The Experts below are selected from a list of 306 Experts worldwide ranked by ideXlab platform
T. Demeechai - One of the best experts on this subject based on the ideXlab platform.
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On noise-limited performance of noncomplementary spectral-amplitude coding optical CDMA systems
IEEE Transactions on Communications, 2006Co-Authors: T. DemeechaiAbstract:Bit-error rate performance of noncomplementary spectral-amplitude coding optical code-division multiple access in digital communication systems is analyzed, taking into account thermal, shot, Source Intensity, and beat noises. This analysis is, in principle, more accurate than a recent work that embodies a significant approximation.
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Noise-limited performance of spectral-amplitude-coding optical CDMA in fibre-optic radio highway networks
IEE Proceedings - Optoelectronics, 2005Co-Authors: T. DemeechaiAbstract:Performance of spectral-amplitude-coding optical code-division multiple-access systems, which may be classified as complementary-coding or non-complementary-coding systems, in fibre-optic radio highway networks is analysed. The carrier-to-noise ratio for an individual mobile terminal is examined, taking into account Source Intensity noise, beat noise, shot noise, and thermal noise. Results are presented assuming time-division multiple access and constant-envelope-type modulation for the air interface.
Tommaso Treu - One of the best experts on this subject based on the ideXlab platform.
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Dissecting the Gravitational Lens B1608+656. I. Lens Potential Reconstruction
The Astrophysical Journal, 2009Co-Authors: Sherry H Suyu, P. J. Marshall, J. P. Mckean, Leon V E Koopmans, Robson David Blandford, Christopher D. Fassnacht, Tommaso TreuAbstract:Strong gravitational lensing is a powerful technique for probing galaxy mass distributions and for measuring cosmological parameters. Lens systems with extended Source-Intensity distributions are particularly useful for this purpose since they provide additional constraints on the lens potential (mass distribution). We present a pixelated approach to modeling the lens potential and Source-Intensity distribution simultaneously. The method makes iterative and perturbative corrections to an initial potential model. For systems with Sources of sufficient extent such that the separate lensed images are connected by Intensity measurements, the accuracy in the reconstructed potential is solely limited by the quality of the data. We apply this potential reconstruction technique to deep Hubble Space Telescope observations of B1608+656, a four-image gravitational lens system formed by a pair of interacting lens galaxies. We present a comprehensive Bayesian analysis of the system that takes into account the extended Source-Intensity distribution, dust extinction, and the interacting lens galaxies. Our approach allows us to compare various models of the components of the lens system, which include the point-spread function (PSF), dust, lens galaxy light, Source-Intensity distribution, and lens potential. Using optimal combinations of the PSF, dust, and lens galaxy light models, we successfully reconstruct both the lens potential and the extended Source-Intensity distribution of B1608+656. The resulting reconstruction can be used as the basis of a measurement of the Hubble constant. As an illustration of the astrophysical applications of our method, we use our reconstruction of the gravitational potential to study the relative distribution of mass and light in the lensing galaxies. We find that the mass-to-light ratio for the primary lens galaxy is (2.0 ± 0.2)h M☉LB,☉^-1 within the Einstein radius (3.9 h^–1 kpc), in agreement with what is found for noninteracting lens galaxies at the same scales.
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Dissecting the gravitational lens B1608+656. I. Lens potential reconstruction
Astrophysical Journal, 2009Co-Authors: Sherry H Suyu, P. J. Marshall, J. P. Mckean, Leon V E Koopmans, Robson David Blandford, Christopher D. Fassnacht, Tommaso TreuAbstract:Strong gravitational lensing is a powerful technique for probing galaxy mass distributions and for measuring cosmological parameters. Lens systems with extended Source-Intensity distributions are particularly useful for this purpose since they provide additional constraints on the lens potential (mass distribution). We present a pixelated approach to modeling the lens potential and Source-Intensity distribution simultaneously. The method makes iterative and perturbative corrections to an initial potential model. For systems with Sources of sufficient extent such that the separate lensed images are connected by Intensity measurements, the accuracy in the reconstructed potential is solely limited by the quality of the data. We apply this potential reconstruction technique to deep Hubble Space Telescope observations of B1608+656, a four-image gravitational lens system formed by a pair of interacting lens galaxies. We present a comprehensive Bayesian analysis of the system that takes into account the extended Source-Intensity distribution, dust extinction, and the interacting lens galaxies. Our approach allows us to compare various models of the components of the lens system, which include the point-spread function (PSF), dust, lens galaxy light, Source-Intensity distribution, and lens potential. Using optimal combinations of the PSF, dust, and lens galaxy light models, we successfully reconstruct both the lens potential and the extended Source-Intensity distribution of B1608+656. The resulting reconstruction can be used as the basis of a measurement of the Hubble constant. As an illustration of the astrophysical applications of our method, we use our reconstruction of the gravitational potential to study the relative distribution of mass and light in the lensing galaxies. We find that the mass-to-light ratio for the primary lens galaxy is (2.0 ± 0.2)h M sun L -1 B,sun within the Einstein radius (3.9 h-1 kpc), in agreement with what is found for noninteracting lens galaxies at the same scales. Based in part on observations made with the NASA/ESA Hubble Space Telescope, obtained at the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS 5-26555. These observations are associated with program GO-10158.
Sherry H Suyu - One of the best experts on this subject based on the ideXlab platform.
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Dissecting the gravitational lens B1608+656 : implications for the Hubble constant
2020Co-Authors: Sherry H SuyuAbstract:Strong gravitational lens systems provide a tool for probing galaxy mass distributions (independent of their light profiles) and for measuring cosmological parameters. In a strong lens system, the background Source Intensity distribution is multiply imaged. If the Source Intensity is time varying, then the multiple images of the variable Source are delayed in time relative to each other due to the different light travel time along the multiple light paths. One can use lens systems to measure the Hubble constant by obtaining the relative time delays between the multiple images and modeling the lens potential. B1608+656 is a quadruply imaged gravitational lens system with a spatially extended Source Intensity distribution and two interacting galaxy lenses. This system is unique in that the three relative time delays between the four images were measured accurately with errors of only a few percent, and it thus provides an opportunity to measure the Hubble constant with high precision. The extended Source Intensity distribution in B1608+656 provides additional constraints on the lens potential, though simultaneous determination of the Source Intensity and lens potential distribution is needed. The presence of dust and interacting galaxy lenses further complicate this system. We present a comprehensive analysis in a Bayesian framework that takes into account the extended Source Intensity distribution, interacting galaxy lenses, and the presence of dust for reconstructing the lens potential. Using the deep HST ACS observations on B1608+656, the resulting statistical uncertainty on H_0 associated with the lens modeling is limited by the uncertainty in the best time delay measurement (~3%). The dominant systematic error on H_0 is due to the effects of the environment on B1608+656 (mass-sheet degeneracy). By using the measured velocity dispersion of the lens galaxies and considering the mass structures along the line of sight to B1608+656, we place constraints on the external convergence associated with galaxy groups and mass structure along the line of sight. The resulting Hubble constant from B1608+656 is H_0 = 72 ± 2 (stat.) ± 4 (syst.) km s^-1 Mpc^-1.
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Dissecting the Gravitational Lens B1608+656. I. Lens Potential Reconstruction
The Astrophysical Journal, 2009Co-Authors: Sherry H Suyu, P. J. Marshall, J. P. Mckean, Leon V E Koopmans, Robson David Blandford, Christopher D. Fassnacht, Tommaso TreuAbstract:Strong gravitational lensing is a powerful technique for probing galaxy mass distributions and for measuring cosmological parameters. Lens systems with extended Source-Intensity distributions are particularly useful for this purpose since they provide additional constraints on the lens potential (mass distribution). We present a pixelated approach to modeling the lens potential and Source-Intensity distribution simultaneously. The method makes iterative and perturbative corrections to an initial potential model. For systems with Sources of sufficient extent such that the separate lensed images are connected by Intensity measurements, the accuracy in the reconstructed potential is solely limited by the quality of the data. We apply this potential reconstruction technique to deep Hubble Space Telescope observations of B1608+656, a four-image gravitational lens system formed by a pair of interacting lens galaxies. We present a comprehensive Bayesian analysis of the system that takes into account the extended Source-Intensity distribution, dust extinction, and the interacting lens galaxies. Our approach allows us to compare various models of the components of the lens system, which include the point-spread function (PSF), dust, lens galaxy light, Source-Intensity distribution, and lens potential. Using optimal combinations of the PSF, dust, and lens galaxy light models, we successfully reconstruct both the lens potential and the extended Source-Intensity distribution of B1608+656. The resulting reconstruction can be used as the basis of a measurement of the Hubble constant. As an illustration of the astrophysical applications of our method, we use our reconstruction of the gravitational potential to study the relative distribution of mass and light in the lensing galaxies. We find that the mass-to-light ratio for the primary lens galaxy is (2.0 ± 0.2)h M☉LB,☉^-1 within the Einstein radius (3.9 h^–1 kpc), in agreement with what is found for noninteracting lens galaxies at the same scales.
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Dissecting the gravitational lens B1608+656. I. Lens potential reconstruction
Astrophysical Journal, 2009Co-Authors: Sherry H Suyu, P. J. Marshall, J. P. Mckean, Leon V E Koopmans, Robson David Blandford, Christopher D. Fassnacht, Tommaso TreuAbstract:Strong gravitational lensing is a powerful technique for probing galaxy mass distributions and for measuring cosmological parameters. Lens systems with extended Source-Intensity distributions are particularly useful for this purpose since they provide additional constraints on the lens potential (mass distribution). We present a pixelated approach to modeling the lens potential and Source-Intensity distribution simultaneously. The method makes iterative and perturbative corrections to an initial potential model. For systems with Sources of sufficient extent such that the separate lensed images are connected by Intensity measurements, the accuracy in the reconstructed potential is solely limited by the quality of the data. We apply this potential reconstruction technique to deep Hubble Space Telescope observations of B1608+656, a four-image gravitational lens system formed by a pair of interacting lens galaxies. We present a comprehensive Bayesian analysis of the system that takes into account the extended Source-Intensity distribution, dust extinction, and the interacting lens galaxies. Our approach allows us to compare various models of the components of the lens system, which include the point-spread function (PSF), dust, lens galaxy light, Source-Intensity distribution, and lens potential. Using optimal combinations of the PSF, dust, and lens galaxy light models, we successfully reconstruct both the lens potential and the extended Source-Intensity distribution of B1608+656. The resulting reconstruction can be used as the basis of a measurement of the Hubble constant. As an illustration of the astrophysical applications of our method, we use our reconstruction of the gravitational potential to study the relative distribution of mass and light in the lensing galaxies. We find that the mass-to-light ratio for the primary lens galaxy is (2.0 ± 0.2)h M sun L -1 B,sun within the Einstein radius (3.9 h-1 kpc), in agreement with what is found for noninteracting lens galaxies at the same scales. Based in part on observations made with the NASA/ESA Hubble Space Telescope, obtained at the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS 5-26555. These observations are associated with program GO-10158.
A. Peter Jardine - One of the best experts on this subject based on the ideXlab platform.
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An improved high Intensity recycling helium-3 beam Source
Review of Scientific Instruments, 2009Co-Authors: A. Peter JardineAbstract:We describe an improved high Intensity, recycling, supersonic atomic beam Source. Changes address several issues previously limiting performance and reliability of the apparatus, including the use of newly available vacuum pumps and modifications to the recycling system. We achieve a Source Intensity of 2.5× 1019 atoms/s/sr, almost twice that previously achievable during recycling. Current limits on Intensity are discussed. © 2009 American Institute of Physics.
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An improved high Intensity recycling helium-3 beam Source
Review of Scientific Instruments, 2009Co-Authors: H. Hedgeland, P. R. Kole, W. Allison, J. Ellis, A. Peter JardineAbstract:We describe an improved high Intensity, recycling, supersonic atomic beam Source. Changes address several issues previously limiting performance and reliability of the apparatus, including the use of newly available vacuum pumps and modifications to the recycling system. We achieve a Source Intensity of 2.5 x 10(19) atoms/s/sr, almost twice that previously achievable during recycling. Current limits on Intensity are discussed.
Robson David Blandford - One of the best experts on this subject based on the ideXlab platform.
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Dissecting the Gravitational Lens B1608+656. I. Lens Potential Reconstruction
The Astrophysical Journal, 2009Co-Authors: Sherry H Suyu, P. J. Marshall, J. P. Mckean, Leon V E Koopmans, Robson David Blandford, Christopher D. Fassnacht, Tommaso TreuAbstract:Strong gravitational lensing is a powerful technique for probing galaxy mass distributions and for measuring cosmological parameters. Lens systems with extended Source-Intensity distributions are particularly useful for this purpose since they provide additional constraints on the lens potential (mass distribution). We present a pixelated approach to modeling the lens potential and Source-Intensity distribution simultaneously. The method makes iterative and perturbative corrections to an initial potential model. For systems with Sources of sufficient extent such that the separate lensed images are connected by Intensity measurements, the accuracy in the reconstructed potential is solely limited by the quality of the data. We apply this potential reconstruction technique to deep Hubble Space Telescope observations of B1608+656, a four-image gravitational lens system formed by a pair of interacting lens galaxies. We present a comprehensive Bayesian analysis of the system that takes into account the extended Source-Intensity distribution, dust extinction, and the interacting lens galaxies. Our approach allows us to compare various models of the components of the lens system, which include the point-spread function (PSF), dust, lens galaxy light, Source-Intensity distribution, and lens potential. Using optimal combinations of the PSF, dust, and lens galaxy light models, we successfully reconstruct both the lens potential and the extended Source-Intensity distribution of B1608+656. The resulting reconstruction can be used as the basis of a measurement of the Hubble constant. As an illustration of the astrophysical applications of our method, we use our reconstruction of the gravitational potential to study the relative distribution of mass and light in the lensing galaxies. We find that the mass-to-light ratio for the primary lens galaxy is (2.0 ± 0.2)h M☉LB,☉^-1 within the Einstein radius (3.9 h^–1 kpc), in agreement with what is found for noninteracting lens galaxies at the same scales.
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Dissecting the gravitational lens B1608+656. I. Lens potential reconstruction
Astrophysical Journal, 2009Co-Authors: Sherry H Suyu, P. J. Marshall, J. P. Mckean, Leon V E Koopmans, Robson David Blandford, Christopher D. Fassnacht, Tommaso TreuAbstract:Strong gravitational lensing is a powerful technique for probing galaxy mass distributions and for measuring cosmological parameters. Lens systems with extended Source-Intensity distributions are particularly useful for this purpose since they provide additional constraints on the lens potential (mass distribution). We present a pixelated approach to modeling the lens potential and Source-Intensity distribution simultaneously. The method makes iterative and perturbative corrections to an initial potential model. For systems with Sources of sufficient extent such that the separate lensed images are connected by Intensity measurements, the accuracy in the reconstructed potential is solely limited by the quality of the data. We apply this potential reconstruction technique to deep Hubble Space Telescope observations of B1608+656, a four-image gravitational lens system formed by a pair of interacting lens galaxies. We present a comprehensive Bayesian analysis of the system that takes into account the extended Source-Intensity distribution, dust extinction, and the interacting lens galaxies. Our approach allows us to compare various models of the components of the lens system, which include the point-spread function (PSF), dust, lens galaxy light, Source-Intensity distribution, and lens potential. Using optimal combinations of the PSF, dust, and lens galaxy light models, we successfully reconstruct both the lens potential and the extended Source-Intensity distribution of B1608+656. The resulting reconstruction can be used as the basis of a measurement of the Hubble constant. As an illustration of the astrophysical applications of our method, we use our reconstruction of the gravitational potential to study the relative distribution of mass and light in the lensing galaxies. We find that the mass-to-light ratio for the primary lens galaxy is (2.0 ± 0.2)h M sun L -1 B,sun within the Einstein radius (3.9 h-1 kpc), in agreement with what is found for noninteracting lens galaxies at the same scales. Based in part on observations made with the NASA/ESA Hubble Space Telescope, obtained at the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS 5-26555. These observations are associated with program GO-10158.
