Download or read book The DAFT FADA Survey I Photometric Redshifts Along Lines of Sight to Clusters in the Z written by and published by . This book was released on 2010 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: As a contribution to the understanding of the dark energy concept, the Dark energy American French Team (DAFT, in French FADA) has started a large project to characterize statistically high redshift galaxy clusters, infer cosmological constraints from Weak Lensing Tomography, and understand biases relevant for constraining dark energy and cluster physics in future cluster and cosmological experiments. Aims. The purpose of this paper is to establish the basis of reference for the photo-z determination used in all our subsequent papers, including weak lensing tomography studies. This project is based on a sample of 91 high redshift (z ≥ 0.4), massive (≈> 3 x 1014 M{sub {circle_dot}}) clusters with existing HST imaging, for which we are presently performing complementary multi-wavelength imaging. This allows us in particular to estimate spectral types and determine accurate photometric redshifts for galaxies along the lines of sight to the first ten clusters for which all the required data are available down to a limit of I{sub AB} = 24./24.5 with the LePhare software. The accuracy in redshift is of the order of 0.05 for the range 0.2 ≤ z ≤ 1.5. We verified that the technique applied to obtain photometric redshifts works well by comparing our results to with previous works. In clusters, photo-z accuracy is degraded for bright absolute magnitudes and for the latest and earliest type galaxies. The photo-z accuracy also only slightly varies as a function of the spectral type for field galaxies. As a consequence, we find evidence for an environmental dependence of the photo-z accuracy, interpreted as the standard used Spectral Energy Distributions being not very well suited to cluster galaxies. Finally, we modeled the LCDCS 0504 mass with the strong arcs detected along this line of sight.
Download or read book Issues in Astronomy and Astrophysics 2012 Edition written by and published by ScholarlyEditions. This book was released on 2013-01-10 with total page 734 pages. Available in PDF, EPUB and Kindle. Book excerpt: Issues in Astronomy and Astrophysics / 2012 Edition is a ScholarlyEditions™ eBook that delivers timely, authoritative, and comprehensive information about Planetary Science. The editors have built Issues in Astronomy and Astrophysics: 2012 Edition on the vast information databases of ScholarlyNews.™ You can expect the information about Planetary Science in this eBook to be deeper than what you can access anywhere else, as well as consistently reliable, authoritative, informed, and relevant. The content of Issues in Astronomy and Astrophysics: 2012 Edition has been produced by the world’s leading scientists, engineers, analysts, research institutions, and companies. All of the content is from peer-reviewed sources, and all of it is written, assembled, and edited by the editors at ScholarlyEditions™ and available exclusively from us. You now have a source you can cite with authority, confidence, and credibility. More information is available at http://www.ScholarlyEditions.com/.
Download or read book Peterson s Graduate Programs in the Physical Sciences Mathematics Agricultural Sciences the Environment Natural Resources 2012 written by Peterson's and published by Peterson's. This book was released on 2011-12-30 with total page 2059 pages. Available in PDF, EPUB and Kindle. Book excerpt: Graduate Programs in the Physical Sciences, Mathematics, Agricultural Sciences, the Environment & Natural Resources 2012 contains more than 2,900 graduate programs in 59 disciplines-including agriculture and food sciences, astronomy and astrophysics, chemistry, physics, mathematics, environmental sciences and management, natural resources, marine sciences, and more. This guide is part of Peterson's six-volume Annual Guides to Graduate Study, the only annually updated reference work of its kind, provides wide-ranging information on the graduate and professional programs offered by U.S.-accredited colleges and universities in the United States and throughout the world. Informative data profiles for more than 2,900 graduate programs in 59 disciplines, including facts and figures on accreditation, degree requirements, application deadlines and contact information, financial support, faculty, and student body profiles. Two-page in-depth descriptions, written by featured institutions, offer complete details on specific graduate programs, schools, or departments as well as information on faculty research and the college or university. Expert advice on the admissions process, financial support, and accrediting agencies. Comprehensive directories list programs in this volume, as well as others in the graduate series. Up-to-date appendixes list institutional changes since the last addition along with abbreviations used in the guide
Download or read book The Canada France Deep Fields Photometric Redshift Survey microform an Investigation of Galaxy Evolution Using Photometric Redshifts written by Mark Brodwin and published by National Library of Canada = Bibliothèque nationale du Canada. This book was released on 2004 with total page 272 pages. Available in PDF, EPUB and Kindle. Book excerpt: Progress in the study of galaxy evolution has traditionally followed from improvements in spectroscopic measurement techniques and subsequent groundbreaking surveys. The advent of large format CCD detectors, coupled with the demonstrated success of the photometric redshift method, has given rise to a new, potentially very powerful alternative. It has, in fact, motivated the present detailed investigation of the potential of photometric redshift surveys to complement, or in some cases, supersede traditional spectroscopic surveys in galaxy evolution studies. This Thesis describes a new deep, wide-field, multi-colour imaging survey, 10 times deeper and 30 times larger than its spectroscopic predecessor, the Canada-France Redshift Survey (CFRS). Highly accurate photometric redshifts, calibrated using hundreds of spectroscopic CFRS galaxies, were measured for tens of thousands of objects, with typical dispersions of only sigma/(1 + z) & lsim; 0.06 to IAB = 24 for z & le; 1.3. For the 1- and 2-point statistics of the galaxy distribution studied in this Thesis, the measurement accuracy is limited not by the photometric redshift error, but rather by the effect of cosmic variance, whose contribution to the total error budget is dominant. Therefore, future studies will be well served by adopting the photometric redshift approach, the efficiency of which will enable them to survey the hundreds or thousands of square degrees required to obtain a fair sample of the Universe. We measure the evolution of galaxy correlations with redshift, a primary observable of the structure formation process, correcting for the dilutive effect of photometric redshift errors on the clustering signal. The high z & sim; 3 correlation amplitude seen in this work provides compelling evidence for the biased galaxy formation paradigm. The measured galaxy correlations from 0 & lsim; z & lsim; 3 are in excellent agreement with the findings of the largest, state-of-the-art spectroscopic studies. A new Bayesian method to measure the galaxy redshift distribution is developed. The accuracy of the method, which incorporates the full redshift likelihood function of each galaxy in an iterative analysis, is demonstrated in extensive Monte Carlo simulations. IAB and RAB redshift distributions, along with the run of median redshifts, are measured in various magnitude ranges, with special attention given to quantifying both random and systematic errors.
Download or read book Photometric Redshifts and Clustering of Emission Line Galaxies Selected Jointly by DES and EBOSS written by and published by . This book was released on 2015 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: We present the results of the first test plates of the extended Baryon Oscillation Spectroscopic Survey. This paper focuses on the emission line galaxies (ELG) population targetted from the Dark Energy Survey (DES) photometry. We analyse the success rate, efficiency, redshift distribution, and clustering properties of the targets. From the 9000 spectroscopic redshifts targetted, 4600 have been selected from the DES photometry. The total success rate for redshifts between 0.6 and 1.2 is 71\% and 68\% respectively for a bright and faint, on average more distant, samples including redshifts measured from a single strong emission line. We find a mean redshift of 0.8 and 0.87, with 15 and 13\% of unknown redshifts respectively for the bright and faint samples. In the redshift range 0.6
Download or read book Clustering at High Redshift written by Alain Mazure and published by . This book was released on 2000 with total page 528 pages. Available in PDF, EPUB and Kindle. Book excerpt: Annotation Astronomers, astrophysicists, and other scientists and researchers from laboratories, observatories, and universities throughout North America, Europe, Asia, and the Middle East present 60 contributions addressing clustering from low to high redshift; clustering measurements in surveys; IR and sub-mm surveys; theory and models; high-redshift clusters of galaxies; QSO absorption lines; primordial galaxies; clustering around QSOs and radio galaxies; and the physics of the intra-cluster medium. Approximately 40 poster sessions are also presented. Lacks an index. Annotation c. Book News, Inc., Portland, OR (booknews.com)
Download or read book Optical Galaxy Cluster Detection Across a Wide Redshift Range written by and published by . This book was released on 2009 with total page 131 pages. Available in PDF, EPUB and Kindle. Book excerpt: The past decade is one of the most exciting period in the history of physics and astronomy. The discovery of cosmic acceleration dramatically changed our understanding about the evolution and constituents of the Universe. To accommodate the new acceleration phase into our well established Big Bang cosmological scenario under the frame work of General Relativity, there must exist a very special substance that has negative pressure and make up about 73% of the total energy density in our Universe. It is called Dark Energy. For the first time people realized that the vast majority of our Universe is made of things that are totally different from the things we are made of. Therefore, one of the major endeavors in physics and astronomy in the coming years is trying to understand, if we can, the nature of dark energy. Understanding dark energy cannot be achieved from pure logic. We need empirical evidence to finally determine about what is dark energy. The better we can constrain the energy density and evolution of the dark energy, the closer we will get to the answer. There are many ways to constrain the energy density and evolution of dark energy, each of which leads to degeneracy in certain directions in the parameter space. Therefore, a combination of complimentary methods will help to reduce the degeneracies and give tighter constraints. Dark energy became dominate over matter in the Universe only very recently (at about z (almost equal to) 1.5) and will affect both the cosmological geometry and large scale structure formation. Among the various experiments, some of them constrain the dark energy mainly via geometry (such as CMB, Supernovae) while some others provides constraints from both structures and geometry (such as BAO, Galaxy Clusters) Galaxy clusters can be used as a sensitive probe for cosmology. A large cluster catalog that extends to high redshift with well measured masses is indispensable for precisely constraining cosmological parameters. Detecting clusters in optical bands is very efficient. Multi-color CCD photometry allows combined detection and redshift estimation for clusters across broad redshift ranges. However, the lack of precise information about galaxy positions along the line of sight leads to contamination by projection, which plagues both cluster detection and the measurement of their properties. The dominance of red sequence galaxies, tightly clustered along the E/S0 ridgeline, provides a powerful method for de-projecting field galaxies. We developed an Error Corrected Gaussian Mixture Model to fit the galaxies color distribution around clusters by taking into account the measurement errors. By this technique, we can detect the red sequence color clustering and extract unbiased information about the evolution of the red sequence ridgeline and its width. Precision measurements of ridgelines yields better estimates of cluster richness and possibly their dynamical state, leading to better estimates of cluster mass. By using the red sequence clustering in color space identified from the Error Corrected Gaussian Mixture Model, together with the projected NFW filter in the projected RA/DEC plane, we developed a new and efficient cluster finding algorithm that can reliably detect galaxy clusters across the redshift range from 0.1 to 1.4. We have also run the cluster finder on legacy SDSS DR7 data and assembled an approximately volume limited cluster catalog across redshifts from 0.1 to 0.5. The algorithm has been tested against a Monte Carlo mock catalog, showing the identified clusters are highly complete and pure. With the completion of this thesis, we build the first and essential step towards precision cluster cosmology. Meanwhile, the large optical cluster catalog across a wide redshift range makes possible the systematic and detailed investigation of cluster formation and evolution.
Download or read book A Faint Galaxy Redshift Survey Behind Massive Clusters written by Brenda Louise Frye and published by . This book was released on 1999 with total page 730 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Seeing Red written by Halton C. Arp and published by Apeiron. This book was released on 1998 with total page 326 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Photometric Redshifts in the IRAC Shallow Survey written by and published by . This book was released on 2006 with total page 37 pages. Available in PDF, EPUB and Kindle. Book excerpt: Accurate photometric redshifts are calculated for nearly 200,000 galaxies to a 4.5 micron flux limit of H"13 [mu]Jy in the 8.5 deg2 Spitzer/IRAC Shallow survey. Using a hybrid photometric redshift algorithm incorporating both neural-net and template-fitting techniques, calibrated with over 15,000 spectroscopic redshifts, a redshift accuracy of [sigma] = 0.06 (1+z) is achieved for 95% of galaxies at 0 z 1.5. The accuracy is [sigma] = 0.12 (1 + z) for 95% of AGN at 0
Download or read book The SDSS Coadd written by and published by . This book was released on 2011 with total page 16 pages. Available in PDF, EPUB and Kindle. Book excerpt: We present and describe a catalog of galaxy photometric redshifts (photo-z's) for the Sloan Digital Sky Survey (SDSS) Coadd Data. We use the Artificial Neural Network (ANN) technique to calculate photo-z's and the Nearest Neighbor Error (NNE) method to estimate photo-z errors for H"13 million objects classified as galaxies in the coadd with r
Download or read book Photometric Redshifts for the Dark Energy Survey and VISTA and Implications for Large Scale Structure written by and published by . This book was released on 2007 with total page 17 pages. Available in PDF, EPUB and Kindle. Book excerpt: We conduct a detailed analysis of the photometric redshift requirements for the proposed Dark Energy Survey (DES) using two sets of mock galaxy simulations and an artificial neural network code-ANNz. In particular, we examine how optical photometry in the DES grizY bands can be complemented with near infra-red photometry from the planned VISTA Hemisphere Survey (VHS) in the JHK{sub s} bands in order to improve the photometric redshift estimate by a factor of two at z> 1. We draw attention to the effects of galaxy formation scenarios such as reddening on the photo-z estimate and using our neural network code, calculate A{sub v} for these reddened galaxies. We also look at the impact of using different training sets when calculating photometric redshifts. In particular, we find that using the ongoing DEEP2 and VVDS-Deep spectroscopic surveys to calibrate photometric redshifts for DES, will prove effective. However we need to be aware of uncertainties in the photometric redshift bias that arise when using different training sets as these will translate into errors in the dark energy equation of state parameter, w. Furthermore, we show that the neural network error estimate on the photometric redshift may be used to remove outliers from our samples before any kind of cosmological analysis, in particular for large-scale structure experiments. By removing all galaxies with a 1[sigma] photo-z scatter greater than 0.1 from our DES+VHS sample, we can constrain the galaxy power spectrum out to a redshift of 2 and reduce the fractional error on this power spectrum by H"5-20% compared to using the entire catalogue.
Download or read book Group finding with Photometric Redshifts written by Bryan Gillis and published by . This book was released on 2010 with total page 48 pages. Available in PDF, EPUB and Kindle. Book excerpt: We present a galaxy group-finding algorithm, the Photo-z Probability Peaks (P3) algorithm, optimized for locating small galaxy groups using photometric redshift data by searching for peaks in the signal-to-noise of the local overdensity of galaxies in a 3-dimensional grid. This method is an improvement over similar matched-filter methods in reducing background contamination through the use of redshift information, allowing it to accurately detect groups to a much lower size limit. We present the results of tests of our algorithm on galaxy catalogues from the Millennium Simulation. For typical settings of our algorithm and photometric redshift accuracy of sigma_z = 0.05 it attains a purity of 84% and detects ~83 groups/deg.^2 with an average group size of 5.5 members. With photometric redshift accuracy of sigma_z = 0.02, it attains a purity of 94% and detects ~80 groups/deg.^2 with an average group size of 6.3 members. We also test our algorithm on data available for the COSMOS field and the presently-available fields from the CFHTLS-Wide survey, presenting preliminary results of this analysis.
Download or read book The Redshift Controversy written by George B. Field and published by Addison Wesley Longman. This book was released on 1973 with total page 360 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Better Input Better Output written by John Bryce Kalmbach and published by . This book was released on 2019 with total page 163 pages. Available in PDF, EPUB and Kindle. Book excerpt: We are at the beginning of an era of large scale survey astronomy where we will soon measure photometry for billions of galaxies. In order to effectively use these galaxies for dark energy measurements we require measurements of the distances to these galaxies. Spectroscopic redshifts are not feasible for more than a small fraction of these galaxies and thus our primary distance measurements will rely on photometric redshift methods. This thesis highlights three challenges in photometric redshift estimation and techniques we developed to tackle these challenges: Using Information Theory to Optimize Bandpasses for Photometric Redshifts: We apply ideas from information theory to create a method for the design of optimal filters for photometric redshift estimation. We show the method applied to a series of simple example filters in order to motivate an intuition for how photometric redshift estimators respond to the properties of photometric passbands. We then design a realistic set of six filters covering optical wavelengths that optimize photometric redshifts for z [less than or equal to] 2. We create a simulated catalog for these optimal filters and use our filters with a photometric redshift estimation code to compare to the filters for the Large Synoptic Survey Telescope (LSST) which have key features in common with our optimal filters. Expanding Template Sets for Template Based Photo-Z Algorithms: Measuring the physical properties of galaxies such as redshift frequently requires the use of Spectral Energy Distributions (SEDs). SED template sets are, however, often small in number and cover limited portions of photometric color space. Here we present a new method to estimate SEDs as a function of color from a small training set of template SEDs. We first cover the mathematical background behind the technique before demonstrating our ability to reconstruct spectra based upon colors and then compare to other common interpolation and extrapolation methods. When the photometric filters and spectra overlap we show reduction of error in the estimated spectra of over 65% compared to the more commonly used techniques. We also show an expansion of the method to wavelengths beyond the range of the photometric filters. Finally, we demonstrate the usefulness of our technique by generating 50 additional SED templates from an original set of 10 and applying the new set to photometric redshift estimation. We are able to reduce the photometric redshifts standard deviation by at least 22.0% and the outlier rejected bias by over 86.2% compared to original set for z [less than or equal to] 3. Color Space Data Augmentation for Photometric Redshifts: When training sets for machine learning methods are not representative of the test set then there can be errors in the resulting estimates. In photometric redshifts this can happen when the color space of the spectroscopic data does not match the observed galaxy color space for an empirical photometric redshift estimation method. We first show how a lack of data in a region of color space of the training data affects photometric redshift estimation and then develop three different methods to add in synthetic training data to the missing area to mitigate the errors. Our best performing method lowers the photo-z bias by 51% and reduces the outlier fraction by 9.6% in the test data that lies in the missing area of color space compared to an unrepresentative training catalog.
Download or read book Pair Analysis of the Photometric Redshift Catalog from the Red Sequence Cluster Survey written by 謝寶慶 and published by . This book was released on 2005 with total page 226 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Catastrophic Photometric Redshift Errors written by and published by . This book was released on 2010 with total page 10 pages. Available in PDF, EPUB and Kindle. Book excerpt: We study the sensitivity of weak lensing surveys to the effects of catastrophic redshift errors - cases where the true redshift is misestimated by a significant amount. To compute the biases in cosmological parameters, we adopt an efficient linearized analysis where the redshift errors are directly related to shifts in the weak lensing convergence power spectra. We estimate the number Nspec of unbiased spectroscopic redshifts needed to determine the catastrophic error rate well enough that biases in cosmological parameters are below statistical errors of weak lensing tomography. While the straightforward estimate of Nspec is ~106 we find that using only the photometric redshifts with z ≤ 2.5 leads to a drastic reduction in Nspec to ~ 30,000 while negligibly increasing statistical errors in dark energy parameters. Therefore, the size of spectroscopic survey needed to control catastrophic errors is similar to that previously deemed necessary to constrain the core of the zs - zp distribution. We also study the efficacy of the recent proposal to measure redshift errors by cross-correlation between the photo-z and spectroscopic samples. We find that this method requires ~ 10% a priori knowledge of the bias and stochasticity of the outlier population, and is also easily confounded by lensing magnification bias. In conclusion, the cross-correlation method is therefore unlikely to supplant the need for a complete spectroscopic redshift survey of the source population.
