Download or read book Atmospheric Dispersion Effects in Weak Lensing Measurements written by and published by . This book was released on 2012 with total page 11 pages. Available in PDF, EPUB and Kindle. Book excerpt: The wavelength dependence of atmospheric refraction causes elongation of finite-bandwidth images along the elevation vector, which produces spurious signals in weak gravitational lensing shear measurements unless this atmospheric dispersion is calibrated and removed to high precision. Because astrometric solutions and PSF characteristics are typically calibrated from stellar images, differences between the reference stars' spectra and the galaxies' spectra will leave residual errors in both the astrometric positions (dr) and in the second moment (width) of the wavelength-averaged PSF (dv) for galaxies. We estimate the level of dv that will induce spurious weak lensing signals in PSF-corrected galaxy shapes that exceed the statistical errors of the DES and the LSST cosmic-shear experiments. We also estimate the dr signals that will produce unacceptable spurious distortions after stacking of exposures taken at different airmasses and hour angles. We also calculate the errors in the griz bands, and find that dispersion systematics, uncorrected, are up to 6 and 2 times larger in g and r bands, respectively, than the requirements for the DES error budget, but can be safely ignored in i and z bands. For the LSST requirements, the factors are about 30, 10, and 3 in g, r, and i bands, respectively. We find that a simple correction linear in galaxy color is accurate enough to reduce dispersion shear systematics to insignificant levels in the r band for DES and i band for LSST, but still as much as 5 times than the requirements for LSST r-band observations. More complex corrections will likely be able to reduce the systematic cosmic-shear errors below statistical errors for LSST r band. But g-band effects remain large enough that it seems likely that induced systematics will dominate the statistical errors of both surveys, and cosmic-shear measurements should rely on the redder bands.

Download or read book The Effects of Refraction and Dispersion on High altitude Measurements of Atmospheric Gases II written by James K. G. Watson and published by . This book was released on 1975 with total page 111 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Impact of Gravitational Lensing on Cosmology IAU S225 written by International Astronomical Union. Symposium and published by Cambridge University Press. This book was released on 2005-09-05 with total page 478 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book contains the proceedings of the International Astronomical Union Symposium no. 225, held in July 2004 at the Ecole Polytechnique Federale de Lausanne (EPFL), in Lausanne, Switzerland. The meeting focused on the applications of gravitational lensing to cosmological physics, and this book summarizes the most recent theoretical and observational developments. With chapters written by leading scientists in the field, this is a valuable resource for professional astronomers and graduate students in astronomy, physics and astro-particle physics.

Download or read book Computation of atmospheric dispersion coefficients from measurements of turbulence parameters written by and published by . This book was released on 1975 with total page 102 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Review of Specific Effects in Atmospheric Dispersion Calculations V 3 written by Commission of the European Communities and published by . This book was released on 1985 with total page 100 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book SIMULATIONS OF TURBULENCE INDUCED ELLIPTICITY OVER LARGE FIELDS OF VIEW written by K. Schlaufman and published by . This book was released on 2004 with total page 9 pages. Available in PDF, EPUB and Kindle. Book excerpt: Atmospheric turbulence can mimic the effects of weak lensing in astronomical images, so it is necessary to understand to what degree turbulence affects weak lensing measurements. In particular, we studied the ellipticity induced upon the point-spread functions (PSFs) of a grid of simulated stars separated by distances (d {approx} 1{prime}) that will be characteristic of Large Synoptic Survey Telescope (LSST) images. We observe that atmospherically induced ellipticity changes on small scales (d

Download or read book Cosmological Physics written by J. A. Peacock and published by Cambridge University Press. This book was released on 1999 with total page 700 pages. Available in PDF, EPUB and Kindle. Book excerpt: A comprehensive and authoritative introduction to contemporary cosmology for advanced undergraduate and graduate students.

Download or read book Review of specific effects in atmospheric dispersion calculations written by B. Y. Underwood and published by . This book was released on 1984 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Review of Specific Effects in Atmospheric Dispersion Calculations Volume 1 Final Report written by and published by . This book was released on 1986 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Gravitational Lensing Strong Weak and Micro written by Peter Schneider and published by Springer Science & Business Media. This book was released on 2006-12-30 with total page 565 pages. Available in PDF, EPUB and Kindle. Book excerpt: The observation, in 1919 by A.S. Eddington and collaborators, of the gra- tational de?ection of light by the Sun proved one of the many predictions of Einstein’s Theory of General Relativity: The Sun was the ?rst example of a gravitational lens. In 1936, Albert Einstein published an article in which he suggested - ing stars as gravitational lenses. A year later, Fritz Zwicky pointed out that galaxies would act as lenses much more likely than stars, and also gave a list of possible applications, as a means to determine the dark matter content of galaxies and clusters of galaxies. It was only in 1979 that the ?rst example of an extragalactic gravitational lens was provided by the observation of the distant quasar QSO 0957+0561, by D. Walsh, R.F. Carswell, and R.J. Weymann. A few years later, the ?rst lens showing images in the form of arcs was detected. The theory, observations, and applications of gravitational lensing cons- tute one of the most rapidly growing branches of astrophysics. The gravi- tional de?ection of light generated by mass concentrations along a light path producesmagni?cation,multiplicity,anddistortionofimages,anddelaysp- ton propagation from one line of sight relative to another. The huge amount of scienti?c work produced over the last decade on gravitational lensing has clearly revealed its already substantial and wide impact, and its potential for future astrophysical applications.

Download or read book WORKBOOK OF ATMOSPHERIC DISPERSION ESTIMATES written by D. Bruce Turner and published by . This book was released on 2020 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: This completely updated and revised Second Edition of the popular Workbook of Atmospheric Dispersion Estimates provides an important foundation for understanding dispersion modeling as it is being practiced today. The book and accompanying diskette will help you determine the impacts of various sources of air pollution, including the effects of wind and turbulence, plume rise, and Gaussian dispersion and its limitations. Information is shown in summary graphs as well as in equations. The programs included on the diskette allow you to "get the feel" for the results you'll obtain through the input of various combinations of parameter values. The sensitivity of data to various parameters can be easily explored by changing one value and seeing the effect on the results. The book presents 37 example problems with solutions to show the estimation of atmospheric pollutant concentrations for many situations.

Download or read book Review of Specific Effects in Atmospheric Dispersion Calculations Volume 2 Final Report written by and published by . This book was released on 1984 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Review of Specific Effects in Atmospheric Dispersion Calculations written by and published by . This book was released on 1984 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Testing New Weak Lensing Measurement Techniques with the Dark Energy Survey written by Christina Irene Krawiec and published by . This book was released on 2018 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: In this dissertation, we first present an analysis on the effect of wind at the Blanco Telescope, the home of the Dark Energy Camera (DECam), on Dark Energy Survey (DES) image quality. We find it to have a likely negligible impact on the weak gravitational lensing measurements conducted with images taken during high wind. We then present the methods and validation of two new techniques in weak lensing shear and magnification measurement. We demonstrate highly accurate recovery of weak gravitational lensing shear using an implementation of the Bayesian Fourier Domain (BFD) method, proposed by Bernstein and Armstrong (2014), extended to correct for selection biases. The BFD formalism is rigorously correct for Nyquist-sampled, background-limited, uncrowded image of background galaxies. We conduct initial tests of this code on ≈109 simulated lensed galaxy images and recover the simulated shear to a fractional accuracy of m = (2.1 [plus/minus] 0.4) × 10-3 , substantially more accurate than has been demonstrated previously for any generally applicable shear measurement method. We also introduce a new Bayesian method for selecting high-redshift galaxies and calculating their magnification around foreground lenses. We apply this method to galaxies from DES Science Verification (SV).Finally, we share the results of a survey conducted with DES collaborators on the collaboration itself, in which we find positive attitudes towards education and public outreach (EPO) in physics and astronomy. We also provide recommendations for current and future surveys on how to increase EPO engagement by scientists.

Download or read book Atmospheric Dispersion Corrector for the ILOCATER Spectrography written by Alissa A. Runyon and published by . This book was released on 2016 with total page 42 pages. Available in PDF, EPUB and Kindle. Book excerpt: As light enters the Earth’s atmosphere it experiences refraction as it changes medium from vacuum to air. The wavelength dependency of this refraction causes dispersion as different wavelengths of light bend differently. In order to create clear images despite the dispersion effects of the Earth’s atmosphere, new imaging techniques must be developed. iLOCATER is a new diffraction limiting, planet-finding spectrograph being designed and built at the University of Notre Dame for use on the Large Binocular Telescope (LBT) in Arizona. To correct for the dispersion from the atmosphere, an atmospheric dispersion corrector (ADC) using two rotating singlet prisms has been designed and tested. This paper discusses the tests of the ADC and verifies its operation on a test system.

Download or read book Annual Review of Astronomy and Astrophysics written by Leo Goldberg and published by . This book was released on 1999-09 with total page 714 pages. Available in PDF, EPUB and Kindle. Book excerpt: Papers from an April 1997 meeting explore recent advances in areas including galactic dynamos, probing the universe with weak lensing, nucleosynthesis in asymptotic giant branch stars, physical conditions in regions of star formation, and high-energy processes in young stellar objects. Other subjects are sources of relativistic jets in the galaxy, elemental abundances in quasistellar objects, origin and evolution of the natural satellites, and far-ultraviolet radiation from elliptical galaxies. Includes a retrospective of 50 years of research at Palomar Observatory. The editor is affiliated with the University of California at San Diego. Annotation copyrighted by Book News, Inc., Portland, OR

Download or read book Fluctuating Concentrations in Atmospheric Dispersion written by George Ellis DeVaull (III) and published by . This book was released on 1990 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: This thesis presents theoretical models and experimental results of average and instantaneous concentration measurements from a series of atmospheric dispersion experiments conducted under both unstable and stable meteorological conditions. The experiments were undertaken at two different sites, over both flat and gently rolling terrain. Two types of surface-level point aerosol sources were used. One is a fog-oil smoke and the other is a hexachloroethane chemical smoke. Measurements of concentration at points along crosswind transects were taken over time periods of an hour at distances to several kilometers from the source. These measurements included both aerosol photometer records of the instantaneous concentration taken at a 1 Hz sampling rate and aspirated filters for mean concentration measurements. The flat terrain site was located at Camp Atterbury, Indiana, while the gently rolling terrain site was near Red Bluff, California. Meteorological measurements at these sites included both tower measurements and upper-air balloon soundings. These measurements were used in determining the atmospheric boundary layer scaling parameters in the unstable tests and in characterizing the complex wind field for the stable tests. The data compare favorably with developed models for both the mean and variance in concentration. Concentration fluctuation intensity ranges from 2 near the plume centerline to greater than 20 at the plume edge. Intermittency is important at all locations, with positive concentrations recorded on the mean plume centerline only 20% to 50% of the time. Point concentration histograms are shown to agree with the exponential distribution for concentrations greater than zero. Spectra of the concentration data show an inertial-convective subrange with a $-$5/3 power law versus frequency behavior. Integral time scales of the concentration records at all individual sampling points are approximately constant within a test and are equal to the mean duration of episodes or bursts in which the concentration is greater than zero. The probability distribution of individual burst durations at each sampler shows an exponential distribution.