Download or read book Photometric Redshifts for Future Cosmological Galaxy Surveys written by Daniel Michael Jones and published by . This book was released on 2019 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Higher Resolution Photometric Redshifts for Cosmological Surveys written by Alex Alarcon Gonzalez and published by . This book was released on 2019 with total page 149 pages. Available in PDF, EPUB and Kindle. Book excerpt: This PhD thesis is focused on the measurement of photometric redshifts in imaging galaxy surveys and its applications to extract cosmological information. In the first part of this thesis we forecast a galaxy survey with very precise redshift information, which can come either from spectroscopy or many narrow band images, using the Fisher matrix formalism. We use galaxy clustering, how galaxies group together in space, dividing a sample into two subsamples using other observable parameters. Using two overlapping subsamples reduces the sample variance in the observables, which improves the precision with which one can measure the expansion and growth history of the universe. In the second part of this thesis we measure highly precise photometric redshifts using the data from a novel imaging galaxy survey PAUS that contains a unique set of 40 narrow band filters. We develop two algorithms which use maximum likelihood or Bayesian evidence statistics to infer the redshift probability of each galaxy, which requires modeling both the continuum and emission line galaxy flux. The algorithm contains several corrections to account for systematic effects present in the data calibration which are tested in simulations developed for this purpose. The measurement of PAUS redshifts enables the science of the galaxy survey and can also be used to calibrate the redshift distribution of lensing surveys. The last part of this thesis implements for the first time a hierarchical Bayesian model in an N-body simulation to measure the redshift distribution of a lensing survey using both photometric and density information. Weak lensing is a very powerful tool to extract cosmological information, but it is very sensitive to any bias in the mean redshift of a sample of source galaxies. This method consistently combines all sources of information and merges the main techniques used in the literature to estimate redshift distributions.
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 Galaxies at High Redshift and their Evolution over Cosmic Time IAU S319 written by Sugata Kaviraj and published by Cambridge University Press. This book was released on 2016-09-15 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: IAU Symposium 319 was the largest galaxy evolution meeting at the IAU General Assembly in 2015. This volume presents a summary of the current state of the art in galaxy evolution studies, and provides a perspective on future large spectro-photometric surveys which will become available in the next decade. Topics covered include the emergence of galaxies and their constituent black holes during the first few billion years, the evolving interstellar medium as seen through modern instrumentation like Herschel, Planck and ALMA, and a look ahead to future ground- and space-based instruments that will become the workhorse facilities of the next decade, such as JWST and the SKA precursors. This volume will appeal to those who are interested in the formation and evolution of galaxies over cosmic time, as well as those who are active in developing, or on the science teams for, new astronomical instrumentation.
Download or read book Optimizing Spectroscopic and Photometric Galaxy Surveys written by and published by . This book was released on 2015 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The combination of multiple cosmological probes can produce measurements of cosmological parameters much more stringent than those possible with any individual probe. We examine the combination of two highly correlated probes of late-time structure growth: (i) weak gravitational lensing from a survey with photometric redshifts and (ii) galaxy clustering and redshift space distortions from a survey with spectroscopic redshifts. We choose generic survey designs so that our results are applicable to a range of current and future photometric redshift (e.g. KiDS, DES, HSC, Euclid) and spectroscopic redshift (e.g. DESI, 4MOST, Sumire) surveys. Combining the surveys greatly improves their power to measure both dark energy and modified gravity. An independent, non-overlapping combination sees a dark energy figure of merit more than 4 times larger than that produced by either survey alone. The powerful synergies between the surveys are strongest for modified gravity, where their constraints are orthogonal, producing a non-overlapping joint figure of merit nearly 2 orders of magnitude larger than either alone. Our projected angular power spectrum formalism makes it easy to model the cross-correlation observable when the surveys overlap on the sky, producing a joint data vector and full covariance matrix. We calculate a same-sky improvement factor, from the inclusion of these cross-correlations, relative to non-overlapping surveys. We find nearly a factor of 4 for dark energy and more than a factor of 2 for modified gravity. The exact forecast figures of merit and same-sky benefits can be radically affected by a range of forecasts assumption, which we explore methodically in a sensitivity analysis. We show that that our fiducial assumptions produce robust results which give a good average picture of the science return from combining photometric and spectroscopic surveys.
Download or read book High Redshift Galaxies written by Immo Appenzeller and published by Springer Science & Business Media. This book was released on 2009-06-17 with total page 353 pages. Available in PDF, EPUB and Kindle. Book excerpt: The high-redshift galaxies became a distinct research ?eld during the ?nal decade of the20thcentury. AtthattimetheLyman-breaktechniquemadeitpossibletoidentify signi?cant samples of such objects, and the new generation of 8 to 10-m telescopes resulted in ?rst good spectroscopic data. Today the high-redshift galaxies have developed into one of the important topics of astrophysics, accounting for about 5–10% of the publications in the major scienti?c journals devoted to astronomy. Because high-redshift galaxies is a rapidly developing ?eld and since new results are published constantly, writing a book on this topic is challenging. On the other hand, in view of the large amount of individual results now in the literature, and in view of the still growing interest in this topic, it appears worthwhile to summarize and evaluate the available data and to provide an introduction for those who wish to enter this ?eld, or who, for various reasons, might be interested in its results. The end of the ?rst decade of the 21st century appears to be a good point in time to attempt such a summary. The current generation of ground-based 8 to 10-m - optical telescopes, the Hubble Space Telescope, and the most important large radio telescopes have by now been in operation since about one or two decades. Although these instruments will continue to produce important scienti?c results for some time to come, many of the initial programs exploiting their unique new possibilities have been completed.
Download or read book Photometric Calibration Procedures written by Velma I. Burns and published by . This book was released on 1972 with total page 40 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book The Discovery of Cosmic Voids written by Laird A. Thompson and published by Cambridge University Press. This book was released on 2020-12-10 with total page 296 pages. Available in PDF, EPUB and Kindle. Book excerpt: The large-scale structure of the Universe is dominated by vast voids with galaxies clustered in knots, sheets, and filaments, forming a great 'cosmic web'. In this personal account of the major astronomical developments leading to this discovery, we learn from Laird A. Thompson, a key protagonist, how the first 3D maps of galaxies were created. Using non-mathematical language, he introduces the standard model of cosmology before explaining how and why ideas about cosmic voids evolved, referencing the original maps, reproduced here. His account tells of the competing teams of observers, racing to publish their results, the theorists trying to build or update their models to explain them, and the subsequent large-scale survey efforts that continue to the present day. This is a well-documented account of the birth of a major pillar of modern cosmology, and a useful case study of the trials surrounding how this scientific discovery became accepted.
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 Astroinformatics IAU S325 written by Massimo Brescia and published by Cambridge University Press. This book was released on 2017-06-15 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Astronomy has become data-driven in ways that are both quantitatively and qualitatively different from the past: data structures are not simple; procedures to gain astrophysical insights are not obvious; and the informational content of the data sets is so high that archival research and data mining are not merely convenient, but obligatory, as researchers who obtain the data can only extract a small fraction of the science enabled by it. IAU Symposium 325 took place at a crucial stage in the development of the field, when many efforts have carried significant achievements, but the widespread groups have just begun to effectively communicate across specialties, to gather and assimilate their achievements, and to consult cross-disciplinary experts. Bringing together astronomers involved in surveys and large simulation projects, computer scientists, data scientists, and companies, this volume showcases their fruitful exchange of ideas, methods, software, and technical capabilities.
Download or read book Science with Astronomical Near Infrared Sky Surveys written by N. Epchtein and published by Springer Science & Business Media. This book was released on 2012-12-06 with total page 271 pages. Available in PDF, EPUB and Kindle. Book excerpt: Outstanding progress in near-infrared detection technology and in real-time image processing has led astronomers to start undertaking all-sky surveys in the 1--2 mum range (project DENIS in Europe and 2MASS in the U.S.A.), surveys which will have a considerable impact in various areas of astronomy. This book gathers the contributions of more than 80 specialists involved in fields of interest as different as low mass stars, late stages of stellar evolution, star formation, stellar populations of the Galaxy and the Magellanic Clouds, the local structure of the Universe, and observational cosmology. It describes the impact on these fields of the exhaustive data bases and catalogs of stars and galaxies that these surveys will provide. The considerable interest of these documents for the future of infrared space and ground-based projects and the complementarity with other currently ongoing or planned surveys in other spectral ranges are emphasized.
Download or read book Evolution of the Galaxy Distribution in Large Cosmological Surveys written by Melody Wolk and published by . This book was released on 2013 with total page 160 pages. Available in PDF, EPUB and Kindle. Book excerpt: The main objective of this thesis is to investigate the relationship between the dark and the luminous part of the Universe. Within the standard cosmological model framework, we will use galaxies as our probes to study the matter distribution in the Universe and its evolution. In order to achieve this goal, we use statistical tools to characterize the way objects are distributed in the sky. We model our measurements using a phenomenological description: the ``halo model''. However, to make robust estimations, we need to have access to a large amount of data which is made possible by the use of photometric redshift surveys. First, we look at the redshift dependence of the hierarchical amplitudes of the galaxy distribution up to order 5 using a wide photometric survey, the Canada-France-Hawaii Telescope Legacy Survey (CFHTLS), from present day up to intermediate redshifts. We interpret these measurements in the perturbation theory framework. We found that in the weakly non-linear regime, our measurements are marginally consistent with the predictions. However, these latter slightly over-predict our measurements, which suggests the existence of higher-order bias terms. Using the halo model, we also showed that the position of the transition between the non-linear and the weakly non-linear regime is fully compatible with theoretical expectations. Then, using two-point statistics on data from the UltraVISTA-COSMOS survey, we investigate the way galaxy clustering depends on the stellar mass and the redshift beyond a redshift of one. We found that, on average, samples with higher stellar mass thresholds have higher mean clustering amplitude meaning that rarer populations are more strongly clustered. We also interpreted these measurements in the context of the halo model. Furthermore, we consider the stellar mass to halo mass ratio and follow the evolution of the peak in this quantity up to redshift z \sim ~2 trying to interpret it in terms of galaxy formation. We showed that, for the full sample, M_{h}^{peak} shifts progressively to higher halo masses at higher redshifts, an effect known as ``anti-hierarchical''. Finally, we summarize our main results and present some of our future projects.
Download or read book The Mass of Galaxies at Low and High Redshift written by Ralf Bender and published by Springer Science & Business Media. This book was released on 2003-01-23 with total page 394 pages. Available in PDF, EPUB and Kindle. Book excerpt: Measuring the masses of galaxies as a function of redshift is perhaps one of the most challenging open issues in current astronomical research. The evolution of the baryonic and dark matter components of galaxies is not only a critical test of the hierarchical formation paradigm, but ultimately also provides new clues on the complex interplay between star formation, the cooling and heating of gas and galaxy merging processes. This book reviews current techniques to measure the baryonic (stellar) and dark masses of nearby galaxies, and focusses on ongoing attempts to measure theses same quantities in galaxies at higher and higher redshifts. It also gives room to future perspectives, with special emphasis on new survey projects and satellite missions.
Download or read book Extending and Implementing the Self calibration of Intrinsic Alignments of Galaxies to Current and Future Weak Lensing Surveys written by Ji Yao and published by . This book was released on 2018 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: This dissertation is about extending and applying the self-calibration method for mitigation of intrinsic alignments (IAs) of galaxies. These IA correlations are due to galaxy formation earlier processes that act as a systematic effect to weak gravitational lensing (WL). For ongoing and future WL surveys to reach their full potential as cosmological probes, these IA systematics must be isolated and removed. There are two types of IAs, the “gravitational shear - intrinsic ellipticity” (GI) and the “intrinsic ellipticity - intrinsic ellipticity” (II) correlation. It can affect the lensing power spectrum at 10% level and cause a mis-estimation of the cosmological parameters, especially in the dark energy equation of state where the bias can be up to 50% and the amplitude of matter power spectrum can be up to 30% . The Self-Calibration (SC) technique has been introduced to subtract the shear-intrinsic (GI) IA contamination in a photometric redshift (photo-z) survey, at a level of 90%. In this work, we present a comparison between the SC technique and the traditional method of modeling IA for an LSST-like survey. We also consider the effect of photometric redshift (photo-z). By comparing the confidence contours of applying SC and using marginalization with modeling IA, we show that SC is competitive with modeling IA method and is applicable to data. We show how several aspects of SC can be improved. The efficiency of the SC method is high in two redshift bins at large separation, but is relatively low in close bin-pairs. Also it doesn’t apply to the auto-spectra where the (II) signal is significant. We present a novel SC method that can solve these problems. By combining our new SC method with the previously existing SC, the effciency for the GI signal in adjacent bins can be improved from ∼ 90% to ∼ 97%, and the II can be measured with ∼ 1% level bias in all bin-pairs. This combined method can largely reduce the residual bias of the SC method and hence improve the accuracy of the best-fit cosmological parameters. We further summarized the current work on SC and discussed its assumptions on the IA models. Finally, we apply the SC to KiDS-450 survey data to test the applicability of the SC method. This photometric survey of ∼ 1.5×107 galaxies is one of the best currently available samples to use. Despite some well-known issues with the photo-zs in this sample, we find what appears to be a significant detection of IA using SC. However, due to the photo-z unreliability, this can be considered as a proof of principle for this moment. Future applications of SC to incoming and future data from surveys such as DES and LSST will allow one to obtain more decisive results using SC.
Download or read book Galaxies at High Redshift and Their Evolution Over Cosmic Time written by International Astronomical Union. Symposium and published by . This book was released on with total page 149 pages. Available in PDF, EPUB and Kindle. Book excerpt: IAU Symposium 319 was the largest galaxy evolution meeting at the IAU General Assembly in 2015. This volume presents a summary of the current state of the art in galaxy evolution studies, and provides a perspective on future large spectro-photometric surveys which will become available in the next decade. Topics covered include the emergence of galaxies and their constituent black holes during the first few billion years, the evolving interstellar medium as seen through modern instrumentation like Herschel, Planck and ALMA, and a look ahead to future ground- and space-based instruments that will become the workhorse facilities of the next decade, such as JWST and the SKA precursors. This volume will appeal to those who are interested in the formation and evolution of galaxies over cosmic time, as well as those who are active in developing, or on the science teams for, new astronomical instrumentation. -- Publisher description.
Download or read book The Universe of Digital Sky Surveys written by Nicola R. Napolitano and published by Springer. This book was released on 2016-05-16 with total page 296 pages. Available in PDF, EPUB and Kindle. Book excerpt: These are the proceedings of a meeting in honour of Massimo Capaccioli at the occasion of his 70th birthday. The conference aimed at summarizing the results from the main current and past digital sky survey projects and at discussing how these can be used to inspire ongoing projects and better plan the future ones. Over the last decades, digital sky surveys performed with dedicated telescopes and finely-tuned wide-field cameras, have revolutionized astronomy. They have become the main tool to investigate the nearby and far away universe, thus providing new insights in the understanding of the galaxy structure and assembly across time, the dark components of the universe, as well as the history of our own galaxy. They have also opened the time domain leading to a new understanding of the transient phenomena in the universe. By providing public access to top quality data, digital surveys have also changed the everyday practice of astronomers who have become less dependent on direct access to large observing facilities. The full scientific exploitation of these surveys has also triggered significant advances in both space and ground based technology and in the field of multi-object spectroscopy. The various sections of this book are devoted to different relevant aspects of astrophysics in the era of digital sky surveys and include both review and shorter, more focused contributions.
Download or read book Multi probe Cluster Cosmology Analyses with Photometric Surveys written by Chun-Hao To and published by . This book was released on 2021 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The universe we live in is expanding faster and faster. This phenomenon called cosmic acceleration is one of the most puzzling cosmological discoveries in the past 25 years: even the least exotic explanation requires a new pervasive energy component in our universe (called dark energy). Despite the mysterious nature of dark energy, a model ($\Lambda$CDM) based on Einstein's general relativity, a cosmological constant (a specific form of dark energy), and slowly moving dark matter, seems to be able to describe a variety of observations from the high- to low-redshift universe. To understand the nature of dark energy and to test the $\Lambda$CDM paradigm, ambitious cosmological surveys, such as the Dark Energy Survey (DES), the Dark Energy Spectroscopic Instrument (DESI), the Rubin Observatory's Legacy Survey of Space and Time (LSST), and the Roman Space Telescope, aim to precisely and robustly measure cosmic structure and its evolution via various cosmological probes, such as weak gravitational lensing, galaxy clustering, and other techniques. Combining multiple cosmological probes (known as multi-probe analyses) provides precise and robust cosmological constraints. Galaxy clustering, weak gravitational lensing, and abundances of galaxy clusters each are sensitive to different aspects of cosmic structure formation and are affected by different astrophysical and observational uncertainties. Thus, their combination is expected to be more precise and robust than any of the probe alone. Among these probes, the abundances and spatial distribution of galaxy clusters, which are associated with the highest peaks in the matter density field, provide powerful probes of cosmic structure and its evolution. This thesis presents original research that improves our understandings of the universe by observations of galaxy clusters. In the three self-contained projects, I (1) develop and validate methods for combining cluster abundances and two-point correlation functions, (2) perform the first blind cosmology analysis on combining cluster abundances, weak gravitational lensing, and galaxy clustering using data taken in the first season (DES-Y1) of the Dark Energy Survey, and (3) quantify the connections between red galaxies and their host dark matter halos by modeling luminosity functions of galaxies in galaxy clusters. While these three projects have already advanced our understandings of the cosmos, they also serve as an example of how one can use millions of clusters expected to be detected with the upcoming surveys in 2020s to improve our knowledge of the universe. These opportunities are also discussed in this thesis.
