| 1. |
- Andersen, Torben, et al.
(författare)
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The Euro50 Extremely Large Telescope
- 2003
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Ingår i: Future Giant Telescopes. Proceedings of the SPIE.. - 081944619X ; 4840, s. 214-225
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Konferensbidrag (refereegranskat)abstract
- Euro50 is a proposed optical telescope with an equivalent primary mirrordiameter of 50 m. Partners of the collaboration are institutes inSweden, Spain, Ireland, Finland, and the UK. The telescope will have asegmented primary mirror and an aplanatic Gregorian configuration withtwo elliptical mirrors. For a 50 m telescope there would be noeconomical advantage in going to a spherical primary. The size of theprimary mirror segments (2 m) has been selected on the basis of aminimization of cost. An adaptive optics system will be integrated intothe telescope. The telescope will have three operational modes: Seeinglimited observations, single conjugate adaptive observations in theK-band, and dual conjugate observations also in the K-band. An upgradeto adaptive optics also in the visible down to 500 nm is foreseen. Therewill be an enclosure to protect the telescope against adverse weatherand wind disturbances. Integrated simulation models are underdevelopment. The project time will be 10 years and the cost some 591MEuros.
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| 2. |
- Snel, Ralph
(författare)
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Crowded Field Photometry and Luminosity Function Analysis as Probes of Galactic Evolution
- 1998
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Crowded field photometry is a powerful method to investigate stellar evolutionary processes in astrophysically interesting regions such as nearby external galaxies and globular cluster cores. While detectors are approaching the physical limits for photon detection, data analysis methods for crowded stellar fields are not yet equally sophisticated. In order to obtain high accuracy of measurements and optimally extract astrophysically relevant information from observational data, it is essential to have thorough understanding of the processes affecting photometric accuracy, and knowledge of the theoretical limits of the information extraction. This thesis discusses data analysis methods for crowded stellar fields, as well as theoretical and practical limits to the accuracy of measurements in CCD based crowded field observations. Conventional crowded field photometry is discussed, with emphasis on detection and measurement of sources in the presence of known and unknown nearby stars. Special attention is given to the stellar luminosity function. A method is presented to derive the luminosity function of stars beyond the observational limit of individually detectable stars. This method uses the histogram of an observed image of a crowded field, and compares this with the histogram of a simulated image, determined with a model luminosity function, an instrument model, and detailed knowledge of the noise in the image. Similarity of histograms is interpreted as similarity of the true and model luminosity functions. An application of this method to a Hubble Space Telescope image of the Large Magellanic Cloud Bar is presented. Completeness of detection of stars in crowded fields, normally determined through artificial star experiments, can be derived from prior assumptions concerning the luminosity function. Three detection algorithms are tested using simulated and observed images, and the results are compared with the theoretically determined completeness of detection. With proper knowledge of the instrument, noise sources, and data analysis methods, it is possible to retrieve additional relevant information from the data, plan instrument configurations and observing strategies, and recognise possible areas of improvement in data analysis methods.
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| 3. |
- Snel, Ralph, et al.
(författare)
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Science with Euro50
- 2002
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Ingår i: Future Research Direction and Visions for Astronomy. - 1996-756X .- 0277-786X. ; 4835, s. 60-71
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Konferensbidrag (refereegranskat)abstract
- ELT science drivers stress aperture, Strehl ratio, PSF definition and stability, field of view, wavelength range, flexibility, low polarisation and thermal emittance, auxiliary instruments, site and infrastructure. Applicable science categories are planets and planetary systems, stars and stellar systems, galaxies and galaxy clusters, and cosmology. ELT observations are needed for our own and other planetary systems. The study of planetary disks and formation requires ELT data. ELT results, with emphasis on PSF quality and stability, are crucial to the search for earth-like planets, especially those favourable for life. Investigation of star formation and stellar evolution requires ELT performance, as does the study of final stellar stages. ELTs are necessary for extremely high time resolution, details of stellar surfaces and astroseismology. Galaxy formation studies will benefit dramatically from ELT data, as will studies of large-scale development of galaxies and galaxy clusters over cosmological time scales. Detecting active galactic nuclei requires ELTs. ELT data are crucial for examining the structure and evolution of the universe. Observations of supernovae and other standard sources over very large distances are necessary for mapping the expansion of the universe and determining its acceleration or deceleration. Comparisons of Euro50 with VLTs and HST show a dramatic gain. The complementarity of Euro50, NGST and ALMA is noted.
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| 4. |
- Snel, Ralph, et al.
(författare)
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Some aspects of science with a 50-m AO telescope
- 2003
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Ingår i: Second Backaskog Workshop on Extremely Large Telescopes (Proceedings of the SPIE). - : SPIE. - 0819452998 ; 5382, s. 57-66
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Konferensbidrag (refereegranskat)abstract
- Among the science challenges of the Extremely Large Telescopes (ELTs),four object types are studied for performance with a 50 m ELT withadaptive optics (AO), Euro50. Emphasis is on planetary systems and verydistant objects. For planetary systems and their evolution, we examinehigh resolution imaging of the nuclei of comets and high-resolutionimaging, photometry and low and intermediate resolution spectroscopy ofKuiper-Belt objects. Imaging of Earth-like planets is discussed. Thevery high contrast imaging necessary for these purposes is discussedtogether with the relevant error sources. Finally, photometry andclassification of supernovae is discussed and examined. The performanceof a 50 m AO ELT is compared to corresponding data obtainable withcurrent VLTs equipped with AO.
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