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 More Things in the Heavens written by Michael Werner and published by Princeton University Press. This book was released on 2019-06-25 with total page 305 pages. Available in PDF, EPUB and Kindle. Book excerpt: A sweeping tour of the infrared universe as seen through the eyes of NASA’s Spitzer Space Telescope Astronomers have been studying the heavens for thousands of years, but until recently much of the cosmos has been invisible to the human eye. Launched in 2003, the Spitzer Space Telescope has brought the infrared universe into focus as never before. Michael Werner and Peter Eisenhardt are among the scientists who worked for decades to bring this historic mission to life. Here is their inside story of how Spitzer continues to carry out cutting-edge infrared astronomy to help answer fundamental questions that have intrigued humankind since time immemorial: Where did we come from? How did the universe evolve? Are we alone? In this panoramic book, Werner and Eisenhardt take readers on a breathtaking guided tour of the cosmos in the infrared, beginning in our solar system and venturing ever outward toward the distant origins of the expanding universe. They explain how astronomers use the infrared to observe celestial bodies that are too cold or too far away for their light to be seen by the eye, to conduct deep surveys of galaxies as they appeared at the dawn of time, and to peer through dense cosmic clouds that obscure major events in the life cycles of planets, stars, and galaxies. Featuring many of Spitzer’s spectacular images, More Things in the Heavens provides a thrilling look at how infrared astronomy is aiding the search for exoplanets and extraterrestrial life, and transforming our understanding of the history and evolution of our universe.

Download or read book NOAO NSO Newsletter written by and published by . This book was released on 2006 with total page 250 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book An IR Selected Galaxy Cluster at Z written by and published by . This book was released on 2006 with total page 7 pages. Available in PDF, EPUB and Kindle. Book excerpt: We report the discovery of a galaxy cluster at z = 1.41. ISCS J143809+341419 was found in the Spitzer/IRAC Shallow Survey of the Bootes field in the NOAO Deep Wide-Field Survey carried out by IRAC. The cluster candidate was initially identified as a high density region of objects with photometric redshifts in the range 1.3

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 A Panchromatic View of Galaxies written by Alessandro Boselli and published by John Wiley & Sons. This book was released on 2012-01-13 with total page 343 pages. Available in PDF, EPUB and Kindle. Book excerpt: Describing how to investigate all kinds of galaxies through a multifrequency analysis, this text is divided into three different sections. The first describes the data currently available at different frequencies, from X-rays to UV, optical, infrared and radio millimetric and centimetric, while explaining their physical meaning. In the second section, the author explains how these data can be used to determine physical parameters and quantities, such as mass and temperature. The final section is devoted to describing how the derived quantities can be used in a multifrequency analysis to study such physical processes as the star formation cycle and constrain models of galaxy evolution. As a result, observers will be able to interpret galaxies and their structure.

Download or read book Photometric Redshifts and High Redshift Galaxies written by Ray J. Weymann and published by . This book was released on 1999 with total page 410 pages. Available in PDF, EPUB and Kindle. Book excerpt: The 52 papers respond to the explosion of the search for and discovery of high redshift galaxies and the application of broad-band photometry to obtain remarkably reliable estimates of the redshifts of galaxies at all redshifts, spurred not only by the Hubble Deep Fields, but also by the advent of wide-field CCDs on ground-based telescopes and the development of sensitive infrared, submillimeter, and millimeter instrumentation. They discuss techniques, findings, and integrating new data into existing models of galaxy formation and evolution.

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 Accurate Photometry and Photometric Redshifts for Cosmological Surveys written by Alberto Molino Benito and published by . This book was released on 2014 with total page 171 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Panoramic Views of Galaxy Formation and Evolution written by Tadayuki Kodama and published by . This book was released on 2008 with total page 572 pages. Available in PDF, EPUB and Kindle. Book excerpt: "These proceedings of the first meeting of the Subaru International Conference Series held in December 2007 in Hayama, Japan, provide unique up-to-date overviews of the history of galaxy formation and the evolution of the universe. Fascinating and comprehensive observational results as well as many important theoretical achievements were presented by more than 150 active researchers from more than 15 countries and regions. The conference started off with results from recent cutting-edge observations of the very high-redshift universe extending into the cosmic reionization era, together with some theoretical interpretations and predictions for the first generation of galaxies. The history of mass distributions and structure formation at later cosmic times, including clusters of galaxies, was discussed extensively in presentations based on various panoramic survey data sets. Our aim was to showcase and understand the intrinsic galaxy-formation bias in the high-redshift universe and also the role of external environmental effects during the hierarchical assembly of galaxies into denser regions. Various populations of distant galaxies at different redshifts, discovered and studies by many different techniques, were introduced along with the physical relationship between these populations. Our discussion were aimed at assembling these pieces of jigsaw puzzles together into a panoramic and yet detailed structures of the Milky Way Galaxy and the Local Group galaxies were also presented and discussed as a complementary approach to the studies of the high-redshift Universe. In total, 19 invited talks, 46 contributed talks, and 87 poster papers combined to build up a picture of the history of galaxies over the cosmic age. This book is suitable for researchers who are interested in both observational and theoretical aspects of galaxy formation and cosmology, and especially for students seeking an overview of knowledge about galaxy formation to date."--Publisher's website

Download or read book Photometric Redshifts and Luminosity Functions from the Spitzer Swire Survey written by and published by . This book was released on 2004 with total page 486 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book National Optical Astronomy Observatories Newsletter written by and published by . This book was released on 2006 with total page 526 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Advances in Machine Learning and Data Mining for Astronomy written by Michael J. Way and published by CRC Press. This book was released on 2012-03-29 with total page 744 pages. Available in PDF, EPUB and Kindle. Book excerpt: Advances in Machine Learning and Data Mining for Astronomy documents numerous successful collaborations among computer scientists, statisticians, and astronomers who illustrate the application of state-of-the-art machine learning and data mining techniques in astronomy. Due to the massive amount and complexity of data in most scientific disciplines

Download or read book Probabilistic Photometric Redshifts in the Era of Petascale Astronomy written by and published by . This book was released on 2014 with total page 188 pages. Available in PDF, EPUB and Kindle. Book excerpt: With the growth of large photometric surveys, accurately estimating photometric redshifts, preferably as a probability density function (PDF), and fully understanding the implicit systematic uncertainties in this process has become increasingly important. These surveys are expected to obtain images of billions of distinct galaxies. As a result, storing and analyzing all of these photometric redshift PDFs will be non-trivial, and this challenge becomes even more severe if a survey plans to compute and store multiple different PDFs. In this thesis, we have developed an end-to-end framework that will compute accurate and robust photometric redshift PDFs for massive data sets by using two new, state-of-the-art machine learning techniques that are based on a random forest and a random atlas, respectively. By using data from several photometric surveys, we demonstrate the applicability of these new techniques, and we demonstrate that our new approach is among the best techniques currently available. We also show how different techniques can be combined by using novel Bayesian techniques to improve the photometric redshift precision to unprecedented levels while also presenting new approaches to better identify outliers. In addition, our framework provides supplementary information regarding the data being analyzed, including unbiased estimates of the accuracy of the technique without resorting to a validation data set, identification of poor photometric redshift areas within the parameter space occupied by the spectroscopic training data, and a quantification of the relative importance of the variables used during the estimation process. Furthermore, we present a new approach to represent and store photometric redshift PDFs by using a sparse representation with outstanding compression and reconstruction capabilities. We also demonstrate how this framework can also be directly incorporated into cosmological analyses. The new techniques presented in this thesis are crucial to enable the development of precision cosmology in the era of petascale astronomical surveys.

Download or read book Photometric Redshifts and Luminosoty Functions from the SPITZER SWIRE Survey written by and published by . This book was released on 2004 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 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: