Mid-infrared sizes of circumstellar disks around Herbig Ae/Be stars measured with MIDI on the VLTI

We present the first long baseline mid-infrared interferometric observations of the circumstellar disks surrounding Herbig Ae/Be stars. The observations were obtained using the mid-infrared interferometric instrument MIDI at the European Southern Observatory (ESO) Very Large Telescope Interferometer VLTI on Cerro Paranal. The 102 m baseline given by the telescopes UT1 and UT3 was employed, which provides a maximum full spatial resolution of 20 milli-arcsec (mas) at a wavelength of 10 μm. The interferometric signal was spectrally dispersed at a resolution of 30, giving spectrally resolved visibility information from 8 μm to 13.5 μm. We observed seven nearby Herbig Ae/Be stars and resolved all objects. The warm dust disk of HD 100546 could even be resolved in single-telescope imaging. Characteristic dimensions of the emitting regions at 10 μm are found to be from 1 AU to 10 AU. The 10 μm sizes of our sample stars correlate with the slope of the 10–25 μm infrared spectrum in the sense that the reddest objects are the largest ones. Such a correlation would be consistent with a different geometry in terms of flaring or flat (self-shadowed) disks for sources with strong or moderate mid-infrared excess, respectively. We compare the observed spectrally resolved visibilities with predictions based on existing models of passive centrally irradiated hydrostatic disks made to fit the SEDs of the observed stars. We find broad qualitative agreement of the spectral shape of visibilities corresponding to these models with our observations. Quantitatively, there are discrepancies that show the need for a next step in modelling of circumstellar disks, satisfying both the spatial constraints such as are now available from the MIDI observations and the flux constraints from the SEDs in a consistent way

Technical Design Report for the: PANDA Micro Vertex Detector

This document illustrates the technical layout and the expected performance of the Micro Vertex Detector (MVD) of the PANDA experiment. The MVD will detect charged particles as close as possible to the interaction zone. Design criteria and the optimisation process as well as the technical solutions chosen are discussed and the results of this process are subjected to extensive Monte Carlo physics studies. The route towards realisation of the detector is outlined.Comment: 189 pages, 225 figures, 41 table

Cold optics of MIDI: the mid-infrared interferometric instrument for the VLTI

ESO's new Very Large Telescope will consist of four 8.2m telescopes and three moveable 1.8m telescopes. Light from these can be combined in the Very Large Telescope Interferometer (VLTI) providing milli-arcsecond resolution with high sensitivity. The VLTI will first operate in the infrared and will produce first fringes in 2001. MIDI is the VLTI instrument for interferometry in the mid-infrared (10-20 microns) and is under development by a German-Dutch-French consortium [MPIA Heidelberg, NOVA/NFRA Netherlands, Observatoire Meudon France]. The initial aim of MIDI is to combine the beams of two telescopes in the 10 micron `N-band' and to achieve spatial resolutions of 20 milli-arcseconds at a spectral resolution of 200-300. Modulation of the optical path difference can be done using piezo-driven mirrors at room temperature, but beam combination and detection of the interferometric signal has to be done at cryogenic temperatures due to the 'thermal' wavelength domain. The MIDI cold bench is therefore mounted inside a cryostat, cooled by means of a closed cycle cooler to about 40K for the cold optics and 8 K for the detector. This poster describes the design and implementation of the MIDI cold bench

First Midi science observations on VLT

The mid-infrared interferometric instrument MIDI has performed its first scientific observations on the Very Large Telescope Interferometer (VLTI) in June 2003. It allows interferometric observations over the 8--13 ‚‚mu; m wavelength range, with a spatial resolution up to 20 milliarcsec, a spectral resolution of 30 and 250, and an expected point source sensitivity of l N = 4 mag or 1 Jy for self-fringe tracking, which is the only observing mode during the first months of operation. We describe briefly the layout of the instrument and present the first status of the MIDI observations of Young Stellar Objects

MIDI combines light from the VLTI: the start of 10 μm interferometry at ESO

International audienceWhen at the beginning of November 2002 the MIDI containers were opened up in Paranal and the team members together with ESO personnel started to assemble the instrument in the VLTI interferometric laboratory, nobody could be completely sure that their ambitious goal could actually be achieved: to bring together for the first time two beams of light from distant giant telescopes at the wavelength of 10 microns and obtaining stable, repeatable and accurate interference fringes. Although the instrument had been designed and built with the utmost care and all laboratory tests in Europe indicated that all specifications were met, going to the sky was another matter. The thermal infrared covers the wavelength range around the peak of the natural emission of a black body with a temperature about 300 K. This is close to the ambient temperature of the telescope mirrors and structure, of the two dozens of mirrors (in each arm) needed to bring the light into the tunnel and the interferometric lab, of all the mechanic structures, and of course of the sky. Therefore, at the wavelengths to which MIDI is sensitive, everything glows brightly! There is no distinction between day and night, and even the brightest stars are just tiny speckles of light in an overwhelmingly bright background. For this reason, previous attempts to perform interferometry in the thermal infrared had to find other ways to combine the light (for example, like Bester et al. (1990), in the style of radiointerferometers, thereby however sacrificing sensitivity), or never achieved a real routine operation. Even the ambitious efforts being carried out at the Keck Interferometer, in spite of having started earlier than at ESO, are so far still confronted with difficulties in this special area

MIDI combines light from the VLTI: the start of 10 μm interferometry at ESO

International audienceWhen at the beginning of November 2002 the MIDI containers were opened up in Paranal and the team members together with ESO personnel started to assemble the instrument in the VLTI interferometric laboratory, nobody could be completely sure that their ambitious goal could actually be achieved: to bring together for the first time two beams of light from distant giant telescopes at the wavelength of 10 microns and obtaining stable, repeatable and accurate interference fringes. Although the instrument had been designed and built with the utmost care and all laboratory tests in Europe indicated that all specifications were met, going to the sky was another matter. The thermal infrared covers the wavelength range around the peak of the natural emission of a black body with a temperature about 300 K. This is close to the ambient temperature of the telescope mirrors and structure, of the two dozens of mirrors (in each arm) needed to bring the light into the tunnel and the interferometric lab, of all the mechanic structures, and of course of the sky. Therefore, at the wavelengths to which MIDI is sensitive, everything glows brightly! There is no distinction between day and night, and even the brightest stars are just tiny speckles of light in an overwhelmingly bright background. For this reason, previous attempts to perform interferometry in the thermal infrared had to find other ways to combine the light (for example, like Bester et al. (1990), in the style of radiointerferometers, thereby however sacrificing sensitivity), or never achieved a real routine operation. Even the ambitious efforts being carried out at the Keck Interferometer, in spite of having started earlier than at ESO, are so far still confronted with difficulties in this special area

MIDI scientific and technical observing modes

International audienc

MIDI scientific and technical observing modes

International audienc