)

We will describe CIRPASS (Cambridge IR PAnoramic Survey Spectrograph) which is a visitor instrument which will first be used on Gemini later this year. It is entirely fibre fed which makes it extremely versatile and easily interfaced to different telescopes including AO-feeds. It has a 490 element IFU which will be used both at the direct f/16 focus and with the AO system Hokupa'a on Gemini-N. The MOS mode will have 128 independent fibres. CIRPASS offers spectral resolutions from R=3,000 to R=26,000 in the wavelength range 0.85 to 1.8 microns and will use a 2kx2k Hawaii-2 array.


Large Quantitative Spectroscopy of Local Group Supergiants

N. Przybilla (USM, Munich), A. Kaufer (ESO, Chile), K.A. Venn (Macalester College, St. Paul), R.P. Kudritzki (IfA, Hawaii), D.J. Lennon (ING, La Palma), J.K. McCarthy (Palomar Observatory)

High resolution spectroscopy of luminous blue supergiants in Local Group galaxies can be performed with the new generation of large telescopes and dedicated instrumentation (VLT/UVES and KECK/HIRES). We present recent results on objects in NGC 6822 and M31, analysed with sophisticated non-LTE/LTE spectrum synthesis techniques. This study provides a wealth of information - detailed stellar parameters, chemical abundances, stellar wind properties, extinction - on single objects in different galactic environments and it also allows for a comparison of the performance of the instruments. Nevertheless, the analyses have to be viewed just as the beginning of further efforts with the future multi-object facilities at the VLT; detailed galactic studies will become feasible at a highly efficient use of telescope time.


Turning the problem around

A. Richichi et al. (ESO)

The mature life of the VLT Interferometer and its instrumentation will start with the availability of the PRIMA dual feed facility. Possible extensions of this latter might also be developed for use with second generation instrumentation, making it possible to combine and phase-reference several beams simultaneously. The introduction of the dual feed in interferometry will create a situation similar to that already experienced in Adaptive Optics, namely the fact that most scientific programs will be limited by the availability of a suitable reference star nearby. With sufficient time available in front of us, we propose to turn the problem around and investigate the surroundings of a large number of suitably bright reference stars, to compile a list of interesting objects which could be studied by the VLTI and its dual feed facility. This would permit to obtain accurate astrometry and/or detailed imaging of objects such as brown dwarfs, (micro)gravitational lenses, extragalactic sources. We discuss the needs and strategies to investigate the surroundings of a number of bright stars, using available near-IR surveys, as well as novel dedicated observations.


Red Extension of the Near Infrared VLTI Instrument AMBER

S. Robbe-Dubois, R.G. Petrov, S. Lagarde, et al.

The initial concept of the near-infrared VLTI instrument AMBER was defined having in mind a future extension of this instrument toward the red, at least down to the H alpha line. As the work has been progressing we had to make some trade off which limit the performance or even the feasibility of a direct extension. However, extending or partially duplicating AMBER to expand it to the red could allow to have a 3 telescopes VLTI instrument working in the visible quite earlier than a fully new and optimized instrument. A particularly important economy could be made in the development of the observation and instrument control software. This paper discusses the limitations, conditions and possibilities of such an extension. It will also tackle the requirements on the VLTI, such as Adaptive Optics modules for the Auxiliary Telescopes, which would be necessary to optimize such a development.


Crowded Field 3D Spectroscopy

M.M. Roth (Astrophysikalisches Institut Potsdam)

8-10m class telescopes are pushing ground-based observations to fainter and fainter limits. The spectroscopy of resolved objects near the crowded regions of nearby galaxies such as supergiants, AGB stars, planetary nebulae etc., which has now become possible even at 4m class telescopes under good seeing conditions, suffers from the contamination of the underlying background of unresolved stellar and gaseous emission. With data from prototype observations it is demonstrated how integral field spectroscopy can help to substantially improve the difficult background subtraction.


Scientific drivers for a future polarimetric mode for the VLTI

F. Vakili (OCA), F. Delplancke (ESO), K. Perraut (LAOG) and C. Stehle (DASGAL-Paris)

The scientific drivers and the concept of a polarimetric instrument for the VLTI, VISPER (Vlti Imaging Spectro-PolarimetER) will be presented.

Many scientific programs in stellar physics as well as in extra-galactic astronomy would benefit from interferometric high-resolution imaging combined with spectroscopy and polarimetric analysis. For example, the detection and characterisation of stellar spots on high-speed rotators needs the accurate measurement of the photometric barycenter differential movement between absorption line wavelengths and the continuum. The addition of polarimetric observations allows getting information related to the stellar magnetic field and gives insights into the star internal structure. This kind of studies requires very accurate measurements of the interferometric fringe phase and visibility as well as good spectral resolution (>10000) and a very stable instrument. As great care was taken of instrumental polarization effects during the design and construction of the VLTI, polarimetry could be straithforwardly implemented in the interferometric laboratory. Moreover, the phase-reference astrometric facility of the VLTI (PRIMA) will offer a very stable and accurate reference to measure small polarization effects on the visibility and astrometric position of the star at certain spectral lines.


MOEMS, key optical components for the future instrumentation of VLT

F. Zamkotsian, D. Burgarella, K. Dohlen, V. Buat and M. Ferrari

(Laboratoire d'Astrophysique de Marseille)

Scientific breakthroughs often follow technological breakthroughs permitting to make significant steps forward. Astronomical research of the next decade is related to the quest for our Origins: How did Galaxies form? How did Stars and Planetary Systems form? Can we detect Life in other Planets? The science requirements provided by those topics are very constraining for the future instrumentation of VLT, calling for high spatial and spectral resolutions, and high dynamic range and sensitivity. We are studying the application of an emerging key technology to achieve these aims. Based on the micro-electronics fabrication process, Micro-Opto-Electro-Mechanical Systems (MOEMS) are compact, scalable, replicable and may be customized for specific tasks. They will be widely integrated in next-generation astronomical instruments, such as Adaptive Optics (AO) systems and Multi-Object Spectrographs.

Using conventional deformable mirror technology, it is impossible to achieve the large number of actuators required for correction of high-order atmospheric perturbations. MOEMS will be able to overcome this limitation, and a long-term goal is the realization of a 100 000-actuator micro-deformable mirror for Extremely Large Telescopes. Future instrumentation of the VLT will also benefit from this technology providing replicable and compact mirrors for various AO systems. We will discuss recent developments of deformable mirrors in our collaboration with micro-opto-electronics laboratories and their integration in the FALCON project (François Hammer et al.).

For Multi-Object Spectroscopy, a promising solution for reconfigurable slit masks is the use of a Micro-Mirror Array (MMA). These electrostatically driven bistable mirrors, with a size of a few tens of micrometers, may generate any required slit configuration. We will present new observational modes provided by this concept and our expertise in the design of spectrographs based on MOEMS.