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Sample records for catastrophic photometric redshift

  1. A GENERAL STUDY OF THE INFLUENCE OF CATASTROPHIC PHOTOMETRIC REDSHIFT ERRORS ON COSMOLOGY WITH COSMIC SHEAR TOMOGRAPHY

    International Nuclear Information System (INIS)

    A goal of forthcoming imaging surveys is to use weak gravitational lensing shear measurements to constrain dark energy. A challenge to this program is that redshifts to the lensed, source galaxies must be determined using photometric, rather than spectroscopic, information. We quantify the importance of uncalibrated photometric redshift outliers to the dark energy goals of forthcoming imaging surveys in a manner that does not assume any particular photometric redshift technique or template. In so doing, we provide an approximate blueprint for computing the influence of specific outlier populations on dark energy constraints. We find that outlier populations whose photo-z distributions are tightly localized about a significantly biased redshift must be controlled to a per-galaxy rate of (1-3) x 10-3 to insure that systematic errors on dark energy parameters are rendered negligible. In the complementary limit, a subset of imaged galaxies with uncalibrated photometric redshifts distributed over a broad range must be limited to fewer than a per-galaxy error rate of F cat ∼-4. Additionally, we explore the relative importance of calibrating the photo-z's of a core set of relatively well-understood galaxies as compared to the need to identify potential catastrophic photo-z outliers. We discuss the degradation of the statistical constraints on dark energy parameters induced by excising source galaxies at high- and low-photometric redshifts, concluding that removing galaxies with photometric redshifts z ph ∼> 2.4 and z ph ∼< 0.3 may mitigate damaging catastrophic redshift outliers at a relatively small (∼<20%) cost in statistical error. In an Appendix, we show that forecasts for the degradation in dark energy parameter constraints due to uncertain photometric redshifts depend sensitively on the treatment of the nonlinear matter power spectrum. In particular, previous work using Peacock and Dodds may have overestimated the photo-z calibration requirements of future

  2. Uncertain Photometric Redshifts

    CERN Document Server

    Polsterer, Kai Lars; Gieseke, Fabian

    2016-01-01

    Photometric redshifts play an important role as a measure of distance for various cosmological topics. Spectroscopic redshifts are only available for a very limited number of objects but can be used for creating statistical models. A broad variety of photometric catalogues provide uncertain low resolution spectral information for galaxies and quasars that can be used to infer a redshift. Many different techniques have been developed to produce those redshift estimates with increasing precision. Instead of providing a point estimate only, astronomers start to generate probabilistic density functions (PDFs) which should provide a characterisation of the uncertainties of the estimation. In this work we present two simple approaches on how to generate those PDFs. We use the example of generating the photometric redshift PDFs of quasars from SDSS(DR7) to validate our approaches and to compare them with point estimates. We do not aim for presenting a new best performing method, but we choose an intuitive approach t...

  3. The impact of photometric redshift errors on weak lensing tomography: a clipping method of the catastrophic errors

    CERN Document Server

    Nishizawa, Atsushi J; Hamana, Takashi; Furusawa, Hisanori

    2010-01-01

    We use the mock catalog of galaxies, constructed based on the COSMOS galaxy catalog including information on photometric redshifts (photo-z) and SED types of galaxies, in order to study how to define a galaxy subsample suitable for weak lensing tomography feasible with optical (and NIR) multi-band data. Since most of useful cosmological information arises from the sample variance limited regime for planned lensing surveys, a suitable subsample can be obtained by discarding a large fraction of galaxies that have less reliable photo-z estimations, mostly photo-z outliers. We develop a method to efficiently identify photo-z outliers by monitoring the width of posterior likelihood unction of redshift estimation for each galaxies. By using the Fisher information matrix formalism, we propagate photo-z errors into biases in cosmological parameters, especially dark energy equation of state parameter w. We found that, by discarding most of ill-defined photo-z galaxies, the bias in w may be reduced to the level compara...

  4. Photometric Redshifts of Submillimeter Galaxies

    CERN Document Server

    Chakrabarti, Sukanya; McKee, Christopher F; Lutz, Dieter; Berta, Stefano; Popesso, Paola; Pozzi, Francesca

    2012-01-01

    We use the photometric redshift method of Chakrabarti & McKee (2008) to infer photometric redshifts of submillimeter galaxies with far-IR (FIR) $\\it{Herschel}$ data obtained as part of the PACS Evolutionary Probe (PEP) program. For the sample with spectroscopic redshifts, we demonstrate the validity of this method over a large range of redshifts ($ 4 \\ga z \\ga 0.3$) and luminosities, finding an average accuracy in $(1+z_{\\rm phot})/(1+z_{\\rm spec})$ of 10%. Thus, this method is more accurate than other FIR photometric redshift methods. This method is different from typical FIR photometric methods in deriving redshifts from the light-to-gas mass ($L/M$) ratio of infrared-bright galaxies inferred from the FIR spectral energy distribution (SED), rather than dust temperatures. Once the redshift is derived, we can determine physical properties of infrared bright galaxies, including the temperature variation within the dust envelope, luminosity, mass, and surface density. We use data from the GOODS-S field to c...

  5. Overconfidence in Photometric Redshift Estimation

    CERN Document Server

    Wittman, David; Tobin, Ryan

    2016-01-01

    We describe a new test of photometric redshift performance given a spectroscopic redshift sample. This test complements the traditional comparison of redshift {\\it differences} by testing whether the probability density functions $p(z)$ have the correct {\\it width}. We test two photometric redshift codes, BPZ and EAZY, on each of two data sets and find that BPZ is consistently overconfident (the $p(z)$ are too narrow) while EAZY produces approximately the correct level of confidence. We show that this is because EAZY models the uncertainty in its spectral energy distribution templates, and that post-hoc smoothing of the BPZ $p(z)$ provides a reasonable substitute for detailed modeling of template uncertainties. Either remedy still leaves a small surplus of galaxies with spectroscopic redshift very far from the peaks. Thus, better modeling of low-probability tails will be needed for high-precision work such as dark energy constraints with the Large Synoptic Survey Telescope and other large surveys.

  6. Overconfidence in photometric redshift estimation

    Science.gov (United States)

    Wittman, David; Bhaskar, Ramya; Tobin, Ryan

    2016-04-01

    We describe a new test of photometric redshift performance given a spectroscopic redshift sample. This test complements the traditional comparison of redshift differences by testing whether the probability density functions p(z) have the correct width. We test two photometric redshift codes, BPZ and EAZY, on each of two data sets and find that BPZ is consistently overconfident (the p(z) are too narrow) while EAZY produces approximately the correct level of confidence. We show that this is because EAZY models the uncertainty in its spectral energy distribution templates, and that post-hoc smoothing of the BPZ p(z) provides a reasonable substitute for detailed modelling of template uncertainties. Either remedy still leaves a small surplus of galaxies with spectroscopic redshift very far from the peaks. Thus, better modelling of low-probability tails will be needed for high-precision work such as dark energy constraints with the Large Synoptic Survey Telescope and other large surveys.

  7. PHOTOMETRIC REDSHIFTS OF SUBMILLIMETER GALAXIES

    Energy Technology Data Exchange (ETDEWEB)

    Chakrabarti, Sukanya [School of Physics and Astronomy, Rochester Institute of Technology, 84 Lomb Memorial Drive, Rochester, NY 14623 (United States); Magnelli, Benjamin; Lutz, Dieter; Berta, Stefano; Popesso, Paola [Max-Planck-Institut fuer Extraterrestrische Physik, Postfach 1312, Giessenbachstrasse 1, D-85741 Garching (Germany); McKee, Christopher F. [Physics and Astronomy Departments, UC Berkeley, Berkeley, CA 94720 (United States); Pozzi, Francesca, E-mail: chakrabarti@astro.rit.edu [Dipartimento di Astronomia, Universita degli Studi di Bologna, Via Ranzani 1, I-40127 Bologna (Italy)

    2013-08-20

    We use the photometric redshift method of Chakrabarti and McKee to infer photometric redshifts of submillimeter galaxies with far-IR (FIR) Herschel data obtained as part of the PACS Evolutionary Probe program. For the sample with spectroscopic redshifts, we demonstrate the validity of this method over a large range of redshifts (4 {approx}> z {approx}> 0.3) and luminosities, finding an average accuracy in (1 + z{sub phot})/(1 + z{sub spec}) of 10%. Thus, this method is more accurate than other FIR photometric redshift methods. This method is different from typical FIR photometric methods in deriving redshifts from the light-to-gas mass (L/M) ratio of infrared-bright galaxies inferred from the FIR spectral energy distribution, rather than dust temperatures. To assess the dependence of our photometric redshift method on the data in this sample, we contrast the average accuracy of our method when we use PACS data, versus SPIRE data, versus both PACS and SPIRE data. We also discuss potential selection effects that may affect the Herschel sample. Once the redshift is derived, we can determine physical properties of infrared-bright galaxies, including the temperature variation within the dust envelope, luminosity, mass, and surface density. We use data from the GOODS-S field to calculate the star formation rate density (SFRD) of submillimeter bright sources detected by AzTEC and PACS. The AzTEC-PACS sources, which have a threshold 850 {mu}m flux {approx}> 5 mJy, contribute 15% of the SFRD from all ultraluminous infrared galaxies (L{sub IR} {approx}> 10{sup 12} L{sub Sun }), and 3% of the total SFRD at z {approx} 2.

  8. A blind test of photometric redshift prediction

    OpenAIRE

    Hogg, David W.; Cohen, Judith G.; Blandford, Roger; Gwyn, Stephen D. J.; Hartwick, F. D. A.; Mobasher, B.; Mazzei, Paula; Sawicki, Marcin; Lin, Huan; Yee, H. K. C.; Connolly, Andrew J; Brunner, Robert J.; Csabai, Istvan; Dickinson, Mark; SubbaRao, Mark U.

    1998-01-01

    Results of a blind test of photometric redshift predictions against spectroscopic galaxy redshifts obtained in the Hubble Deep Field with the Keck Telescope are presented. The best photometric redshift schemes predict spectroscopic redshifts with a redshift accuracy of |Delta-z|

  9. A blind test of photometric redshift prediction

    CERN Document Server

    Hogg, D W; Blandford, R D; Gwyn, S D J; Hartwick, F D A; Mobasher, B; Mazzei, P; Sawicki, M; Lin, H; Yee, H K C; Connolly, A J; Brunner, R J; Csabai, I; Dickinson, M; Subba-Rao, M; Szalay, A S; Fernández-Soto, A; Lanzetta, K M; Yahil, A; Hogg, David W.; Cohen, Judith G.; Blandford, Roger; Gwyn, Stephen D. J.; Mazzei, Paula; Sawicki, Marcin; Lin, Huan; Connolly, Andrew J.; Brunner, Robert J.; Csabai, Istvan; Dickinson, Mark; Rao, Mark U. Subba; Szalay, Alexander S.; Fernandez-Soto, Alberto; Lanzetta, Kenneth M.; Yahil, Amos

    1998-01-01

    Results of a blind test of photometric redshift predictions against spectroscopic galaxy redshifts obtained in the Hubble Deep Field with the Keck Telescope are presented. The best photometric redshift schemes predict spectroscopic redshifts with a redshift accuracy of |Delta-z|<0.1 for more than 68 percent of sources and with |Delta-z|<0.3 for 100 percent, when single-feature spectroscopic redshifts are removed from consideration. This test shows that photometric redshift schemes work well at least when the photometric data are of high quality and when the sources are at moderate redshifts.

  10. Neural Networks and Photometric Redshifts

    OpenAIRE

    Tagliaferri, Roberto; Longo, Giuseppe; Andreon, Stefano; Capozziello, Salvatore; Donalek, Ciro; Giordano, Gerardo

    2002-01-01

    We present a neural network based approach to the determination of photometric redshift. The method was tested on the Sloan Digital Sky Survey Early Data Release (SDSS-EDR) reaching an accuracy comparable and, in some cases, better than SED template fitting techniques. Different neural networks architecture have been tested and the combination of a Multi Layer Perceptron with 1 hidden layer (22 neurons) operated in a Bayesian framework, with a Self Organizing Map used to estimate the accuracy...

  11. Cosmology with photometric redshift surveys

    CERN Document Server

    Blake, C; Blake, Chris; Bridle, Sarah

    2004-01-01

    We explore the utility of future photometric redshift imaging surveys for delineating the large-scale structure of the Universe, and assess the resulting constraints on the cosmological model. We perform two complementary types of analysis: (1) We quantify the statistical confidence and accuracy with which such surveys will be able to detect and measure characteristic features in the clustering power spectrum such as the acoustic oscillations and the turnover, in a model-independent fashion. For example, we show that a 10000 sq deg imaging survey with depth r = 22.5 and photometric redshift accuracy dz/(1+z) = 0.03 will detect the acoustic oscillations with 99.9% confidence, measuring the associated cosmological scale with 2% precision. Such a survey will also detect the turnover with 95% confidence, determining the corresponding scale with 20% accuracy. (2) By assuming a Lambda-CDM cosmology we calculate the confidence with which a non-zero baryon fraction can be deduced from such future surveys. After margi...

  12. Error analysis of the photometric redshift tecnique

    OpenAIRE

    Fernandez-Soto, A.; Lanzetta, K. M.; Chen, H. -W.; Levine, B.; Yahata, N.

    2001-01-01

    We present a calculation of the systematic component of the error budget in the photometric redshift technique. We make use of it to describe a simple technique that allows for the assignation of confidence limits to redshift measurements obtained through photometric methods. We show that our technique, through the calculation of a redshift probability function, gives complete information on the probable redshift of an object and its associated confidence intervals. This information can and m...

  13. Neural Networks and Photometric Redshifts

    CERN Document Server

    Tagliaferri, R; Andreon, S; Capozziello, S; Donalek, C; Giordano, G; Tagliaferri, Roberto; Longo, Giuseppe; Andreon, Stefano; Capozziello, Salvatore; Donalek, Ciro; Giordano, Gerardo

    2002-01-01

    We present a neural network based approach to the determination of photometric redshift. The method was tested on the Sloan Digital Sky Survey Early Data Release (SDSS-EDR) reaching an accuracy comparable and, in some cases, better than SED template fitting techniques. Different neural networks architecture have been tested and the combination of a Multi Layer Perceptron with 1 hidden layer (22 neurons) operated in a Bayesian framework, with a Self Organizing Map used to estimate the accuracy of the results, turned out to be the most effective. In the best experiment, the implemented network reached an accuracy of 0.020 (interquartile error) in the range 0

  14. Error analysis of the photometric redshift tecnique

    CERN Document Server

    Fernández-Soto, A; Chen, H W; Levine, B; Yahata, N

    2002-01-01

    We present a calculation of the systematic component of the error budget in the photometric redshift technique. We make use of it to describe a simple technique that allows for the assignation of confidence limits to redshift measurements obtained through photometric methods. We show that our technique, through the calculation of a redshift probability function, gives complete information on the probable redshift of an object and its associated confidence intervals. This information can and must be used in the calculation of any observable quantity which makes use of the redshift.

  15. Photometric Redshifts of Galaxies in the Hubble Deep Field

    OpenAIRE

    Lanzetta, Kenneth M.; Fernandez-Soto, Alberto; Yahil, Amos

    1997-01-01

    We describe our application of broad-band photometric redshift techniques to faint galaxies in the Hubble Deep Field. To magnitudes AB(8140) < 26, the accuracy of the photometric redshifts is a few tenths and the reliability of the photometric redshifts approaches 100%. At fainter magnitudes the effects of photometric error on the photometric redshifts can be rigorously quantified and accounted for. We argue that broad-band photometric redshift techniques can be applied to accurately and reli...

  16. Novel Methods for Predicting Photometric Redshifts

    Data.gov (United States)

    National Aeronautics and Space Administration — We calculate photometric redshifts from the Sloan Digital Sky Survey Main Galaxy Sample, The Galaxy Evolution Explorer All Sky Survey, and The Two Micron All Sky...

  17. Photometric Redshifts of Galaxies in the Hubble Deep Field

    CERN Document Server

    Lanzetta, K M; Yahil, A; Lanzetta, Kenneth M.; Fernandez-Soto, Alberto; Yahil, Amos

    1997-01-01

    We describe our application of broad-band photometric redshift techniques to faint galaxies in the Hubble Deep Field. To magnitudes AB(8140) < 26, the accuracy of the photometric redshifts is a few tenths and the reliability of the photometric redshifts approaches 100%. At fainter magnitudes the effects of photometric error on the photometric redshifts can be rigorously quantified and accounted for. We argue that broad-band photometric redshift techniques can be applied to accurately and reliably estimate redshifts of galaxies that are up to many magnitudes fainter than the spectroscopic limit.

  18. Photometric Redshifts in the IRAC Shallow Survey

    Energy Technology Data Exchange (ETDEWEB)

    Brodwin, M; Brown, M; Ashby, M; Bian, C; Brand, K; Dey, A; Eisenhardt, P; Eisenstein, D; Gonzalez, A; Huang, J; Kochanek, C; McKenzie, E; Pahre, M; Smith, H; Soifer, B; Stanford, S; Stern, D; Elston, R

    2006-06-13

    Accurate photometric redshifts are calculated for nearly 200,000 galaxies to a 4.5 micron flux limit of {approx} 13 {micro}Jy in the 8.5 deg{sup 2} 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 < z < 3. Redshift probability functions, central to several ongoing studies of the galaxy population, are computed for the full sample. We demonstrate that these functions accurately represent the true redshift probability density, allowing the calculation of valid confidence intervals for all objects. These probability functions have already been used to successfully identify a population of Spitzer-selected high redshift (z > 1) galaxy clusters. We present one such spectroscopically confirmed cluster at = 1.24, ISCS J1434.2+3426. Finally, we present a measurement of the 4.5 {micro}m-selected galaxy redshift distribution.

  19. Using gamma regression for photometric redshifts of survey galaxies

    CERN Document Server

    Elliott, J; Krone-Martins, A; Cameron, E; Ishida, E E O; Hilbe, J

    2015-01-01

    Machine learning techniques offer a plethora of opportunities in tackling big data within the astronomical community. We present the set of Generalized Linear Models as a fast alternative for determining photometric redshifts of galaxies, a set of tools not commonly applied within astronomy, despite being widely used in other professions. With this technique, we achieve catastrophic outlier rates of the order of ~1%, that can be achieved in a matter of seconds on large datasets of size ~1,000,000. To make these techniques easily accessible to the astronomical community, we developed a set of libraries and tools that are publicly available.

  20. Hierarchical Bayesian inference of galaxy redshift distributions from photometric surveys

    CERN Document Server

    Leistedt, Boris; Peiris, Hiranya V

    2016-01-01

    Accurately characterizing the redshift distributions of galaxies is essential for analysing deep photometric surveys and testing cosmological models. We present a technique to simultaneously infer redshift distributions and individual redshifts from photometric galaxy catalogues. Our model constructs a piecewise constant representation (effectively a histogram) of the distribution of galaxy types and redshifts, the parameters of which are efficiently inferred from noisy photometric flux measurements. This approach can be seen as a generalization of template-fitting photometric redshift methods and relies on a library of spectral templates to relate the photometric fluxes of individual galaxies to their redshifts. We illustrate this technique on simulated galaxy survey data, and demonstrate that it delivers correct posterior distributions on the underlying type and redshift distributions, as well as on the individual types and redshifts of galaxies. We show that even with uninformative priors, large photometri...

  1. A Unified Theory of Photometric Redshifts

    CERN Document Server

    Budavari, Tamas

    2008-01-01

    We present a rigorous mathematical solution to the generalized photometric inversion problem. The challenge we address is to meaningfully constrain unknown properties of astronomical sources based on given observables, usually multicolor photometry, with the help of a training set that provides an empirical relation between the measurements and the desired quantities. Photometric redshift estimation is an example of such methods. We establish a formalism that blurs the boundary between the traditional empirical and template fitting algorithms, as both are just special cases that are discussed in detail to put them in context. The new approach enables the development of more sophisticated methods that go beyond the classic techniques to combine their advantages. The basic concepts are illustrated in a simple case that is analogous to the classic empirical methods. We look at the directions for further improvement as well as the technical aspects of practical implementations, and study the qualities of the cali...

  2. A CRITICAL ASSESSMENT OF PHOTOMETRIC REDSHIFT METHODS: A CANDELS INVESTIGATION

    Energy Technology Data Exchange (ETDEWEB)

    Dahlen, Tomas; Ferguson, Henry C. [Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218 (United States); Mobasher, Bahram [Department of Physics and Astronomy, University of California, Riverside, CA 92521 (United States); Faber, Sandra M.; Barro, Guillermo; Guo, Yicheng [UCO/Lick Observatory, Department of Astronomy and Astrophysics, University of California, Santa Cruz, CA 95064 (United States); Finkelstein, Steven L. [Department of Astronomy, The University of Texas at Austin, Austin, TX 78712 (United States); Finlator, Kristian [Dark Cosmology Centre, Niels Bohr Institute, University of Copenhagen (Denmark); Fontana, Adriano [INAF-Osservatorio Astronomico di Roma, Via Frascati 33, I-00040, Monteporzio (Italy); Gruetzbauch, Ruth [Center for Astronomy and Astrophysics, Observatorio Astronomico de Lisboa, Tapada da Ajuda, 1349-018 Lisboa (Portugal); Johnson, Seth [Department of Astronomy, University of Massachusetts, 710 North Pleasant Street, Amherst, MA 01003 (United States); Pforr, Janine; Dickinson, Mark E. [NOAO, 950 N. Cherry Avenue, Tucson, AZ 85719 (United States); Salvato, Mara; Wuyts, Stijn [Max-Planck-Institut für extraterrestrische Physik, Giessenbachstrasse 1, D-85748 Garching bei München (Germany); Wiklind, Tommy [Joint ALMA Observatory, Alonso de Cordova 3107, Vitacura, Santiago (Chile); Acquaviva, Viviana [Physics Department, CUNY NYC College of Technology, 300 Jay Street, Brooklyn, NY 11201 (United States); Huang, Jiasheng [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States); Huang, Kuang-Han [Department of Physics and Astronomy, Johns Hopkins University, 3400 North Charles Street, Baltimore, MD 21218 (United States); Newman, Jeffrey A., E-mail: dahlen@stsci.edu [Department of Physics and Astronomy, University of Pittsburgh, Pittsburgh, PA 15260 (United States); and others

    2013-10-01

    We present results from the Cosmic Assembly Near-infrared Deep Extragalactic Legacy Survey (CANDELS) photometric redshift methods investigation. In this investigation, the results from 11 participants, each using a different combination of photometric redshift code, template spectral energy distributions (SEDs), and priors, are used to examine the properties of photometric redshifts applied to deep fields with broadband multi-wavelength coverage. The photometry used includes U-band through mid-infrared filters and was derived using the TFIT method. Comparing the results, we find that there is no particular code or set of template SEDs that results in significantly better photometric redshifts compared to others. However, we find that codes producing the lowest scatter and outlier fraction utilize a training sample to optimize photometric redshifts by adding zero-point offsets, template adjusting, or adding extra smoothing errors. These results therefore stress the importance of the training procedure. We find a strong dependence of the photometric redshift accuracy on the signal-to-noise ratio of the photometry. On the other hand, we find a weak dependence of the photometric redshift scatter with redshift and galaxy color. We find that most photometric redshift codes quote redshift errors (e.g., 68% confidence intervals) that are too small compared to that expected from the spectroscopic control sample. We find that all codes show a statistically significant bias in the photometric redshifts. However, the bias is in all cases smaller than the scatter; the latter therefore dominates the errors. Finally, we find that combining results from multiple codes significantly decreases the photometric redshift scatter and outlier fraction. We discuss different ways of combining data to produce accurate photometric redshifts and error estimates.

  3. Hierarchical Bayesian inference of galaxy redshift distributions from photometric surveys

    Science.gov (United States)

    Leistedt, Boris; Mortlock, Daniel J.; Peiris, Hiranya V.

    2016-08-01

    Accurately characterizing the redshift distributions of galaxies is essential for analysing deep photometric surveys and testing cosmological models. We present a technique to simultaneously infer redshift distributions and individual redshifts from photometric galaxy catalogues. Our model constructs a piecewise constant representation (effectively a histogram) of the distribution of galaxy types and redshifts, the parameters of which are efficiently inferred from noisy photometric flux measurements. This approach can be seen as a generalization of template-fitting photometric redshift methods and relies on a library of spectral templates to relate the photometric fluxes of individual galaxies to their redshifts. We illustrate this technique on simulated galaxy survey data, and demonstrate that it delivers correct posterior distributions on the underlying type and redshift distributions, as well as on the individual types and redshifts of galaxies. We show that even with uninformative priors, large photometric errors and parameter degeneracies, the redshift and type distributions can be recovered robustly thanks to the hierarchical nature of the model, which is not possible with common photometric redshift estimation techniques. As a result, redshift uncertainties can be fully propagated in cosmological analyses for the first time, fulfilling an essential requirement for the current and future generations of surveys.

  4. Photometric Redshift Estimation on SDSS Data Using Random Forests

    CERN Document Server

    Carliles, Samuel; Heinis, Sebastien; Priebe, Carey; Szalay, Alexander

    2007-01-01

    Given multiband photometric data from the SDSS DR6, we estimate galaxy redshifts. We employ a Random Forest trained on color features and spectroscopic redshifts from 80,000 randomly chosen primary galaxies yielding a mapping from color to redshift such that the difference between the estimate and the spectroscopic redshift is small. Our methodology results in tight RMS scatter in the estimates limited by photometric errors. Additionally, this approach yields an error distribution that is nearly Gaussian with parameter estimates giving reliable confidence intervals unique to each galaxy photometric redshift.

  5. A Critical Assessment of Photometric Redshift Methods: A CANDELS Investigation

    CERN Document Server

    Dahlen, Tomas; Faber, Sandra M; Ferguson, Henry C; Barro, Guillermo; Finkelstein, Steven L; Finlator, Kristian; Fontana, Adriano; Gruetzbauch, Ruth; Johnson, Seth; Pforr, Janine; Salvato, Mara; Wiklind, Tommy; Wuyts, Stijn; Acquaviva, Viviana; Dickinson, Mark E; Guo, Yicheng; Huang, Jiasheng; Huang, Kuang-Han; Newman, Jeffrey A; Bell, Eric F; Conselice, Christopher J; Galametz, Audrey; Gawiser, Eric; Giavalisco, Mauro; Grogin, Norman A; Hathi, Nimish; Kocevski, Dale; Koekemoer, Anton M; Koo, David C; Lee, Kyoung-Soo; McGrath, Elizabeth J; Papovich, Casey; Peth, Michael; Ryan, Russell; Somerville, Rachel; Weiner, Benjamin; Wilson, Grant

    2013-01-01

    We present results from the Cosmic Assembly Near-infrared Deep Extragalactic Legacy Survey (CANDELS) photometric redshift methods investigation. In this investigation, the results from eleven participants, each using a different combination of photometric redshift code, template spectral energy distributions (SEDs) and priors, are used to examine the properties of photometric redshifts applied to deep fields with broad-band multi-wavelength coverage. The photometry used includes U-band through mid-infrared filters and was derived using the TFIT method. Comparing the results, we find that there is no particular code or set of template SEDs that results in significantly better photometric redshifts compared to others. However, we find codes producing the lowest scatter and outlier fraction utilize a training sample to optimize photometric redshifts by adding zero-point offsets, template adjusting or adding extra smoothing errors. These results therefore stress the importance of the training procedure. We find a...

  6. Photometric Redshifts for Galaxies in the GOODS Southern Field

    OpenAIRE

    Mobasher, B.; Idzi, R.; Benitez, N.; Cimatti, A.; Cristiani, S.; Daddi, E.; Dahlen, T.; Dickinson, M.; Erben, T.; Ferguson, H. C.; Giavalisco, M.; Grogin, N.A.; Koekemoer, A. M.; Mignoli, M.; Moustakas, L. A.

    2003-01-01

    We use extensive multi-wavelength photometric data from the Great Observatories Origins Deep Survey (GOODS) to estimate photometric redshifts for a sample of 434 galaxies with spectroscopic redshifts in the Chandra Deep Field South. Using the Bayesian method, which incorporates redshift/magnitude priors, we estimate photometric redshifts for galaxies in the range 18 < R (AB) < 25.5, giving an rms scatter of 0.11. The outlier fraction is < 10%, with the outlier-clipped rms being 0.047. We exam...

  7. Photometric redshift estimation using Gaussian processes

    CERN Document Server

    Bonfield, D G; Davey, N; Jarvis, M J; Abdalla, F B; Banerji, M; Adams, R G

    2009-01-01

    We present a comparison between Gaussian processes (GPs) and artificial neural networks (ANNs) as methods for determining photometric redshifts for galaxies, given training set data. In particular, we compare their degradation in performance as the training set size is reduced, either at random or according to an upper limit in magnitude, as might be caused by the observational limitations of spectroscopy. We find that performance with large, complete training sets is very similar. Training sets with brighter magnitude limits than the test data do not strongly affect the performance of either algorithm, until the limits are so severe that they remove almost all of the high-redshift training objects; in this case the GP algorithm produces smoother and less biased results at the expense of larger scatter. If the size of training set is reduced by random sampling, the RMS errors of both methods increase, but they do so to a lesser extent and in a much smoother manner for the case of GP regression; for the exampl...

  8. PHOTOMETRIC REDSHIFTS FOR QUASARS IN MULTI-BAND SURVEYS

    International Nuclear Information System (INIS)

    The Multi Layer Perceptron with Quasi Newton Algorithm (MLPQNA) is a machine learning method that can be used to cope with regression and classification problems on complex and massive data sets. In this paper, we give a formal description of the method and present the results of its application to the evaluation of photometric redshifts for quasars. The data set used for the experiment was obtained by merging four different surveys (Sloan Digital Sky Survey, GALEX, UKIDSS, and WISE), thus covering a wide range of wavelengths from the UV to the mid-infrared. The method is able (1) to achieve a very high accuracy, (2) to drastically reduce the number of outliers and catastrophic objects, and (3) to discriminate among parameters (or features) on the basis of their significance, so that the number of features used for training and analysis can be optimized in order to reduce both the computational demands and the effects of degeneracy. The best experiment, which makes use of a selected combination of parameters drawn from the four surveys, leads, in terms of Δznorm (i.e., (zspec – zphot)/(1 + zspec)), to an average of Δznorm = 0.004, a standard deviation of σ = 0.069, and a median absolute deviation, MAD = 0.02, over the whole redshift range (i.e., zspec ≤ 3.6), defined by the four-survey cross-matched spectroscopic sample. The fraction of catastrophic outliers, i.e., of objects with photo-z deviating more than 2σ from the spectroscopic value, is <3%, leading to σ = 0.035 after their removal, over the same redshift range. The method is made available to the community through the DAMEWARE Web application

  9. SuperNova Acceleration Probe (SNAP): Investigating Photometric Redshift Optimization

    CERN Document Server

    Dahlen, Tomas; Jouvel, Stephanie; Kneib, Jean-Paul; Ilbert, Olivier; Arnouts, Stephane; Bernstein, Gary; Rhodes, Jason

    2007-01-01

    The aim of this paper is to investigate ways to optimize the accuracy of photometric redshifts for a SNAP like mission. We focus on how the accuracy of the photometric redshifts depends on the magnitude limit and signal-to-noise ratio, wave-length coverage, number of filters and their shapes and observed galaxy type. We use simulated galaxy catalogs constructed to reproduce observed galaxy luminosity functions from GOODS, and derive photometric redshifts using a template fitting method. By using a catalog that resembles real data, we can estimate the expected number density of galaxies for which photometric redshifts can be derived. We find that the accuracy of photometric redshifts is strongly dependent on the signal-to-noise (S/N) (i.e., S/N>10 is needed for accurate photometric redshifts). The accuracy of the photometric redshifts is also dependent on galaxy type, with smaller scatter for earlier type galaxies. Comparing results using different filter sets, we find that including the U-band is important fo...

  10. Exploring the SDSS photometric galaxies with clustering redshifts

    Science.gov (United States)

    Rahman, Mubdi; Mendez, Alexander J.; Ménard, Brice; Scranton, Ryan; Schmidt, Samuel J.; Morrison, Christopher B.; Budavári, Tamás

    2016-07-01

    We apply clustering-based redshift inference to all extended sources from the Sloan Digital Sky Survey photometric catalogue, down to magnitude r = 22. We map the relationships between colours and redshift, without assumption of the sources' spectral energy distributions (SEDs). We identify and locate star-forming quiescent galaxies, and active galactic nuclei, as well as colour changes due to spectral features, such as the 4000 Å break, redshifting through specific filters. Our mapping is globally in good agreement with colour-redshift tracks computed with SED templates, but reveals informative differences, such as the need for a lower fraction of M-type stars in certain templates. We compare our clustering-redshift estimates to photometric redshifts and find these two independent estimators to be in good agreement at each limiting magnitude considered. Finally, we present the global clustering-redshift distribution of all Sloan extended sources, showing objects up to z ˜ 0.8. While the overall shape agrees with that inferred from photometric redshifts, the clustering-redshift technique results in a smoother distribution, with no indication of structure in redshift space suggested by the photometric-redshift estimates (likely artefacts imprinted by their spectroscopic training set). We also infer a higher fraction of high-redshift objects. The mapping between the four observed colours and redshift can be used to estimate the redshift probability distribution function of individual galaxies. This work is an initial step towards producing a general mapping between redshift and all available observables in the photometric space, including brightness, size, concentration, and ellipticity.

  11. Exploring the SDSS Photometric Galaxies with Clustering Redshifts

    Science.gov (United States)

    Rahman, Mubdi; Mendez, Alexander J.; Ménard, Brice; Scranton, Ryan; Schmidt, Samuel J.; Morrison, Christopher B.; Budavári, Tamás

    2016-04-01

    We apply clustering-based redshift inference to all extended sources from the Sloan Digital Sky Survey photometric catalogue, down to magnitude r = 22. We map the relationships between colours and redshift, without assumption of the sources' spectral energy distributions (SED). We identify and locate star-forming, quiescent galaxies, and AGN, as well as colour changes due to spectral features, such as the 4000 Å break, redshifting through specific filters. Our mapping is globally in good agreement with colour-redshift tracks computed with SED templates, but reveals informative differences, such as the need for a lower fraction of M-type stars in certain templates. We compare our clustering-redshift estimates to photometric redshifts and find these two independent estimators to be in good agreement at each limiting magnitude considered. Finally, we present the global clustering-redshift distribution of all Sloan extended sources, showing objects up to z ˜ 0.8. While the overall shape agrees with that inferred from photometric redshifts, the clustering redshift technique results in a smoother distribution, with no indication of structure in redshift space suggested by the photometric redshift estimates (likely artifacts imprinted by their spectroscopic training set). We also infer a higher fraction of high redshift objects. The mapping between the four observed colours and redshift can be used to estimate the redshift probability distribution function of individual galaxies. This work is an initial step towards producing a general mapping between redshift and all available observables in the photometric space, including brightness, size, concentration, and ellipticity.

  12. Photometric redshift estimation for quasars by integration of KNN and SVM

    Science.gov (United States)

    Han, Bo; Ding, Hong-Peng; Zhang, Yan-Xia; Zhao, Yong-Heng

    2016-05-01

    The massive photometric data collected from multiple large-scale sky surveys offer significant opportunities for measuring distances of celestial objects by photometric redshifts. However, catastrophic failure is an unsolved problem with a long history and it still exists in the current photometric redshift estimation approaches (such as the k-nearest neighbor (KNN) algorithm). In this paper, we propose a novel two-stage approach by integration of KNN and support vector machine (SVM) methods together. In the first stage, we apply the KNN algorithm to photometric data and estimate their corresponding z phot. Our analysis has found two dense regions with catastrophic failure, one in the range of z phot ɛ [0.3, 1.2] and the other in the range of zphot ɛ [1.2, 2.1]. In the second stage, we map the photometric input pattern of points falling into the two ranges from their original attribute space into a high dimensional feature space by using a Gaussian kernel function from an SVM. In the high dimensional feature space, many outliers resulting from catastrophic failure by simple Euclidean distance computation in KNN can be identified by a classification hyperplane of SVM and can be further corrected. Experimental results based on the Sloan Digital Sky Survey (SDSS) quasar data show that the two-stage fusion approach can significantly mitigate catastrophic failure and improve the estimation accuracy of photometric redshifts of quasars. The percents in different |δz| ranges and root mean square (rms) error by the integrated method are 83.47%, 89.83%, 90.90% and 0.192, respectively, compared to the results by KNN (71.96%, 83.78%, 89.73% and 0.204).

  13. Exploring the SDSS Photometric Galaxies with Clustering Redshifts

    CERN Document Server

    Rahman, Mubdi; Ménard, Brice; Scranton, Ryan; Schmidt, Samuel J; Morrison, Christopher B; Budavári, Tamás

    2015-01-01

    We apply clustering-based redshift inference to all extended sources from the Sloan Digital Sky Survey photometric catalogue, down to magnitude r = 22. We map the relationships between colours and redshift, without assumption of the sources' spectral energy distributions (SED). We identify and locate star-forming, quiescent galaxies, and AGN, as well as colour changes due to spectral features, such as the 4000 \\AA{} break, redshifting through specific filters. Our mapping is globally in good agreement with colour-redshift tracks computed with SED templates, but reveals informative differences, such as the need for a lower fraction of M-type stars in certain templates. We compare our clustering-redshift estimates to photometric redshifts and find these two independent estimators to be in good agreement at each limiting magnitude considered. Finally, we present the global clustering-redshift distribution of all Sloan extended sources, showing objects up to z ~ 0.8. While the overall shape agrees with that infer...

  14. CHARACTERIZING AND PROPAGATING MODELING UNCERTAINTIES IN PHOTOMETRICALLY DERIVED REDSHIFT DISTRIBUTIONS

    International Nuclear Information System (INIS)

    The uncertainty in the redshift distributions of galaxies has a significant potential impact on the cosmological parameter values inferred from multi-band imaging surveys. The accuracy of the photometric redshifts measured in these surveys depends not only on the quality of the flux data, but also on a number of modeling assumptions that enter into both the training set and spectral energy distribution (SED) fitting methods of photometric redshift estimation. In this work we focus on the latter, considering two types of modeling uncertainties: uncertainties in the SED template set and uncertainties in the magnitude and type priors used in a Bayesian photometric redshift estimation method. We find that SED template selection effects dominate over magnitude prior errors. We introduce a method for parameterizing the resulting ignorance of the redshift distributions, and for propagating these uncertainties to uncertainties in cosmological parameters.

  15. Photometric Redshifts for Quasars in Multi-band Surveys

    Science.gov (United States)

    Brescia, M.; Cavuoti, S.; D'Abrusco, R.; Longo, G.; Mercurio, A.

    2013-08-01

    The Multi Layer Perceptron with Quasi Newton Algorithm (MLPQNA) is a machine learning method that can be used to cope with regression and classification problems on complex and massive data sets. In this paper, we give a formal description of the method and present the results of its application to the evaluation of photometric redshifts for quasars. The data set used for the experiment was obtained by merging four different surveys (Sloan Digital Sky Survey, GALEX, UKIDSS, and WISE), thus covering a wide range of wavelengths from the UV to the mid-infrared. The method is able (1) to achieve a very high accuracy, (2) to drastically reduce the number of outliers and catastrophic objects, and (3) to discriminate among parameters (or features) on the basis of their significance, so that the number of features used for training and analysis can be optimized in order to reduce both the computational demands and the effects of degeneracy. The best experiment, which makes use of a selected combination of parameters drawn from the four surveys, leads, in terms of Δz norm (i.e., (z spec - z phot)/(1 + z spec)), to an average of Δz norm = 0.004, a standard deviation of σ = 0.069, and a median absolute deviation, MAD = 0.02, over the whole redshift range (i.e., z spec objects with photo-z deviating more than 2σ from the spectroscopic value, is <3%, leading to σ = 0.035 after their removal, over the same redshift range. The method is made available to the community through the DAMEWARE Web application.

  16. Color-redshift Relations and Photometric Redshift Estimations of Quasars in Large Sky Surveys

    CERN Document Server

    Wu, X B; Zhou, X; Wu, Xue-Bing; Zhang, Wei; Zhou, Xu

    2004-01-01

    With a recently constructed composite quasar spectrum and the \\chi^2 minimization technique, we demonstrated a general method to estimate the photometric redshifts of a large sample of quasars by deriving the theoretical color-redshift relations and comparing the theoretical colors with the observed ones. We estimated the photometric redshifts from the 5-band SDSS photometric data of 18678 quasars in the first major data release of SDSS and compare them with the spectroscopic redshifts. The redshift difference is smaller than 0.1 for 47% of quasars and 0.2 for 68 % of them. Based on the calculation of the theoretical color-color diagrams of stars, galaxies and quasars in both the SDSS and BATC photometric systems, we expected that with the BATC system of 15 intermediate filters we would be able to select candidates of high redshift quasars more efficiently than in the SDSS, provided the BATC survey could detect objects with magnitude fainter than 21.

  17. COSMOS PHOTOMETRIC REDSHIFTS WITH 30-BANDS FOR 2-deg(2)

    NARCIS (Netherlands)

    Ilbert, O.; Capak, P.; Salvato, M.; Aussel, H.; McCracken, H. J.; Sanders, D. B.; Scoville, N.; Kartaltepe, J.; Arnouts, S.; Le Floc'h, E.; Mobasher, B.; Taniguchi, Y.; Lamareille, F.; Leauthaud, A.; Sasaki, S.; Thompson, D.; Zamojski, M.; Zamorani, G.; Bardelli, S.; Bolzonella, M.; Bongiorno, A.; Brusa, M.; Caputi, K. I.; Carollo, C. M.; Contini, T.; Cook, R.; Coppa, G.; Cucciati, O.; De La Torre, S.; de Ravel, L.; Franzetti, P.; Garilli, B.; Hasinger, G.; Iovino, A.; Kampczyk, P.; Kneib, J. -P.; Knobel, C.; Kovac, K.; Le Borgne, J. F.; Le Brun, V.; Le Fevre, O.; Lilly, S.; Looper, D.; Maier, C.; Mainieri, V.; Mellier, Y.; Mignoli, M.; Murayama, T.; Pello, R.; Peng, Y.; Perez-Montero, E.; Renzini, A.; Ricciardelli, E.; Schiminovich, D.; Scodeggio, M.; Shioya, Y.; Silverman, J.; Surace, J.; Tanaka, M.; Tasca, L.; Tresse, L.; Vergani, D.; Zucca, E.

    2009-01-01

    We present accurate photometric redshifts (photo-z) in the 2-deg(2) COSMOS field. The redshifts are computed with 30 broad, intermediate, and narrowbands covering the UV (Galaxy Evolution Explorer), visible near-IR (NIR; Subaru, Canada-France-Hawaii Telescope (CFHT), United Kingdom Infrared Telescop

  18. Photometric redshifts for the SDSS Data Release 12

    Science.gov (United States)

    Beck, Róbert; Dobos, László; Budavári, Tamás; Szalay, Alexander S.; Csabai, István

    2016-08-01

    We present the methodology and data behind the photometric redshift data base of the Sloan Digital Sky Survey (SDSS) Data Release 12. We adopt a hybrid technique, empirically estimating the redshift via local regression on a spectroscopic training set, then fitting a spectrum template to obtain K-corrections and absolute magnitudes. The SDSS spectroscopic catalogue was augmented with data from other, publicly available spectroscopic surveys to mitigate target selection effects. The training set is comprised of 1976 978 galaxies, and extends up to redshift z ≈ 0.8, with a useful coverage of up to z ≈ 0.6. We provide photometric redshifts and realistic error estimates for the 208 474 076 galaxies of the SDSS primary photometric catalogue. We achieve an average bias of overline{Δ z_{norm}} = {5.84 × 10^{-5}}, a standard deviation of σ(Δznorm) = 0.0205, and a 3σ outlier rate of Po = 4.11 per cent when cross-validating on our training set. The published redshift error estimates and photometric error classes enable the selection of galaxies with high-quality photometric redshifts. We also provide a supplementary error map that allows additional, sophisticated filtering of the data.

  19. Photometric Redshift Estimation for Quasars by Integration of KNN and SVM

    CERN Document Server

    Han, Bo; Zhang, Yanxia; Zhao, Yongheng

    2016-01-01

    The massive photometric data collected from multiple large-scale sky surveys offer significant opportunities for measuring distances of celestial objects by photometric redshifts. However, catastrophic failure is still an unsolved problem for a long time and exists in the current photometric redshift estimation approaches (such as $k$-nearest-neighbor). In this paper, we propose a novel two-stage approach by integration of $k$-nearest-neighbor (KNN) and support vector machine (SVM) methods together. In the first stage, we apply KNN algorithm on photometric data and estimate their corresponding z$_{\\rm phot}$. By analysis, we find two dense regions with catastrophic failure, one in the range of z$_{\\rm phot}\\in[0.3,1.2]$, the other in the range of z$_{\\rm phot}\\in [1.2,2.1]$. In the second stage, we map the photometric input pattern of points falling into the two ranges from original attribute space into a high dimensional feature space by Gaussian kernel function in SVM. In the high dimensional feature space,...

  20. Probabilistic Photometric Redshifts in the Era of Petascale Astronomy

    Energy Technology Data Exchange (ETDEWEB)

    Carrasco Kind, Matias [Univ. of Illinois, Urbana-Champaign, IL (United States)

    2014-01-01

    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

  1. Galaxy clustering with photometric surveys using PDF redshift information

    Science.gov (United States)

    Asorey, J.; Carrasco Kind, M.; Sevilla-Noarbe, I.; Brunner, R. J.; Thaler, J.

    2016-06-01

    Photometric surveys produce large-area maps of the galaxy distribution, but with less accurate redshift information than is obtained from spectroscopic methods. Modern photometric redshift (photo-z) algorithms use galaxy magnitudes, or colours, that are obtained through multiband imaging to produce a probability density function (PDF) for each galaxy in the map. We used simulated data to study the effect of using different photo-z estimators to assign galaxies to redshift bins in order to compare their effects on angular clustering and galaxy bias measurements. We found that if we use the entire PDF, rather than a single-point (mean or mode) estimate, the deviations are less biased, especially when using narrow redshift bins. When the redshift bin widths are Δz = 0.1, the use of the entire PDF reduces the typical measurement bias from 5 per cent, when using single point estimates, to 3 per cent.

  2. Photometric redshift techniques of quasars in big-data era

    Science.gov (United States)

    Zhang, Yanxia

    2015-08-01

    With the availability of the huge amounts of data from ground- and space-based large multiband photometric surveys, photometric redshifts provide an estimate for the distance of an astronomical object and have become a crucial tool for extragalactic astronomy and cosmology. Various phtometric redshift approaches are in bloom. Their performance and efficiency not only depend on completeness and quality of data, but also on the volume of data. The increase of data volume lead to different choice of techniques. We present various data mining methods used for photometric redshift estimation of quasars and compare their advantages and disadvantages. In the big-data era, the methods fit for large-scale data are in great requirement.

  3. Triplets of Quasars at high redshift I: Photometric data

    OpenAIRE

    Alonso, M. Victoria; Coldwell, Georgina V.; Sochting, Ilona; Bornancini, Carlos; Smith, Malcolm G.; Lambas, Diego Garcia; Rest, Armin

    2008-01-01

    We have conducted an optical and infrared imaging in the neighbourhoods of 4 triplets of quasars. R, z', J and Ks images were obtained with MOSAIC II and ISPI at Cerro Tololo Interamerican Observatory. Accurate relative photometry and astrometry were obtained from these images for subsequent use in deriving photometric redshifts. We analyzed the homogeneity and depth of the photometric catalog by comparing with results coming from the literature. The good agreement shows that our magnitudes a...

  4. Photometric Redshift with Bayesian Priors on Physical Properties of Galaxies

    CERN Document Server

    Tanaka, Masayuki

    2015-01-01

    We present a proof-of-concept analysis of photometric redshifts with Bayesian priors on physical properties of galaxies. This concept is particularly suited for upcoming/on-going large imaging surveys, in which only several broad-band filters are available and it is hard to break some of the degeneracies in the multi-color space. We construct model templates of galaxies using a stellar population synthesis code and apply Bayesian priors on physical properties such as stellar mass and star formation rate. These priors are a function of redshift and they effectively evolve the templates with time in an observationally motivated way. We demonstrate that the priors help reduce the degeneracy and deliver significantly improved photometric redshifts. Furthermore, we show that a template error function, which corrects for systematic flux errors in the model templates as a function of rest-frame wavelength, delivers further improvements. One great advantage of our technique is that we simultaneously measure redshifts...

  5. Measuring photometric redshifts using galaxy images and Deep Neural Networks

    Science.gov (United States)

    Hoyle, B.

    2016-07-01

    We propose a new method to estimate the photometric redshift of galaxies by using the full galaxy image in each measured band. This method draws from the latest techniques and advances in machine learning, in particular Deep Neural Networks. We pass the entire multi-band galaxy image into the machine learning architecture to obtain a redshift estimate that is competitive, in terms of the measured point prediction metrics, with the best existing standard machine learning techniques. The standard techniques estimate redshifts using post-processed features, such as magnitudes and colours, which are extracted from the galaxy images and are deemed to be salient by the user. This new method removes the user from the photometric redshift estimation pipeline. However we do note that Deep Neural Networks require many orders of magnitude more computing resources than standard machine learning architectures, and as such are only tractable for making predictions on datasets of size ≤50k before implementing parallelisation techniques.

  6. Modelling multimodal photometric redshift regression with noisy observations

    CERN Document Server

    Kügler, S D

    2016-01-01

    In this work, we are trying to extent the existing photometric redshift regression models from modeling pure photometric data back to the spectra themselves. To that end, we developed a PCA that is capable of describing the input uncertainty (including missing values) in a dimensionality reduction framework. With this "spectrum generator" at hand, we are capable of treating the redshift regression problem in a fully Bayesian framework, returning a posterior distribution over the redshift. This approach allows therefore to approach the multimodal regression problem in an adequate fashion. In addition, input uncertainty on the magnitudes can be included quite naturally and lastly, the proposed algorithm allows in principle to make predictions outside the training values which makes it a fascinating opportunity for the detection of high-redshifted quasars.

  7. Measuring photometric redshifts using galaxy images and Deep Neural Networks

    CERN Document Server

    Hoyle, Ben

    2015-01-01

    We propose a new method to estimate the photometric redshift of galaxies by using the full galaxy image in each measured band. This method draws from the latest techniques and advances in machine learning, in particular Deep Neural Networks. We pass the entire multi-band galaxy image into the machine learning architecture to obtain a redshift estimate that is competitive with the best existing standard machine learning techniques. The standard techniques estimate redshifts using post-processed features, such as magnitudes and colours, which are extracted from the galaxy images and are deemed to be salient by the user. This new method removes the user from the photometric redshift estimation pipeline. However we do note that Deep Neural Networks require many orders of magnitude more computing resources than standard machine learning architectures.

  8. Photometric redshifts and selection of high redshift galaxies in the NTT and Hubble Deep Fields

    CERN Document Server

    Fontana, A; Poli, F; Giallongo, E; Arnouts, S; Cristiani, S; Moorwood, A F M; Saracco, P

    2000-01-01

    We present and compare in this paper new photometric redshift catalogs of the galaxies in three public fields: the NTT Deep Field, the HDF-N and the HDF-S. Photometric redshifts have been obtained for thewhole sample, by adopting a $\\chi^2$ minimization technique on a spectral library drawn from the Bruzual and Charlot synthesis models, with the addition of dust and intergalactic absorption. The accuracy, determined from 125 galaxies with known spectroscopic redshifts, is $\\sigma_z\\sim 0.08 (0.3)$ in the redshift intervals $z=0-1.5 (1.5-3.5)$. The global redshift distribution of I-selected galaxies shows a distinct peak at intermediate redshifts, z~0.6 at I_{AB}5 candidates in the HDF filter set and that the 4 brightest candidates at $z>5$ in the HDF-S are indeed most likely M stars. (ABRIDGED)

  9. A sparse Gaussian process framework for photometric redshift estimation

    Science.gov (United States)

    Almosallam, Ibrahim A.; Lindsay, Sam N.; Jarvis, Matt J.; Roberts, Stephen J.

    2016-01-01

    Accurate photometric redshifts are a lynchpin for many future experiments to pin down the cosmological model and for studies of galaxy evolution. In this study, a novel sparse regression framework for photometric redshift estimation is presented. Synthetic data set simulating the Euclid survey and real data from SDSS DR12 are used to train and test the proposed models. We show that approaches which include careful data preparation and model design offer a significant improvement in comparison with several competing machine learning algorithms. Standard implementations of most regression algorithms use the minimization of the sum of squared errors as the objective function. For redshift inference, this induces a bias in the posterior mean of the output distribution, which can be problematic. In this paper, we directly minimize the target metric Δz = (zs - zp)/(1 + zs) and address the bias problem via a distribution-based weighting scheme, incorporated as part of the optimization objective. The results are compared with other machine learning algorithms in the field such as artificial neural networks (ANN), Gaussian processes (GPs) and sparse GPs. The proposed framework reaches a mean absolute Δz = 0.0026(1 + zs), over the redshift range of 0 ≤ zs ≤ 2 on the simulated data, and Δz = 0.0178(1 + zs) over the entire redshift range on the SDSS DR12 survey, outperforming the standard ANNz used in the literature. We also investigate how the relative size of the training sample affects the photometric redshift accuracy. We find that a training sample of >30 per cent of total sample size, provides little additional constraint on the photometric redshifts, and note that our GP formalism strongly outperforms ANNz in the sparse data regime for the simulated data set.

  10. A Sparse Gaussian Process Framework for Photometric Redshift Estimation

    CERN Document Server

    Almosallam, Ibrahim A; Jarvis, Matt J; Roberts, Stephen J

    2015-01-01

    Accurate photometric redshift are a lynchpin for many future experiments to pin down the cosmological model and for studies of galaxy evolution. In this study, a novel sparse regression framework for photometric redshift estimation is presented. Data from a simulated survey was used to train and test the proposed models. We show that approaches which include careful data preparation and model design offer a significant improvement in comparison with several competing machine learning algorithms. Standard implementation of most regression algorithms has as the objective the minimization of the sum of squared errors. For redshift inference, however, this induces a bias in the posterior mean of the output distribution, which can be problematic. In this paper we optimize to directly target minimizing $\\Delta z = (z_\\textrm{s} - z_\\textrm{p})/(1+z_\\textrm{s})$ and address the bias problem via a distribution-based weighting scheme, incorporated as part of the optimization objective. The results are compared with ot...

  11. Evolution of Galaxy Luminosity Function Using Photometric Redshifts

    CERN Document Server

    Ramos, B H F; Benoist, C; da Costa, L N; Maia, M A G; Makler, M; Ogando, R L C; de Simoni, F; Mesquita, A A

    2011-01-01

    We examine the impact of using photometric redshifts for studying the evolution of both the global galaxy luminosity function (LF) and that for different galaxy types. To this end we compare LFs obtained using photometric redshifts from the CFHT Legacy Survey (CFHTLS) D1 field with those from the spectroscopic survey VIMOS VLT Deep Survey (VVDS) comprising ~4800 galaxies. We find that for z<2, in the interval of magnitudes considered by this survey, the LFs obtained using photometric and spectroscopic redshifts show a remarkable agreement. This good agreement led us to use all four Deep fields of CFHTLS comprising ~386000 galaxies to compute the LF of the combined fields and estimate directly the error in the parameters based on field-to-field variation. We find that the characteristic absolute magnitude M* of Schechter fits fades by ~0.7mag from z~1.8 to z~0.3, while the characteristic density phi* increases by a factor of ~4 in the same redshift bin. We use the galaxy classification provided by the templ...

  12. Photometric redshifts for the SDSS Data Release 12

    CERN Document Server

    Beck, Róbert; Budavári, Tamás; Szalay, Alexander S; Csabai, István

    2016-01-01

    We present the methodology and data behind the photometric redshift database of the Sloan Digital Sky Survey Data Release 12 (SDSS DR12). We adopt a hybrid technique, empirically estimating the redshift via local regression on a spectroscopic training set, then fitting a spectrum template to obtain K-corrections and absolute magnitudes. The SDSS spectroscopic catalog was augmented with data from other, publicly available spectroscopic surveys to mitigate target selection effects. The training set is comprised of $1,976,978$ galaxies, and extends up to redshift $z\\approx 0.8$, with a useful coverage of up to $z\\approx 0.6$. We provide photometric redshifts and realistic error estimates for the $208,474,076$ galaxies of the SDSS primary photometric catalog. We achieve an average bias of $\\overline{\\Delta z_{\\mathrm{norm}}} = -0.0012$, a standard deviation of $\\sigma \\left(\\Delta z_{\\mathrm{norm}}\\right)=0.0249$, and a $3\\sigma$ outlier rate of $P_o=1.6\\%$ when cross-validating on our training set. The published...

  13. Estimating Photometric Redshifts of Quasars via K-nearest Neighbor Approach Based on Large Survey Databases

    CERN Document Server

    Yanxia, Zhang; Nanbo, Peng; Yongheng, Zhao; Xue-bing, Wu

    2013-01-01

    We apply one of lazy learning methods named k-nearest neighbor algorithm (kNN) to estimate the photometric redshifts of quasars, based on various datasets from the Sloan Digital Sky Survey (SDSS), UKIRT Infrared Deep Sky Survey (UKIDSS) and Wide-field Infrared Survey Explorer (WISE) (the SDSS sample, the SDSS-UKIDSS sample, the SDSS-WISE sample and the SDSS-UKIDSS-WISE sample). The influence of the k value and different input patterns on the performance of kNN is discussed. kNN arrives at the best performance when k is different with a special input pattern for a special dataset. The best result belongs to the SDSS-UKIDSS-WISE sample. The experimental results show that generally the more information from more bands, the better performance of photometric redshift estimation with kNN. The results also demonstrate that kNN using multiband data can effectively solve the catastrophic failure of photometric redshift estimation, which is met by many machine learning methods. By comparing the performance of various m...

  14. Machine Learning based photometric redshifts for the KiDS ESO DR2 galaxies

    CERN Document Server

    Cavuoti, Stefano; Tortora, Crescenzo; Longo, Giuseppe; Napolitano, Nicola R; Radovich, Mario; La Barbera, Francesco; Capaccioli, Massimo; de Jong, Jelte T A; Getman, Fedor; Grado, Aniello; Paolillo, Maurizio

    2015-01-01

    We estimated photometric redshifts (zphot) for more than 1.1 million galaxies of the ESO Public Kilo-Degree Survey (KiDS) Data Release 2. KiDS is an optical wide-field imaging survey carried out with the VLT Survey Telescope (VST) and the OmegaCAM camera, which aims at tackling open questions in cosmology and galaxy evolution, such as the origin of dark energy and the channel of galaxy mass growth. We present a catalogue of photometric redshifts obtained using the Multi Layer Perceptron with Quasi Newton Algorithm (MLPQNA) model, provided within the framework of the DAta Mining and Exploration Web Application REsource (DAMEWARE). These photometric redshifts are based on a spectroscopic knowledge base which was obtained by merging spectroscopic datasets from GAMA (Galaxy And Mass Assembly) data release 2 and SDSS-III data release 9. The overall 1 sigma uncertainty on Delta z = (zspec - zphot) / (1+ zspec) is ~ 0.03, with a very small average bias of ~ 0.001, a NMAD of ~ 0.02 and a fraction of catastrophic outl...

  15. Mapping the Galaxy Color-Redshift Relation: Optimal Photometric Redshift Calibration Strategies for Cosmology Surveys

    CERN Document Server

    Masters, Daniel; Stern, Daniel; Ilbert, Olivier; Salvato, Mara; Schmidt, Samuel; Longo, Giuseppe; Rhodes, Jason; Paltani, Stephane; Mobasher, Bahram; Hoekstra, Henk; Hildebrandt, Hendrik; Coupon, Jean; Steinhardt, Charles; Speagle, Josh; Faisst, Andreas; Kalinich, Adam; Brodwin, Mark; Brescia, Massimo; Cavuoti, Stefano

    2015-01-01

    Calibrating the photometric redshifts of >10^9 galaxies for upcoming weak lensing cosmology experiments is a major challenge for the astrophysics community. The path to obtaining the required spectroscopic redshifts for training and calibration is daunting, given the anticipated depths of the surveys and the difficulty in obtaining secure redshifts for some faint galaxy populations. Here we present an analysis of the problem based on the self-organizing map, a method of mapping the distribution of data in a high-dimensional space and projecting it onto a lower-dimensional representation. We apply this method to existing photometric data from the COSMOS survey selected to approximate the anticipated Euclid weak lensing sample, enabling us to robustly map the empirical distribution of galaxies in the multidimensional color space defined by the expected Euclid filters. Mapping this multicolor distribution lets us determine where - in galaxy color space - redshifts from current spectroscopic surveys exist and whe...

  16. The SDSS Coadd: A Galaxy Photometric Redshift Catalog

    International Nuclear Information System (INIS)

    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 ∼ 13 million objects classified as galaxies in the coadd with r 68 = 0.036. After presenting our results and quality tests, we provide a short guide for users accessing the public data.

  17. New Improved Photometric Redshifts of Galaxies in the HDF

    OpenAIRE

    Furusawa, Hisanori; Shimasaku, Kazuhiro; Doi, Mamoru; Okamura, Sadanori

    1999-01-01

    We report new improved photometric redshifts of 1048 galaxies in the Hubble Deep Field (HDF). A standard chi^2 minimizing method is applied to seven-color UBVIJHK photometry by Fernandez-Soto, Lanzetta, & Yahil (1999). We use 187 template SEDs representing a wide variety of morphology and age of observed galaxies based on a population synthesis model by Kodama & Arimoto (1997). We introduce two new recipes. First, the amount of the internal absorption is changed as a free parameter in the ran...

  18. Mapping the Galaxy Color–Redshift Relation: Optimal Photometric Redshift Calibration Strategies for Cosmology Surveys

    Science.gov (United States)

    Masters, Daniel; Capak, Peter; Stern, Daniel; Ilbert, Olivier; Salvato, Mara; Schmidt, Samuel; Longo, Giuseppe; Rhodes, Jason; Paltani, Stephane; Mobasher, Bahram; Hoekstra, Henk; Hildebrandt, Hendrik; Coupon, Jean; Steinhardt, Charles; Speagle, Josh; Faisst, Andreas; Kalinich, Adam; Brodwin, Mark; Brescia, Massimo; Cavuoti, Stefano

    2015-11-01

    Calibrating the photometric redshifts of ≳109 galaxies for upcoming weak lensing cosmology experiments is a major challenge for the astrophysics community. The path to obtaining the required spectroscopic redshifts for training and calibration is daunting, given the anticipated depths of the surveys and the difficulty in obtaining secure redshifts for some faint galaxy populations. Here we present an analysis of the problem based on the self-organizing map, a method of mapping the distribution of data in a high-dimensional space and projecting it onto a lower-dimensional representation. We apply this method to existing photometric data from the COSMOS survey selected to approximate the anticipated Euclid weak lensing sample, enabling us to robustly map the empirical distribution of galaxies in the multidimensional color space defined by the expected Euclid filters. Mapping this multicolor distribution lets us determine where—in galaxy color space—redshifts from current spectroscopic surveys exist and where they are systematically missing. Crucially, the method lets us determine whether a spectroscopic training sample is representative of the full photometric space occupied by the galaxies in a survey. We explore optimal sampling techniques and estimate the additional spectroscopy needed to map out the color–redshift relation, finding that sampling the galaxy distribution in color space in a systematic way can efficiently meet the calibration requirements. While the analysis presented here focuses on the Euclid survey, similar analysis can be applied to other surveys facing the same calibration challenge, such as DES, LSST, and WFIRST.

  19. New Improved Photometric Redshifts of Galaxies in the HDF

    CERN Document Server

    Furusawa, H; Doi, M; Okamura, S; Furusawa, Hisanori; Shimasaku, Kazuhiro; Doi, Mamoru; Okamura, Sadanori

    1999-01-01

    We report new improved photometric redshifts of 1048 galaxies in the HubbleDeep Field (HDF). A standard chi^2 minimizing method is applied to seven-colorUBVIJHK photometry by Fernandez-Soto, Lanzetta, & Yahil (1999). We use 187template SEDs representing a wide variety of morphology and age of observedgalaxies based on a population synthesis model by Kodama & Arimoto (1997). Weintroduce two new recipes. First, the amount of the internal absorption ischanged as a free parameter in the range of E(B-V)=0.0 to 0.5 with an intervalof 0.1. Second, the absorption due to intergalactic HI clouds is also changedby a factor of 0.5, 1.0, and 1.5 around the opacity given by Madau (1995). Thetotal number of template SEDs is thus 187x6x3=3,366, except for the redshiftgrid. The dispersion sigma_z of our photometric redshifts with respect tospectroscopic redshifts is sigma_z=0.08 and 0.24 for z2, respectively,which are smaller than the corresponding values (sigma_z=0.09 and 0.45) byFernandez-Soto et al. Improvement is ...

  20. A new method to search for high-redshift clusters using photometric redshifts

    Energy Technology Data Exchange (ETDEWEB)

    Castignani, G.; Celotti, A. [SISSA, Via Bonomea 265, I-34136 Trieste (Italy); Chiaberge, M.; Norman, C., E-mail: castigna@sissa.it [Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218 (United States)

    2014-09-10

    We describe a new method (Poisson probability method, PPM) to search for high-redshift galaxy clusters and groups by using photometric redshift information and galaxy number counts. The method relies on Poisson statistics and is primarily introduced to search for megaparsec-scale environments around a specific beacon. The PPM is tailored to both the properties of the FR I radio galaxies in the Chiaberge et al. sample, which are selected within the COSMOS survey, and to the specific data set used. We test the efficiency of our method of searching for cluster candidates against simulations. Two different approaches are adopted. (1) We use two z ∼ 1 X-ray detected cluster candidates found in the COSMOS survey and we shift them to higher redshift up to z = 2. We find that the PPM detects the cluster candidates up to z = 1.5, and it correctly estimates both the redshift and size of the two clusters. (2) We simulate spherically symmetric clusters of different size and richness, and we locate them at different redshifts (i.e., z = 1.0, 1.5, and 2.0) in the COSMOS field. We find that the PPM detects the simulated clusters within the considered redshift range with a statistical 1σ redshift accuracy of ∼0.05. The PPM is an efficient alternative method for high-redshift cluster searches that may also be applied to both present and future wide field surveys such as SDSS Stripe 82, LSST, and Euclid. Accurate photometric redshifts and a survey depth similar or better than that of COSMOS (e.g., I < 25) are required.

  1. Triplets of Quasars at high redshift I: Photometric data

    CERN Document Server

    Alonso, M Victoria; Sochting, Ilona; Bornancini, Carlos; Smith, Malcolm G; Lambas, Diego Garcia; Rest, Armin

    2008-01-01

    We have conducted an optical and infrared imaging in the neighbourhoods of 4 triplets of quasars. R, z', J and Ks images were obtained with MOSAIC II and ISPI at Cerro Tololo Interamerican Observatory. Accurate relative photometry and astrometry were obtained from these images for subsequent use in deriving photometric redshifts. We analyzed the homogeneity and depth of the photometric catalog by comparing with results coming from the literature. The good agreement shows that our magnitudes are reliable to study large scale structure reaching limiting magnitudes of R = 24.5, z' = 22.5, J = 20.5 and Ks = 19.0. With this catalog we can study the neighbourhoods of the triplets of quasars searching for galaxy overdensities such as groups and galaxy clusters.

  2. Spectroscopic Needs for Training of LSST Photometric Redshifts

    CERN Document Server

    Abate, Alexandra; Schmidt, Samuel J

    2014-01-01

    This white paper summarizes those conclusions of the Snowmass White Paper "Spectroscopic Needs for Imaging Dark Energy Experiments" (arXiv:1309.5384) which are relevant to the training of LSST photometric redshifts; i.e., the use of spectroscopic redshifts to improve algorithms and reduce photo-z errors. The larger and more complete the available training set is, the smaller the RMS error in photo-z estimates should be, increasing LSST's constraining power. Among the better US-based options for this work are the proposed MANIFEST fiber feed for the Giant Magellan Telescope or (with lower survey speed) the WFOS spectrograph on the Thirty Meter Telescope (TMT). Due to its larger field of view and higher multiplexing, the PFS spectrograph on Subaru would be able to obtain a baseline training sample faster than TMT; comparable performance could be achieved with a highly-multiplexed spectrograph on Gemini with at least a 20 arcmin diameter field of view.

  3. Reconstructing the galaxy density field with photometric redshifts: I. Methodology and validation on stellar mass functions

    CERN Document Server

    Malavasi, Nicola; Cucciati, Olga; Bardelli, Sandro; Cimatti, Andrea

    2016-01-01

    Measuring environment for large numbers of distant galaxies is still an open problem, for which we need galaxy positions and redshifts. Photometric redshifts are more easily available for large numbers of galaxies, but at the price of larger uncertainties than spectroscopic ones. In this work we study how photometric redshifts affect the measurement of galaxy environment and how this may limit an analysis of the galaxy stellar mass function (GSMF) in different environments. Using mock galaxy catalogues, we measured the environment with a fixed aperture method, using each galaxy's true and photometric redshifts. We varied the fixed aperture volume parameters and the photometric redshift uncertainties. We then computed GSMF as a function of redshift and environment. We found that only when using high-precision photometric redshifts with $\\sigma_{\\Delta z/(1+z)} \\le 0.01$, the most extreme environments can be reconstructed in a fairly accurate way, with a fraction $\\ge 60\\div 80\\%$ of galaxies placed in the corr...

  4. ESTIMATING PHOTOMETRIC REDSHIFTS OF QUASARS VIA THE k-NEAREST NEIGHBOR APPROACH BASED ON LARGE SURVEY DATABASES

    International Nuclear Information System (INIS)

    We apply one of the lazy learning methods, the k-nearest neighbor (kNN) algorithm, to estimate the photometric redshifts of quasars based on various data sets from the Sloan Digital Sky Survey (SDSS), the UKIRT Infrared Deep Sky Survey (UKIDSS), and the Wide-field Infrared Survey Explorer (WISE; the SDSS sample, the SDSS-UKIDSS sample, the SDSS-WISE sample, and the SDSS-UKIDSS-WISE sample). The influence of the k value and different input patterns on the performance of kNN is discussed. kNN performs best when k is different with a special input pattern for a special data set. The best result belongs to the SDSS-UKIDSS-WISE sample. The experimental results generally show that the more information from more bands, the better performance of photometric redshift estimation with kNN. The results also demonstrate that kNN using multiband data can effectively solve the catastrophic failure of photometric redshift estimation, which is met by many machine learning methods. Compared with the performance of various other methods of estimating the photometric redshifts of quasars, kNN based on KD-Tree shows superiority, exhibiting the best accuracy.

  5. Robust Machine Learning Applied to Astronomical Datasets II: Quantifying Photometric Redshifts for Quasars Using Instance-Based Learning

    CERN Document Server

    Ball, N M; Myers, A D; Strand, N E; Alberts, S L; Tcheng, D; Llora, X; Ball, Nicholas M.; Brunner, Robert J.; Myers, Adam D.; Strand, Natalie E.; Alberts, Stacey L.; Tcheng, David; Llor\\`a, Xavier

    2006-01-01

    We apply instance-based machine learning to the task of estimating photometric redshifts for 55,746 objects spectroscopically classified as quasars in the Fifth Data Release of the Sloan Digital Sky Survey, and compare the results obtained to those from an empirical color-redshift relation (CZR). In contrast to previously published results using CZRs, we find that the instance-based photometric redshifts are assigned with no regions of catastrophic failure. Remaining outliers are simply scattered about the ideal relation, in a similar manner to the pattern seen in the optical for normal galaxies at redshifts z < ~1. The instance-based algorithm is trained on a representative sample of the data and pseudo-blind-tested on the remaining unseen data. The variance between the photometric and spectroscopic redshifts is sigma = 0.123 +/- 0.002 (compared to sigma = 0.265 +/- 0.006 for the CZR), and 54.9 +/- 0.7%, 73.3 +/- 0.6%, and 80.7 +/- 0.3% of the objects are within delta z < 0.1, 0.2, and 0.3 respectively...

  6. Exhausting the Information: Novel Bayesian Combination of Photometric Redshift PDFs

    CERN Document Server

    Kind, M Carrasco

    2014-01-01

    The estimation and utilization of photometric redshift (photo-z) PDFs has become increasingly important over the last few years. Primarily this is because of the prominent role photo-z PDFs play in enabling photometric survey data to be used to make cosmological constraints, especially when compared to single estimates. Currently there exist a wide variety of algorithms to compute photo-z's, each with their own strengths and weaknesses. In this paper, we present a novel and efficient Bayesian framework that combines the results from different photo-z techniques into a more powerful and robust estimate by maximizing the information from the photometric data. To demonstrate this we use a supervised machine learning technique based on prediction trees and a random forest, an unsupervised method based on self organizing maps and a random atlas, and a standard template fitting method but can be easily extend to other existing techniques. We use data from the DEEP2 survey and more than $10^6$ galaxies from the SDSS...

  7. Submegaparsec individual photometric redshift estimation from cosmic web constraints

    Science.gov (United States)

    Aragon-Calvo, M. A.; Weygaert, Rien van de; Jones, Bernard J. T.; Mobasher, Bahram

    2015-11-01

    We present a method, PhotoWeb, for estimating photometric redshifts of individual galaxies, and their equivalent distance, with megaparsec and even submegaparsec accuracy using the cosmic web as a constraint over photo-z estimates. PhotoWeb redshift errors of individual galaxies are of the order of Δz ≃ 0.0007, compared to errors of Δz ≃ 0.02 for current photo-z techniques. The mean redshift error is of the order of Δz ≃ 5 × 10-5-5 × 10-4 compared to mean errors in the range Δz ≃ 0.001-0.01 for the best available photo-z estimates in the literature. Current photo-z techniques produce redshift estimates with large errors due to the poor constraining power the galaxy's spectral energy distribution and projected clustering can provide. The cosmic web, on the other hand, provides the strongest constraints on the position of galaxies. The network of walls, filaments and voids occupy ˜ 10 per centof the volume of the Universe, yet they contain ˜ 95 per centof galaxies. The cosmic web, being a cellular system with well-defined boundaries, defines a restricted set of intermittent positions a galaxy can occupy along a given line of sight. Using the information in the density field computed from spectroscopic redshifts, we can narrow the possible locations of a given galaxy along the line of sight from a single broad probability distribution (from photo-z) to one or a few narrow peaks. Our first results improve previous photo-z errors by more than one order of magnitude allowing submegaparsec errors in some cases. Such accurate estimates for tens of millions of galaxies will allow unprecedented galaxy-Large Scale Structure (LSS) studies. In this work, we apply our technique to the Sloan Digital Sky Survey photo-z galaxy sample and discuss its performance and future improvements.

  8. A new method to search for high redshift clusters using photometric redshifts

    CERN Document Server

    Castignani, Gianluca; Celotti, Annalisa; Norman, Colin

    2014-01-01

    We describe a new method (Poisson Probability Method, PPM) to search for high redshift galaxy clusters and groups by using photometric redshift information and galaxy number counts. The method relies on Poisson statistics and is primarily introduced to search for Mpc-scale environments around a specific beacon. The PPM is tailored to both the properties of the FR I radio galaxies in the Chiaberge et al. (2009) sample, that are selected within the COSMOS survey, and on the specific dataset used. We test the efficiency of our method of searching for cluster candidates against simulations. Two different approaches are adopted. i) We use two z~1 X-ray detected cluster candidates found in the COSMOS survey and we shift them to higher redshift up to z=2. We find that the PPM detects the cluster candidates up to z=1.5, and it correctly estimates both the redshift and size of the two clusters. ii) We simulate spherically symmetric clusters of different size and richness, and we locate them at different redshifts (i.e...

  9. Tracing The Sound Horizon Scale With Photometric Redshift Surveys

    CERN Document Server

    Sanchez, E; Garcia-Bellido, J; Gaztanaga, E; de Simoni, F; Crocce, M; Cabre, A; Fosalba, P; Alonso, D

    2010-01-01

    We propose a new method for cosmological parameters extraction using the baryon acoustic oscillation scale as a standard ruler in deep galaxy surveys with photometric determination of redshifts. The method consists in a simple empirical parametric fit to the angular 2-point correlation function w(theta). It is parametrized as a power law to describe the continuum plus a Gaussian to describe the BAO bump. The location of the Gaussian is used as the basis for the measurement of the sound horizon scale. This method, although simple, actually provides a robust estimation, since the inclusion of the power law and the use of the Gaussian removes the shifts which affect the local maximum. We discuss the effects of projection bias, non-linearities, redshift space distortions and photo-z precision, and apply our method to a mock catalog of the Dark Energy Survey, built upon a large N-body simulation provided by the MICE collaboration. We discuss the main systematic errors associated to our method and show that they ar...

  10. QSO Selection and Photometric Redshifts with Neural Networks

    CERN Document Server

    Yeche, Ch; Rich, J; Aubourg, E; Busca, N; Hamilton, J -Ch; Goff, J -M Le; Paris, I; Peirani, S; Pichon, Ch; Rollinde, E; Vargas-Magana, M

    2009-01-01

    Baryonic Acoustic Oscillations (BAO) and their effects on the matter power spectrum can be studied by using the Lyman-alpha absorption signature of the matter density field along quasar (QSO) lines of sight. A measurement sufficiently accurate to provide useful cosmological constraints requires the observation of ~100000 quasars in the redshift range 2.2redshifts, we have developed an Artificial Neural Networks (NN) with a multilayer perceptron architecture. The input variables are photometric measurements, i.e. the object magnitudes and their errors in the five bands (ugriz) of the SDSS photometry. For target selection, we ac...

  11. The SDSS Coadd: A Galaxy Photometric Redshift Catalog

    Energy Technology Data Exchange (ETDEWEB)

    Reis, Ribamar R.R.; /Fermilab /Rio de Janeiro Federal U.; Soares-Santos, Marcelle; /Fermilab /Inst. Geo. Astron., Havana /Sao Paulo U.; Annis, James; /Fermilab; Dodelson, Scott; /Fermilab /Chicago U. /Chicago U., KICP; Hao, Jiangang; /Fermilab; Johnston, David; /Fermilab; Kubo, Jeffrey; /Fermilab; Lin, Huan; /Fermilab; Seo, Hee-Jong; /UC, Berkeley; Simet, Melanie; /Chicago U.

    2011-11-01

    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 {approx} 13 million objects classified as galaxies in the coadd with r < 24.5. The photo-z and photo-z error estimators are trained and validated on a sample of {approx} 89, 000 galaxies that have SDSS photometry and spectroscopic redshifts measured by the SDSS Data Release 7 (DR7), the Canadian Network for Observational Cosmology Field Galaxy Survey (CNOC2), the Deep Extragalactic Evolutionary Probe Data Release 3(DEEP2 DR3), the SDSS-III's Baryon Oscillation Spectroscopic Survey (BOSS), the Visible imaging Multi-Object Spectrograph - Very Large Telescope Deep Survey (VVDS) and the WiggleZ Dark Energy Survey. For the best ANN methods we have tried, we find that 68% of the galaxies in the validation set have a photo-z error smaller than {sigma}{sub 68} = 0.036. After presenting our results and quality tests, we provide a short guide for users accessing the public data.

  12. Photometric redshifts with the Multilayer Perceptron Neural Network: application to the HDF-S and SDSS

    OpenAIRE

    Vanzella, E.; Cristiani, S.; Fontana, A.; M. Nonino(INAF/OAT); Arnouts, S.; Giallongo, E.; Grazian, A.; Fasano, G.; Popesso, P.; Saracco, P.; Zaggia, S.

    2003-01-01

    We present a technique for the estimation of photometric redshifts based on feed-forward neural networks. The Multilayer Perceptron (MLP) Artificial Neural Network is used to predict photometric redshifts in the HDF-S from an ultra deep multicolor catalog. Various possible approaches for the training of the neural network are explored, including the deepest and most complete spectroscopic redshift catalog currently available (the Hubble Deep Field North dataset) and models of the spectral ene...

  13. PHOTOMETRIC REDSHIFTS AND QUASAR PROBABILITIES FROM A SINGLE, DATA-DRIVEN GENERATIVE MODEL

    International Nuclear Information System (INIS)

    We describe a technique for simultaneously classifying and estimating the redshift of quasars. It can separate quasars from stars in arbitrary redshift ranges, estimate full posterior distribution functions for the redshift, and naturally incorporate flux uncertainties, missing data, and multi-wavelength photometry. We build models of quasars in flux-redshift space by applying the extreme deconvolution technique to estimate the underlying density. By integrating this density over redshift, one can obtain quasar flux densities in different redshift ranges. This approach allows for efficient, consistent, and fast classification and photometric redshift estimation. This is achieved by combining the speed obtained by choosing simple analytical forms as the basis of our density model with the flexibility of non-parametric models through the use of many simple components with many parameters. We show that this technique is competitive with the best photometric quasar classification techniques—which are limited to fixed, broad redshift ranges and high signal-to-noise ratio data—and with the best photometric redshift techniques when applied to broadband optical data. We demonstrate that the inclusion of UV and NIR data significantly improves photometric quasar-star separation and essentially resolves all of the redshift degeneracies for quasars inherent to the ugriz filter system, even when included data have a low signal-to-noise ratio. For quasars spectroscopically confirmed by the SDSS 84% and 97% of the objects with Galaxy Evolution Explorer UV and UKIDSS NIR data have photometric redshifts within 0.1 and 0.3, respectively, of the spectroscopic redshift; this amounts to about a factor of three improvement over ugriz-only photometric redshifts. Our code to calculate quasar probabilities and redshift probability distributions is publicly available.

  14. QSO Photometric Redshift estimation for the XMM-Newton/2dF Survey

    CERN Document Server

    Kitsionas, S; Georgantopoulos, I; Georgakakis, A; Giannakis, O

    2003-01-01

    The technique of estimating redshifts using photometric rather than spectroscopic observations has recently received great attention due to its simplicity and the accuracy of the results obtained. In this work, we estimate photometric redshifts for an X-ray selected QSO sample. This is the first time this technique is applied on such a sample. We first calculate the accuracy of the results obtained by comparing photometric to spectroscopic redshifts for a sub-sample of our QSO sample: for the majority (~67%) of the objects in this sub-sample, photometric redshift estimates are correct within Dz<0.3. We then derive the photometric redshift distribution for the whole QSO sample. In the future, we expect to use the photometric redshift distribution in order to derive the distributions of properties such as the Hardness Ratio and hence the hydrogen column density, the luminosity function etc. As an example, we estimate here the dependence of the Hardness Ratio of the QSO sample on photometric redshift.

  15. Machine-learning-based photometric redshifts for galaxies of the ESO Kilo-Degree Survey data release 2

    Science.gov (United States)

    Cavuoti, S.; Brescia, M.; Tortora, C.; Longo, G.; Napolitano, N. R.; Radovich, M.; Barbera, F. La; Capaccioli, M.; de Jong, J. T. A.; Getman, F.; Grado, A.; Paolillo, M.

    2015-09-01

    We have estimated photometric redshifts (zphot) for more than 1.1 million galaxies of the public European Southern Observatory (ESO) Kilo-Degree Survey (KiDS) data release 2. KiDS is an optical wide-field imaging survey carried out with the Very Large Telescope (VLT) Survey Telescope (VST) and the OmegaCAM camera, which aims to tackle open questions in cosmology and galaxy evolution, such as the origin of dark energy and the channel of galaxy mass growth. We present a catalogue of photometric redshifts obtained using the Multi-Layer Perceptron with Quasi-Newton Algorithm (MLPQNA) model, provided within the framework of the DAta Mining and Exploration Web Application REsource (DAMEWARE). These photometric redshifts are based on a spectroscopic knowledge base that was obtained by merging spectroscopic data sets from the Galaxy and Mass Assembly (GAMA) data release 2 and the Sloan Digital Sky Survey III (SDSS-III) data release 9. The overall 1σ uncertainty on Δz = (zspec - zphot)/(1 + zspec) is ˜0.03, with a very small average bias of ˜0.001, a normalized median absolute deviation of ˜0.02 and a fraction of catastrophic outliers (|Δz| > 0.15) of ˜0.4 per cent.

  16. The Overlooked Potential of Generalized Linear Models in Astronomy-II: Gamma regression and photometric redshifts

    CERN Document Server

    Elliott, J; Krone-Martins, A; Cameron, E; Ishida, E E O; Hilbe, J

    2014-01-01

    Machine learning techniques offer a precious tool box for use within astronomy to solve problems involving so-called big data. They provide a means to make accurate predictions about a particular system without prior knowledge of the underlying physical processes of the data. In this article, and the companion papers of this series, we present the set of Generalized Linear Models (GLMs) as a fast alternative method for tackling general astronomical problems, including the ones related to the machine learning paradigm. To demonstrate the applicability of GLMs to inherently positive and continuous physical observables, we explore their use in estimating the photometric redshifts of galaxies from their multi-wavelength photometry. Using the gamma family with a log link function we predict redshifts from the photo-z Accuracy Testing simulated catalogue and a subset of the Sloan Digital Sky Survey from Data Release 10. We obtain fits that result in catastrophic outlier rates as low as ~1% for simulated and ~2% for...

  17. Getting leverage on inflation with a large photometric redshift survey

    CERN Document Server

    Basse, Tobias; Hannestad, Steen; Wong, Yvonne Y Y

    2015-01-01

    We assess the potential of a future large-volume photometric redshift survey to constrain observational inflationary parameters using three large-scale structure observables: the angular shear and galaxy power spectra, and the cluster mass function measured through weak lensing. When used in combination with Planck-like CMB measurements, we find that the spectral index n_s can be constrained to a 1 sigma precision of up to 0.0025. The sensitivity to the running of the spectral index can potentially improve to 0.0017, roughly a factor of five better than the present 1 sigma~constraint from Planck and auxiliary CMB data, allowing us to test the assumptions of the slow-roll scenario with unprecedented accuracy. Interestingly, neither CMB+shear nor CMB+galaxy nor CMB+clusters alone can achieve this level of sensitivity; it is the combined power of all three probes that conspires to break the different parameter degeneracies inherent in each type of observations. We make our forecast software publicly available vi...

  18. PhotoRaptor - Photometric Research Application To Redshifts

    CERN Document Server

    Cavuoti, Stefano; De Stefano, Virgilio; Longo, Giuseppe

    2016-01-01

    Due to the necessity to evaluate photo-z for a variety of huge sky survey data sets, it seemed important to provide the astronomical community with an instrument able to fill this gap. Besides the problem of moving massive data sets over the network, another critical point is that a great part of astronomical data is stored in private archives that are not fully accessible on line. So, in order to evaluate photo-z it is needed a desktop application that can be downloaded and used by everyone locally, i.e. on his own personal computer or more in general within the local intranet hosted by a data center. The name chosen for the application is PhotoRApToR, i.e. Photometric Research Application To Redshift (Cavuoti et al. 2015, 2014; Brescia 2014b). It embeds a machine learning algorithm and special tools dedicated to preand post-processing data. The ML model is the MLPQNA (Multi Layer Perceptron trained by the Quasi Newton Algorithm), which has been revealed particularly powerful for the photo-z calculation on t...

  19. An Improved Technique for Increasing the Accuracy of Photometrically Determined Redshifts for ___Blended___ Galaxies

    Energy Technology Data Exchange (ETDEWEB)

    Parker, Ashley Marie; /Marietta Coll. /SLAC

    2012-08-24

    The redshift of a galaxy can be determined by one of two methods; photometric or spectroscopic. Photometric is a term for any redshift determination made using the magnitudes of light in different filters. Spectroscopic redshifts are determined by measuring the absorption spectra of the object then determining the difference in wavelength between the 'standard' absorption lines and the measured ones, making it the most accurate of the two methods. The data for this research was collected from SDSS DR8 and then separated into blended and non-blended galaxy sets; the definition of 'blended' is discussed in the Introduction section. The current SDSS photometric redshift determination method does not discriminate between blended and non-blended data when it determines the photometric redshift of a given galaxy. The focus of this research was to utilize machine learning techniques to determine if a considerably more accurate photometric redshift determination method could be found, for the case of the blended and non-blended data being treated separately. The results show a reduction of 0.00496 in the RMS error of photometric redshift determinations for blended galaxies and a more significant reduction of 0.00827 for non-blended galaxies, illustrated in Table 2.

  20. CFHTLenS and RCSLenS: Testing Photometric Redshift Distributions Using Angular Cross-Correlations with Spectroscopic Galaxy Surveys

    CERN Document Server

    Choi, Ami; Blake, Chris; Hildebrandt, Hendrik; Duncan, Christopher A J; Erben, Thomas; Nakajima, Reiko; Van Waerbeke, Ludovic; Viola, Massimo

    2015-01-01

    We determine the accuracy of galaxy redshift distributions as estimated from photometric redshift probability distributions $p(z)$. Our method utilises measurements of the angular cross-correlation between photometric galaxies and an overlapping sample of galaxies with spectroscopic redshifts. We describe the redshift leakage from a galaxy photometric redshift bin $j$ into a spectroscopic redshift bin $i$ using the sum of the $p(z)$ for the galaxies residing in bin $j$. We can then predict the angular cross-correlation between photometric and spectroscopic galaxies due to intrinsic galaxy clustering when $i \

  1. A Photometric Redshift Galaxy Catalog from the Red-Sequence Cluster Survey

    CERN Document Server

    Hsieh, B C; Lin, H; Gladders, M D

    2005-01-01

    The Red-Sequence Cluster Survey (RCS) provides a large and deep photometric catalog of galaxies in the $z'$ and $R_c$ bands for ~90 square degrees of sky, and supplemental $V$ and $B$ data have been obtained for 33.6 deg$^{2}$. We compile a photometric redshift catalog from these 4-band data by utilizing the empirical quadratic polynomial photometric redshift fitting technique in combination with CNOC2 and GOODS/HDF-N redshift data. The training set includes 4924 spectral redshifts. The resulting catalog contains more than one million galaxies with photometric redshifts $< 1.5$ and $R_c < 24$, giving an rms scatter $\\sigma(\\Delta{z}) < 0.06$ within the redshift range $0.2 < z < 0.5$ and $\\sigma(\\Delta{z}) < 0.11$ for galaxies at $0.0 < z < 1.5$. We describe the empirical quadratic polynomial photometric redshift fitting technique which we use to determine the relation between redshift and photometry. A kd-tree algorithm is used to divide up our sample to improve the accuracy of our cat...

  2. The Stony Brook Photometric Redshifts of Faint Galaxies in the Hubble Deep Fields

    CERN Document Server

    Lanzetta, K M; Fernández-Soto, A; Pascarelle, S; Pütter, R C; Yahata, N; Yahil, A; Lanzetta, Kenneth M.; Chen, Hsiao-Wen; Fernandez-Soto, Alberto; Pascarelle, Sebastian; Puetter, Rick; Yahata, Noriaki; Yahil, Amos

    1999-01-01

    We report on some aspects of the current status of our efforts to establish properties of faint galaxies by applying our photometric redshift technique to faint galaxies in the HDF and HDF-S WFPC2 and NICMOS fields.

  3. Robust Machine Learning Applied to Astronomical Data Sets. II. Quantifying Photometric Redshifts for Quasars Using Instance-based Learning

    Science.gov (United States)

    Ball, Nicholas M.; Brunner, Robert J.; Myers, Adam D.; Strand, Natalie E.; Alberts, Stacey L.; Tcheng, David; Llorà, Xavier

    2007-07-01

    We apply instance-based machine learning in the form of a k-nearest neighbor algorithm to the task of estimating photometric redshifts for 55,746 objects spectroscopically classified as quasars in the Fifth Data Release of the Sloan Digital Sky Survey. We compare the results obtained to those from an empirical color-redshift relation (CZR). In contrast to previously published results using CZRs, we find that the instance-based photometric redshifts are assigned with no regions of catastrophic failure. Remaining outliers are simply scattered about the ideal relation, in a manner similar to the pattern seen in the optical for normal galaxies at redshifts zblind-tested on the remaining unseen data. The variance between the photometric and spectroscopic redshifts is σ2=0.123+/-0.002 (compared to σ2=0.265+/-0.006 for the CZR), and 54.9%+/-0.7%, 73.3%+/-0.6%, and 80.7%+/-0.3% of the objects are within Δz<0.1, 0.2, and 0.3, respectively. We also match our sample to the Second Data Release of the Galaxy Evolution Explorer legacy data, and the resulting 7642 objects show a further improvement, giving a variance of σ2=0.054+/-0.005, with 70.8%+/-1.2%, 85.8%+/-1.0%, and 90.8%+/-0.7% of objects within Δz<0.1, 0.2, and 0.3. We show that the improvement is indeed due to the extra information provided by GALEX, by training on the same data set using purely SDSS photometry, which has a variance of σ2=0.090+/-0.007. Each set of results represents a realistic standard for application to further data sets for which the spectra are representative.

  4. On the compared accuracy and reliability of spectroscopic and photometric redshift measurements

    OpenAIRE

    Fernandez-Soto, Alberto; Lanzetta, Kenneth M.; Chen, Hsiao-Wen; Pascarelle, Sebastian M.; Yahata, Noriaki

    2000-01-01

    We present a comparison between the spectroscopic catalog of the HDF recently published by Cohen et al and the redshifts measured by our group for those objects using photometric techniques. We perform this comparison in order to characterize the errors associated to the photometric redshift technique. The spectroscopic sample includes over 140 objects in the HDF proper, representing the deepest, cleanest, most complete spectroscopic catalog ever compiled. We study each object for which our r...

  5. GPz: Non-stationary sparse Gaussian processes for heteroscedastic uncertainty estimation in photometric redshift

    CERN Document Server

    Almosallam, Ibrahim A; Roberts, Stephen J

    2016-01-01

    The next generation of cosmology experiments will be required to use photometric redshifts rather than spectroscopic redshifts. Obtaining accurate and well-characterized photometric redshift distributions is therefore critical for Euclid, the Large Synoptic Survey Telescope and the Square Kilometre Array. However, determining accurate variance predictions alongside single point estimates of photometric redshifts is crucial, as they can be used to optimize the sample of galaxies for the specific experiment (e.g. weak lensing, baryon acoustic oscillations, supernovae), trading off between completeness and reliability in the galaxy sample. The various sources of uncertainty (and noise) in measurements of the photometry and redshifts put a lower bound on the accuracy that any model can hope to achieve. The intrinsic uncertainty associated with estimates is often non-uniform and input-dependent. However, existing approaches are susceptible to outliers and do not take into account variance induced by non-uniform da...

  6. The VIPERS Multi-Lambda Survey. I. UV and near-IR observations, multi-colour catalogues, and photometric redshifts

    Science.gov (United States)

    Moutard, T.; Arnouts, S.; Ilbert, O.; Coupon, J.; Hudelot, P.; Vibert, D.; Comte, V.; Conseil, S.; Davidzon, I.; Guzzo, L.; Llebaria, A.; Martin, C.; McCracken, H. J.; Milliard, B.; Morrison, G.; Schiminovich, D.; Treyer, M.; Van Werbaeke, L.

    2016-05-01

    We present observations collected in the CFHTLS-VIPERS region in the ultraviolet with the GALEX satellite (far- and near-ultraviolet channels) and in the near-infrared with the CFHT/WIRCam camera (Ks band) over an area of 22 and 27 deg2, respectively. The depth of the photometry was optimised to measure the physical properties (e.g., star formation rate, stellar masses) of all the galaxies in the VIPERS spectroscopic survey. The large volume explored by VIPERS will enable a unique investigation of the relationship between the galaxy properties and their environment (density field and cosmic web) at high redshift (0.5 ≤ z ≤ 1.2). In this paper, we present the observations, the data reductions, and the build-up of the multi-colour catalogues. The CFHTLS-T0007 (gri-χ2) images are used as reference to detect and measure the Ks-band photometry, while the T0007 u∗-selected sources are used as priors to perform the GALEX photometry based on a dedicated software (EMphot). Our final sample reaches NUVAB ~ 25 (at 5σ) and KAB ~ 22 (at 3σ). The large spectroscopic sample (~51 000 spectroscopic redshifts) allows us to highlight the robustness of our star/galaxy separation and the reliability of our photometric redshifts with a typical accuracy of σz ≤ 0.04 and a fraction of catastrophic failures η ≤ 2% down to i ~ 23. We present various tests on the Ks-band completeness and photometric redshift accuracy by comparing our results with existing overlapping deep photometric catalogues. Finally, we discuss the BzK sample of passive and active galaxies at high redshift and the evolution of galaxy morphology in the (NUV-r) vs. (r-Ks) diagram at low redshift (z ≤ 0.25) based on the high image quality of the CFHTLS. The catalogue is available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (http://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/590/A102The images, catalogues, and photometric redshifts for 1.5 million sources (down to NUV

  7. THE NEXT GENERATION VIRGO CLUSTER SURVEY. XV. THE PHOTOMETRIC REDSHIFT ESTIMATION FOR BACKGROUND SOURCES

    Energy Technology Data Exchange (ETDEWEB)

    Raichoor, A.; Mei, S.; Huertas-Company, M.; Licitra, R. [GEPI, Observatoire de Paris, CNRS, Université Paris Diderot, 61 Avenue de l' Observatoire, F-75014 Paris (France); Erben, T.; Hildebrandt, H. [Argelander-Institut für Astronomie, University of Bonn, Auf dem Hügel 71, D-53121 Bonn (Germany); Ilbert, O.; Boissier, S.; Boselli, A. [Aix Marseille Université, CNRS, Laboratoire d' Astrophysique de Marseille, UMR 7326, F-13388 Marseille (France); Ball, N. M.; Côté, P.; Ferrarese, L.; Gwyn, S. D. J.; Kavelaars, J. J. [Herzberg Institute of Astrophysics, National Research Council of Canada, Victoria, BC V9E 2E7 (Canada); Chen, Y.-T. [Insitute of Astronomy and Astrophysics, Academia Sinica, P.O. Box 23-141, Taipei 106, Taiwan (China); Cuillandre, J.-C. [Canada-France-Hawaïi Telescope Corporation, Kamuela, HI 96743 (United States); Duc, P. A. [Laboratoire AIM Paris-Saclay, CEA/IRFU/SAp, CNRS/INSU, Université Paris Diderot, F-91191 Gif-sur-Yvette Cedex (France); Durrell, P. R. [Department of Physics and Astronomy, Youngstown State University, Youngstown, OH 44555 (United States); Guhathakurta, P. [UCO/Lick Observatory, Department of Astronomy and Astrophysics, University of California Santa Cruz, 1156 High Street, Santa Cruz, CA 95064 (United States); Lançon, A., E-mail: anand.raichoor@obspm.fr [Observatoire Astronomique de Strasbourg, Université de Strasbourg, CNRS, UMR 7550, 11 rue de l' Université, F-67000 Strasbourg (France); and others

    2014-12-20

    The Next Generation Virgo Cluster Survey (NGVS) is an optical imaging survey covering 104 deg{sup 2} centered on the Virgo cluster. Currently, the complete survey area has been observed in the u*giz bands and one third in the r band. We present the photometric redshift estimation for the NGVS background sources. After a dedicated data reduction, we perform accurate photometry, with special attention to precise color measurements through point-spread function homogenization. We then estimate the photometric redshifts with the Le Phare and BPZ codes. We add a new prior that extends to i {sub AB} = 12.5 mag. When using the u* griz bands, our photometric redshifts for 15.5 mag ≤ i ≲ 23 mag or z {sub phot} ≲ 1 galaxies have a bias |Δz| < 0.02, less than 5% outliers, a scatter σ{sub outl.rej.}, and an individual error on z {sub phot} that increases with magnitude (from 0.02 to 0.05 and from 0.03 to 0.10, respectively). When using the u*giz bands over the same magnitude and redshift range, the lack of the r band increases the uncertainties in the 0.3 ≲ z {sub phot} ≲ 0.8 range (–0.05 < Δz < –0.02, σ{sub outl.rej} ∼ 0.06, 10%-15% outliers, and z {sub phot.err.} ∼ 0.15). We also present a joint analysis of the photometric redshift accuracy as a function of redshift and magnitude. We assess the quality of our photometric redshifts by comparison to spectroscopic samples and by verifying that the angular auto- and cross-correlation function w(θ) of the entire NGVS photometric redshift sample across redshift bins is in agreement with the expectations.

  8. The Effect of Dust on Photometric Redshift Measurement; A Self-consistent Technique

    CERN Document Server

    Mobasher, B; Mobasher, Bahram; Mazzei, Paola

    2000-01-01

    A new method is developed for estimating photometric redshifts to galaxies, using realistic template SEDs, extending over four decades in wavelength (i.e. from 0.05 micron to 1 mm). The template SEDs are constructed for four different spectral types of galaxies (elliptical, spiral, irregular and starburst), satisfying the following characteristics: a). they are normalised to produce the observed colours of galaxies at z ~ 0; b). incorporate the chemo-photometric spectral evolution of galaxies of different types, in agreement with the observations; c). allow treatment of dust contribution and its evolution with redshift, consistent with the spectral evolution model; d). include absorption and re-emission of radiation by dust and hence, realistic estimates of the far-infrared radiation; e). include correction for inter-galactic absorption by Lyman continuum and Lyman forest. Using these template SEDs, the photometric redshifts are estimated to an accuracy of ~ 0.11. The effect on the estimated photometric redsh...

  9. TPZ : Photometric redshift PDFs and ancillary information by using prediction trees and random forests

    CERN Document Server

    Kind, M Carrasco

    2013-01-01

    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. In this paper, we present a new, publicly available, parallel, machine learning algorithm that generates photometric redshift PDFs by using prediction trees and random forest techniques, which we have named TPZ. This new algorithm incorporates measurement errors into the calculation while also dealing efficiently with missing values in the data. In addition, our implementation of this algorithm 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, a quantification of the relative importance of the variables used to con...

  10. Photometric redshifts and K-corrections for Sloan Digital Sky Survey Seven Data Release

    CERN Document Server

    O'Mill, Ana Laura; Lambas, Diego García; Sodré, Laerte

    2010-01-01

    We present a catalogue of galaxy photometric redshifts and k-corrections for the Sloan Digital Sky Survey Seven Data Release (SDSS-DR7), available on the World Wide Web. The photometric redshifts were estimated with an artificial neural network using five ugriz bands, concentration indices and Petrosian radii in the g and r bands. We have explored our redshift estimates with different training set concluding that the best choice to improve redshift accuracy comprises the Main Galaxies Sample (MGS), the Luminous Red Galaxies, and galaxies of active galactic nuclei covering the redshift range 0photometric redshift estimates agree with the spectroscopic values within rms=0.0227. The derived distribution of photometric redshifts in the range 0

  11. SDSS-IV: The Clustering of eBOSS LRGs using photometric redshifts

    Science.gov (United States)

    Prakash, Abhishek; SDSS-IV/eBOSS

    2016-01-01

    SDSS-IV/eBOSS is producing an exciting data set for cosmology which will add to our understanding of the large-scale structure of the Universe. The Luminous Red Galaxy (LRG) component of this survey will cover a redshift regime barely explored by SDSS-III/BOSS and will allow a ˜1% measurement of the Baryon Acoustic Oscillation (BAO) scale and a 4.0% Redshift Space Distortion (RSD) measurement using a relatively uniform set of luminous, early-type galaxies in the redshift range 0.6 Digital Sky Survey (SDSS), using photometric redshifts. Although spectroscopic redshifts provide stronger constraints on large scale measurements, these results demonstrate the ability to make precise clustering measurements with photometric surveys.

  12. On the compared accuracy and reliability of spectroscopic and photometric redshift measurements

    CERN Document Server

    Fernández-Soto, A; Chen, H W; Pascarelle, S M; Yahata, N; Fernandez-Soto, Alberto; Lanzetta, Kenneth M.; Chen, Hsiao-Wen; Pascarelle, Sebastian M.; Yahata, Noriaki

    2000-01-01

    Recently Cohen et al have presented a careful compilation of all the spectroscopic redshifts measured in the HDF and flanking fields. Incorporating previously published results, corrections to previous wrong values, and data of their own, they include over 140 objects in the HDF. In this paper we present the comparison between their spectroscopic redshifts and the redshifts that our group has measured for the same objects using photometric techniques, in order to characterize the errors associated to the photometric redshift technique. We particularly study each object for which our redshift and the one by Cohen et al seem to disagree. In most of those cases the photometric evidence we put forth is strong enough to call for a careful review of the spectroscopic values, as they seem to be in error. We show that it is possible to characterize the systematic errors associated to our technique, which when combined with the photometric errors, allows us to obtain complete information on the redshift of each galaxy...

  13. SOMz: photometric redshift PDFs with self organizing maps and random atlas

    CERN Document Server

    Kind, M Carrasco

    2013-01-01

    In this paper we explore the applicability of the unsupervised machine learning technique of Self Organizing Maps (SOM) to estimate galaxy photometric redshift probability density functions (PDFs). This technique takes a spectroscopic training set, and maps the photometric attributes, but not the redshifts, to a two dimensional surface by using a process of competitive learning where neurons compete to more closely resemble the training data multidimensional space. The key feature of a SOM is that it retains the topology of the input set, revealing correlations between the attributes that are not easily identified. We test three different 2D topological mapping: rectangular, hexagonal, and spherical, by using data from the DEEP2 survey. We also explore different implementations and boundary conditions on the map and also introduce the idea of a random atlas where a large number of different maps are created and their individual predictions are aggregated to produce a more robust photometric redshift PDF. We a...

  14. Photometry and Photometric Redshifts of Galaxies in the Hubble Deep Field South Nicmos Field

    CERN Document Server

    Chen, H W; Lanzetta, K M; Pascarelle, S M; Pütter, R C; Yahata, N; Yahil, A; Chen, Hsiao-Wen; Fernandez-Soto, Alberto; Lanzetta, Kenneth M.; Pascarelle, Sebastian M.; Puetter, Richard C.; Yahata, Noriaki; Yahil, Amos

    1998-01-01

    We present an electronic catalog of infrared and optical photometry and photometric redshifts of 323 galaxies in the Hubble Deep Field South NICMOS field at http://www.ess.sunysb.edu/astro/hdfs/home.html. The analysis is based on infrared images obtained with the Hubble Space Telescope using the Near Infrared Camera and Multi-Object Spectrograph and the Space Telescope Imaging Spectrograph together with optical images obtained with the Very Large Telescope. The infrared and optical photometry is measured by means of a new quasi-optimal photometric technique that fits model spatial profiles of the galaxies determined by Pixon image reconstruction techniques to the images. In comparison with conventional methods, the new technique provides higher signal-to-noise-ratio measurements and accounts for uncertainty correlations between nearby, overlapping neighbors. The photometric redshifts are measured by means of our redshift likelihood technique, incorporating six spectrophotometric templates which, by comparison...

  15. Improving photometric redshifts with Ly$\\alpha$ tomography

    CERN Document Server

    Schmittfull, Marcel

    2016-01-01

    Forming a three dimensional view of the Universe is a long-standing goal of astronomical observations, and one that becomes increasingly difficult at high redshift. In this paper we discuss how tomography of the intergalactic medium (IGM) at $z\\simeq 2.5$ can be used to estimate the redshifts of massive galaxies in a large volume of the Universe based on spectra of galaxies in their background. Our method is based on the fact that hierarchical structure formation leads to a strong dependence of the halo density on large-scale environment. A map of the latter can thus be used to refine our knowledge of the redshifts of halos and the galaxies and AGN which they host. We show that tomographic maps of the IGM at a resolution of $2.5\\,h^{-1}$Mpc can determine the redshifts of more than 90 per cent of massive galaxies with redshift uncertainty $\\Delta z/(1+z)=0.01$. Higher resolution maps allow such redshift estimation for lower mass galaxies and halos.

  16. Improving photometric redshifts with Lyα tomography

    Science.gov (United States)

    Schmittfull, Marcel; White, Martin

    2016-08-01

    Forming a three dimensional view of the Universe is a long-standing goal of astronomical observations, and one that becomes increasingly difficult at high redshift. In this paper we discuss how tomography of the intergalactic medium (IGM) at z ≃ 2.5 can be used to estimate the redshifts of massive galaxies in a large volume of the Universe based on spectra of galaxies in their background. Our method is based on the fact that hierarchical structure formation leads to a strong dependence of the halo density on large-scale environment. A map of the latter can thus be used to refine our knowledge of the redshifts of halos and the galaxies and AGN which they host. We show that tomographic maps of the IGM at a resolution of 2.5 h-1Mpc can determine the redshifts of more than 90 per cent of massive galaxies with redshift uncertainty Δz/(1 + z) = 0.01. Higher resolution maps allow such redshift estimation for lower mass galaxies and halos.

  17. Simultaneous Estimation of Photometric Redshifts and SED Parameters: Improved Techniques and a Realistic Error Budget

    CERN Document Server

    Acquaviva, Viviana; Gawiser, Eric

    2015-01-01

    We seek to improve the accuracy of joint galaxy photometric redshift estimation and spectral energy distribution (SED) fitting. By simulating different sources of uncorrected systematic errors, we demonstrate that if the uncertainties on the photometric redshifts are estimated correctly, so are those on the other SED fitting parameters, such as stellar mass, stellar age, and dust reddening. Furthermore, we find that if the redshift uncertainties are over(under)-estimated, the uncertainties in SED parameters tend to be over(under)-estimated by similar amounts. These results hold even in the presence of severe systematics and provide, for the first time, a mechanism to validate the uncertainties on these parameters via comparison with spectroscopic redshifts. We propose a new technique (annealing) to re-calibrate the joint uncertainties in the photo-z and SED fitting parameters without compromising the performance of the SED fitting + photo-z estimation. This procedure provides a consistent estimation of the mu...

  18. Simultaneous Estimation of Photometric Redshifts and SED Parameters: Improved Techniques and a Realistic Error Budget

    Science.gov (United States)

    Acquaviva, Viviana; Raichoor, Anand; Gawiser, Eric

    2015-05-01

    We seek to improve the accuracy of joint galaxy photometric redshift estimation and spectral energy distribution (SED) fitting. By simulating different sources of uncorrected systematic errors, we demonstrate that if the uncertainties in the photometric redshifts are estimated correctly, so are those on the other SED fitting parameters, such as stellar mass, stellar age, and dust reddening. Furthermore, we find that if the redshift uncertainties are over(under)-estimated, the uncertainties in SED parameters tend to be over(under)-estimated by similar amounts. These results hold even in the presence of severe systematics and provide, for the first time, a mechanism to validate the uncertainties on these parameters via comparison with spectroscopic redshifts. We propose a new technique (annealing) to re-calibrate the joint uncertainties in the photo-z and SED fitting parameters without compromising the performance of the SED fitting + photo-z estimation. This procedure provides a consistent estimation of the multi-dimensional probability distribution function in SED fitting + z parameter space, including all correlations. While the performance of joint SED fitting and photo-z estimation might be hindered by template incompleteness, we demonstrate that the latter is “flagged” by a large fraction of outliers in redshift, and that significant improvements can be achieved by using flexible stellar populations synthesis models and more realistic star formation histories. In all cases, we find that the median stellar age is better recovered than the time elapsed from the onset of star formation. Finally, we show that using a photometric redshift code such as EAZY to obtain redshift probability distributions that are then used as priors for SED fitting codes leads to only a modest bias in the SED fitting parameters and is thus a viable alternative to the simultaneous estimation of SED parameters and photometric redshifts.

  19. A Model-Independent Photometric Redshift Estimator for Type Ia Supernovae

    CERN Document Server

    Wang, Y

    2006-01-01

    The use of type Ia supernovae (SNe Ia) as cosmological standard candles is fundamental in modern observational cosmology. In this letter, we derive a simple empirical photometric redshift estimator for SNe Ia using a training set of SNe Ia with multiband ($griz$) light-curves and spectroscopic redshifts obtained by the Supernova Legacy Survey (SNLS). This estimator is analytical and model-independent; it does not use spectral templates. We use all the available SNe Ia from SNLS with near maximum photometry in $griz$ (a total of 40 SNe Ia) to train and test our photometric redshift estimator. The difference between the estimated redshifts $z_{phot}$ and the spectroscopic redshifts $z_{spec}$, $(z_{phot}-z_{spec})/(1+z_{spec})$, has rms dispersions of 0.031 for 20 SNe Ia used in the training set, and 0.050 for 20 SNe Ia not used in the training set. The dispersion is of the same order of magnitude as the flux uncertainties at peak brightness for the SNe Ia. There are no outlyers. This photometric redshift estim...

  20. The SCUBA HAlf Degree Extragalactic Survey (SHADES) - IV: Radio-mm-FIR photometric redshifts

    CERN Document Server

    Aretxaga, I; Coppin, K; Mortier, A M J; Wagg, J; Dunlop, J S; Chapin, E L; Eales, S A; Gaztañaga, E; Halpern, M; Ivison, R J; van Kampen1, E; Scott, D; Serjeant, S; Smail, I; Babbedge, T; Benson, A J; Chapman, S; Clements, D L; Dunne, L; Dye, S; Farrah, D; Jarvis, M J; Mann, R G; Pope, A; Priddey, R; Rawlings, S; Seigar, M; Silva, L; Simpson, C; Vaccari, M; Aretxaga, Itziar; Hughes, David H.; Coppin, Kristen; Mortier, Angela M.J.; Wagg, Jeff; Dunlop, James S.; Chapin, Edward L.; Eales, Stephen A.; Gaztanaga, Enrique; Halpern, Mark; Ivison, Rob J.; Kampen1, Eelco van; Scott, Douglas; Serjeant, Stephen; Smail, Ian; Babbedge, Thomas; Benson, Andrew J.; Chapman, Scott; Clements, David L.; Dunne, Loretta; Dye, Simon; Farrah, Duncan; Jarvis, Matthew J.; Mann, Robert G.; Pope, Alexandra; Priddey, Robert; Rawlings, Steve; Seigar, Marc; Silva, Laura; Simpson, Chris; Vaccari, Mattia

    2007-01-01

    We present the redshift distribution of the SHADES galaxy population based on the rest-frame radio-mm-FIR colours of 120 robustly detected 850um sources in the Lockman Hole East (LH) and Subaru XMM-Newton Deep Field (SXDF). The redshift distribution derived from the full SED information is shown to be narrower than that determined from the radio-submm spectral index, as more photometric bands contribute to higher redshift accuracies. The redshift of sources derived from at least two photometric bands peaks at z ~ 2.4 and has a near-Gaussian distribution, with 50 per cent (interquartile) of sources at z=1.8-3.1. We find a statistically-significant difference between the measured redshift distributions in the two fields; the SXDF peaking at a slightly lower redshift (median z ~ 2.2) than the LH (median z ~ 2.7), which we attribute to the noise-properties of the photometric observations. We demonstrate however that there could also be field-to-field variations that are consistent with the measured differences in...

  1. DISSECTING PHOTOMETRIC REDSHIFT FOR ACTIVE GALACTIC NUCLEUS USING XMM- AND CHANDRA-COSMOS SAMPLES

    International Nuclear Information System (INIS)

    In this paper, we release accurate photometric redshifts for 1692 counterparts to Chandra sources in the central square degree of the Cosmic Evolution Survey (COSMOS) field. The availability of a large training set of spectroscopic redshifts that extends to faint magnitudes enabled photometric redshifts comparable to the highest quality results presently available for normal galaxies. We demonstrate that morphologically extended, faint X-ray sources without optical variability are more accurately described by a library of normal galaxies (corrected for emission lines) than by active galactic nucleus (AGN) dominated templates, even if these sources have AGN-like X-ray luminosities. Preselecting the library on the bases of the source properties allowed us to reach an accuracy σΔz/(1+zspec)∼0.015 with a fraction of outliers of 5.8% for the entire Chandra-COSMOS sample. In addition, we release revised photometric redshifts for the 1735 optical counterparts of the XMM-detected sources over the entire 2 deg2 of COSMOS. For 248 sources, our updated photometric redshift differs from the previous release by Δz > 0.2. These changes are predominantly due to the inclusion of newly available deep H-band photometry (HAB = 24 mag). We illustrate once again the importance of a spectroscopic training sample and how an assumption about the nature of a source together, with the number and the depth of the available bands, influences the accuracy of the photometric redshifts determined for AGN. These considerations should be kept in mind when defining the observational strategies of upcoming large surveys targeting AGNs, such as eROSITA at X-ray energies and the Australian Square Kilometre Array Pathfinder Evolutionary Map of the Universe in the radio band.

  2. A new catalog of photometric redshifts in the Hubble Deep Field

    OpenAIRE

    Fernandez-Soto, A.; Lanzetta, K. M.; Yahil, A.

    1998-01-01

    Using the newly available infrared images of the Hubble Deep Field in the J, H, and K bands and an optimal photometric method, we have refined a technique to estimate the redshifts of 1067 galaxies. A detailed comparison of our results with the spectroscopic redshifts in those cases where the latter are available shows that this technique gives very good results for bright enough objects (AB(8140) < 26.0). From a study of the distribution of residuals (Dz(rms)/(1+z) ~ 0.1 at all redshifts) we...

  3. I. Apples to apples $A^2$: photometric redshift predictions for next-generation surveys

    CERN Document Server

    Ascaso, Begoña; Benítez, Narciso

    2015-01-01

    This is the first of a series of papers where we compare the expected performance of two of the largest stage IV next-generation surveys in the optical and infrared (LSST and Euclid), with a particular focus on cluster surveys. In this first paper, we introduce the mock catalogues we have utilized in this work, an N-body simulation+semi-analytical cone with a posterior modification with PhotReal, a technique which modifies the original photometry to make it more realistic by using an empirical library of spectral templates. We have confirmed the reliability of the mock catalogue by comparing the obtained color-magnitude relation, the luminosity and mass function and the angular correlation function with those of real data. We also analyze the behavior of the expected photometric redshifts for each different survey, in terms of photometric redshift resolution, photometric redshift bias and fraction of outliers. In addition, we discuss the benefits of using the BPZ \\emph{odds} photometric redshift quality param...

  4. CLASH: Photometric redshifts with 16 HST bands in galaxy cluster fields

    CERN Document Server

    Jouvel, S; Lahav, O; Seitz, S; Molino, A; Coe, D; Postman, M; Moustakas, L; Benìtez, N; Rosati, P; Balestra, I; Grillo, C; Bradley, L; Fritz, A; Kelson, D; Koekemoer, A M; Lemze, D; Medezinski, E; Mercurio, A; Moustakas, J; Nonino, M; Scodeggio, M; Zheng, W; Zitrin, A; Bartelmann, M; Bouwens, R; Broadhurst, T; Donahue, M; Ford, H; Graves, G; Infante, L; Jimenez-Teja, Y; Lazkoz, R; Melchior, P; Meneghetti, M; Merten, J; Ogaz, S; Umetsu, K

    2013-01-01

    The Cluster Lensing And Supernovae survey with Hubble (CLASH) is an Hubble Space Telescope (HST) Multi-Cycle Treasury program observing 25 massive galaxy clusters. CLASH observations are carried out in 16 bands from UV to NIR to derive accurate and reliable estimates of photometric redshifts. We present the CLASH photometric redshifts and study the photometric redshift accuracy of the arcs in more detail for the case of MACS1206.2-0847. We use the publicly available Le Phare and BPZ photometric redshift codes on 17 CLASH galaxy clusters. Using Le Phare code for objects with StoN>=10, we reach a precision of 3%(1+z) for the strong lensing arcs, which is reduced to 2.4%(1+z) after removing outliers. For galaxies in the cluster field the corresponding values are 4%(1+z) and 3%(1+z). Using mock galaxy catalogues, we show that 3%(1+z) precision is what one would expect from the CLASH photometry when taking into account extinction from dust, emission lines and the finite range of SEDs included in the photo-z templa...

  5. GASDRA: Galaxy Spectrum Dynamic Range Analysis for Photometric Redshift Filter Partition Optimization

    International Nuclear Information System (INIS)

    The photometric redshift is an active area of research. It is becoming the preferred method for redshift measurement above spectroscopy one for large surveys. In these surveys, the requirement in redshift precision is relaxed in benefit of obtaining the measurements of large number of galaxies. One of the more relevant decisions to be taken in the design of a photometric redshift experiment is the number of filters since it affects deeply to the precision and survey time. Currently, there is not a clear method for evaluating the impact in both precision and exposure time of a determined filter partition set and usually it is determined by detailed simulations on the behavior of photo-z algorithms. In this note we describe GASDRA, a new method for extracting the minimal signal to noise requirement, depending on the number of filters needed for preserving the filtered spectrum shape, and hence to make feasible the spectrum identification. The application of this requirement guaranties a determined precision in the spectrum measurement. Although it cannot be translated directly to absolute photometric redshift error, it does provide a method for comparing the relative precision achieved in the spectrum representation by different sets of filters. We foresee that this relative precision is close related to photo-z error. In addition, we can evaluate the impact in the exposure time of any filter partition set with respect to other. (Author) 11 refs.

  6. Photometric redshifts with the Multilayer Perceptron Neural Network: application to the HDF-S and SDSS

    CERN Document Server

    Vanzella, E; Fontana, A; Nonino, M; Arnouts, S; Giallongo, E; Grazian, A; Fasano, G; Popesso, P; Saracco, P; Zaggia, S R

    2003-01-01

    We present a technique for the estimation of photometric redshifts based on feed-forward neural networks. The Multilayer Perceptron (MLP) Artificial Neural Network is used to predict photometric redshifts in the HDF-S from an ultra deep multicolor catalog. Various possible approaches for the training of the neural network are explored, including the deepest and most complete spectroscopic redshift catalog currently available (the Hubble Deep Field North dataset) and models of the spectral energy distribution of galaxies available in the literature. The MLP can be trained on observed data, theoretical data and mixed samples. The prediction of the method is tested on the spectroscopic sample in the HDF-S (44 galaxies). Over the entire redshift range, $0.1photometric and spectroscopic redshifts in the HDF-S is good: the training on mixed data produces sigma_z(test) ~ 0.11, showing that model libraries together with observed data provide a sufficiently complete description...

  7. GASDRA: Galaxy Spectrum Dynamic Range Analysis for Photometric Redshift Filter Partition Optimization

    Energy Technology Data Exchange (ETDEWEB)

    Vicente, J. de; Sanchez, E.; Sevilla, I.; Castilla, J.; Ponce, R.; Sanchez, F. J.

    2012-04-11

    The photometric redshift is an active area of research. It is becoming the preferred method for redshift measurement above spectroscopy one for large surveys. In these surveys, the requirement in redshift precision is relaxed in benefit of obtaining the measurements of large number of galaxies. One of the more relevant decisions to be taken in the design of a photometric redshift experiment is the number of filters since it affects deeply to the precision and survey time. Currently, there is not a clear method for evaluating the impact in both precision and exposure time of a determined filter partition set and usually it is determined by detailed simulations on the behavior of photo-z algorithms. In this note we describe GASDRA, a new method for extracting the minimal signal to noise requirement, depending on the number of filters needed for preserving the filtered spectrum shape, and hence to make feasible the spectrum identification. The application of this requirement guaranties a determined precision in the spectrum measurement. Although it cannot be translated directly to absolute photometric redshift error, it does provide a method for comparing the relative precision achieved in the spectrum representation by different sets of filters. We foresee that this relative precision is close related to photo-z error. In addition, we can evaluate the impact in the exposure time of any filter partition set with respect to other. (Author) 11 refs.

  8. Photometric redshifts with Quasi Newton Algorithm (MLPQNA). Results in the PHAT1 contest

    CERN Document Server

    Cavuoti, Stefano; Longo, Giuseppe; Mercurio, Amata

    2012-01-01

    Context. Since the advent of modern multiband digital sky surveys, photometric redshifts (photo-z's) have become relevant if not crucial to many fields of observational cosmology, from the characterization of cosmic structures, to weak and strong lensing. Aims. We describe an application to an astrophysical context, namely the evaluation of photometric redshifts, of MLPQNA, a machine learning method based on Quasi Newton Algorithm. Methods. Empirical methods for photo-z's evaluation are based on the interpolation of a priori knowledge (spectroscopic redshifts or SED templates) and represent an ideal test ground for neural networks based methods. The MultiLayer Perceptron with Quasi Newton learning rule (MLPQNA) described here is a computing effective implementation of Neural Networks and is offered to the community through the DAMEWARE (DAta Mining & Exploration Web Application REsource) infrastructure. Results. The PHAT contest (Hildebrandt et al. 2010) provides a standard dataset to test old and new met...

  9. Photometric Selection of High-Redshift Type Ia Supernova Candidates

    Science.gov (United States)

    Sullivan, M.; Howell, D. A.; Perrett, K.; Nugent, P. E.; Astier, P.; Aubourg, E.; Balam, D.; Basa, S.; Carlberg, R. G.; Conley, A.; Fabbro, S.; Fouchez, D.; Guy, J.; Hook, I.; Lafoux, H.; Neill, J. D.; Pain, R.; Palanque-Delabrouille, N.; Pritchet, C. J.; Regnault, N.; Rich, J.; Taillet, R.; Aldering, G.; Baumont, S.; Bronder, J.; Filiol, M.; Knop, R. A.; Perlmutter, S.; Tao, C.

    2006-02-01

    We present a method for selecting high-redshift Type Ia supernovae (SNe Ia) located via rolling SN searches. The technique, using both color and magnitude information of events from only two to three epochs of multiband real-time photometry, is able to discriminate between SNe Ia and core-collapse SNe. Furthermore, for SNe Ia the method accurately predicts the redshift, phase, and light-curve parameterization of these events based only on pre-maximum-light data. We demonstrate the effectiveness of the technique on a simulated survey of SNe Ia and core-collapse SNe, where the selection method effectively rejects most core-collapse SNe while retaining SNe Ia. We also apply the selection code to real-time data acquired as part of the Canada-France-Hawaii Telescope Supernova Legacy Survey (SNLS). During the period 2004 May to 2005 January in the SNLS, 440 SN candidates were discovered, of which 70 were confirmed spectroscopically as SNe Ia and 15 as core-collapse events. For this test data set, the selection technique correctly identifies 100% of the identified SNe II as non-SNe Ia with only a 1%-2% false rejection rate. The predicted parameterization of the SNe Ia has a precision of Δz/(1+zspec)<0.09 in redshift and +/-2-3 rest-frame days in phase, providing invaluable information for planning spectroscopic follow-up observations. We also investigate any bias introduced by this selection method on the ability of surveys such as SNLS to measure cosmological parameters (e.g., w and ΩM) and find any effect to be negligible.

  10. Photometric selection of high-redshift type Ia supernovae

    CERN Document Server

    Sullivan, M; Perrett, K; Nugent, P; Astier, Pierre; Aubourg, E; Balam, D; Basa, S; Carlberg, R; Conley, A; Fabbro, S; Fouchez, D; Guy, J; Hook, I; Lafoux, H; Neill, J D; Pain, R; Palanque-Delabrouille, Nathalie; Pritchet, C; Regnault, N; Rich, J; Taillet, R; Aldering, G; Baumont, S; Bronder, J; Filiol, M; Knop, R; Perlmutter, S; Tao, C

    2005-01-01

    We present a method for selecting high-redshift type Ia supernovae (SNe Ia) located via rolling SN searches. The technique, using both color and magnitude information of events from only 2-3 epochs of multi-band real-time photometry, is able to discriminate between SNe Ia and core collapse SNe. Furthermore, for the SNe Ia, the method accurately predicts the redshift, phase and light-curve parameterization of these events based only on pre-maximum-light data. We demonstrate the effectiveness of the technique on a simulated survey of SNe Ia and core-collapse SNe, where the selection method effectively rejects most core-collapse SNe while retaining SNe Ia. We also apply the selection code to real-time data acquired as part of the Canada-France-Hawaii Telescope Supernova Legacy Survey (SNLS). During the period May 2004 to January 2005 in the SNLS, 440 SN candidates were discovered of which 70 were confirmed spectroscopically as SNe Ia and 15 as core-collapse events. For this test dataset, the selection technique ...

  11. Robust photometric redshift determinations of gamma-ray burst afterglows at z ≳ 2

    Science.gov (United States)

    Curran, P. A.; Wijers, R. A. M. J.; Heemskerk, M. H. M.; Starling, R. L. C.; Wiersema, K.; van der Horst, A. J.

    2008-11-01

    Context: Theory suggests that about 10% of Swift-detected gamma-ray bursts (GRBs) will originate at redshifts, z, greater than 5 yet a number of high redshift candidates may be left unconfirmed due to the lack of measured redshifts. Aims: Here we introduce our code, GRBz, a method of simultaneous multi-parameter fitting of GRB afterglow optical and near infrared, spectral energy distributions. It allows for early determinations of the photometric redshift, spectral index and host extinction to be made. Methods: We assume that GRB afterglow spectra are well represented by a power-law decay and model the effects of absorption due to the Lyman forest and host extinction. We use a genetic algorithm-based routine to simultaneously fit the parameters of interest, and a Monte Carlo error analysis. Results: We use GRBs of previously determined spectroscopic redshifts to prove our method, while also introducing new near infrared data of GRB 990510 which further constrains the value of the host extinction. Conclusions: Our method is effective in estimating the photometric redshift of GRBs, relatively unbiased by assumptions of the afterglow spectral index or the host galaxy extinction. Monte Carlo error analysis is required as the method of error estimate based on the optimum population of the genetic algorithm underestimates errors significantly.

  12. WISE × SuperCOSMOS Photometric Redshift Catalog: 20 Million Galaxies over 3/pi Steradians

    Science.gov (United States)

    Bilicki, Maciej; Peacock, John A.; Jarrett, Thomas H.; Cluver, Michelle E.; Maddox, Natasha; Brown, Michael J. I.; Taylor, Edward N.; Hambly, Nigel C.; Solarz, Aleksandra; Holwerda, Benne W.; Baldry, Ivan; Loveday, Jon; Moffett, Amanda; Hopkins, Andrew M.; Driver, Simon P.; Alpaslan, Mehmet; Bland-Hawthorn, Joss

    2016-07-01

    We cross-match the two currently largest all-sky photometric catalogs—mid-infrared Wide-field Infrared Survey Explorer and SuperCOSMOS scans of UKST/POSS-II photographic plates—to obtain a new galaxy sample that covers 3π steradians. In order to characterize and purify the extragalactic data set, we use external GAMA and Sloan Digital Sky Survey spectroscopic information to define quasar and star loci in multicolor space, aiding the removal of contamination from our extended source catalog. After appropriate data cleaning, we obtain a deep wide-angle galaxy sample that is approximately 95% pure and 90% complete at high Galactic latitudes. The catalog contains close to 20 million galaxies over almost 70% of the sky, outside the Zone of Avoidance and other confused regions, with a mean surface density of more than 650 sources per square degree. Using multiwavelength information from two optical and two mid-IR photometric bands, we derive photometric redshifts for all the galaxies in the catalog, using the ANNz framework trained on the final GAMA-II spectroscopic data. Our sample has a median redshift of {z}{med}=0.2, with a broad {dN}/{dz} reaching up to z > 0.4. The photometric redshifts have a mean bias of | δ z| ∼ {10}-3, a normalized scatter of σ z = 0.033, and less than 3% outliers beyond 3σ z . Comparison with external data sets shows no significant variation of photo-z quality with sky position. Together with the overall statistics, we also provide a more detailed analysis of photometric redshift accuracy as a function of magnitudes and colors. The final catalog is appropriate for “all-sky” three-dimensional (3D) cosmology to unprecedented depths, in particular through cross-correlations with other large-area surveys. It should also be useful for source preselection and identification in forthcoming surveys, such as TAIPAN or WALLABY.

  13. A new method to assign galaxy cluster membership using photometric redshifts

    CERN Document Server

    Castignani, Gianluca

    2016-01-01

    We introduce a new effective strategy to assign group and cluster membership probabilities $P_{mem}$ to galaxies using photometric redshift information. Large dynamical ranges both in halo mass and cosmic time are considered. The method takes the magnitude distribution of both cluster and field galaxies as well as the radial distribution of galaxies in clusters into account using a non-parametric formalism and relies on Bayesian inference to take photometric redshift uncertainties into account. We successfully test the method against 1,208 galaxy clusters within redshifts $z=0.05-2.55$ and masses $10^{13.29-14.80}~M_\\odot$ drawn from wide field simulated galaxy mock catalogs developed for the Euclid mission. Median purity $(55^{+17}_{-15})\\%$ and completeness $(95^{+5}_{-10})\\%$ are reached for galaxies brighter than 0.25$L_\\ast$ within $r_{200}$ of each simulated halo and for a statistical photometric redshift accuracy $\\sigma((z_s-z_p)/(1+z_s))=0.03$. The mean values $\\overline{\\mathsf{p}}=56\\%$ and $\\overl...

  14. Dissecting Photometric redshift for Active Galactic Nuclei using XMM- and Chandra-COSMOS samples

    CERN Document Server

    Salvato, M; Hasinger, G; Rau, A; Civano, F; Zamorani, G; Brusa, M; Elvis, M; Vignali, C; Aussel, H; Comastri, A; Fiore, F; Floc'h, E Le; Mainieri, V; Bardelli, S; Bolzonella, M; Bongiorno, A; Capak, P; Caputi, K; Cappelluti, N; Carollo, C M; Contini, T; Garilli, B; Iovino, A; Fotopoulou, S; Fruscione, A; Gilli, R; Halliday, C; Kneib, J-P; Kakazu, Y; Kartaltepe, J S; Koekemoer, A M; Kovac, K; Ideue, Y; Ikeda, H; Impey, C D; Fevre, O Le; Lamareille, F; Lanzuisi, G; Borgne, J-F Le; Brun, V Le; Lilly, S J; Maier, C; Manohar, S; Masters, D; McCracken, H; Messias, H; Mignoli, M; Mobasher, B; Nagao, T; Pello, R; Puccetti, S; Renzini, E Perez Montero A; Sargent, M; Sanders, D B; Scodeggio, M; Scoville, N; Shopbell, P; Silvermann, J; Taniguchi, Y; Tasca, L; Tresse, L; Trump, J R; Zucca, E

    2011-01-01

    With this paper, we release accurate photometric redshifts for 1692 counterparts to Chandra sources in the central square degree of the COSMOS field. The availability of a large training set of spectroscopic redshifts that extends to faint magnitudes enabled photometric redshifts comparable to the highest quality results presently available for normal galaxies. We demonstrate that morphologically extended, faint X-ray sources without optical variability are more accurately described by a library of normal galaxies (corrected for emission lines) than by AGN-dominated templates, even if these sources have AGN-like X-ray luminosities. Preselecting the library on the bases of the source properties allowed us to reach an accuracy sigma_(Delta z/(1+z_spec)) \\sim0.015 with a fraction of outliers of 5.8% for the entire Chandra-COSMOS sample. In addition, we release revised photometric redshifts for the 1735 optical counterparts of the XMM-detected sources over the entire 2 sq. deg.of COSMOS. For 248 sources, our upda...

  15. Photometry and Photometric Redshifts of Faint Galaxies in the Hubble Deep Field South NICMOS Field

    CERN Document Server

    Yahata, N; Chen, H W; Fernández-Soto, A; Pascarelle, S M; Yahil, A; Pütter, R C; Yahata, Noriaki; Lanzetta, Kenneth M.; Chen, Hsiao-Wen; Fernandez-Soto, Alberto; Pascarelle, Sebastian M.; Yahil, Amos; Puetter, Richard C.

    2000-01-01

    We present a catalog of photometry and photometric redshifts of 335 faint objects in the HDF-S NICMOS field. The analysis is based on (1) infrared images obtained with the Hubble Space Telescope (HST) using the Near Infrared Camera and Multi-Object Spectrograph (NICMOS) with the F110W, F160W, and F222M filters, (2) an optical image obtained with HST using the Space Telescope Imaging Spectrograph (STIS) with no filter, and (3) optical images obtained with the European Southern Observatory (ESO) Very Large Telescope (VLT) with U, B, V, R, and I filters. The primary utility of the catalog of photometric redshifts is as a survey of faint galaxies detected in the NICMOS F160W and F222M images. The sensitivity of the survey varies significantly with position, reaching a limiting depth of AB(16,000) ~ 28.7 and covering 1.01 arcmin^2 to AB(16,000) = 27 and 1.05 arcmin^2 to AB(16,000) = 26.5. The catalog of photometric redshifts identifies 21 galaxies (or 60f the total) of redshift z > 5, 8 galaxies (or 2563641f the t...

  16. Spectroscopic Needs for Imaging Dark Energy Experiments: Photometric Redshift Training and Calibration

    CERN Document Server

    Newman, J; Abdalla, F; Allam, S; Allen, S; Ansari, R; Bailey, S; Barkhouse, W; Beers, T; Blanton, M; Brodwin, M; Brownstein, J; Brunner, R; Carrasco-Kind, M; Cervantes-Cota, J; Chisari, E; Colless, M; Comparat, J; Coupon, J; Cheu, E; Cunha, C; de la Macorra, A; Dell'Antonio, I; Frye, B; Gawiser, E; Gehrels, N; Grady, K; Hagen, A; Hall, P; Hearin, A; Hildebrandt, H; Hirata, C; Ho, S; Honscheid, K; Huterer, D; Ivezic, Z; Kneib, J -P; Kruk, J; Lahav, O; Mandelbaum, R; Marshall, J; Matthews, D; Ménard, B; Miquel, R; Moniez, M; Moos, W; Moustakas, J; Papovich, C; Peacock, J; Park, C; Rhodes, J; Ricol, J-S; Sadeh, I; Slozar, A; Schmidt, S; Stern, D; Tyson, T; von der Linden, A; Wechsler, R; Wood-Vasey, W; Zentner, A

    2013-01-01

    Large sets of objects with spectroscopic redshift measurements will be needed for imaging dark energy experiments to achieve their full potential, serving two goals:_training_, i.e., the use of objects with known redshift to develop and optimize photometric redshift algorithms; and_calibration_, i.e., the characterization of moments of redshift (or photo-z error) distributions. Better training makes cosmological constraints from a given experiment stronger, while highly-accurate calibration is needed for photo-z systematics not to dominate errors. In this white paper, we investigate the required scope of spectroscopic datasets which can serve both these purposes for ongoing and next-generation dark energy experiments, as well as the time required to obtain such data with instruments available in the next decade. Large time allocations on kilo-object spectrographs will be necessary, ideally augmented by infrared spectroscopy from space. Alternatively, precision calibrations could be obtained by measuring cross...

  17. Photometric redshifts and clustering of emission line galaxies selected jointly by DES and eBOSS

    Energy Technology Data Exchange (ETDEWEB)

    Jouvel, S.; et al.

    2015-09-23

    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 0.6redshifts, the mean redshift for the bright and faint sample is 0.85 and 0.9 respectively. Star contamination is lower than 2\\%. We measure a galaxy bias averaged on scales of 1 and 10~Mpc/h of 1.72 \\pm 0.1 for the bright sample and of 1.78 \\pm 0.12 for the faint sample. The error on the galaxy bias have been obtained propagating the errors in the correlation function to the fitted parameters. This redshift evolution for the galaxy bias is in agreement with theoretical expectations for a galaxy population with MB-5\\log h < -21.0. We note that biasing is derived from the galaxy clustering relative to a model for the mass fluctuations. We investigate the quality of the DES photometric redshifts and find that the outlier fraction can be reduced using a comparison between template fitting and neural network, or using a random forest algorithm.

  18. Deriving Photometric Redshifts using Fuzzy Archetypes and Self-Organizing Maps. II. Comparing Sampling Techniques Using Mock Data

    CERN Document Server

    Speagle, Joshua S

    2015-01-01

    In a companion paper, we proposed combining large numbers of "fuzzy archetypes" with Self-Organizing Maps (SOMs) to derive photometric redshifts in a data-driven way. In this paper, we investigate the performance of several sampling approaches that build on this general idea using a mock catalog designed to approximately simulate LSST ($ugrizY$) and Euclid ($YJH$) data from $z=0-6$ at fixed LSST $Y=24$ mag. We test eight different approaches: two brute-force methods, two Markov Chain Monte Carlo (MCMC)-based methods, two hierarchical sampling methods, and two "quick-search" methods based on quantities derived during the initial SOM training process. We find most methods perform reasonably well with small catastrophic outlier fractions and are able to robustly identify redshift probability distribution functions that are multi-modal and/or poorly constrained. Once these insecure objects are removed, the results are generally in good agreement with the strict accuracy requirements necessary to meet Euclid weak ...

  19. Photometric Redshift Probability Distributions for Galaxies in the SDSS DR8

    CERN Document Server

    Sheldon, Erin S; Mandelbaum, Rachel; Brinkmann, J; Weaver, Benjamin A

    2011-01-01

    We present redshift probability distributions for galaxies in the SDSS DR8 imaging data. We used the nearest-neighbor weighting algorithm presented in Lima et al. 2008 and Cunha et al. 2009 to derive the ensemble redshift distribution N(z), and individual redshift probability distributions P(z) for galaxies with r < 21.8. As part of this technique, we calculated weights for a set of training galaxies with known redshifts such that their density distribution in five dimensional color-magnitude space was proportional to that of the photometry-only sample, producing a nearly fair sample in that space. We then estimated the ensemble N(z) of the photometric sample by constructing a weighted histogram of the training set redshifts. We derived P(z) s for individual objects using the same technique, but limiting to training set objects from the local color-magnitude space around each photometric object. Using the P(z) for each galaxy, rather than an ensemble N(z), can reduce the statistical error in measurements t...

  20. The Herschel Multi-Tiered Extragalactic Survey: SPIRE-mm Photometric Redshifts

    CERN Document Server

    Roseboom, I G; Greve, T R; Amblard, A; Arumugam, V; Auld, R; Aussel, H; Bethermin, M; Blain, A; Bock, J; Boselli, A; Brisbin, D; Buat, V; Burgarella, D; Castro-Rodriguez, N; Cava, A; Chanial, P; Chapin, E; Chapman, S; Clements, D L; Conley, A; Conversi, L; Cooray, A; Dowell, C D; Dunlop, J S; Dwek, E; Eales, S; Elbaz, D; Farrah, D; Franceschini, A; Glenn, J; Griffin, M; Halpern, M; Hatziminaoglou, E; Ibar, E; Isaak, K; Lagache, G; Levenson, L; Lu, N; Madden, S; Maffei, B; Mainetti, G; Marchetti, L; Marsden, G; Morrison, G; Mortier, A M J; Nguyen, H T; O'Halloran, B; Oliver, S J; Omont, A; Page, M J; Panuzzo, P; Papageorgiou, A; Pearson, C P; Perez-Fournon, I; Pohlen, M; Rawlings, J I; Raymond, G; Rigopoulou, D; Rizzo, D; Rodighiero, G; Rowan-Robinson, M; Schulz, B; Scott, Douglas; Seymour, N; Shupe, D L; Smith, A J; Stevens, J A; Symeonidis, M; Trichas, M; Tugwell, K E; Vaccari, M; Valtchanov, I; Vieira, J D; Viero, M P; Vigroux, L; Wardlow, J; Wang, L; Wright, G; Xu, C K; Zemcov, M

    2011-01-01

    We investigate the potential of submm-mm and submm-mm-radio photometric redshifts using a sample of mm-selected sources as seen at 250, 350 and 500 {\\mu}m by the SPIRE instrument on Herschel. From a sample of 63 previously identified mm-sources with reliable radio identifications in the GOODS-N and Lockman Hole North fields 46 (73 per cent) are found to have detections in at least one SPIRE band. We explore the observed submm/mm colour evolution with redshift, finding that the colours of mm-sources are adequately described by a modified blackbody with constant optical depth {\\tau} = ({\

  1. The Efficacy of Galaxy Shape Parameters in Photometric Redshift Estimation: A Neural Network Approach

    International Nuclear Information System (INIS)

    We present a determination of the effects of including galaxy morphological parameters in photometric redshift estimation with an artificial neural network method. Neural networks, which recognize patterns in the information content of data in an unbiased way, can be a useful estimator of the additional information contained in extra parameters, such as those describing morphology, if the input data are treated on an equal footing. We show that certain principal components of the morphology information are correlated with galaxy type. However, we find that for the data used the inclusion of morphological information does not have a statistically significant benefit for photometric redshift estimation with the techniques employed here. The inclusion of these parameters may result in a trade-off between extra information and additional noise, with the additional noise becoming more dominant as more parameters are added.

  2. Photometric redshift estimation based on data mining with PhotoRApToR

    Science.gov (United States)

    Cavuoti, S.; Brescia, M.; De Stefano, V.; Longo, G.

    2015-03-01

    Photometric redshifts (photo-z) are crucial to the scientific exploitation of modern panchromatic digital surveys. In this paper we present PhotoRApToR (Photometric Research Application To Redshift): a Java/C ++ based desktop application capable to solve non-linear regression and multi-variate classification problems, in particular specialized for photo-z estimation. It embeds a machine learning algorithm, namely a multi-layer neural network trained by the Quasi Newton learning rule, and special tools dedicated to pre- and post-processing data. PhotoRApToR has been successfully tested on several scientific cases. The application is available for free download from the DAME Program web site.

  3. Photometric redshift estimation based on data mining with PhotoRApToR

    CERN Document Server

    Cavuoti, Stefano; De Stefano, Virgilio; Longo, Giuseppe

    2015-01-01

    Photometric redshifts (photo-z) are crucial to the scienti?c exploitation of modern panchromatic digital surveys. In this paper we present PhotoRApToR (Photometric Research Application To Redshift): a Java/C++ based desktop application capable to solve non-linear regression and multi-variate classi?cation problems, in particular specialized for photo-z estimation. It embeds a machine learning algorithm, namely a multilayer neural network trained by the Quasi Newton learning rule, and special tools dedicated to pre- and postprocessing data. PhotoRApToR has been successfully tested on several scienti?c cases. The application is available for free download from the DAME Program web site.

  4. Photometry and Photometric Redshifts of Galaxies in the Hubble Deep Field South Nicmos Field

    OpenAIRE

    Chen, Hsiao-Wen; Fernandez-Soto, Alberto; Lanzetta, Kenneth M.; Pascarelle, Sebastian M.; Puetter, Richard C.; Yahata, Noriaki; Yahil, Amos

    1998-01-01

    We present an electronic catalog of infrared and optical photometry and photometric redshifts of 323 galaxies in the Hubble Deep Field South NICMOS field at http://www.ess.sunysb.edu/astro/hdfs/home.html. The analysis is based on infrared images obtained with the Hubble Space Telescope using the Near Infrared Camera and Multi-Object Spectrograph and the Space Telescope Imaging Spectrograph together with optical images obtained with the Very Large Telescope. The infrared and optical photometry...

  5. PHOTOMETRIC REDSHIFT PROBABILITY DISTRIBUTIONS FOR GALAXIES IN THE SDSS DR8

    International Nuclear Information System (INIS)

    We present redshift probability distributions for galaxies in the Sloan Digital Sky Survey (SDSS) Data Release 8 imaging data. We used the nearest-neighbor weighting algorithm to derive the ensemble redshift distribution N(z), and individual redshift probability distributions P(z) for galaxies with r < 21.8 and u < 29.0. As part of this technique, we calculated weights for a set of training galaxies with known redshifts such that their density distribution in five-dimensional color-magnitude space was proportional to that of the photometry-only sample, producing a nearly fair sample in that space. We estimated the ensemble N(z) of the photometric sample by constructing a weighted histogram of the training-set redshifts. We derived P(z)'s for individual objects by using training-set objects from the local color-magnitude space around each photometric object. Using the P(z) for each galaxy can reduce the statistical error in measurements that depend on the redshifts of individual galaxies. The spectroscopic training sample is substantially larger than that used for the DR7 release. The newly added PRIMUS catalog is now the most important training set used in this analysis by a wide margin. We expect the primary sources of error in the N(z) reconstruction to be sample variance and spectroscopic failures: The training sets are drawn from relatively small volumes of space, and some samples have large incompleteness. Using simulations we estimated the uncertainty in N(z) due to sample variance at a given redshift to be ∼10%-15%. The uncertainty on calculations incorporating N(z) or P(z) depends on how they are used; we discuss the case of weak lensing measurements. The P(z) catalog is publicly available from the SDSS Web site.

  6. Pan-STARRS1 variability of XMM-COSMOS AGN. I. Impact on photometric redshifts

    Science.gov (United States)

    Simm, T.; Saglia, R.; Salvato, M.; Bender, R.; Burgett, W. S.; Chambers, K. C.; Draper, P. W.; Flewelling, H.; Kaiser, N.; Kudritzki, R.-P.; Magnier, E. A.; Metcalfe, N.; Tonry, J. L.; Wainscoat, R. J.; Waters, C.

    2015-12-01

    Aims: Upcoming large area sky surveys like Euclid and eROSITA, which are dedicated to studying the role of dark energy in the expansion history of the Universe and the three-dimensional mass distribution of matter, crucially depend on accurate photometric redshifts. The identification of variable sources, such as active galactic nuclei (AGNs), and the achievable redshift accuracy for varying objects are important in view of the science goals of the Euclid and eROSITA missions. Methods: We probe AGN optical variability for a large sample of X-ray-selected AGNs in the XMM-COSMOS field, using the multi-epoch light curves provided by the Pan-STARRS1 (PS1) 3π and Medium Deep Field surveys. To quantify variability we employed a simple statistic to estimate the probability of variability and the normalized excess variance to measure the variability amplitude. Utilizing these two variability parameters, we defined a sample of varying AGNs for every PS1 band. We investigated the influence of variability on the calculation of photometric redshifts by applying three different input photometry sets for our fitting procedure. For each of the five PS1 bands gP1, rP1, iP1, zP1, and yP1, we chose either the epochs minimizing the interval in observing time, the median magnitude values, or randomly drawn light curve points to compute the redshift. In addition, we derived photometric redshifts using PS1 photometry extended by GALEX/IRAC bands. Results: We find that the photometry produced by the 3π survey is sufficient to reliably detect variable sources provided that the fractional variability amplitude is at least ~3%. Considering the photometric redshifts of variable AGNs, we observe that minimizing the time spacing of the chosen points yields superior photometric redshifts in terms of the percentage of outliers (33%) and accuracy (0.07), outperforming the other two approaches. Drawing random points from the light curve gives rise to typically 57% of outliers and an accuracy of

  7. Photometric redshift analysis in the Dark Energy Survey Science Verification data

    CERN Document Server

    Sánchez, C; Lin, H; Miquel, R; Abdalla, F B; Amara, A; Banerji, M; Bonnett, C; Brunner, R; Capozzi, D; Carnero, A; Castander, F J; da Costa, L A N; Cunha, C; Fausti, A; Gerdes, D; Greisel, N; Gschwend, J; Hartley, W; Jouvel, S; Lahav, O; Lima, M; Maia, M A G; Martí, P; Ogando, R L C; Ostrovski, F; Pellegrini, P; Rau, M M; Sadeh, I; Seitz, S; Sevilla-Noarbe, I; Sypniewski, A; de Vicente, J; Abbot, T; Allam, S S; Atlee, D; Bernstein, G; Bernstein, J P; Buckley-Geer, E; Burke, D; Childress, M J; Davis, T; DePoy, D L; Dey, A; Desai, S; Diehl, H T; Doel, P; Estrada, J; Evrard, A; Fernández, E; Finley, D; Flaugher, B; Gaztanaga, E; Glazebrook, K; Honscheid, K; Kim, A; Kuehn, K; Kuropatkin, N; Lidman, C; Makler, M; Marshall, J L; Nichol, R C; Roodman, A; Sánchez, E; Santiago, B X; Sako, M; Scalzo, R; Smith, R C; Swanson, M E C; Tarle, G; Thomas, D; Tucker, D L; Uddin, S A; Valdés, F; Walker, A; Yuan, F; Zuntz, J

    2014-01-01

    We present results from a study of the photometric redshift performance of the Dark Energy Survey (DES), using the early data from a Science Verification (SV) period of observations in late 2012 and early 2013 that provided science-quality images for almost 200 sq.~deg.~at the nominal depth of the survey. We assess the photometric redshift performance using about 15000 galaxies with spectroscopic redshifts available from other surveys. These galaxies are used, in different configurations, as a calibration sample, and photo-$z$'s are obtained and studied using most of the existing photo-$z$ codes. A weighting method in a multi-dimensional color-magnitude space is applied to the spectroscopic sample in order to evaluate the photo-$z$ performance with sets that mimic the full DES photometric sample, which is on average significantly deeper than the calibration sample due to the limited depth of spectroscopic surveys. Empirical photo-$z$ methods using, for instance, Artificial Neural Networks or Random Forests, y...

  8. Photometric redshifts with the quasi Newton algorithm (MLPQNA) Results in the PHAT1 contest

    Science.gov (United States)

    Cavuoti, S.; Brescia, M.; Longo, G.; Mercurio, A.

    2012-10-01

    Context. Since the advent of modern multiband digital sky surveys, photometric redshifts (photo-z's) have become relevant if not crucial to many fields of observational cosmology, such as the characterization of cosmic structures and the weak and strong lensing. Aims: We describe an application to an astrophysical context, namely the evaluation of photometric redshifts, of MLPQNA, which is a machine-learning method based on the quasi Newton algorithm. Methods: Theoretical methods for photo-z evaluation are based on the interpolation of a priori knowledge (spectroscopic redshifts or SED templates), and they represent an ideal comparison ground for neural network-based methods. The MultiLayer Perceptron with quasi Newton learning rule (MLPQNA) described here is an effective computing implementation of neural networks exploited for the first time to solve regression problems in the astrophysical context. It is offered to the community through the DAMEWARE (DAta Mining & Exploration Web Application REsource) infrastructure. Results: The PHAT contest (Hildebrandt et al. 2010, A&A, 523, A31) provides a standard dataset to test old and new methods for photometric redshift evaluation and with a set of statistical indicators that allow a straightforward comparison among different methods. The MLPQNA model has been applied on the whole PHAT1 dataset of 1984 objects after an optimization of the model performed with the 515 available spectroscopic redshifts as training set. When applied to the PHAT1 dataset, MLPQNA obtains the best bias accuracy (0.0006) and very competitive accuracies in terms of scatter (0.056) and outlier percentage (16.3%), scoring as the second most effective empirical method among those that have so far participated in the contest. MLPQNA shows better generalization capabilities than most other empirical methods especially in the presence of underpopulated regions of the knowledge base.

  9. CFHTLenS and RCSLenS: Testing Photometric Redshift Distributions Using Angular Cross-Correlations with Spectroscopic Galaxy Surveys

    Science.gov (United States)

    Choi, A.; Heymans, C.; Blake, C.; Hildebrandt, H.; Duncan, C. A. J.; Erben, T.; Nakajima, R.; Van Waerbeke, L.; Viola, M.

    2016-09-01

    We determine the accuracy of galaxy redshift distributions as estimated from photometric redshift probability distributions p(z). Our method utilises measurements of the angular cross-correlation between photometric galaxies and an overlapping sample of galaxies with spectroscopic redshifts. We describe the redshift leakage from a galaxy photometric redshift bin j into a spectroscopic redshift bin i using the sum of the p(z) for the galaxies residing in bin j. We can then predict the angular cross-correlation between photometric and spectroscopic galaxies due to intrinsic galaxy clustering when i ≠ j as a function of the measured angular cross-correlation when i = j. We also account for enhanced clustering arising from lensing magnification using a halo model. The comparison of this prediction with the measured signal provides a consistency check on the validity of using the summed p(z) to determine galaxy redshift distributions in cosmological analyses, as advocated by the Canada-France-Hawaii Telescope Lensing Survey (CFHTLenS). We present an analysis of the photometric redshifts measured by CFHTLenS, which overlaps the Baryon Oscillation Spectroscopic Survey (BOSS). We also analyse the Red-sequence Cluster Lensing Survey (RCSLenS), which overlaps both BOSS and the WiggleZ Dark Energy Survey. We find that the summed p(z) from both surveys are generally biased with respect to the true underlying distributions. If unaccounted for, this bias would lead to errors in cosmological parameter estimation from CFHTLenS by less than ˜4%. For photometric redshift bins which spatially overlap in 3-D with our spectroscopic sample, we determine redshift bias corrections which can be used in future cosmological analyses that rely on accurate galaxy redshift distributions.

  10. Photometric redshift requirements for lens galaxies in galaxy-galaxy lensing analyses

    CERN Document Server

    Nakajima, R; Seljak, U; Cohn, J D; Reyes, R; Cool, R

    2011-01-01

    Weak gravitational lensing is a valuable probe of galaxy formation and cosmology. Here we quantify the effects of using photometric redshifts (photo-z) in galaxy-galaxy lensing, for both sources and lenses, both for the immediate goal of using galaxies with photo-z as lenses in the Sloan Digital Sky Survey (SDSS) and as a demonstration of methodology for large, upcoming weak lensing surveys that will by necessity be dominated by lens samples with photo-z. We calculate the bias in the lensing mass calibration as well as consequences for absolute magnitude (i.e., k-corrections) and stellar mass estimates, for a large sample of SDSS Data Release 8 (DR8) galaxies. The redshifts are obtained with the template based photo-z code ZEBRA on the SDSS DR8 ugriz photometry. We assemble and characterise the calibration samples (~9k spectroscopic redshifts from four surveys) to obtain photometric redshift errors and lensing biases corresponding to our full SDSS DR8 lens and source catalogues. Our tests of the calibration s...

  11. A new catalog of photometric redshifts in the Hubble Deep Field

    CERN Document Server

    Fernández-Soto, A; Yahil, A

    1999-01-01

    Using the newly available infrared images of the Hubble Deep Field in the J, H, and K bands and an optimal photometric method, we have refined a technique to estimate the redshifts of 1067 galaxies. A detailed comparison of our results with the spectroscopic redshifts in those cases where the latter are available shows that this technique gives very good results for bright enough objects (AB(8140) < 26.0). From a study of the distribution of residuals (Dz(rms)/(1+z) ~ 0.1 at all redshifts) we conclude that the observed errors are mainly due to cosmic variance. This very important result allows for the assessment of errors in quantities to be directly or indirectly measured from the catalog. We present some of the statistical properties of the ensemble of galaxies in the catalog, and finish by presenting a list of bright high-redshift (z ~ 5) candidates extracted from our catalog, together with recent spectroscopic redshift determinations confirming that two of them are at z=5.34 and z=5.60.

  12. Robust photometric redshift determinations of gamma-ray burst afterglows at z > 2

    CERN Document Server

    Curran, P A; Heemskerk, M H M; Starling, R L C; Wiersema, K; Van der Horst, A J

    2008-01-01

    Theory suggests that about 10% of Swift-detected gamma-ray bursts (GRBs) will originate at redshifts greater than 5 yet a number of high redshift candidates may be left unconfirmed due to the lack of measured redshifts. Here we introduce our code, GRBz, a method of simultaneous multi-parameter fitting of GRB afterglow optical and near infrared, spectral energy distributions. It allows for early determinations of the photometric redshift, spectral index and host extinction to be made. We assume that GRB afterglow spectra are well represented by a power-law decay and model the effects of absorption due to the Lyman forest and host extinction. We use a genetic algorithm-based routine to simultaneously fit the parameters of interest, and a Monte Carlo error analysis. We use GRBs of previously determined spectroscopic redshifts to prove our method, while also introducing new near infrared data of GRB 990510 which further constrains the value of the host extinction. Our method is effective in estimating the photome...

  13. ANNz2 - Photometric redshift and probability density function estimation using machine learning methods

    CERN Document Server

    Sadeh, Iftach; Lahav, Ofer

    2015-01-01

    We present ANNz2, a new implementation of the public software for photometric redshift (photo-z) estimation of Collister and Lahav (2004). Large photometric galaxy surveys are important for cosmological studies, and in particular for characterizing the nature of dark energy. The success of such surveys greatly depends on the ability to measure photo-zs, based on limited spectral data. ANNz2 utilizes multiple machine learning methods, such as artificial neural networks, boosted decision/regression trees and k-nearest neighbours. The objective of the algorithm is to dynamically optimize the performance of the photo-z estimation, and to properly derive the associated uncertainties. In addition to single-value solutions, the new code also generates full probability density functions (PDFs) in two different ways. In addition, estimators are incorporated to mitigate possible problems of spectroscopic training samples which are not representative or are incomplete. ANNz2 is also adapted to provide optimized solution...

  14. A PUBLIC Ks -SELECTED CATALOG IN THE COSMOS/ULTRAVISTA FIELD: PHOTOMETRY, PHOTOMETRIC REDSHIFTS, AND STELLAR POPULATION PARAMETERS ,

    International Nuclear Information System (INIS)

    We present a catalog covering 1.62 deg2 of the COSMOS/UltraVISTA field with point-spread function (PSF) matched photometry in 30 photometric bands. The catalog covers the wavelength range 0.15-24 μm including the available GALEX, Subaru, Canada-France-Hawaii Telescope, VISTA, and Spitzer data. Catalog sources have been selected from the DR1 UltraVISTA Ks band imaging that reaches a depth of K s,tot = 23.4 AB (90% completeness). The PSF-matched catalog is generated using position-dependent PSFs ensuring accurate colors across the entire field. Also included is a catalog of photometric redshifts (z phot) for all galaxies computed with the EAZY code. Comparison with spectroscopy from the zCOSMOS 10k bright sample shows that up to z ∼ 1.5 the z phot are accurate to Δz/(1 + z) = 0.013, with a catastrophic outlier fraction of only 1.6%. The z phot also show good agreement with the z phot from the NEWFIRM Medium Band Survey out to z ∼ 3. A catalog of stellar masses and stellar population parameters for galaxies determined using the FAST spectral energy distribution fitting code is provided for all galaxies. Also included are rest-frame U – V and V – J colors, L 2800 and L IR. The UVJ color-color diagram confirms that the galaxy bi-modality is well-established out to z ∼ 2. Star-forming galaxies also obey a star-forming 'main sequence' out to z ∼ 2.5, and this sequence evolves in a manner consistent with previous measurements. The COSMOS/UltraVISTA Ks -selected catalog covers a unique parameter space in both depth, area, and multi-wavelength coverage and promises to be a useful tool for studying the growth of the galaxy population out to z ∼ 3-4.

  15. THE SLOAN DIGITAL SKY SURVEY CO-ADD: A GALAXY PHOTOMETRIC REDSHIFT CATALOG

    International Nuclear Information System (INIS)

    We present and describe a catalog of galaxy photometric redshifts (photo-z) for the Sloan Digital Sky Survey (SDSS) Co-add Data. We use the artificial neural network (ANN) technique to calculate the photo-z and the nearest neighbor error method to estimate photo-z errors for ∼13 million objects classified as galaxies in the co-add with r 68 = 0.031. After presenting our results and quality tests, we provide a short guide for users accessing the public data.

  16. Photometry and Photometric Redshifts of Faint Galaxies in the Hubble Deep Field South NICMOS Field

    OpenAIRE

    Yahata, Noriaki; Lanzetta, Kenneth M.; Chen, Hsiao-Wen; Fernandez-Soto, Alberto; Pascarelle, Sebastian M.; Yahil, Amos; Puetter, Richard C.

    2000-01-01

    We present a catalog of photometry and photometric redshifts of 335 faint objects in the HDF-S NICMOS field. The analysis is based on (1) infrared images obtained with the Hubble Space Telescope (HST) using the Near Infrared Camera and Multi-Object Spectrograph (NICMOS) with the F110W, F160W, and F222M filters, (2) an optical image obtained with HST using the Space Telescope Imaging Spectrograph (STIS) with no filter, and (3) optical images obtained with the European Southern Observatory (ESO...

  17. Deriving Photometric Redshifts using Fuzzy Archetypes and Self-Organizing Maps. I. Methodology

    CERN Document Server

    Speagle, Joshua S

    2015-01-01

    We propose a method to substantially increase the flexibility and power of template fitting-based photometric redshifts by transforming a large numbers of galaxy spectral templates into a corrresponding collection of "fuzzy archetypes" using a suitable set of perturbative priors designed to account for empirical variation in dust attenuation and emission line strengths. To bypass widely seperated degeneracies in parameter space (e.g., the redshift-reddening degeneracy), we train Self-Organizing Maps (SOMs) on a large "model catalogs" generated from appropriate Monte Carlo sampling of our fuzzy archetypes to cluster the predicted observables in a topologically smooth fashion. Subsequent sampling over the SOM then allows full reconstruction of the relevant probability distribution functions (PDFs) using the associated set of inverse mappings from the SOM to the underlying model parameters. This combined approach enables the multi-modal exploration of known variation among galaxy spectral energy distributions (S...

  18. A Photometric Redshift of z ~ 9.4 for GRB 090429B

    CERN Document Server

    Cucchiara, A; Fox, D B; Tanvir, N R; Ukwatta, T N; Berger, E; Krühler, T; Yoldaş, A Küpcü; Wu, X F; Toma1, K; Greiner, J; E., F Olivares; Rowlinson, A; Amati, L; Sakamoto, T; Roth, K; Stephens, A; Fynbo, J P U; Hjorth, J; Malesani, D; Jakobsson, P; Wiersema, K; O'Brien, P T; Soderberg, A M; Foley, R J; Fruchter, A S; Rhoads, J; Rutledge, R E; Schmidt, B P; Dopita, M A; Podsiadlowski, P; Willingale, R; Wolf, C; Kulkarni, S R; D'Avanzo, P

    2011-01-01

    Gamma-ray bursts (GRBs) serve as powerful probes of the early Universe, with their luminous afterglows revealing the locations and physical properties of star forming galaxies at the highest redshifts, and potentially locating first generation (Population III) stars. Since GRB afterglows have intrinsically very simple spectra, they allow robust redshifts from low signal to noise spectroscopy, or photometry. Here we present a photometric redshift of $z \\sim 9.4$ for the {\\em Swift} detected GRB 090429B based on deep observations with Gemini-North, the Very Large Telescope, and the GRB Optical and Near-infrared Detector. Assuming an Small Magellanic Cloud dust law (which has been found in a majority of GRB sight-lines), the 90% likelihood range for the redshift is $9.067$. The non-detection of the host galaxy to deep limits ($Y$(AB) $\\sim 28$, which would correspond roughly to 0.001$L^*$ at $z=1$) in our late time optical and infrared observations with the {\\em Hubble Space Telescope}, strongly supports the ext...

  19. Mining the SDSS archive. I. Photometric redshifts in the nearby universe

    CERN Document Server

    Raffaele, D A; Giuseppe, L; Massimo, B; Maurizio, P; Elisabetta, D F; Roberto, T; Antonino, Staiano; Giuseppe, Longo; Massimo, Brescia; Maurizio, Paolillo; Elisabetta, De Filippis; Roberto, Tagliaferri

    2007-01-01

    We present a supervised neural network approach to the determination of photometric redshifts. The method was tuned to match the characteristics of the Sloan Digital Sky Survey and it exploits the spectroscopic redshifts provided by this unique survey. In order to train, validate and test the networks we used two galaxy samples drawn from the SDSS spectroscopic dataset: the general galaxy sample (GG) and the luminous red galaxies subsample (LRG). The method consists of a two steps approach. In the first step, objects are classified in nearby (z<0.25) and distant (0.25redshift ranges. Using a standard MLP operated in a Bayesian framework, the optimal architectures were found to require 1 hidden layer of 24 (24) and 24 (25) neurons for the GG (LRG) sample. The presence of systematic deviations was then corrected by interpolating the resulting redshifts. The final results on the GG dataset give a r...

  20. Galaxy clustering, photometric redshifts and diagnosis of systematics in the DES Science Verification data

    CERN Document Server

    Crocce, M; Bauer, A H; Ross, A J; Sevilla-Noarbe, I; Giannantonio, T; Sobreira, F; Sanchez, J; Gaztanaga, E; Kind, M Carrasco; Sanchez, C; Bonnett, C; Benoit-Levy, A; Brunner, R J; Rosell, A Carnero; Cawthon, R; Fosalba, P; Hartley, W; Kim, E J; Leistedt, B; Miquel, R; Percival, W J; Rosenfeld, R; Rykoff, E S; Sanchez, E; Abbott, T; Abdalla, F B; Allam, S; Banerji, M; Bernstein, G M; Bertin, E; Brooks, D; Buckley-Geer, E; Burke, D L; Capozzi, D; Castander, F J; Cunha, C E; D'Andrea, C B; da Costa, L N; Desai, S; Diehl, H T; Eifler, T F; Evrard, A E; Neto, A Fausti; Fernandez, E; Finley, D A; Flaugher, B; Frieman, J; Gerdes, D W; Gruen, D; Gruendl, R A; Gutierrez, G; Honscheid, K; James, D J; Kuehn, K; Kuropatkin, N; Lahav, O; Li, T S; Lima, M; Maia, M A G; March, M; Marshall, J L; Martini, P; Melchior, P; Miller, C J; Neilsen, E; Nichol, R C; Nord, B; Ogando, R; Plazas, A A; Romer, A K; Sako, M; Santiago, B; Schubnell, M; Smith, R C; Soares-Santos, M; Suchyta, E; Swanson, M E C; Tarle, G; Thaler, J; Thomas, D; Vikram, V; Walker, A R; Wechsler, R H; Weller, J; Zuntz, J

    2015-01-01

    We study the clustering of galaxies detected at $i<22.5$ in the Science Verification observations of the Dark Energy Survey (DES). Two-point correlation functions are measured using $2.3\\times 10^6$ galaxies over a contiguous 116 deg$^2$ region in five bins of photometric redshift width $\\Delta z = 0.2$ in the range $0.2 < z < 1.2.$ The impact of photometric redshift errors are assessed by comparing results using a template-based photo-$z$ algorithm (BPZ) to a machine-learning algorithm (TPZ). A companion paper (Leistedt et al 2015) presents maps of several observational variables (e.g. seeing, sky brightness) which could modulate the galaxy density. Here we characterize and mitigate systematic errors on the measured clustering which arise from these observational variables, in addition to others such as Galactic dust and stellar contamination. After correcting for systematic effects we measure galaxy bias over a broad range of linear scales relative to mass clustering predicted from the Planck $\\Lam...

  1. WISE x SuperCOSMOS photometric redshift catalog: 20 million galaxies over 3pi steradians

    CERN Document Server

    Bilicki, M; Jarrett, T H; Cluver, M E; Maddox, N; Brown, M J I; Taylor, E N; Hambly, N C; Solarz, A; Holwerda, B W; Baldry, I; Loveday, J; Moffett, A; Hopkins, A M; Driver, S P; Alpaslan, M; Bland-Hawthorn, J

    2016-01-01

    We cross-match the two currently largest all-sky photometric catalogs, mid-infrared WISE and SuperCOSMOS scans of UKST/POSS-II photographic plates, to obtain a new galaxy sample that covers 3pi steradians. In order to characterize and purify the extragalactic dataset, we use external GAMA and SDSS spectroscopic information to define quasar and star loci in multicolor space, aiding the removal of contamination from our extended-source catalog. After appropriate data cleaning we obtain a deep wide-angle galaxy sample that is approximately 95% pure and 90% complete at high Galactic latitudes. The catalog contains close to 20 million galaxies over almost 70% of the sky, outside the Zone of Avoidance and other confused regions, with a mean surface density of over 650 sources per square degree. Using multiwavelength information from two optical and two mid-IR photometric bands, we derive photometric redshifts for all the galaxies in the catalog, using the ANNz framework trained on the final GAMA-II spectroscopic da...

  2. UV-to-FIR analysis of Spitzer/IRAC sources in the Extended Groth Strip II: Photometric redshifts, Stellar masses and Star formation rates

    CERN Document Server

    Barro, Guillermo; Gallego, Jesus; Ashby, Matthew L N; Kajisawa, Masaru; Miyazaki, Satoshi; Villar, Victor; Yamada, Toru; Zamorano, Jaime

    2011-01-01

    Based on the ultraviolet to far-infrared photometry already compiled and presented in a companion paper (Barro et al. 2011a, Paper I), we present a detailed SED analysis of nearly 80,000 IRAC 3.6+4.5 micron selected galaxies in the Extended Groth Strip. We estimate photometric redshifts, stellar masses, and star formation rates separately for each galaxy in this large sample. The catalog includes 76,936 sources with [3.6] < 23.75 (85% completeness level of the IRAC survey) over 0.48 square degrees. The typical photometric redshift accuracy is Delta z/(1+z)=0.034, with a catastrophic outlier fraction of just 2%. We quantify the systematics introduced by the use of different stellar population synthesis libraries and IMFs in the calculation of stellar masses. We find systematic offsets ranging from 0.1 to 0.4 dex, with a typical scatter of 0.3 dex. We also provide UV- and IR-based SFRs for all sample galaxies, based on several sets of dust emission templates and SFR indicators. We evaluate the systematic dif...

  3. Cosmology with photometric weak lensing surveys: constraints with redshift tomography of convergence peaks and moments

    CERN Document Server

    Petri, Andrea; Haiman, Zoltán

    2016-01-01

    Weak gravitational lensing is becoming a mature technique for constraining cosmological parameters, and future surveys will be able to constrain the dark energy equation of state $w$. When analyzing galaxy surveys, redshift information has proven to be a valuable addition to angular shear correlations. We forecast parameter constraints on the triplet $(\\Omega_m,w,\\sigma_8)$ for an LSST-like photometric galaxy survey, using tomography of the shear-shear power spectrum, convergence peak counts and higher convergence moments. We find that redshift tomography with the power spectrum reduces the area of the $1\\sigma$ confidence interval in $(\\Omega_m,w)$ space by a factor of 8 with respect to the case of the single highest redshift bin. We also find that adding non-Gaussian information from the peak counts and higher-order moments of the convergence field and its spatial derivatives further reduces the constrained area in $(\\Omega_m,w)$ by a factor of 3 and 4, respectively. When we add cosmic microwave background ...

  4. Photometric Redshifts for the Large-Area Stripe 82X Multiwavelength Survey

    Science.gov (United States)

    Tasnim Ananna, Tonima; Salvato, Mara; Urry, C. Megan; LaMassa, Stephanie M.; STRIPE 82X

    2016-06-01

    The Stripe 82X survey currently includes 6000 X-ray sources in 31.3 square degrees of XMM-Newton and Chandra X-ray coverage, most of which are AGN. Using a maximum-likelihood approach, we identified optical and infrared counterparts in the SDSS, VHS K-band and WISE W1-band catalogs. 1200 objects which had different best associations in different catalogs were checked by eye. Our most recent paper provided the multiwavelength catalogs for this sample. More than 1000 counterparts have spectroscopic redshifts, either from SDSS spectroscopy or our own follow-up program. Using the extensive multiwavelength data in this field, we provide photometric redshift estimates for most of the remaining sources, which are 80-90% accurate according to the training set. Our sample has a large number of candidates that are very faint in optical and bright in IR. We expect a large fraction of these objects to be the obscured AGN sample we need to complete the census on black hole growth at a range of redshifts.

  5. Pan-STARRS1 variability of XMM-COSMOS AGN. I. Impact on photometric redshifts

    CERN Document Server

    Simm, T; Salvato, M; Bender, R; Burgett, W S; Chambers, K C; Draper, P W; Flewelling, H; Kaiser, N; Kudritzki, R -P; Magnier, E A; Metcalfe, N; Tonry, J L; Wainscoat, R J; Waters, C

    2015-01-01

    [Abbreviated] Upcoming large area sky surveys like EUCLID and eROSITA crucially depend on accurate photometric redshifts (photo-z). The identification of variable sources, such as AGNs, and the achievable redshift accuracy for varying objects are important in view of the science goals of the EUCLID and eROSITA missions. We probe AGN optical variability for a large sample of X-ray-selected AGNs in the XMM-COSMOS field, using the light curves provided by the Pan-STARRS1 (PS1) 3pi and MDF04 surveys. Utilizing two different variability parameters, we defined a sample of varying AGNs for every PS1 band. We investigated the influence of variability on the calculation of photo-z by applying three different input photometry sets for our fitting procedure. For each of the five PS1 bands, we chose either the epochs minimizing the interval in observing time, the median magnitude values, or randomly drawn light curve points to compute the redshift. In addition, we derived photo-z using PS1 photometry extended by GALEX/IR...

  6. Photo-$z$ with CuBAN$z$: An improved photometric redshift estimator using Clustering aided Back Propagation Neural network

    CERN Document Server

    Samui, Saumyadip

    2016-01-01

    We present an improved photometric redshift estimator code, CuBAN$z$, that is publicly available at https://goo.gl/fpk90V}{https://goo.gl/fpk90V. It uses the back propagation neural network along with clustering of the training set, which makes it more efficient than existing neural network codes. In CuBAN$z$, the training set is divided into several self learning clusters with galaxies having similar photometric properties and spectroscopic redshifts within a given span. The clustering algorithm uses the color information (i.e. $u-g$, $g-r$ etc.) rather than the apparent magnitudes at various photometric bands as the photometric redshift is more sensitive to the flux differences between different bands rather than the actual values. Separate neural networks are trained for each cluster using all possible colors, magnitudes and uncertainties in the measurements. For a galaxy with unknown redshift, we identify the closest possible clusters having similar photometric properties and use those clusters to get the...

  7. NEW APPROACHES TO PHOTOMETRIC REDSHIFT PREDICTION VIA GAUSSIAN PROCESS REGRESSION IN THE SLOAN DIGITAL SKY SURVEY

    International Nuclear Information System (INIS)

    Expanding upon the work of Way and Srivastava we demonstrate how the use of training sets of comparable size continue to make Gaussian process regression (GPR) a competitive approach to that of neural networks and other least-squares fitting methods. This is possible via new large-size matrix inversion techniques developed for Gaussian processes (GPs) that do not require that the kernel matrix be sparse. This development, combined with a neural-network kernel function appears to give superior results for this problem. Our best-fit results for the Sloan Digital Sky Survey (SDSS) Main Galaxy Sample using u, g, r, i, z filters gives an rms error of 0.0201 while our results for the same filters in the luminous red galaxy sample yield 0.0220. We also demonstrate that there appears to be a minimum number of training-set galaxies needed to obtain the optimal fit when using our GPR rank-reduction methods. We find that morphological information included with many photometric surveys appears, for the most part, to make the photometric redshift evaluation slightly worse rather than better. This would indicate that most morphological information simply adds noise from the GP point of view in the data used herein. In addition, we show that cross-match catalog results involving combinations of the Two Micron All Sky Survey, SDSS, and Galaxy Evolution Explorer have to be evaluated in the context of the resulting cross-match magnitude and redshift distribution. Otherwise one may be misled into overly optimistic conclusions.

  8. The ALHAMBRA Survey: Bayesian Photometric Redshifts with 23 bands for 3 squared degrees

    CERN Document Server

    Molino, A; Moles, M; Fernández-Soto, A; Cristóbal-Hornillos, D; Ascaso, B; Jiménez-Teja, Y; Schoenell, W; Arnalte-Mur, P; Pović, M; Coe, D; López-Sanjuan, C; Díaz-García, L A; Varela, J; Matute, I; Masegosa, J; Márquez, I; Perea, J; Del Olmo, A; Husillos, C; Alfaro, E; Aparicio-Villegas, T; Cerviño, M; Huertas-Company, M; Aguerri, A L; Broadhurst, T; Cabrera-Caño, J; Cepa, J; Delgado, R M González; Infante, L; Martínez, V J; Prada, F; Quintana, J M

    2013-01-01

    The ALHAMBRA (Advance Large Homogeneous Area Medium Band Redshift Astronomical) survey has observed 8 different regions of the sky, including sections of the COSMOS, DEEP2, ELAIS, GOODS-N, SDSS and Groth fields using a new photometric system with 20 contiguous ~ $300\\AA$ filters covering the optical range, combining them with deep $JHKs$ imaging. The observations, carried out with the Calar Alto 3.5m telescope using the wide field (0.25 sq. deg FOV) optical camera LAICA and the NIR instrument Omega-2000, correspond to ~700hrs on-target science images. The photometric system was designed to maximize the effective depth of the survey in terms of accurate spectral-type and photo-zs estimation along with the capability of identification of relatively faint emission lines. Here we present multicolor photometry and photo-zs for ~438k galaxies, detected in synthetic F814W images, complete down to I~24.5 AB, taking into account realistic noise estimates, and correcting by PSF and aperture effects with the ColorPro so...

  9. CANDELS/GOODS-S, CDFS, ECDFS: Photometric Redshifts For Normal and for X-Ray-Detected Galaxies

    CERN Document Server

    Hsu, Li-Ting; Nandra, Kirpal; Brusa, Marcella; Bender, Ralf; Buchner, Johannes; Donley, Jennifer L; Kocevski, Dale D; Guo, Yicheng; Hathi, Nimish P; Rangel, Cyprian; Willner, S P; Brightman, Murray; Georgakakis, Antonis; Budavári, Tamás; Szalay, Alexander S; Ashby, Matthew L N; Barro, Guillermo; Dahlen, Tomas; Faber, Sandra M; Ferguson, Henry C; Galametz, Audrey; Grazian, Andrea; Grogin, Norman A; Huang, Kuang-Han; Koekemoer, Anton M; Lucas, Ray A; McGrath, Elizabeth; Mobasher, Bahram; Peth, Michael; Rosario, David J; Trump, Jonathan R

    2014-01-01

    We present photometric redshifts and associated probability distributions for all detected sources in the Extended Chandra Deep Field South (ECDFS). The work makes use of the most up-to-date data from the Cosmic Assembly Near-IR Deep Legacy Survey (CANDELS) and the Taiwan ECDFS Near-Infrared Survey (TENIS) in addition to other data. We also revisit multi-wavelength counterparts for published X-ray sources from the 4Ms-CDFS and 250ks-ECDFS surveys, finding reliable counterparts for 1207 out of 1259 sources ($\\sim 96\\%$). Data used for photometric redshifts include intermediate-band photometry deblended using the TFIT method, which is used for the first time in this work. Photometric redshifts for X-ray source counterparts are based on a new library of AGN/galaxy hybrid templates appropriate for the faint X-ray population in the CDFS. Photometric redshift accuracy for normal galaxies is 0.010 and for X-ray sources is 0.014, and outlier fractions are $4\\%$ and $5.4\\%$ respectively. The results within the CANDELS...

  10. The impact of JWST broad-band filter choice on photometric redshift estimation

    CERN Document Server

    Bisigello, L; Colina, L; Fèvre, O Le; Nørgaard-Nielsen, H U; Pérez-González, P G; Pye, J; van der Werf, P; Ilbert, O; Grogin, N; Koekemoer, A

    2016-01-01

    The determination of galaxy redshifts in James Webb Space Telescope (JWST)'s blank-field surveys will mostly rely on photometric estimates, based on the data provided by JWST's Near-Infrared Camera (NIRCam) at 0.6-5.0 {\\mu}m and Mid Infrared Instrument (MIRI) at {\\lambda}>5.0 {\\mu}m. In this work we analyse the impact of choosing different combinations of NIRCam and MIRI broad-band filters (F070W to F770W), as well as having ancillary data at {\\lambda}=10, but the zphot quality significantly degrades at S/N<=5. Adding MIRI photometry with one magnitude brighter depth than the NIRCam depth allows for a redshift recovery of 83-99%, depending on SED type, and its effect is particularly noteworthy for galaxies with nebular emission. The vast majority of NIRCam galaxies with [F150W]=29 AB mag at z=7-10 will be detected with MIRI at [F560W, F770W]<28 mag if these sources are at least mildly evolved or have spectra with emission lines boosting the mid-infrared fluxes.

  11. Accuracy of photometric redshifts for future weak lensing surveys from space

    CERN Document Server

    Bellagamba, Fabio; Moscardini, Lauro; Bolzonella, Micol

    2012-01-01

    Photometric redshifts are a key tool to extract as much information as possible from planned cosmic shear experiments. In this work we aim to test the performances that can be achieved with observations in the near-infrared from space and in the optical from the ground. This is done by performing realistic simulations of multi-band observations of a patch of the sky, and submitting these mock images to software usually applied to real images to extract the photometry and then a redshift estimate for each galaxy. In this way we mimic the most relevant sources of uncertainty present in real data analysis, including blending and light pollution between galaxies. As an example we adopt the infrared setup of the ESA-proposed Euclid mission, while we simulate different observations in the optical, modifying filters, exposure times and seeing values. Finally, we consider directly some future ground-based experiments, such as LSST, Pan-Starrs and DES. The results highlight the importance of u-band observations, espec...

  12. Galaxy cluster searches based on photometric redshifts in the four CFHTLS Wide fields

    CERN Document Server

    Durret, F; Cappi, A; Maurogordato, S; Marquez, I; Ilbert, O; Coupon, J; Arnouts, S; Benoist, C; Blaizot, J; Edorh, T M; Garilli, B; Guennou, L; Brun, V Le; Fevre, O Le; Mazure, A; McCracken, H J; Mellier, Y; Mezrag, C; Slezak, E; Tresse, L; Ulmer, M P

    2011-01-01

    We have developed a method for detecting clusters in large imaging surveys, based on the detection of structures in galaxy density maps made in slices of photometric redshifts. This method was first applied to the Canada France Hawaii Telescope Legacy Survey (CFHTLS) Deep 1 field by Mazure et al. (2007), then to all the Deep and Wide CFHTLS fields available in the T0004 data release by Adami et al. (2010). The validity of the cluster detection rate was estimated by applying the same procedure to galaxies from the Millennium simulation. Here we analyse with the same method the full CFHTLS Wide survey, based on the T0006 data release. In a total area of 154 deg2, we have detected 4061 candidate clusters at 3sigma or above (6802 at 2sigma and above), in the redshift range 0.1<=z<=1.15, with estimated mean masses between 1.3 10^14 and 12.6 10^14 M_solar. This catalogue of candidate clusters will be available online via VizieR. We compare our detections with those made in various CFHTLS analyses with other m...

  13. A blind test of photometric redshifts on ground-based data

    CERN Document Server

    Hildebrandt, H; Benítez, N

    2008-01-01

    Aims. We analyse the relative performance of different photo-z codes in blind applications to ground-based data. Methods. We tested the codes on imaging datasets with different depths and filter coverages and compared the results to large spectroscopic catalogues. The photo-z error behaviour was analysed to select cleaner subsamples with more secure photo-z estimates. We consider Hyperz, BPZ, and the code used in the CADIS, COMBO-17, and HIROCS surveys. Results. The photo-z error estimates of the three codes do not correlate tightly with the accuracy of the photo-z's. While very large errors sometimes indicate a true catastrophic photo-z failure, smaller errors are usually not meaningful. For any given dataset, we find significant differences in redshift accuracy and outlier rates between the different codes when compared to spectroscopic redshifts. However, different codes excel in different regimes. The agreement between different sets of photo-z's is better for the subsample with secure spectroscopic redsh...

  14. Can We Detect the Color–Density Relation with Photometric Redshifts?

    Science.gov (United States)

    Lai, Chuan-Chin; Lin, Lihwai; Jian, Hung-Yu; Chiueh, Tzi-Hong; Merson, Alex; Baugh, Carlton M.; Foucaud, Sebastien; Chen, Chin-Wei; Chen, Wen-Ping

    2016-07-01

    A variety of methods have been proposed to define and to quantify galaxy environments. While these techniques work well in general with spectroscopic redshift samples, their application to photometric redshift surveys remains uncertain. To investigate whether galaxy environments can be robustly measured with photo-z samples, we quantify how the density measured with the nearest-neighbor approach is affected by photo-z uncertainties by using the Durham mock galaxy catalogs in which the 3D real-space environments and the properties of galaxies are known exactly. Furthermore, we present an optimization scheme in the choice of parameters used in the 2D projected measurements that yield the tightest correlation with respect to the 3D real-space environments. By adopting the optimized parameters in the density measurements, we show that the correlation between the 2D projected optimized density and the real-space density can still be revealed, and the color–density relation is also visible out to z ∼ 0.8 even for a photo-z uncertainty ({σ }{{{Δ }}z/(1+z)}) up to 0.06. We find that at redshifts 0.3 Medium Deep Survey (PS-MDS), one of the largest deep optical imaging surveys. Using data from ∼5 square degrees of survey area, our results show that it is possible to measure local density and to probe the color–density relation with 3σ confidence level out to z ∼ 0.8 in the PS-MDS. The color–density relation, however, quickly degrades for data covering smaller areas.

  15. The LABOCA survey of the Extended Chandra Deep Field South: A photometric redshift survey of submillimetre galaxies

    CERN Document Server

    Wardlow, J L; Coppin, K E K; Alexander, D M; Brandt, W N; Danielson, A L R; Luo, B; Swinbank, A M; Walter, F; Weiss, A; Xue, Y Q; Zibetti, S; Bertoldi, F; Biggs, A D; Chapman, S C; Dannerbauer, H; Dunlop, J S; Gawiser, E; Ivison, R J; Knudsen, K K; Kovacs, A; Lacey, C G; Menten, K M; Padilla, N; Rix, H -W; van der Werf, P P

    2010-01-01

    [abridged] We derive photometric redshifts from 17-band optical to mid-IR photometry of 74 robust counterparts to 68 of the 126 submillimetre galaxies (SMGs) selected at 870um by LABOCA observations in the ECDFS. The median photometric redshift of identified SMGs is z=2.2\\pm0.1, the interquartile range is z=1.8-2.7 and we identify 10 (~15%) high-redshift (z>3) SMGs. We derive a simple redshift estimator for SMGs based on the 3.6 and 8um fluxes, which is accurate to Delta_z~0.4 for SMGs at z3 and hence ~30% of all SMGs have z>3. We estimate that the full S_870um>4mJy SMG population has a median redshift of 2.5\\pm0.6. In contrast to previous suggestions we find no significant correlation between S_870um and redshift. The median stellar mass of the SMGs derived from SED fitting is (9.2\\pm0.9)x10^10Msun and the interquartile range is (4.7-14)x10^10Msun, although we caution that uncertainty in the star-formation histories results in a factor of ~5 uncertainty in these stellar masses. The median characteristic dust...

  16. Photometric Redshifts and Model Spectral Energy Distributions of Galaxies From the SDSS-III BOSS DR10 Data

    CERN Document Server

    Greisel, N; Drory, N; Bender, R; Saglia, R P; Snigula, J

    2015-01-01

    We construct a set of model spectra specifically designed to match the colours of the BOSS CMASS galaxies and to be used with photometric redshift template fitting techniques. As a basis we use a set of spectral energy distributions (SEDs) of single and composite stellar population models. These models cannot describe well the whole colour range populated by the CMASS galaxies at all redshifts, wherefore we modify them by multiplying the SEDs with $\\lambda^{-\\beta}$ for $\\lambda>\\lambda_i$ for different values of $\\lambda_i$ and $\\beta$. When fitting these SEDs to the colours of the CMASS sample, with a burst and dust components in superposition, we can recreate the location in colour spaces inhabited by the CMASS galaxies. From the best fitting models we select a small subset in a two-dimensional plane, whereto the galaxies were mapped by a self-organizing map. These models are used for the estimation of photometric redshifts with a Bayesian template fitting code. The photometric redshifts with the novel tem...

  17. TWO MICRON ALL SKY SURVEY PHOTOMETRIC REDSHIFT CATALOG: A COMPREHENSIVE THREE-DIMENSIONAL CENSUS OF THE WHOLE SKY

    International Nuclear Information System (INIS)

    Key cosmological applications require the three-dimensional (3D) galaxy distribution on the entire celestial sphere. These include measuring the gravitational pull on the Local Group, estimating the large-scale bulk flow, and testing the Copernican principle. However, the largest all-sky redshift surveys—the 2MASS Redshift Survey and IRAS Point Source Catalog Redshift Survey—have median redshifts of only z = 0.03 and sample the very local universe. All-sky galaxy catalogs exist that reach much deeper—SuperCOSMOS in the optical, the Two Micron All Sky Survey (2MASS) in the near-IR, and WISE in the mid-IR—but these lack complete redshift information. At present, the only rapid way toward larger 3D catalogs covering the whole sky is through photometric redshift techniques. In this paper we present the 2MASS Photometric Redshift catalog (2MPZ) containing one million galaxies, constructed by cross-matching Two Micron All Sky Survey Extended Source Catalog (2MASS XSC), WISE, and SuperCOSMOS all-sky samples and employing the artificial neural network approach (the ANNz algorithm), trained on such redshift surveys as the Sloan Digital Sky Survey, 6dFGS, and 2dFGRS. The derived photometric redshifts have errors nearly independent of distance, with an all-sky accuracy of σ z = 0.015 and a very small percentage of outliers. In this way, we obtain redshift estimates with a typical precision of 12% for all the 2MASS XSC galaxies that lack spectroscopy. In addition, we have made an early effort toward probing the entire 3D sky beyond 2MASS, by pairing up WISE with SuperCOSMOS and training the ANNz on GAMA redshift data currently reaching to z med ∼ 0.2. This has yielded photo-z accuracies comparable to those in the 2MPZ. These all-sky photo-z catalogs, with a median z ∼ 0.1 for the 2MPZ, and significantly deeper for future WISE-based samples, will be the largest and most complete of their kind for the foreseeable future

  18. Analytic Photometric Redshift Estimator for Type Ia Supernovae From the Large Synoptic Survey Telescope

    CERN Document Server

    Wang, Yun; Kuhlmann, S

    2015-01-01

    Accurate and precise photometric redshifts (photo-z's) of Type Ia supernovae (SNe Ia) can enable the use of SNe Ia, measured only with photometry, to probe cosmology. This dramatically increases the science return of supernova surveys planned for the Large Synoptic Survey Telescope (LSST). In this paper we describe a significantly improved version of the simple analytic photo-z estimator proposed by Wang (2007) and further developed by Wang, Narayan, and Wood-Vasey (2007). We apply it to 55,422 simulated SNe Ia generated using the SNANA package with the LSST filters. We find that the estimated errors on the photo-z's, \\sigma(z_{phot})/(1+z_{phot}), can be used as filters to produce a set of photo-z's that have high precision, accuracy, and purity. Using SN Ia colors as well as SN Ia peak magnitude in the $i$ band, we obtain a set of photo-z's with 2 percent accuracy (with \\sigma(z_{phot}-z_{spec})/(1+z_{spec}) = 0.02), a bias in z_{phot} (the mean of z_{phot}-z_{spec}) of -9 X 10^{-5}, and an outlier fraction...

  19. Structure detection in the D1 CFHTLS deep field using accurate photometric redshifts: a benchmark

    CERN Document Server

    Mazure, A; Pierre, M; Lefèvre, O; Arnouts, S; Duc, P A; Ilbert, O; Le Brun, V; Meneux, B; Pacaud, F; Surdej, J; Valtchanov, I

    2007-01-01

    We investigate structures in the D1 CFHTLS deep field in order to test the method that will be applied to generate homogeneous samples of clusters and groups of galaxies in order to constrain cosmology and detailed physics of groups and clusters. Adaptive kernel technique is applied on galaxy catalogues. This technique needs none of the usual a-priori assumptions (luminosity function, density profile, colour of galaxies) made with other methods. Its main drawback (decrease of efficiency with increasing background) is overcame by the use of narrow slices in photometric redshift space. There are two main concerns in structure detection. One is false detection and the second, the evaluation of the selection function in particular if one wants "complete" samples. We deal here with the first concern using random distributions. For the second, comparison with detailed simulations is foreseen but we use here a pragmatic approach with comparing our results to GalICS simulations to check that our detection number is n...

  20. A Custom Support Vector Machine Analysis of the Efficacy of Galaxy Shape Information in Photometric Redshift Estimation

    CERN Document Server

    Jones, Evan

    2016-01-01

    Aims: We present an analysis of the effects of integrating galaxy morphological information in photometric redshift (photo-z) estimation with a custom support vector machine (SVM) classification package. We also present a comparison with other methods. Statistical correlations between galaxy shape information and redshift that are not degenerate with photometric band magnitudes would be evident through an improvement in the accuracy of photo-z estimations, or possibly even in a lack of significant loss of accuracy in light of the noise introduced by including additional parameters. Methods: SVM algorithms, a type of machine learning, utilize statistical learning theory and optimization theory to construct predictive models based on the information content of data in a way that can treat different input types symmetrically, which can be a useful estimator of the additional information contained in parameters, such as those describing the morphology of the galaxies. The custom SVM classification code we have de...

  1. The large area KX quasar catalogue: I. Analysis of the photometric redshift selection and the complete quasar catalogue

    OpenAIRE

    Maddox, Natasha; Hewett, Paul C.; Peroux, Celine; Nestor, Daniel B.; Wisotzki, Lutz

    2012-01-01

    The results of a large area, ~600 deg^2, K-band flux-limited spectroscopic survey for luminous quasars are presented. The survey utilises the UKIRT Infrared Deep Sky Survey (UKIDSS) Large Area Survey (LAS) in regions of sky within the Sloan Digital Sky Survey (SDSS) footprint. The K-band excess (KX) of all quasars with respect to Galactic stars is exploited in combination with a photometric redshift/classification scheme to identify quasar candidates for spectroscopic follow-up observations. ...

  2. Apples to apples A2 - I. Realistic galaxy simulated catalogues and photometric redshift predictions for next-generation surveys

    Science.gov (United States)

    Ascaso, B.; Mei, S.; Benítez, N.

    2015-11-01

    We present new mock catalogues for two of the largest Stage IV next-generation surveys in the optical and infrared: Large Synoptic Sky Telescope (LSST) and Euclid, based on an N-body simulation+semi-analytical cone with a posterior modification with PHOTREAL. This technique modifies the original photometry by using an empirical library of spectral templates to make it more realistic. The reliability of the catalogues is confirmed by comparing the obtained colour-magnitude relation, the luminosity and mass function and the angular correlation function with those of real data. Consistent comparisons between the expected photometric redshifts for different surveys are also provided. Very deep near-infrared surveys such as Euclid will provide very good performance (Δz/(1 + z) ˜ 0.025-0.053) down to H ˜ 24 AB mag and up to z ˜ 3 depending on the optical observations available from the ground, whereas extremely deep optical surveys such as LSST will obtain an overall lower photometric redshift resolution (Δz/(1 + z) ˜ 0.045) down to i ˜ 27.5 AB mag, being considerably improved (Δz/(1 + z) ˜ 0.035) if we restrict the sample down to i ˜ 24 AB mag. Those numbers can be substantially upgraded by selecting a subsample of galaxies with the best quality photometric redshifts. We finally discuss the impact that these surveys will have for the community in terms of photometric redshift legacy. This is the first of a series of papers where we set a framework for comparability between mock catalogues and observations with a particular focus on cluster surveys. The Euclid and LSST mocks are made publicly available.

  3. The ASTRODEEP Frontier Fields catalogues. II. Photometric redshifts and rest frame properties in Abell-2744 and MACS-J0416

    Science.gov (United States)

    Castellano, M.; Amorín, R.; Merlin, E.; Fontana, A.; McLure, R. J.; Mármol-Queraltó, E.; Mortlock, A.; Parsa, S.; Dunlop, J. S.; Elbaz, D.; Balestra, I.; Boucaud, A.; Bourne, N.; Boutsia, K.; Brammer, G.; Bruce, V. A.; Buitrago, F.; Capak, P.; Cappelluti, N.; Ciesla, L.; Comastri, A.; Cullen, F.; Derriere, S.; Faber, S. M.; Giallongo, E.; Grazian, A.; Grillo, C.; Mercurio, A.; Michałowski, M. J.; Nonino, M.; Paris, D.; Pentericci, L.; Pilo, S.; Rosati, P.; Santini, P.; Schreiber, C.; Shu, X.; Wang, T.

    2016-05-01

    Aims: We present the first public release of photometric redshifts, galaxy rest frame properties and associated magnification values in the cluster and parallel pointings of the first two Frontier Fields, Abell-2744 and MACS-J0416. The released catalogues aim to provide a reference for future investigations of extragalactic populations in these legacy fields: from lensed high-redshift galaxies to cluster members themselves. Methods: We exploit a multiwavelength catalogue, ranging from Hubble Space Telescope (HST) to ground-based K and Spitzer IRAC, which is specifically designed to enable detection and measurement of accurate fluxes in crowded cluster regions. The multiband information is used to derive photometric redshifts and physical properties of sources detected either in the H-band image alone, or from a stack of four WFC3 bands. To minimize systematics, median photometric redshifts are assembled from six different approaches to photo-z estimates. Their reliability is assessed through a comparison with available spectroscopic samples. State-of-the-art lensing models are used to derive magnification values on an object-by-object basis by taking into account sources positions and redshifts. Results: We show that photometric redshifts reach a remarkable ~3-5% accuracy. After accounting for magnification, the H-band number counts are found to be in agreement at bright magnitudes with number counts from the CANDELS fields, while extending the presently available samples to galaxies that, intrinsically, are as faint as H ~ 32-33, thanks to strong gravitational lensing. The Frontier Fields allow the galaxy stellar mass distribution to be probed, depending on magnification, at 0.5-1.5 dex lower masses with respect to extragalactic wide fields, including sources at Mstar ~ 107-108 M⊙ at z > 5. Similarly, they allow the detection of objects with intrinsic star formation rates (SFRs) >1 dex lower than in the CANDELS fields reaching 0.1-1 M⊙/yr at z ~ 6-10. The

  4. The VLT observations of the HDF-S NICMOS field photometric catalog and high redshift galaxy candidates

    CERN Document Server

    Fontana, A; Fosbury, R A E; Giallongo, E; Hook, R N; Poli, F; Renzini, A; Rosati, P; Viezzer, R

    1999-01-01

    We present the deep UBVRI observations of the HDF-S NICMOS field obtained as part of the Science Verification of the VLT Unit 1 telescope. The images have been used to construct object catalogs and to obtain photometric redshifts. The effective field of view is $\\simeq 70\\times70$ arcsec$^2$, and the formal $5\\sigma$ limiting magnitudes (in a 2 FWHM aperture) are 26.3, 27.8, 27.5, 26.9, 25.2 in the $U$, $B$, $V$, $R$ and $I$ bands, respectively. Thanks to the sub-arcsecond image quality, relatively long exposure time, and large collecting area of the VLT, this is the deepest set of multicolor images ever obtained from a ground-based telescope. Galaxy counts have been derived independently in each band, and show no significant departures from previous data from wider areas. A multicolor photometric catalog of all the galaxies selected in the $R$ band has also been obtained and used to derive photometric redshifts for all galaxies with $R \\leq 26.5 $, using also the J,H and K magnitudes from the NICMOS deep obs...

  5. Simultaneous Constraints on Cosmology and Photometric Redshift Bias from Weak Lensing and Galaxy Clustering

    CERN Document Server

    Samuroff, S; Bridle, SL; Zuntz, J; MacCrann, N; Krause, E; Eifler, T; Kirk, D

    2016-01-01

    We investigate the expected cosmological constraints from a combination of weak lensing and large-scale galaxy clustering using realistic redshift distributions. Introducing a systematic bias in the weak lensing redshift distributions (of 0.05 in redshift) produces a $>2\\sigma$ bias in the recovered matter power spectrum amplitude and dark energy equation of state, for preliminary Stage III surveys. We demonstrate that these cosmological errors can be largely removed by marginalising over unknown biases in the assumed weak lensing redshift distributions, if we assume high quality redshift information for the galaxy clustering sample. Furthermore the cosmological constraining power is mostly retained despite removing much of the information on the weak lensing redshift distribution biases. We show that this comes from complementary degeneracy directions between cosmic shear and the combination of galaxy clustering with cross-correlation between shear and galaxy number density. Finally we examine how the self-c...

  6. Measuring the Dark Matter Halo Mass of X-ray AGN at z~1 using photometric redshifts

    OpenAIRE

    Mountrichas, G.; Georgakakis, A.; Finoguenov, A.; Erfanianfar, G.; Cooper, M. C.; Coil, A. L.; Laird, E. S.; Nandra, K.; Newman, J. A.

    2012-01-01

    Data from the AEGIS, COSMOS and ECDFS surveys are combined to infer the bias and dark matter halo mass of moderate luminosity [LX(2-10 keV) = 42.9 erg s-1] X-ray AGN at z~1 via their cross-correlation function with galaxies. In contrast to standard cross-correlation function estimators, we present a method that requires spectroscopy only for the AGN and uses photometric redshift probability distribution functions for galaxies to determine the projected real-space AGN/galaxy cross-correlation ...

  7. On the variable color of the images of a single source in a gravitational mirage: consequences for the photometric redshift

    CERN Document Server

    Alard, C

    2010-01-01

    In gravitational lensing the average colors of the images are not identical to the average color of the source. The highly non-linear mapping of gravitational lensing does not preserve the color balance of the source, and this mapping is different for each image. The color distortion of the images is illustrated using HST images of the lens SL2SJ02140. It is shown that in this lens the color of the images is variable, reflecting the variable color of the source. The average color of the images in SL2SJ02140 are interpreted as a variable amplification of different sources regions with different colors. The variation of the average image colors affects the measurements of the photometric redshift of the images. This is especially true for SL2SJ02140 where the color variations due to the non-linear mapping of the lens simulates pseudo redshifts variations.

  8. Exploring Photometric Redshifts as an Optimization Problem: An Ensemble MCMC and Simulated Annealing-Driven Template-Fitting Approach

    CERN Document Server

    Speagle, Joshua S; Eisenstein, Daniel J; Masters, Daniel C; Steinhardt, Charles L

    2015-01-01

    Using a grid of $\\sim 2$ million elements ($\\Delta z = 0.005$) adapted from COSMOS photometric redshift (photo-z) searches, we investigate the general properties of template-based photo-z likelihood surfaces. We find these surfaces are filled with numerous local minima and large degeneracies that generally confound rapid but "greedy" optimization schemes, even with additional stochastic sampling methods. In order to robustly and efficiently explore these surfaces, we develop BAD-Z [Brisk Annealing-Driven Redshifts (Z)], which combines ensemble Markov Chain Monte Carlo (MCMC) sampling with simulated annealing to sample arbitrarily large, pre-generated grids in approximately constant time. Using a mock catalog of 384,662 objects, we show BAD-Z samples $\\sim 40$ times more efficiently compared to a brute-force counterpart while maintaining similar levels of accuracy. Our results represent first steps toward designing template-fitting photo-z approaches limited mainly by memory constraints rather than computation...

  9. Photometric redshifts and clustering of emission line galaxies selected jointly by DES and eBOSS

    CERN Document Server

    Jouvel, S; Comparat, J; Carnero, A; Camacho, H; Abdalla, F B; Kneib, J-P; Merson, A; Lima, M; Sobreira, F; da Costa, Luiz; Prada, F; Zhu, G B; Benoit-Levy, A; De La Macora, A; Kuropatkin, N; Lin, H; Abbott, T M C; Allam, S; Banerji, M; Bertin, E; Brooks, D; Capozzi, D; Kind, M Carrasco; Carretero, J; Castander, F J; Cunha, C E; Desai, S; Doel, P; Eifler, T F; Estrada, J; Neto, A Fausti; Flaugher, B; Fosalba, P; Frieman, J; Gaztanaga, E; Gerdes, D W; Gruen, D; Gruendl, R A; Gutierrez, G; Honscheid, K; James, D J; Kuehn, K; Lahav, O; Li, T S; Maia, M A G; March, M; Marshall, J L; Miquel, R; Percival, W J; Plazas, A A; Reil, K; Romer, A K; Roodman, A; Rykoff, E S; Sako, M; Sanchez, E; Santiago, B; Scarpine, V; Sevilla-Noarbe, I; Santos, M Soares; Suchyta, E; Tarle, G; Thaler, J; Thomas, D; Walker, A; Zhang, Y

    2015-01-01

    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 0.6redshifts, the mean redshift for the bright and faint sample is 0.85 and 0.9 respectively. Star contamination is lower than 2\\%. We measure a galaxy bias averaged on scales of 1 and 10~...

  10. 3D-HST WFC3-SELECTED PHOTOMETRIC CATALOGS IN THE FIVE CANDELS/3D-HST FIELDS: PHOTOMETRY, PHOTOMETRIC REDSHIFTS, AND STELLAR MASSES

    International Nuclear Information System (INIS)

    The 3D-HST and CANDELS programs have provided WFC3 and ACS spectroscopy and photometry over ≈900 arcmin2 in five fields: AEGIS, COSMOS, GOODS-North, GOODS-South, and the UKIDSS UDS field. All these fields have a wealth of publicly available imaging data sets in addition to the Hubble Space Telescope (HST) data, which makes it possible to construct the spectral energy distributions (SEDs) of objects over a wide wavelength range. In this paper we describe a photometric analysis of the CANDELS and 3D-HST HST imaging and the ancillary imaging data at wavelengths 0.3-8 μm. Objects were selected in the WFC3 near-IR bands, and their SEDs were determined by carefully taking the effects of the point-spread function in each observation into account. A total of 147 distinct imaging data sets were used in the analysis. The photometry is made available in the form of six catalogs: one for each field, as well as a master catalog containing all objects in the entire survey. We also provide derived data products: photometric redshifts, determined with the EAZY code, and stellar population parameters determined with the FAST code. We make all the imaging data that were used in the analysis available, including our reductions of the WFC3 imaging in all five fields. 3D-HST is a spectroscopic survey with the WFC3 and ACS grisms, and the photometric catalogs presented here constitute a necessary first step in the analysis of these grism data. All the data presented in this paper are available through the 3D-HST Web site (http://3dhst.research.yale.edu)

  11. 3D-HST WFC3-SELECTED PHOTOMETRIC CATALOGS IN THE FIVE CANDELS/3D-HST FIELDS: PHOTOMETRY, PHOTOMETRIC REDSHIFTS, AND STELLAR MASSES

    Energy Technology Data Exchange (ETDEWEB)

    Skelton, Rosalind E. [South African Astronomical Observatory, PO Box 9, Observatory, Cape Town 7935 (South Africa); Whitaker, Katherine E. [Astrophysics Science Division, Goddard Space Flight Center, Greenbelt, MD 20771 (United States); Momcheva, Ivelina G.; Van Dokkum, Pieter G.; Bezanson, Rachel; Leja, Joel; Nelson, Erica J.; Oesch, Pascal [Department of Astronomy, Yale University, 260 Whitney Avenue, New Haven, CT 06511 (United States); Brammer, Gabriel B. [Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218 (United States); Labbé, Ivo; Franx, Marijn; Fumagalli, Mattia [Leiden Observatory, Leiden University, Leiden (Netherlands); Van der Wel, Arjen; Da Cunha, Elisabete; Maseda, Michael V. [Max Planck Institute for Astronomy (MPIA), Königstuhl 17, D-69117, Heidelberg (Germany); Förster Schreiber, Natascha [Max-Planck-Institut für extraterrestrische Physik, Giessenbachstrasse, D-85748 Garching (Germany); Kriek, Mariska [Astronomy Department, University of California, Berkeley, CA 94720 (United States); Lundgren, Britt F. [Department of Astronomy, University of Wisconsin-Madison, 475 North Charter Street, Madison, WI 53706 (United States); Magee, Daniel [Department of Astronomy and Astrophysics, University of California, Santa Cruz, CA (United States); Marchesini, Danilo, E-mail: ros@saao.ac.za [Department of Physics and Astronomy, Tufts University, Medford, MA 02155 (United States); and others

    2014-10-01

    The 3D-HST and CANDELS programs have provided WFC3 and ACS spectroscopy and photometry over ≈900 arcmin{sup 2} in five fields: AEGIS, COSMOS, GOODS-North, GOODS-South, and the UKIDSS UDS field. All these fields have a wealth of publicly available imaging data sets in addition to the Hubble Space Telescope (HST) data, which makes it possible to construct the spectral energy distributions (SEDs) of objects over a wide wavelength range. In this paper we describe a photometric analysis of the CANDELS and 3D-HST HST imaging and the ancillary imaging data at wavelengths 0.3-8 μm. Objects were selected in the WFC3 near-IR bands, and their SEDs were determined by carefully taking the effects of the point-spread function in each observation into account. A total of 147 distinct imaging data sets were used in the analysis. The photometry is made available in the form of six catalogs: one for each field, as well as a master catalog containing all objects in the entire survey. We also provide derived data products: photometric redshifts, determined with the EAZY code, and stellar population parameters determined with the FAST code. We make all the imaging data that were used in the analysis available, including our reductions of the WFC3 imaging in all five fields. 3D-HST is a spectroscopic survey with the WFC3 and ACS grisms, and the photometric catalogs presented here constitute a necessary first step in the analysis of these grism data. All the data presented in this paper are available through the 3D-HST Web site (http://3dhst.research.yale.edu)

  12. Precise photometric redshifts with a narrow-band filter set: The PAU Survey at the William Herschel Telescope

    CERN Document Server

    Martí, Pol; Castander, Francisco J; Gaztañaga, Enrique; Eriksen, Martin; Sánchez, Carles

    2014-01-01

    The Physics of the Accelerating Universe (PAU) survey at the William Herschel Telescope (WHT) will use a new optical camera (PAUCam) with a large set of narrow-band filters to perform a photometric galaxy survey with a quasi-spectroscopic redshift precision of \\sigma(z)/(1 + z) ~ 0.0035 and map the large-scale structure of the universe in three dimensions up to i_AB < 22.5-23.0. In this paper we present a detailed photo-z performance study using photometric simulations for 40 equally-spaced 12.5-nm-wide (FWHM) filters with a ~25% overlap and spanning the wavelength range from 450 nm to 850 nm, together with a ugrizY broad-band filter system. We then present the migration matrix r_ij, containing the probability that a galaxy in a true redshift bin j is measured in a photo-z bin i, and study its effect on the determination of galaxy auto- and cross-correlations. Finally, we also study the impact on the photo-z performance of small variations of the filter set in terms of width, wavelength coverage, etc., and...

  13. Quasi-stellar objects in the ALHAMBRA survey. I. Photometric redshift accuracy based on 23 optical-NIR filter photometry

    Science.gov (United States)

    Matute, I.; Márquez, I.; Masegosa, J.; Husillos, C.; del Olmo, A.; Perea, J.; Alfaro, E. J.; Fernández-Soto, A.; Moles, M.; Aguerri, J. A. L.; Aparicio-Villegas, T.; Benítez, N.; Broadhurst, T.; Cabrera-Cano, J.; Castander, F. J.; Cepa, J.; Cerviño, M.; Cristóbal-Hornillos, D.; Infante, L.; González Delgado, R. M.; Martínez, V. J.; Molino, A.; Prada, F.; Quintana, J. M.

    2012-06-01

    Context. Even the spectroscopic capabilities of today's ground and space-based observatories can not keep up with the enormous flow of detections (>105 deg-2) unveiled in modern cosmological surveys as: i) would be required enormous telescope time to perform the spectroscopic follow-ups and ii) spectra remain unattainable for the fainter detected population. In the past decade, the typical accuracy of photometric redshift (photo-z) determination has drastically improved. Nowdays, it has become a perfect complement to spectroscopy, closing the gap between photometric surveys and their spectroscopic follow-ups. The photo-z precision for active galactic nuclei (AGN) has always lagged behind that for the galaxy population owing to the lack of proper templates and their intrinsic variability. Aims: Our goal is to characterize the ability of the Advanced Large, Homogeneous Area Medium-Band Redshift Astronomical (ALHAMBRA) survey in assigning accurate photo-z's to broad-line AGN (BLAGN) and quasi-stellar objects (QSOs) based on their ALHAMBRA very-low-resolution optical-near-infrared (NIR) spectroscopy. This will serve as a benchmark for any future compilation of ALHAMBRA selected QSOs and the basis for the statistical analysis required to derive luminosity functions up to z ~ 5. Methods: We selected a sample of spectroscopically identified BLAGN and QSOs and used a library of templates (including the SEDs of AGN and both normal and starburst galaxies, as well as stars) to fit the 23 photometric data points provided by ALHAMBRA in the optical and NIR (20 medium-band optical filters plus the standard JHKs). Results: We find that the ALHAMBRA photometry is able to provide an accurate photo-z and spectral classification for ~88% of the 170 spectroscopically identified BLAGN/QSOs over 2.5 deg2 in different areas of the survey and brighter than m678 = 23.5 (equivalent to rSLOAN ~ 24.0). The derived photo-z accuracy is below 1% and is comparable to the most recent results in

  14. Accurate PSF-matched photometry and photometric redshifts for the extreme deep field with the Chebyshev-Fourier functions

    Science.gov (United States)

    Jiménez-Teja, Y.; Benítez, N.; Molino, A.; Fernandes, C. A. C.

    2015-10-01

    Photometric redshifts, which have become the cornerstone of several of the largest astronomical surveys like PanStarrs, DES, J-PAS and LSST, require precise measurements of galaxy photometry in different bands using a consistent physical aperture. This is not trivial, due to the variation in the shape and width of the point spread function (PSF) introduced by wavelength differences, instrument positions and atmospheric conditions. Current methods to correct for this effect rely on a detailed knowledge of PSF characteristics as a function of the survey coordinates, which can be difficult due to the relative paucity of stars tracking the PSF behaviour. Here we show that it is possible to measure accurate, consistent multicolour photometry without knowing the shape of the PSF. The Chebyshev-Fourier functions (CHEFs) can fit the observed profile of each object and produce high signal-to-noise integrated flux measurements unaffected by the PSF. These total fluxes, which encompass all the galaxy populations, are much more useful for galaxy evolution studies than aperture photometry. We compare the total magnitudes and colours obtained using our software to traditional photometry with SEXTRACTOR, using real data from the COSMOS survey and the Hubble Ultra-Deep Field (HUDF). We also apply the CHEF technique to the recently published eXtreme Deep Field (XDF) and compare the results to those from COLORPRO on the HUDF. We produce a photometric catalogue with 35 732 sources (10 823 with signal-to-noise ratio ≥5), reaching a photometric redshift precision of 2 per cent due to the extraordinary depth and wavelength coverage of the eXtreme Deep Field images.

  15. The Blanco Cosmology Survey: Data Reduction, Calibration and Photometric Redshift Estimation to Four Distant Galaxy Clusters Discovered by the South Pole Telescope

    Science.gov (United States)

    Ngeow, Chow Choong; Mohr, J.; Zenteno, A.; Data Management, DES; BCS; SPT Collaborations

    2009-01-01

    The Blanco Cosmology Survey (BCS) is designed to enable a study of the cosmic acceleration using multiple techniques. To date, BCS has acquired Sloan griz band imaging data from 60 nights (15 nights per year from 2005 to 2008) using the Blanco 4m Telescope located at CTIO. The astronomical imaging data taken from this survey have been processed on high performance computer TeraGrid platforms at NCSA, using the automated Dark Energy Survey (DES) data management (DM) system. The DES DM system includes (1) middlewares for controlling and managing the processing jobs, and serve as an application container encapsulating the scientific codes; and (2) DES archive, which includes filesystem nodes, a relational database and a data access framework, to support the pipeline processing, data storage and scientific analyzes. Photometric solution module (PSM) were run on photometric nights to determine the zeropoints (ZP) and other photometric solutions. We remapped and coadded the images that lie within the pre-defined coadd tiles in the sky. When running the coaddition pipeline, we determined the ZP for each images using the photometric ZP from PSM, the magnitude offsets between overlapping images, and the sky brightness ratio for CCDs within a given exposure. We also applied aperture correction and color-term correction to the coadded catalogs. Satisfactory photometric and astrometric precision were achieved. These enabled initial estimation of photometric redshifts using ANNz codes, trained from 5000 galaxies with spectroscopic redshifts. RMS in the photometric redshifts ranges from 0.05 to 0.1 in sigma_z/(1+z) for redshift extended to z=1. We used the BCS data to optically confirm and estimate redshifts for four of the highest S/N galaxy clusters discovered with the South Pole Telescope using the Sunyaev-Zel'dovich Effect.

  16. UVUDF: Ultraviolet Through Near-infrared Catalog and Photometric Redshifts of Galaxies in the Hubble Ultra Deep Field

    CERN Document Server

    Rafelski, Marc; Gardner, Jonathan P; Coe, Dan; Bond, Nicholas A; Koekemoer, Anton M; Grogin, Norman; Kurczynski, Peter; McGrath, Elizabeth J; Bourque, Matthew; Atek, Hakim; Brown, Thomas M; Colbert, James W; Codoreanu, Alex; Ferguson, Henry C; Finkelstein, Steven L; Gawiser, Eric; Giavalisco, Mauro; Gronwall, Caryl; Hanish, Daniel J; Lee, Kyoung-Soo; Mehta, Vihang; de Mello, Duilia F; Ravindranath, Swara; Ryan, Russell E; Scarlata, Claudia; Siana, Brian; Soto, Emmaris; Voyer, Elysse N

    2015-01-01

    We present photometry and derived redshifts from up to eleven bandpasses for 9927 galaxies in the Hubble Ultra Deep field (UDF), covering an observed wavelength range from the near-ultraviolet (NUV) to the near-infrared (NIR) with Hubble Space Telescope observations. Our Wide Field Camera 3 (WFC3)/UV F225W, F275W, and F336W image mosaics from the ultra-violet UDF (UVUDF) imaging campaign are newly calibrated to correct for charge transfer inefficiency, and use new dark calibrations to minimize background gradients and pattern noise. Our NIR WFC3/IR image mosaics combine the imaging from the UDF09 and UDF12 campaigns with CANDELS data to provide NIR coverage for the entire UDF field of view. We use aperture-matched point-spread function corrected photometry to measure photometric redshifts in the UDF, sampling both the Lyman break and Balmer break of galaxies at z~0.8-3.4, and one of the breaks over the rest of the redshift range. Our comparison of these results with a compilation of robust spectroscopic redsh...

  17. The ASTRODEEP Frontier Fields Catalogues: II - Photometric redshifts and rest-frame properties in Abell-2744 and MACS-J0416

    CERN Document Server

    Castellano, M; Merlin, E; Fontana, A; McLure, R J; Mármol-Queraltó, E; Mortlock, A; Parsa, S; Dunlop, J S; Elbaz, D; Balestra, I; Boucaud, A; Bourne, N; Boutsia, K; Brammer, G; Bruce, V A; Buitrago, F; Capak, P; Cappelluti, N; Ciesla, L; Comastri, A; Cullen, F; Derriere, S; Faber, S M; Giallongo, E; Grazian, A; Grillo, C; Mercurio, A; Michalowski, M; Nonino, M; Paris, D; Pentericci, L; Pilo, S; Rosati, P; Santini, P; Schreiber, C; Shu, X; Wang, T

    2016-01-01

    We present the first public release of photometric redshifts, galaxy rest-frame properties and associated magnification values in the cluster and parallel pointings of the first two Frontier Fields, Abell-2744 and MACS-J0416. We exploit a multi-wavelength catalogue ranging from HST to ground-based K and Spitzer IRAC which is specifically designed to enable detection and measurement of accurate fluxes in crowded cluster regions. The multi-band information is used to derive photometric redshifts and physical properties of sources detected either in the H-band image alone or from a stack of four WFC3 bands. To minimize systematics median photometric redshifts are assembled from six different approaches to photo-z estimates. Their reliability is assessed through a comparison with available spectroscopic samples. State of the art lensing models are used to derive magnification values on an object-by-object basis by taking into account sources positions and redshifts. We show that photometric redshifts reach a rema...

  18. Photometric Redshifts for DPOSS Galaxy Clusters at z < 0.4

    CERN Document Server

    Gal, R R; Djorgovski, S G; Brunner, R J; De Carvalho, R R

    1999-01-01

    We report on the creation of an unbiased catalog of galaxy clusters from the galaxy catalogs derived from the digitized POSS-II (DPOSS). Utilizing the g-r color information, we show that it is possible to estimate redshifts for galaxy clusters at z<0.4 with an rms accuracy of 0.01.

  19. Accurate PSF-matched photometry and photometric redshifts for the Extreme Deep Field with the Chebyshev-Fourier functions

    CERN Document Server

    Jiménez-Teja, Y; Molino, A; Fernandes, C A C

    2015-01-01

    Photometric redshifts, which have become the cornerstone of several of the largest astronomical surveys like PanStarrs, DES, J-PAS or the LSST, require precise measurements of galaxy photometry in different bands using a consistent physical aperture. This is not trivial, due to the variation in the shape and width of the Point Spread Function (PSF) introduced by wavelength differences, instrument positions and atmospheric conditions. Current methods to correct for this effect rely on a detailed knowledge of the PSF characteristics as a function of the survey coordinates, which can be difficult due to the relative paucity of stars tracking the PSF behaviour. Here we show that it is possible to measure accurate, consistent multicolour photometry without knowing the shape of PSF. The Chebyshev-Fourier Functions (CHEFs) can fit the observed profile of each object and produce high signal-to-noise integrated flux measurements unaffected by the PSF. These total fluxes, which encompass all the galaxy populations, are...

  20. Photometric/Spectroscopic Redshift Identification of Faint Galaxies in STIS Slitless Spectroscopy Observations

    CERN Document Server

    Chen, H W; Pascarelle, S; Chen, Hsiao-Wen; Lanzetta, Kenneth M.

    1999-01-01

    We present a new spectrum extraction technique which employs optimal weights for the spectral extraction, deblends the overlapping spectra, determines the precise sky background, and takes into account correlations between errors correctly for STIS slitless observations. We obtained roughly 250 optimally extracted spectra in a deep STIS field as well as self-confirming redshift measurements for these objects, including a galaxy at $z=6.68$. In addition, we identified five isolated emission-line objects in the dispersed image that were not accounted for by objects detected in the direct image. Assuming that these are \\lya\\ emission line galaxies at high redshifts and adopting a simple on a likelihood analysis, that \\lya\\ emission line galaxies at $\\langle density measured in Lyman break galaxies at $z\\approx 4$.

  1. Photometric/Spectroscopic Redshift Identification of Faint Galaxies in STIS Slitless Spectroscopy Observations

    OpenAIRE

    Chen, Hsiao-Wen; Lanzetta, Kenneth M.; Pascarelle, Sebastian

    1999-01-01

    We present a new spectrum extraction technique which employs optimal weights for the spectral extraction, deblends the overlapping spectra, determines the precise sky background, and takes into account correlations between errors correctly for STIS slitless observations. We obtained roughly 250 optimally extracted spectra in a deep STIS field as well as self-confirming redshift measurements for these objects, including a galaxy at $z=6.68$. In addition, we identified five isolated emission-li...

  2. Measuring the Dark Matter Halo Mass of X-ray AGN at z~1 using photometric redshifts

    CERN Document Server

    Mountrichas, G; Finoguenov, A; Erfanianfar, G; Cooper, M C; Coil, A L; Laird, E S; Nandra, K; Newman, J A

    2012-01-01

    Data from the AEGIS, COSMOS and ECDFS surveys are combined to infer the bias and dark matter halo mass of moderate luminosity [LX(2-10 keV) = 42.9 erg s-1] X-ray AGN at z~1 via their cross-correlation function with galaxies. In contrast to standard cross-correlation function estimators, we present a method that requires spectroscopy only for the AGN and uses photometric redshift probability distribution functions for galaxies to determine the projected real-space AGN/galaxy cross-correlation function. The estimated dark matter halo mass of X-ray AGN in the combined AEGIS, COSMOS and ECDFS fields is ~13h-1M_solar, in agreement with previous studies at similar redshift and luminosity ranges. Removing from the sample the 5 per cent of the AGN associated with X-ray selected groups results in a reduction by about 0.5 dex in the inferred AGN dark matter halo mass. The distribution of AGN in dark matter halo mass is therefore skewed and the bulk of the population lives in moderate mass haloes. This result favour col...

  3. Bayesian Redshift Classification of Emission-line Galaxies with Photometric Equivalent Widths

    CERN Document Server

    Leung, Andrew S; Gawiser, Eric; Ciardullo, Robin; Komatsu, Eiichiro; Zeimann, Gregory R; Bridge, Joanna S; Feldmeier, John J; Finkelstein, Steven L; Gebhardt, Karl; Gronwall, Caryl; Hagen, Alex; Hill, Gary J; Schneider, Donald P

    2015-01-01

    We present a Bayesian approach to the redshift classification of emission-line galaxies when only a single emission line is detected spectroscopically. We consider the case of surveys for high-redshift ${\\rm Ly{\\alpha}}$-emitting galaxies (LAEs), which have traditionally been classified via an inferred rest-frame equivalent width $(W_{\\rm Ly\\alpha})$ greater than $20 {\\rm \\,\\AA}$. Our Bayesian method relies on known prior probabilities in measured emission-line luminosity functions and equivalent width distributions for the galaxy populations in question, and it returns the probability that an object is an LAE given the characteristics observed. This approach will be directly relevant for the Hobby-Eberly Telescope Dark Energy Experiment (HETDEX), which seeks to classify $\\sim$$10^6$ emission-line galaxies into LAEs and low-redshift [O II] emitters. For a simulated HETDEX catalog with realistic measurement noise, our Bayesian method recovers $86\\%$ of LAEs missed by the traditional $W_{\\rm Ly\\alpha} > 20 {\\rm...

  4. THE NEWFIRM MEDIUM-BAND SURVEY: PHOTOMETRIC CATALOGS, REDSHIFTS, AND THE BIMODAL COLOR DISTRIBUTION OF GALAXIES OUT TO z ∼ 3

    International Nuclear Information System (INIS)

    We present deep near-IR (NIR) medium-bandwidth photometry over the wavelength range 1-1.8 μm in the All-wavelength Extended Groth strip International Survey (AEGIS) and Cosmic Evolution Survey (COSMOS) fields. The observations were carried out using the NOAO Extremely Wide-Field Infrared Imager (NEWFIRM) on the Mayall 4 m Telescope on Kitt Peak as part of the NEWFIRM Medium-Band Survey (NMBS), an NOAO survey program. In this paper, we describe the full details of the observations, data reduction, and photometry for the survey. We also present a public K-selected photometric catalog, along with accurate photometric redshifts. The redshifts are computed with 37 (20) filters in the COSMOS (AEGIS) fields, combining the NIR medium-bandwidth data with existing UV (Galaxy Evolution Explorer), visible and NIR (Canada-France-Hawaii Telescope and Subaru Telescope), and mid-IR (Spitzer/IRAC) imaging. We find excellent agreement with publicly available spectroscopic redshifts, with σz/(1 + z) ∼ 1%-2% for ∼4000 galaxies at z = 0-3. The NMBS catalogs contain ∼13,000 galaxies at z > 1.5 with accurate photometric redshifts and rest-frame colors. Due to the increased spectral resolution obtained with the five NIR medium-band filters, the median 68% confidence intervals of the photometric redshifts of both quiescent and star-forming galaxies are a factor of about two times smaller when comparing catalogs with medium-band NIR photometry to NIR broadband photometry. We show evidence for a clear bimodal color distribution between quiescent and star-forming galaxies that persists to z ∼ 3, a higher redshift than has been probed so far.

  5. Photometric Selection of High-Redshift Type Ia SupernovaCandidates

    Energy Technology Data Exchange (ETDEWEB)

    Sullivan, M.; Howell, D.A.; Perrett, K.; Nugent, P.E.; Astier,P.; Aubourg, E.; Balam, D.; Basa, S.; Carlberg, R.G.; Conley, A.; Fabbro,S.; Fouchez, D.; Guy, J.; Hook, I.; Lafoux, H.; Neill, J.D.; Pain, R.; Palanque-Delabrouille, N.; Pritchet, C.J.; Regnault, N.; Rich, J.; Taillet, R.; Aldering, G.; Baumont, S.; Bronder, J.; Filiol, M.; Knop,R.A.; Perlmutter, S.; Tao, C.

    2006-02-01

    We present a method for selecting high-redshift Type Ia supernovae (SNe Ia) located via rolling SN searches. The technique, using both color and magnitude information of events from only two to three epochs of multiband real-time photometry, is able to discriminate between SNe Ia and core-collapse SNe. Furthermore, for SNe Ia the method accurately predicts the redshift, phase, and light-curve parameterization of these events based only on pre-maximum-light data. We demonstrate the effectiveness of the technique on a simulated survey of SNe Ia and core-collapse SNe, where the selection method effectively rejects most core-collapse SNe while retaining SNe Ia. We also apply the selection code to real-time data acquired as part of the Canada-France-Hawaii Telescope Supernova Legacy Survey (SNLS). During the period 2004 May to 2005 January in the SNLS, 440 SN candidates were discovered, of which 70 were confirmed spectroscopically as SNe Ia and 15 as core-collapse events. For this test data set, the selection technique correctly identifies 100 percent of the identified SNe II as non-SNe Ia with only a 1 percent-2 percent false rejection rate. The predicted parameterization of the SNe Ia has a precision of bar DELTA z bar/(1+zspec)<0.09 in redshift and +-2-3 rest-frame days in phase, providing invaluable information for planning spectroscopic follow-up observations. We also investigate any bias introduced by this selection method on the ability of surveys such as SNLS to measure cosmological parameters (e.g., w and OMEGA M) and find any effect to be negligible.

  6. Redshift

    CERN Document Server

    Clark, Stuart

    1997-01-01

    The light emitted by celestial objects can have its wavelength "stretched" in different ways before it is observed by astronomers. These stretching phenomena are collectively called "redshift". They influence virtually all aspects of astronomy and even underpin the "Big Bang" theory of the creation of the universe. This book details the types of redshift and explains their myriad of uses. It begins by introducing the nature of light and the problems involved in measuring its properties. After explaining the redshift phenomena and their uses, the book touches on the age and size of the universe; two subjects embroiled in controversy because of our current interpretation of the redshift. Less conventional theories are then expressed. As a by-product of the explanation of redshift, the book offers the reader a basic understanding of Einstein's theory of relativity. Mathematical treatments of the concepts introduced in the text are boxed off and should not detract from the book's readibility, but allow it to be u...

  7. Photometric Selection of High-Redshift Type Ia SupernovaCandidates

    Energy Technology Data Exchange (ETDEWEB)

    Sullivan, M.; Howell, D.A.; Perrett, K.; Nugent, P.E.; Astier,P.; Aubourg, E.; Balam, D.; Basa, S.; Carlberg, R.G.; Conley, A.; Fabbro,S.; Fouchez, D.; Guy, J.; Hook, I.; Lafoux, H.; Neill, J.D.; Pain, R.; Palanque-Delabrouille, N.; Pritchet, C.J.; Regnault, N.; Rich, J.; Taillet, R.; Aldering, G.; Baumont, S.; Bronder, J.; Filiol, M.; Knop,R.A.; Perlmutter, S.; Tao, C.

    2006-02-01

    We present a method for selecting high-redshift Type Iasupernovae (SNe Ia) located via rolling SN searches. The technique, usingboth color and magnitude information of events from only two to threeepochs of multiband real-time photometry, is able to discriminate betweenSNe Ia and core-collapse SNe. Furthermore, for SNe Ia the methodaccurately predicts the redshift, phase, and light-curve parameterizationof these events based only on pre-maximum-light data. We demonstrate theeffectiveness of the technique on a simulated survey of SNe Ia andcore-collapse SNe, where the selection method effectively rejects mostcore-collapse SNe while retaining SNe Ia. We also apply the selectioncode to real-time data acquired as part of the Canada-France-HawaiiTelescope Supernova Legacy Survey (SNLS). During the period 2004 May to2005 January in the SNLS, 440 SN candidates were discovered, of which 70were confirmed spectroscopically as SNe Ia and 15 as core-collapseevents. For this test data set, the selection technique correctlyidentifies 100 percent of the identified SNe II as non-SNe Ia with only a1 percent-2 percent false rejection rate. The predicted parameterizationof the SNe Ia has a precision of bar DELTAz bar/(1+zspec)<0.09 inredshift and +-2-3 rest-frame days in phase, providing invaluableinformation for planning spectroscopic follow-up observations. We alsoinvestigate any bias introduced by this selection method on the abilityof surveys such as SNLS to measure cosmological parameters (e.g., w andOMEGA M) and find any effect to be negligible.

  8. Feature importance for machine learning redshifts applied to SDSS galaxies

    CERN Document Server

    Hoyle, Ben; Zitlau, Roman; Steiz, Stella; Weller, Jochen

    2014-01-01

    We present an analysis of importance feature selection applied to photometric redshift estimation using the machine learning architecture Random Decision Forests (RDF) with the ensemble learning routine Adaboost. We select a list of 85 easily measured (or derived) photometric quantities (or 'features') and spectroscopic redshifts for almost two million galaxies from the Sloan Digital Sky Survey Data Release 10. After identifying which features have the most predictive power, we use standard artificial Neural Networks (aNN) to show that the addition of these features, in combination with the standard magnitudes and colours, improves the machine learning redshift estimate by 18% and decreases the catastrophic outlier rate by 32%. We further compare the redshift estimate from RDF using the ensemble learning routine Adaboost with those from two different aNNs, and with photometric redshifts available from the SDSS. We find that the RDF requires orders of magnitude less computation time than the aNNs to obtain a m...

  9. Galaxy clustering, photometric redshifts and diagnosis of systematics in the DES Science Verification data

    Science.gov (United States)

    Crocce, M.; Carretero, J.; Bauer, A. H.; Ross, A. J.; Sevilla-Noarbe, I.; Giannantonio, T.; Sobreira, F.; Sanchez, J.; Gaztanaga, E.; Kind, M. Carrasco; Sánchez, C.; Bonnett, C.; Benoit-Lévy, A.; Brunner, R. J.; Rosell, A. Carnero; Cawthon, R.; Fosalba, P.; Hartley, W.; Kim, E. J.; Leistedt, B.; Miquel, R.; Peiris, H. V.; Percival, W. J.; Rosenfeld, R.; Rykoff, E. S.; Sánchez, E.; Abbott, T.; Abdalla, F. B.; Allam, S.; Banerji, M.; Bernstein, G. M.; Bertin, E.; Brooks, D.; Buckley-Geer, E.; Burke, D. L.; Capozzi, D.; Castander, F. J.; Cunha, C. E.; D'Andrea, C. B.; da Costa, L. N.; Desai, S.; Diehl, H. T.; Eifler, T. F.; Evrard, A. E.; Neto, A. Fausti; Fernandez, E.; Finley, D. A.; Flaugher, B.; Frieman, J.; Gerdes, D. W.; Gruen, D.; Gruendl, R. A.; Gutierrez, G.; Honscheid, K.; James, D. J.; Kuehn, K.; Kuropatkin, N.; Lahav, O.; Li, T. S.; Lima, M.; Maia, M. A. G.; March, M.; Marshall, J. L.; Martini, P.; Melchior, P.; Miller, C. J.; Neilsen, E.; Nichol, R. C.; Nord, B.; Ogando, R.; Plazas, A. A.; Romer, A. K.; Sako, M.; Santiago, B.; Schubnell, M.; Smith, R. C.; Soares-Santos, M.; Suchyta, E.; Swanson, M. E. C.; Tarle, G.; Thaler, J.; Thomas, D.; Vikram, V.; Walker, A. R.; Wechsler, R. H.; Weller, J.; Zuntz, J.; DES Collaboration

    2016-02-01

    We study the clustering of galaxies detected at i errors is assessed by comparing results using a template-based photo-z algorithm (BPZ) to a machine-learning algorithm (TPZ). A companion paper presents maps of several observational variables (e.g. seeing, sky brightness) which could modulate the galaxy density. Here we characterize and mitigate systematic errors on the measured clustering which arise from these observational variables, in addition to others such as Galactic dust and stellar contamination. After correcting for systematic effects, we measure galaxy bias over a broad range of linear scales relative to mass clustering predicted from the Planck Λ cold dark matter model, finding agreement with the Canada-France-Hawaii Telescope Legacy Survey (CFHTLS) measurements with χ2 of 4.0 (8.7) with 5 degrees of freedom for the TPZ (BPZ) redshifts. We test a `linear bias' model, in which the galaxy clustering is a fixed multiple of the predicted non-linear dark matter clustering. The precision of the data allows us to determine that the linear bias model describes the observed galaxy clustering to 2.5 per cent accuracy down to scales at least 4-10 times smaller than those on which linear theory is expected to be sufficient.

  10. Upper bound of 0.28 eV on neutrino masses from the largest photometric redshift survey.

    Science.gov (United States)

    Thomas, Shaun A; Abdalla, Filipe B; Lahav, Ofer

    2010-07-16

    We present a new limit of ∑m(v) ≤ 0.28 (95% CL) on the sum of the neutrino masses assuming a flat ΛCDM cosmology. This relaxes slightly to ∑m(ν) ≤ 0.34 and ∑m(v) ≤ 0.47 when quasinonlinear scales are removed and w≠ -1, respectively. These are derived from a new photometric catalogue of over 700,000 luminous red galaxies (MegaZ DR7) with a volume of 3.3  (Gpc h(-1))(3) and redshift range 0.45 baryon acoustic oscillations, supernovae, and a Hubble Space Telescope prior on h. When combined with WMAP these data are as constraining as adding all supernovae and baryon oscillation data available. The upper limit is one of the tightest constraints on the neutrino from cosmology or particle physics. Further, if these bounds hold, they all predict that current-to-next generation neutrino experiments, such as KATRIN, are unlikely to obtain a detection. PMID:20867754

  11. Robust photometric redshift determinations of gamma-ray burst afterglows at z greater than or similar to 2

    NARCIS (Netherlands)

    P.A. Curran; R.A.M.J. Wijers; M.H.M. Heemskerk; R.L.C. Starling; K. Wiersema; A.J. van der Horst

    2008-01-01

    Context. Theory suggests that about 10% of Swift-detected gamma-ray bursts (GRBs) will originate at redshifts, z, greater than 5 yet a number of high redshift candidates may be left unconfirmed due to the lack of measured redshifts. Aims. Here we introduce our code, GRBz, a method of simultaneous mu

  12. The DAFT/FADA survey. I.Photometric redshifts along lines of sight to clusters in the z=[0.4,0.9] interval

    Energy Technology Data Exchange (ETDEWEB)

    Guennou, L.; /Northwestern U. /Marseille, Lab. Astrophys.; Adami, C.; /Marseille, Lab. Astrophys.; Ulmer, M.P.; /Northwestern U. /Marseille, Lab. Astrophys.; LeBrun, V.; /Marseille, Lab. Astrophys.; Durret, F.; /Paris, Inst. Astrophys.; Johnston, D.; /Fermilab; Ilbert, O.; /Marseille, Lab. Astrophys.; Clowe, D.; /Ohio U.; Gavazzi, R.; /Paris, Inst. Astrophys.; Murphy, K.; /Ohio U.; Schrabback, T.; /Leiden Observ. /Fermilab

    2010-08-01

    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 {ge} 0.4), massive ({approx}> 3 x 10{sup 14} 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 {le} z {le} 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.

  13. The Subaru-XMM-Newton Deep Survey (SXDS) VIII.: Multi-wavelength Identification, Optical/NIR Spectroscopic Properties, and Photometric Redshifts of X-ray Sources

    CERN Document Server

    Akiyama, Masayuki; Watson, Mike G; Furusawa, Hisanori; Takata, Tadafumi; Simpson, Chris; Morokuma, Tomoki; Yamada, Toru; Ohta, Kouji; Iwamuro, Fumihide; Yabe, Kiyoto; Tamura, Naoyuki; Moritani, Yuuki; Takato, Naruhisa; Kimura, Masahiko; Maihara, Toshinori; Dalton, Gavin; Lewis, Ian; Lee, Hanshin; Lake, Emma Curtis; Macaulay, Edward; Clarke, Frazer; Silverman, John D; Croom, Scott; Ouchi, Masami; Hanami, Hitoshi; Tello, J Diaz; Yoshikawa, Tomohiro; Fujishiro, Naofumi; Sekiguchi, Kazuhiro

    2015-01-01

    We report the multi-wavelength identification of the X-ray sources found in the Subaru-XMM-Newton Deep Survey (SXDS) using deep imaging data covering the wavelength range between the far-UV to the mid-IR. We select a primary counterpart of each X-ray source by applying the likelihood ratio method to R-band, 3.6micron, near-UV, and 24micron source catalogs as well as matching catalogs of AGN candidates selected in 1.4GHz radio and i'-band variability surveys. Once candidates of Galactic stars, ultra-luminous X-ray sources in a nearby galaxy, and clusters of galaxies are removed there are 896 AGN candidates in the sample. We conduct spectroscopic observations of the primary counterparts with multi-object spectrographs in the optical and NIR; 65\\% of the X-ray AGN candidates are spectroscopically-identified. For the remaining X-ray AGN candidates, we evaluate their photometric redshift with photometric data in 15 bands. Utilising the multi-wavelength photometric data of the large sample of X-ray selected AGNs, w...

  14. High-precision Photometric Redshifts from Spitzer/IRAC: Extreme [3.6]-[4.5] Colors Identify Galaxies in the Redshift Range z~6.6-6.9

    CERN Document Server

    Smit, Renske; Franx, Marijn; Oesch, Pascal A; Ashby, Matthew L N; Willner, S P; Labbe, Ivo; Holwerda, Benne; Fazio, Giovanni G; Huang, J -S

    2014-01-01

    One of the most challenging aspects of studying galaxies in the z>~7 universe is the infrequent confirmation of their redshifts through spectroscopy, a phenomenon thought to occur from the increasing opacity of the intergalactic medium to Lya photons at z>6.5. The resulting redshift uncertainties inhibit the efficient search for [C II] in z~7 galaxies with sub-mm instruments such as ALMA, given their limited scan speed for faint lines. One means by which to improve the precision of the inferred redshifts is to exploit the potential impact of strong nebular emission lines on the colors of z~4-8 galaxies as observed by Spitzer/IRAC. At z~6.8, galaxies exhibit IRAC colors as blue as [3.6]-[4.5] ~-1, likely due to the contribution of [O III]+Hb to the 3.6 mum flux combined with the absence of line contamination in the 4.5 mum band. In this paper we explore the use of extremely blue [3.6]-[4.5] colors to identify galaxies in the narrow redshift window z~6.6-6.9. When combined with an I-dropout criterion, we demons...

  15. The Ultraviolet Luminosity Density of the Universe from Photometric Redshifts of Galaxies in the Hubble Deep Field

    CERN Document Server

    Pascarelle, S M; Fernández-Soto, A

    1998-01-01

    Studies of the Hubble Deep Field (HDF) and other deep surveys have revealed an apparent peak in the ultraviolet (UV) luminosity density, and therefore the star-formation rate density, of the Universe at redshifts 15.

  16. The Ultraviolet Luminosity Density of the Universe from Photometric Redshifts of Galaxies in the Hubble Deep Field

    OpenAIRE

    Pascarelle, S. M.; Lanzetta, K. M.; Fernandez-Soto, A.

    1998-01-01

    Studies of the Hubble Deep Field (HDF) and other deep surveys have revealed an apparent peak in the ultraviolet (UV) luminosity density, and therefore the star-formation rate density, of the Universe at redshifts 1

  17. The Ultraviolet Luminosity Density of the Universe from Photometric Redshifts of Galaxies in the Hubble Deep Field

    CERN Document Server

    Pascarelle, S M; Fernández-Soto, A; Pascarelle, Sebastian M.; Lanzetta, Kenneth M.; Fernandez-Soto, Alberto

    1998-01-01

    Studies of the Hubble Deep Field (HDF) and other deep surveys have revealed an apparent peak in the ultraviolet (UV) luminosity density, and therefore the star-formation rate density, of the Universe at redshifts 12.

  18. The DAFT/FADA survey. I.Photometric redshifts along lines of sight to clusters in the z=[0.4,0.9] interval

    CERN Document Server

    Guennou, L; Ulmer, M P; LeBrun, V; Durret, F; Johnston, D; Ilbert, O; Clowe, D; Gavazzi, R; Murphy, K; Schrabback, T; Allam, S; Annis, J; Basa, S; Benoist, C; Biviano, A; Cappi, A; Kubo, J M; Marshall, P; Mazure, A; Rostagni, F; Russeil, D; Slezak, E

    2010-01-01

    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. 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 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_AB=24/24.5 with the LePhare s...

  19. Baryon acoustic oscillations with the cross-correlation of spectroscopic and photometric samples

    CERN Document Server

    Nishizawa, Atsushi J; Takada, Masahiro

    2013-01-01

    The baryon acoustic oscillation (BAO) experiment requires a sufficiently dense sampling of large-scale structure tracers with spectroscopic redshift, which is observationally expensive especially at high redshifts $z\\simgt 1$. Here we present an alternative route of the BAO analysis that uses the cross-correlation of sparse spectroscopic tracers with a much denser photometric sample, where the spectroscopic tracers can be quasars or bright, rare galaxies that are easier to access spectroscopically. We show that measurements of the cross-correlation as a function of the transverse comoving separation rather than the angular separation avoid a smearing of the BAO feature without mixing the different scales at different redshifts in the projection, even for a wide redshift slice $\\Delta z\\simeq 1$. The bias, scatter, and catastrophic redshift errors of the photometric sample affect only the overall normalization of the cross-correlation which can be marginalized over when constraining the angular diameter distan...

  20. THE MULTIWAVELENGTH SURVEY BY YALE-CHILE (MUSYC): DEEP MEDIUM-BAND OPTICAL IMAGING AND HIGH-QUALITY 32-BAND PHOTOMETRIC REDSHIFTS IN THE ECDF-S

    International Nuclear Information System (INIS)

    We present deep optical 18-medium-band photometry from the Subaru telescope over the ∼30' x 30' Extended Chandra Deep Field-South, as part of the Multiwavelength Survey by Yale-Chile (MUSYC). This field has a wealth of ground- and space-based ancillary data, and contains the GOODS-South field and the Hubble Ultra Deep Field. We combine the Subaru imaging with existing UBVRIzJHK and Spitzer IRAC images to create a uniform catalog. Detecting sources in the MUSYC 'BVR' image we find ∼40,000 galaxies with R AB 3.5. For 0.1 < z < 1.2, we find a 1σ scatter in Δz/(1 + z) of 0.007, similar to results obtained with a similar filter set in the COSMOS field. As a demonstration of the data quality, we show that the red sequence and blue cloud can be cleanly identified in rest-frame color-magnitude diagrams at 0.1 < z < 1.2. We find that ∼20% of the red sequence galaxies show evidence of dust emission at longer rest-frame wavelengths. The reduced images, photometric catalog, and photometric redshifts are provided through the public MUSYC Web site.

  1. Parasitic Light in NGST instruments the accuracy of photometric redshifts and the effect of filter leaks in the visible and near IR camera

    CERN Document Server

    Cristiani, S; Fosbury, R A E

    2001-01-01

    A detailed analysis of NGST multiband photometry applied to the reference case of the study of high-redshift galaxies has been carried out with simulations based on galaxy SEDs derived from the currently available empirical and model templates and on plausible standard filter-sets. In order to correctly identify star forming galaxies in the redshift range 52 and avoid confusion with other SEDs it is mandatory to have photometric information in optical bands, besides a standard IR filter-set like F110 F160 K L M. In particular by adding the V606, I814 and z-Gunn filters a good discrimination is obtained above z>5 for star forming galaxies and z>1 for early-types. The case for an extension of the NGST wavelength domain to the optical range is therefore strongly supported by this analysis. The effects of leaks in the filter blocking have also been investigated. In spite of rather pessimistic assumptions (a constant leak at a level of 10^{-4} of the peak transmission over the whole spectral range or a leak of Gau...

  2. The Subaru-XMM-Newton Deep Survey (SXDS). VIII. Multi-wavelength identification, optical/NIR spectroscopic properties, and photometric redshifts of X-ray sources†

    Science.gov (United States)

    Akiyama, Masayuki; Ueda, Yoshihiro; Watson, Mike G.; Furusawa, Hisanori; Takata, Tadafumi; Simpson, Chris; Morokuma, Tomoki; Yamada, Toru; Ohta, Kouji; Iwamuro, Fumihide; Yabe, Kiyoto; Tamura, Naoyuki; Moritani, Yuuki; Takato, Naruhisa; Kimura, Masahiko; Maihara, Toshinori; Dalton, Gavin; Lewis, Ian; Lee, Hanshin; Curtis-Lake, Emma; Macaulay, Edward; Clarke, Frazer; Silverman, John D.; Croom, Scott; Ouchi, Masami; Hanami, Hitoshi; Díaz Tello, Jorge; Yoshikawa, Tomohiro; Fujishiro, Naofumi; Sekiguchi, Kazuhiro

    2015-10-01

    We report on the multi-wavelength identification of the X-ray sources found in the Subaru-XMM-Newton Deep Survey (SXDS) using deep imaging data covering the wavelength range between the far-UV and mid-IR (MIR). We select a primary counterpart of each X-ray source by applying the likelihood ratio method to R-band, 3.6 μm, near-UV, and 24 μm source catalogs as well as matching catalogs of active galactic nucleus (AGN) candidates selected in 1.4 GHz radio and i '-band variability surveys. Once candidates for Galactic stars, ultra-luminous X-ray sources in a nearby galaxy, and clusters of galaxies are removed there are 896 AGN candidates in the sample. We conduct spectroscopic observations of the primary counterparts with multi-object spectrographs in the optical and NIR; 65% of the X-ray AGN candidates are spectroscopically identified. For the remaining X-ray AGN candidates, we evaluate their photometric redshift with photometric data in 15 bands. Utilizing the multi-wavelength photometric data of the large sample of X-ray-selected AGNs, we evaluate the stellar masses, M*, of the host galaxies of the narrow-line AGNs. The distribution of the stellar mass is remarkably constant from z = 0.1 to 4.0. The relation between M* and 2-10 keV luminosity can be explained with strong cosmological evolution of the relationship between the black hole mass and M*. We also evaluate the scatter of the UV-MIR spectral energy distribution (SED) of the X-ray AGNs as a function of X-ray luminosity and absorption by the nucleus. The scatter is compared with galaxies which have redshift and stellar mass distribution matched with the X-ray AGN. The UV-NIR (near-IR) SEDs of obscured X-ray AGNs are similar to those of the galaxies in the matched sample. In the NIR-MIR range, the median SEDs of X-ray AGNs are redder, but the scatter of the SEDs of the X-ray AGN broadly overlaps that of the galaxies in the matched sample.

  3. THE PHOTOMETRIC CLASSIFICATION SERVER FOR Pan-STARRS1

    International Nuclear Information System (INIS)

    The Pan-STARRS1 survey is obtaining multi-epoch imaging in five bands (gP1 rP1 iP1 zP1 yP1) over the entire sky north of declination –30 deg. We describe here the implementation of the Photometric Classification Server (PCS) for Pan-STARRS1. PCS will allow the automatic classification of objects into star/galaxy/quasar classes based on colors and the measurement of photometric redshifts for extragalactic objects, and will constrain stellar parameters for stellar objects, working at the catalog level. We present tests of the system based on high signal-to-noise photometry derived from the Medium-Deep Fields of Pan-STARRS1, using available spectroscopic surveys as training and/or verification sets. We show that the Pan-STARRS1 photometry delivers classifications and photometric redshifts as good as the Sloan Digital Sky Survey (SDSS) photometry to the same magnitude limits. In particular, our preliminary results, based on this relatively limited data set down to the SDSS spectroscopic limits, and therefore potentially improvable, show that stars are correctly classified as such in 85% of cases, galaxies in 97%, and QSOs in 84%. False positives are less than 1% for galaxies, ≈19% for stars, and ≈28% for QSOs. Moreover, photometric redshifts for 1000 luminous red galaxies up to redshift 0.5 are determined to 2.4% precision (defined as 1.48 × Median|zphot – zspec|/(1 + z)) with just 0.4% catastrophic outliers and small (–0.5%) residual bias. For bluer galaxies up to the same redshift, the residual bias (on average –0.5%) trend, percentage of catastrophic failures (1.2%), and precision (4.2%) are higher, but still interestingly small for many science applications. Good photometric redshifts (to 5%) can be obtained for at most 60% of the QSOs of the sample. PCS will create a value-added catalog with classifications and photometric redshifts for eventually many millions of sources.

  4. Galaxies at Redshifts z > 5

    OpenAIRE

    Lanzetta, Kenneth M.; Chen, Hsiao-Wen; Pascarelle, Sebastian; Yahata, Noriaki

    1998-01-01

    Here we describe our attempts to establish statistically complete samples of very high redshift galaxies by obtaining photometric redshifts of galaxies in Medium Deep Survey (MDS) fields and photometric and spectroscopic redshifts of galaxies in very deep STIS slitless spectroscopy fields. On the basis of this analysis, we have identified galaxies of redshift z = 4.92 in an MDS field and of redshift z = 6.68 in a very deep STIS field.

  5. The VIPERS Multi-Lambda Survey - I: UV and NIR Observations, multi-color catalogs and photometric redshifts

    CERN Document Server

    Moutard, T; Ilbert, O; Coupon, J; Hudelot, P; Vibert, D; Comte, V; Conseil, S; Davidzon, I; Guzzo, L; Llebaria, A; Martin, C; McCracken, H J; Milliard, B; Morrison, G E; Schiminovich, D; Treyer, M; Van Werbaeke, L

    2016-01-01

    We present observations collected in the CFHTLS-VIPERS region in the ultraviolet (UV) with the GALEX satellite (far and near UV channels) and the near infrared with the CFHT/WIRCam camera ($K_s$-band) over an area of 22 and 27 deg$^2$, respectively. The depth of the photometry was optimized to measure the physical properties (e.g., SFR, stellar masses) of all the galaxies in the VIPERS spectroscopic survey. The large volume explored by VIPERS will enable a unique investigation of the relationship between the galaxy properties and their environment (density field and cosmic web) at high redshift (0.5 < z < 1.2). In this paper, we present the observations, the data reductions and the build-up of the multi-color catalogs. The CFHTLS-T0007 (gri-{\\chi}^2) images are used as reference to detect and measure the $K_s$-band photometry, while the T0007 u-selected sources are used as priors to perform the GALEX photometry based on a dedicated software (EMphot). Our final sample reaches $NUV_{AB}$~25 (at 5{\\sigma})...

  6. AzTEC/ASTE 1.1 mm survey of SSA22: Counterpart identification and photometric redshift survey of submillimeter galaxies

    CERN Document Server

    Umehata, H; Kohno, K; Hatsukade, B; Scott, K S; Kubo, M; Yamada, T; Ivison, R J; Cybulski, R; Aretxaga, I; Austermann, J; Hughes, D H; Ezawa, H; Hayashino, T; Ikarashi, S; Iono, D; Kawabe, R; Matsuda, Y; Matsuo, H; Nakanishi, K; Oshima, T; Perera, T; Takata, T; Wilson, G W; Yun, M S

    2014-01-01

    We present the results from a 1.1 mm imaging survey of the SSA22 field, known for having an overdensity of z=3.1 Lyman-alpha emitting galaxies (LAEs), taken with the AzTEC camera on the Atacama Submillimeter Telescope Experiment (ASTE). We imaged a 950 arcmin$^2$ field down to a 1 sigma sensitivity of 0.7-1.3 mJy/beam to find 125 submillimeter galaxies (SMGs) with a signal to noise ratio >= 3.5. Counterpart identification using radio and near/mid-infrared data was performed and one or more counterpart candidates were found for 59 SMGs. Photometric redshifts based on optical to near-infrared images were evaluated for 45 SMGs of these SMGs with Spitzer/IRAC data, and the median value is found to be z=2.4. By combining these estimation with estimates from the literature we determined that 10 SMGs might lie within the large-scale structure at z=3.1. The two-point angular cross-correlation function between LAEs and SMGs indicates that the positions of the SMGs are correlated with the z=3.1 protocluster. These resu...

  7. A direct probe of cosmological power spectra of the peculiar velocity field and the gravitational lensing magnification from photometric redshift surveys

    CERN Document Server

    Nusser, Adi; Feix, Martin

    2012-01-01

    The cosmological peculiar velocity field (deviations from the pure Hubble flow) of matter carries significant information on dark energy, dark matter and the underlying theory of gravity on large scales. Peculiar motions of galaxies introduce systematic deviations between the observed galaxy redshifts z and the corresponding cosmological redshifts z_cos. A novel method for estimating the angular power spectrum of the peculiar velocity field based on observations of galaxy redshifts and apparent magnitudes m (or equivalently fluxes) is presented. This method exploits the fact that a mean relation between z_cos and m of galaxies can be derived from all galaxies in a redshift-magnitude survey. Given a galaxy magnitude, it is shown that the z_cos(m) relation yields its cosmological redshift with a 1-sigma error of sigma_z~0.3 for a survey like Euclid (~10^9 galaxies at z<~2), and can be used to constrain the angular power spectrum of z-z_cos(m) with a high signal-to-noise ratio. At large angular separations co...

  8. A direct probe of cosmological power spectra of the peculiar velocity field and the gravitational lensing magnification from photometric redshift surveys

    International Nuclear Information System (INIS)

    The cosmological peculiar velocity field (deviations from the pure Hubble flow) of matter carries significant information on dark energy, dark matter and the underlying theory of gravity on large scales. Peculiar motions of galaxies introduce systematic deviations between the observed galaxy redshifts z and the corresponding cosmological redshifts zcos. A novel method for estimating the angular power spectrum of the peculiar velocity field based on observations of galaxy redshifts and apparent magnitudes m (or equivalently fluxes) is presented. This method exploits the fact that a mean relation between zcos and m of galaxies can be derived from all galaxies in a redshift-magnitude survey. Given a galaxy magnitude, it is shown that the zcos(m) relation yields its cosmological redshift with a 1σ error of σz ∼ 0.3 for a survey like Euclid ( ∼ 109 galaxies at z∼cos(m) with a high signal-to-noise ratio. At large angular separations corresponding to l∼cos(m) relation caused by gravitational lensing magnification dominate, allowing us to probe the line-of-sight integral of the gravitational potential. Effects related to the environmental dependence in the luminosity function can easily be computed and their contamination removed from the estimated power spectra. The amplitude of the combined velocity and lensing power spectra at z ∼ 1 can be measured with ∼<5% accuracy

  9. The Chandra COSMOS Legacy Survey: Clustering of X-ray selected AGN at 2.9photometric redshift Probability Distribution Functions

    CERN Document Server

    Allevato, V; Finoguenov, A; Marchesi, S; Zamorani, G; Hasinger, G; Salvato, M; Miyaji, T; Gilli, R; Cappelluti, N; Brusa, M; Suh, H; Lanzuisi, G; Trakhtenbrot, B; Griffiths, R; Vignali, C; Schawinski, K; Karim, A

    2016-01-01

    We present the measurement of the projected and redshift space 2-point correlation function (2pcf) of the new catalog of Chandra COSMOS-Legacy AGN at 2.9$\\leq$z$\\leq$5.5 ($\\langle L_{bol} \\rangle \\sim$10$^{46}$ erg/s) using the generalized clustering estimator based on phot-z probability distribution functions (Pdfs) in addition to any available spec-z. We model the projected 2pcf estimated using $\\pi_{max}$ = 200 h$^{-1}$ Mpc with the 2-halo term and we derive a bias at z$\\sim$3.4 equal to b = 6.6$^{+0.60}_{-0.55}$, which corresponds to a typical mass of the hosting halos of log M$_h$ = 12.83$^{+0.12}_{-0.11}$ h$^{-1}$ M$_{\\odot}$. A similar bias is derived using the redshift-space 2pcf, modelled including the typical phot-z error $\\sigma_z$ = 0.052 of our sample at z$\\geq$2.9. Once we integrate the projected 2pcf up to $\\pi_{max}$ = 200 h$^{-1}$ Mpc, the bias of XMM and \\textit{Chandra} COSMOS at z=2.8 used in Allevato et al. (2014) is consistent with our results at higher redshift. The results suggest only...

  10. Climate catastrophes

    Science.gov (United States)

    Budyko, Mikhail

    1999-05-01

    Climate catastrophes, which many times occurred in the geological past, caused the extinction of large or small populations of animals and plants. Changes in the terrestrial and marine biota caused by the catastrophic climate changes undoubtedly resulted in considerable fluctuations in global carbon cycle and atmospheric gas composition. Primarily, carbon dioxide and other greenhouse gas contents were affected. The study of these catastrophes allows a conclusion that climate system is very sensitive to relatively small changes in climate-forcing factors (transparency of the atmosphere, changes in large glaciations, etc.). It is important to take this conclusion into account while estimating the possible consequences of now occurring anthropogenic warming caused by the increase in greenhouse gas concentration in the atmosphere.

  11. Measuring galaxy environments in large scale photometric surveys

    CERN Document Server

    Etherington, James

    2015-01-01

    The properties of galaxies in the local universe have been shown to depend upon their environment. Future large scale photometric surveys such as DES and Euclid will be vital to gain insight into the evolution of galaxy properties and the role of environment. Large samples come at the cost of redshift precision and this affects the measurement of environment. We study this by measuring environments using SDSS spectroscopic and photometric redshifts and also simulated photometric redshifts with a range of uncertainties. We consider the Nth nearest neighbour and fixed aperture methods and evaluate the impact of the aperture parameters and the redshift uncertainty. We find that photometric environments have a smaller dynamic range than spectroscopic measurements because uncertain redshifts scatter galaxies from dense environments into less dense environments. At the expected redshift uncertainty of DES, 0.1, there is Spearman rank correlation coefficient of 0.4 between the measurements using the optimal paramete...

  12. Resounding Catastrophe

    DEFF Research Database (Denmark)

    Kristensen, Thomas Bjørnsten

    2012-01-01

    The article discusses specific aesthetic strategies for articulating and describing the catastrophic event of 9/11 by focusing on its auditory aspects. This is done through a reading of the American media- and sound artist Stephen Vitiello’s work and novelist Don DeLillo’s Falling Man....

  13. New Approaches To Photometric Redshift Prediction

    Data.gov (United States)

    National Aeronautics and Space Administration — Expanding upon the work of Way & Srivastava (2006) we demonstrate how the use of training sets of comparable size continue to make Gaussian Process Regression a...

  14. Catastrophe medicine; Medecine de catastrophe

    Energy Technology Data Exchange (ETDEWEB)

    Lebreton, A. [Service Technique de l`Energie Electrique et des Grands Barrages (STEEGB), (France)

    1996-12-31

    The `Catastrophe Medicine` congress which took place in Amiens (France) in December 5 to 7 1996 was devoted to the assessment and management of risks and hazards in natural and artificial systems. The methods of risk evaluation and prevision were discussed in the context of dams accidents with the analysis of experience feedbacks and lessons gained from the organisation of emergency plans. Three round table conferences were devoted to the importance of psychological aspects during such major crises. (J.S.)

  15. Reconstructing the galaxy redshift distribution from angular cross power spectra

    CERN Document Server

    Sun, L; Tao, C

    2015-01-01

    The control of photometric redshift (photo-$z$) errors is a crucial and challenging task for precision weak lensing cosmology. The spacial cross-correlations (equivalently, the angular cross power spectra) of galaxies between tomographic photo-$z$ bins are sensitive to the true redshift distribution $n_i(z)$ of each bin and hence can help calibrate the photo-$z$ error distribution for weak lensing surveys. Using Fisher matrix analysis, we investigate the contributions of various components of the angular power spectra to the constraints of $n_i(z)$ parameters and demonstrate the importance of the cross power spectra therein, especially when catastrophic photo-$z$ errors are present. We further study the feasibility of reconstructing $n_i(z)$ from galaxy angular power spectra using Markov Chain Monte Carlo estimation. Considering an LSST-like survey with $10$ photo-$z$ bins, we find that the underlying redshift distribution can be determined with a fractional precision ($\\sigma(\\theta)/\\theta$ for parameter $\\...

  16. Seizing Catastrophes

    DEFF Research Database (Denmark)

    Kublitz, Anja

    2013-01-01

    Based on fieldwork among Palestinians in Denmark the article investigates the Palestinian temporality of Nakba that is equivalent to a time of security in the sense that it is concerned with existential threats and emergency action. The Arabic term Nakba literally means catastrophe and is in...... Palestinian national discourse used to designate the Arab-Israeli war of 1948, when more than half of the Palestinian population were expelled from their homeland – a reverse national myth about how Palestine failed to come into being. Yet, according to Palestinians in Denmark, the Nakba cannot be relegated...

  17. Astrometric Redshifts for Quasars

    CERN Document Server

    Kaczmarczik, Michael C; Mehta, Sajjan S; Schlegel, David J

    2009-01-01

    The wavelength dependence of atmospheric refraction causes differential chromatic refraction (DCR), whereby objects imaged at different optical/UV wavelengths are observed at slightly different positions in the plane of the detector. Strong spectral features induce changes in the effective wavelengths of broad-band filters that are capable of producing significant positional offsets with respect to standard DCR corrections. We examine such offsets for broad-emission-line (type 1) quasars from the Sloan Digital Sky Survey (SDSS) spanning 0redshift and airmass. This astrometric information can be used to break degeneracies in photometric redshifts of quasars (or other emission-line sources) and, for extreme cases, may be suitable for determining "astrometric redshifts". On the SDSS's southern equatorial stripe, where it is pos...

  18. Cosmological Constraints with Clustering-Based Redshifts

    CERN Document Server

    Kovetz, Ely D; Rahman, Mubdi

    2016-01-01

    We demonstrate that observations lacking reliable redshift information, such as photometric and radio continuum surveys, can produce robust measurements of cosmological parameters when empowered by clustering-based redshift estimation. This method infers the redshift distribution based on the spatial clustering of sources, using cross-correlation with a reference dataset with known redshifts. Applying this method to the existing SDSS photometric galaxies, and projecting to future radio continuum surveys, we show that sources can be efficiently divided into several redshift bins, increasing their ability to constrain cosmological parameters. We forecast constraints on the dark-energy equation-of-state and on local non-gaussianity parameters. We explore several pertinent issues, including the tradeoff between including more sources versus minimizing the overlap between bins, the shot-noise limitations on binning, and the predicted performance of the method at high redshifts. Remarkably, we find that, once this ...

  19. SPIDERz: SuPport vector classification for IDEntifying Redshifts

    Science.gov (United States)

    Jones, Evan; Singal, J.

    2016-08-01

    SPIDERz (SuPport vector classification for IDEntifying Redshifts) applies powerful support vector machine (SVM) optimization and statistical learning techniques to custom data sets to obtain accurate photometric redshift (photo-z) estimations. It is written for the IDL environment and can be applied to traditional data sets consisting of photometric band magnitudes, or alternatively to data sets with additional galaxy parameters (such as shape information) to investigate potential correlations between the extra galaxy parameters and redshift.

  20. Probing the sparse tails of redshift distributions with Voronoi tessellations

    CERN Document Server

    Granett, Benjamin R

    2016-01-01

    We introduce an algorithm to estimate the redshift distribution of a sample of galaxies selected photometrically given a subsample with measured spectroscopic redshifts. The approach uses a non-parametric Voronoi tessellation density estimator to interpolate the galaxy distribution in the redshift and photometric color space. We test the method on a mock dataset with a known color-redshift distribution. We find that the Voronoi tessellation estimator performs well at reconstructing the tails of the redshift distribution of individual galaxies and gives unbiased estimates of the first and second moments. The source code is publicly available at http://bitbucket.org/bengranett/tailz.

  1. Coherent catastrophism

    Science.gov (United States)

    Asher, D. J.; Clube, S. V. M.; Napier, W. M.; Steel, D. I.

    We review the theoretical and observational evidence that, on timescales relevant to mankind, the prime collision hazard is posed by temporally correlated impacts (coherent catastrophism, Δt ˜ 10 2-10 4 yr) rather than random ones (stochastic catastrophism, Δt ˜ 10 5-10 8 yr). The mechanism whereby coherent incursions into and through the terrestrial atmosphere occur is described as being the result of giant cometary bodies arriving in orbits with perihelia in the inner solar system. Hierarchical fragmentation of such large (100 km-plus) bodies — due to thermal stresses near perihelion, collisions in the asteroid belt, or passages through the Jovian Roche radius — results in numerous ˜kilometre-sized objects being left in short-period orbits, and appearing in telescopic searches as Apollo-type asteroids. Many more smaller objects, in the 10-100 metre size range and only recently observed, by the Spacewatch team, are expected to be in replenished clusters in particular orbits as a result of continuing disintegrations of large, differentiated, cometary objects. Gravitational perturbations by Jupiter bring these clusters around to have a node at 1 AU in a cyclic fashion, leading to impacts at certain times of year every few years during active periods lasting a few centuries, such periods being separated by intervals of a few millennia. Furthermore, fragmentations within the hierarchy result in significant bombardment commensurabilities ( Δt ˜ 10-10 2 yr) during active periods occurring at random intervals ( Δt ˜ 10 2-10 3 yr). It appears that the Earth has been subject to such impacts since the break-up of such a comet ˜2×10 4 years ago; currently we are not passing through a high-risk epoch, although some phenomena originating in the products of this break-up have been observed in the 20th century. This most recent hierarchical disintegration, associated with four well-known meteor showers and termed the Taurid Complex, is now recognized as resulting

  2. Reverse Catastrophe

    Directory of Open Access Journals (Sweden)

    Przemysław Czapliński

    2015-01-01

    Full Text Available The principal notion of the article–a “backward catastrophe”– stands for a catastrophe which occurs unseen until it becomes recognized and which broadens its destructive activity until it has been recognized. This concept in the article has been referred to the Shoah. The main thesis is that the recognition of the actual influence of the Holocaust began in Polish culture in the mid-1980s (largely it started with the film by Claude Lanzmann Shoah and the essay by Jan Błoński Biedni Polacy patrzą na getto [“The Poor Poles Look at the Ghetto”], that is when the question: “What happened to the Jews”, assumes the form: “Did the things that happened to the Jews, also happened to the Poles?”. Cognitive and ethical reorientation leads to the revealing of the hidden consequences of the Holocaust reaching as far as the present day and undermining the foundations of collective identity. In order to understand this situation (and adopt potentially preventive actions Polish society should be recognized as a postcatastrophic one.

  3. Catastrophic volcanism

    Science.gov (United States)

    Lipman, Peter W.

    1988-01-01

    Since primitive times, catastrophes due to volcanic activity have been vivid in the mind of man, who knew that his activities in many parts of the world were threatened by lava flows, mudflows, and ash falls. Within the present century, increasingly complex interactions between volcanism and the environment, on scales not previously experienced historically, have been detected or suspected from geologic observations. These include enormous hot pyroclastic flows associated with collapse at source calderas and fed by eruption columns that reached the stratosphere, relations between huge flood basalt eruptions at hotspots and the rifting of continents, devastating laterally-directed volcanic blasts and pyroclastic surges, great volcanic-generated tsunamis, climate modification from volcanic release of ash and sulfur aerosols into the upper atmosphere, modification of ocean circulation by volcanic constructs and attendent climatic implications, global pulsations in intensity of volcanic activity, and perhaps triggering of some intense terrestrial volcanism by planetary impacts. Complex feedback between volcanic activity and additional seemingly unrelated terrestrial processes likely remains unrecognized. Only recently has it become possible to begin to evaluate the degree to which such large-scale volcanic processes may have been important in triggering or modulating the tempo of faunal extinctions and other evolutionary events. In this overview, such processes are examined from the viewpoint of a field volcanologist, rather than as a previous participant in controversies concerning the interrelations between extinctions, impacts, and volcanism.

  4. Catastrophes control problem

    International Nuclear Information System (INIS)

    The problem of catastrophe control is discussed. Catastrophe control aims to withdraw responsible engineering constructions out of the catastrophe. The mathematical framework of catastrophes control systems is constructed. It determines the principles of systems filling by the concrete physical contents and, simultaneously, permits to employ modern control methods for the synthesis of optimal withdrawal strategy for protected objects

  5. Anomaly detection for machine learning redshifts applied to SDSS galaxies

    CERN Document Server

    Hoyle, Ben; Paech, Kerstin; Bonnett, Christopher; Seitz, Stella; Weller, Jochen

    2015-01-01

    We present an analysis of anomaly detection for machine learning redshift estimation. Anomaly detection allows the removal of poor training examples, which can adversely influence redshift estimates. Anomalous training examples may be photometric galaxies with incorrect spectroscopic redshifts, or galaxies with one or more poorly measured photometric quantity. We select 2.5 million 'clean' SDSS DR12 galaxies with reliable spectroscopic redshifts, and 6730 'anomalous' galaxies with spectroscopic redshift measurements which are flagged as unreliable. We contaminate the clean base galaxy sample with galaxies with unreliable redshifts and attempt to recover the contaminating galaxies using the Elliptical Envelope technique. We then train four machine learning architectures for redshift analysis on both the contaminated sample and on the preprocessed 'anomaly-removed' sample and measure redshift statistics on a clean validation sample generated without any preprocessing. We find an improvement on all measured stat...

  6. Correcting cosmological parameter biases for all redshift surveys induced by estimating and reweighting redshift distributions

    CERN Document Server

    Rau, Markus Michael; Paech, Kerstin; Seitz, Stella

    2016-01-01

    Photometric redshift uncertainties are a major source of systematic error for ongoing and future photometric surveys. We study different sources of redshift error caused by common suboptimal binning techniques and propose methods to resolve them. The selection of a too large bin width is shown to oversmooth small scale structure of the radial distribution of galaxies. This systematic error can significantly shift cosmological parameter constraints by up to $6 \\, \\sigma$ for the dark energy equation of state parameter $w$. Careful selection of bin width can reduce this systematic by a factor of up to 6 as compared with commonly used current binning approaches. We further discuss a generalised resampling method that can correct systematic and statistical errors in cosmological parameter constraints caused by uncertainties in the redshift distribution. This can be achieved without any prior assumptions about the shape of the distribution or the form of the redshift error. Our methodology allows photometric surve...

  7. Cosmological forecasts from photometric measurements of the angular correlation function

    International Nuclear Information System (INIS)

    We study forecasts for the accuracy of the determination of cosmological parameters from future large-scale photometric surveys obtained using the full shape of the 2-point galaxy angular correlation function. The effects of linear redshift-space distortion, photometric redshift Gaussian errors, galaxy bias and nonlinearities in the power spectrum are included on our analysis. The Fisher information matrix is constructed with the full covariance matrix, including the correlation between nearby redshift shells arising from the photometric redshift error. We show that under some reasonable assumptions, a survey such as the imminent Dark Energy Survey should be able to constrain the dark energy equation of state parameter w and the cold dark matter density Ωcdm with a precision of the order of 20% and 13%, respectively, from the full shape of the angular correlation function alone. When combined with priors from other observations the precision in the determination of these parameters improve to 8% and 4%, respectively.

  8. Cosmological forecasts from photometric measurements of the angular correlation function

    CERN Document Server

    Sobreira, F; Rosenfeld, R; da Costa, L A N; Maia, M A G; Makler, M

    2011-01-01

    We study forecasts for the accuracy of the determination of cosmological parameters from future large scale photometric surveys obtained using the full shape of the 2-point galaxy angular correlation function. The effects of linear redshift-space distortion, photometric redshift gaussian errors, galaxy bias and non-linearities in the power spectrum are included on our analysis. The Fisher information matrix is constructed with the full covariance matrix, including the correlation between nearby redshift shells arising from the photometric redshift error. We show that under some reasonable assumptions, a survey such as the imminent Dark Energy Survey should be able to constrain the dark energy equation of state parameter w and the cold dark matter density \\Omega_{cdm} with a precison of the order of 20% and 13% respectively from the full shape of the angular correlation function alone. When combined with priors from other observations the precision in the determination of these parameters improve to 8% and 4% ...

  9. The FourStar Galaxy Evolution Survey (ZFOURGE): ultraviolet to far-infrared catalogs, medium-bandwidth photometric redshifts with improved accuracy, stellar masses, and confirmation of quiescent galaxies to z~3.5

    CERN Document Server

    Straatman, Caroline M S; Quadri, Ryan F; Labbe, Ivo; Glazebrook, Karl; Persson, S Eric; Papovich, Casey; Tran, Kim-Vy H; Brammer, Gabriel B; Cowley, Michael; Tomczak, Adam; Nanayakkara, Themiya; Alcorn, Leo; Allen, Rebecca; Broussard, Adam; van Dokkum, Pieter; Forrest, Ben; van Houdt, Josha; Kacprzak, Glenn G; Kawinwanichakij, Lalitwadee; Kelson, Daniel D; Lee, Janice; McCarthy, Patrick J; Mehrtens, Nicola; Monson, Andrew; Murphy, David; Rees, Glen; Tilvi, Vithal; Whitaker, Katherine E

    2016-01-01

    The FourStar galaxy evolution survey (ZFOURGE) is a 45 night legacy program with the FourStar near-infrared camera on Magellan and one of the most sensitive surveys to date. ZFOURGE covers a total of $400\\ \\mathrm{arcmin}^2$ in cosmic fields CDFS, COSMOS and UDS, overlapping CANDELS. We present photometric catalogs comprising $>70,000$ galaxies, selected from ultradeep $K_s$-band detection images ($25.5-26.5$ AB mag, $5\\sigma$, total), and $>80\\%$ complete to $K_s\\times15$.

  10. High-Redshift Galaxies: The HDF and More

    OpenAIRE

    Fernandez-Soto, A.; Lanzetta, K. M.; Yahil, A.

    1998-01-01

    We review our present knowledge of high-redshift galaxies, emphasizing particularly their physical properties and the ways in which they relate to present-day galaxies. We also present a catalogue of photometric redshifts of galaxies in the Hubble Deep Field and discuss the possibilities that this kind of study offers to complete the standard spectroscopically based surveys.

  11. High-Redshift Galaxies The HDF and More

    CERN Document Server

    Fernández-Soto, A; Yahil, A

    1998-01-01

    We review our present knowledge of high-redshift galaxies, emphasizing particularly their physical properties and the ways in which they relate to present-day galaxies. We also present a catalogue of photometric redshifts of galaxies in the Hubble Deep Field and discuss the possibilities that this kind of study offers to complete the standard spectroscopically based surveys.

  12. Galaxies of Redshift z > 5 The View from Stony Brook

    CERN Document Server

    Lanzetta, K M; Fernández-Soto, A; Pascarelle, S; Yahata, N; Yahil, A; Lanzetta, Kenneth M.; Chen, Hsiao-Wen; Fernandez-Soto, Alberto; Pascarelle, Sebastian; Yahata, Noriaki; Yahil, Amos

    1999-01-01

    We report on some aspects of our efforts to establish properties of the extremely faint galaxy population by applying our photometric redshift technique to the HDF and HDF-S WFPC2 and NICMOS fields. We find that cosmological surface brightness dimming effects play a dominant role in setting what is observed at redshifts z > 2, that the comoving number density of high intrinsic surface brightness regions increases monotonically with increasing redshift, and that previous estimates neglect a significant or dominant fraction of the ultraviolet luminosity density of the universe due to surface brightness effects. The ultraviolet luminosity density of the universe plausibly increases monotonically with increasing redshift to redshifts beyond z = 5.

  13. Estimating Redshifts for Long Gamma-Ray Bursts

    OpenAIRE

    Xiao, Limin; Schaefer, Bradley E.

    2009-01-01

    We are constructing a program to estimate the redshifts for GRBs from the original Swift light curves and spectra, aiming to get redshifts for the Swift bursts \\textit{without} spectroscopic or photometric redshifts. We derive the luminosity indicators from the light curves and spectra of each burst, including the lag time between low and high photon energy light curves, the variability of the light curve, the peak energy of the spectrum, the number of peaks in the light curve, and the minimu...

  14. Galaxies of Redshift z > 5: The View from Stony Brook

    OpenAIRE

    Lanzetta, Kenneth M.; Chen, Hsiao-Wen; Fernandez-Soto, Alberto; Pascarelle, Sebastian; Yahata, Noriaki; Yahil, Amos

    1999-01-01

    We report on some aspects of our efforts to establish properties of the extremely faint galaxy population by applying our photometric redshift technique to the HDF and HDF-S WFPC2 and NICMOS fields. We find that cosmological surface brightness dimming effects play a dominant role in setting what is observed at redshifts z > 2, that the comoving number density of high intrinsic surface brightness regions increases monotonically with increasing redshift, and that previous estimates neglect a si...

  15. Bayesian redshift-space distortions correction from galaxy redshift surveys

    Science.gov (United States)

    Kitaura, Francisco-Shu; Ata, Metin; Angulo, Raul E.; Chuang, Chia-Hsun; Rodríguez-Torres, Sergio; Monteagudo, Carlos Hernández; Prada, Francisco; Yepes, Gustavo

    2016-03-01

    We present a Bayesian reconstruction method which maps a galaxy distribution from redshift- to real-space inferring the distances of the individual galaxies. The method is based on sampling density fields assuming a lognormal prior with a likelihood modelling non-linear stochastic bias. Coherent redshift-space distortions are corrected in a Gibbs-sampling procedure by moving the galaxies from redshift- to real-space according to the peculiar motions derived from the recovered density field using linear theory. The virialized distortions are corrected by sampling candidate real-space positions along the line of sight, which are compatible with the bulk flow corrected redshift-space position adding a random dispersion term in high-density collapsed regions (defined by the eigenvalues of the Hessian). This approach presents an alternative method to estimate the distances to galaxies using the three-dimensional spatial information, and assuming isotropy. Hence the number of applications is very broad. In this work, we show the potential of this method to constrain the growth rate up to k ˜ 0.3 h Mpc-1. Furthermore it could be useful to correct for photometric redshift errors, and to obtain improved baryon acoustic oscillations (BAO) reconstructions.

  16. A Spectral Model for Multimodal Redshift Estimation

    CERN Document Server

    Kugler, Sven D; Polsterer, Kai L

    2016-01-01

    We present a physically inspired model for the problem of redshift estimation. Typically, redshift estimation has been treated as a regression problem that takes as input magnitudes and maps them to a single target redshift. In this work we acknowledge the fact that observed magnitudes may actually admit multiple plausible redshifts, i.e. the distribution of redshifts explaining the observed magnitudes (or colours) is multimodal. Hence, employing one of the standard regression models, as is typically done, is insufficient for this kind of problem, as most models implement either one-to-one or many-to-one mappings. The observed multimodality of solutions is a direct consequence of (a) the variety of physical mechanisms that give rise to the observations, (b) the limited number of measurements available and (c) the presence of noise in photometric measurements. Our proposed solution consists in formulating a model from first principles capable of generating spectra. The generated spectra are integrated over fil...

  17. The Angular Power Spectra of Photometric SDSS LRGs

    CERN Document Server

    Thomas, Shaun A; Lahav, Ofer

    2010-01-01

    We construct new galaxy angular power spectra based on the extended, updated and final SDSS II Luminous Red Galaxy (LRG) photometric redshift survey: MegaZ DR7. Encapsulating 7746 deg^{2} we utilise 723,556 photometrically determined LRGs between 0.45 < z < 0.65 in a 3.3 (Gpc h^{-1})^3 spherical harmonic analysis of the galaxy distribution. By combining four photometric redshift bins we find preliminary parameter constraints of f_{b} = \\Omega_{b}/\\Omega_{m} = 0.173 +/- 0.046 and \\Omega_{m} = 0.260 +/- 0.035 assuming H_{0} = 75 km s^{-1} Mpc^{-1}, n_{s}=1 and \\Omega_{k} = 0. These limits are consistent with the CMB and the previous data release (DR4). The C_{\\ell} are sensitive to redshift space distortions and therefore we also recast our constraints into a measurement of \\beta ~ \\Omega_{m}^{0.55}/b in different redshift shells. The robustness of these power spectra with respect to a number of potential systematics such as extinction, photometric redshift and ANNz training set extrapolation are examined...

  18. The Ongoing Catastrophe

    DEFF Research Database (Denmark)

    Kublitz, Anja

    2016-01-01

    as camps. Based on fieldwork among Palestinians in the Danish camps, this article explores why my interlocutors describe their current lives as a catastrophe. Al-Nakba literally means the catastrophe and, in Palestinian national discourse, it is used to designate the event of 1948, when the Palestinians...

  19. Understanding Atmospheric Catastrophes

    Science.gov (United States)

    Chao, Winston C.

    2009-01-01

    The atmosphere, as in other parts of nature, is full of phenomena that involve rapid transitions from one (quasi-) equilibrium state to another--- i.e. catastrophes. These (quasi-) equilibria are the multiple solutions of the same dynamical system. Unlocking the mystery behind a catastrophe reveals not only the physical mechanism responsible for the transition, but also how the (quasi-) equilibria before and after the transition are maintained. Each catastrophe is different, but they do have some common traits. Understanding these common traits is the first step in studying these catastrophes. In this seminar, three examples chosen based on the speaker's research interest--tropical cyclogenesis, stratospheric sudden warming, and monsoon onset--are given to illustrate how atmospheric catastrophes can be studied.

  20. Habitability and cosmic catastrophes

    CERN Document Server

    Hanslmeier, Arnold; McKay, Christopher P

    2008-01-01

    Catastrophic cosmic events such as asteroid impacts appear in the range of some 100 million years and have drastically affected evolution. The author discusses whether and how such events could have occurred in recently found extrasolar planetary systems.

  1. Catastrophic Antiphospholipid Syndrome.

    Science.gov (United States)

    El-Shereef, Rawhya R; El-Abedin, Zein; Abdel Aziz, Rashad; Talat, Ibrahim; Saleh, Mohammed; Abdel-Samia, Hanna; Sameh, Amro; Sharha, Mahmoud

    2016-01-01

    This paper reports one case of successfully treated patients suffering from a rare entity, the catastrophic antiphospholipid syndrome (CAPS). Management of this patient is discussed in detail. PMID:27375916

  2. Catastrophic Antiphospholipid Syndrome

    Directory of Open Access Journals (Sweden)

    Rawhya R. El-Shereef

    2016-01-01

    Full Text Available This paper reports one case of successfully treated patients suffering from a rare entity, the catastrophic antiphospholipid syndrome (CAPS. Management of this patient is discussed in detail.

  3. Entanglement in quantum catastrophes

    CERN Document Server

    Emary, C; Brandes, T; Emary, Clive; Lambert, Neill; Brandes, Tobias

    2005-01-01

    We classify entanglement singularities for various two-mode bosonic systems in terms of catastrophe theory. Employing an abstract phase-space representation, we obtain exact results in limiting cases for the entropy in cusp, butterfly, and two-dimensional catastrophes. We furthermore use numerical results to extract the scaling of the entropy with the non-linearity parameter, and discuss the role of mixing entropies in more complex systems.

  4. Catastrophes in surface scattering

    International Nuclear Information System (INIS)

    Theoretical and experimental studies concerning atom-surface interactions in the energy range from hyperthermal to approximately 100 eV are reported. An extended study of the interaction of low energetic alkalis (sodium and potassium) with a silver crystal is presented. Finally the ultimate experimental result in this research, the first observation of catastrophes in surface scattering, is shown. The results clearly indicate the strength of the catastrophe analysis in gas-surface scattering. 218 refs.; 40 figs.; 170 schemes; 4 tabs

  5. High redshift galaxies in the ALHAMBRA survey: I. selection method and number counts based on redshift PDFs

    CERN Document Server

    Viironen, K; López-Sanjuan, C; Varela, J; Chaves-Montero, J; Cristóbal-Hornillos, D; Molino, A; Fernández-Soto, A; Ascaso, B; Cenarro, A J; Cerviño, M; Cepa, J; Ederoclite, A; Márquez, I; Masegosa, J; Moles, M; Oteo, I; Pović, M; Aguerri, J A L; Alfaro, E; Aparicio-Villegas, T; Benítez, N; Broadhurst, T; Cabrera-Caño, J; Castander, J F; Del Olmo, A; Delgado, R M González; Husillos, C; Infante, L; Martínez, V J; Perea, J; Prada, F; Quintana, J M

    2015-01-01

    Context. Most observational results on the high redshift restframe UV-bright galaxies are based on samples pinpointed using the so called dropout technique or Ly-alpha selection. However, the availability of multifilter data allows now replacing the dropout selections by direct methods based on photometric redshifts. In this paper we present the methodology to select and study the population of high redshift galaxies in the ALHAMBRA survey data. Aims. Our aim is to develop a less biased methodology than the traditional dropout technique to study the high redshift galaxies in ALHAMBRA and other multifilter data. Thanks to the wide area ALHAMBRA covers, we especially aim at contributing in the study of the brightest, less frequent, high redshift galaxies. Methods. The methodology is based on redshift probability distribution functions (zPDFs). It is shown how a clean galaxy sample can be obtained by selecting the galaxies with high integrated probability of being within a given redshift interval. However, reach...

  6. Statistical Classification Techniques for Photometric Supernova Typing

    CERN Document Server

    Newling, James; Bassett, Bruce; Campbell, Heather; Hlozek, Renée; Kunz, Martin; Lampeitl, Hubert; Martin, Bryony; Nichol, Robert; Parkinson, David; Smith, Mathew

    2010-01-01

    Future photometric supernova surveys will produce vastly more candidates than can be followed up spectroscopically, highlighting the need for effective classification methods based on lightcurves alone. Here we introduce boosting and kernel density estimation techniques which have minimal astrophysical input, and compare their performance on 20,000 simulated Dark Energy Survey lightcurves. We demonstrate that these methods are comparable to the best template fitting methods currently used, and in particular do not require the redshift of the host galaxy or candidate. However both methods require a training sample that is representative of the full population, so typical spectroscopic supernova subsamples will lead to poor performance. To enable the full potential of such blind methods, we recommend that representative training samples should be used and so specific attention should be given to their creation in the design phase of future photometric surveys.

  7. Photometric classification of type Ia supernovae in the SuperNova Legacy Survey with supervised learning

    CERN Document Server

    Möller, A; Leloup, C; Neveu, J; Palanque-Delabrouille, N; Rich, J; Carlberg, R; Lidman, C; Pritchet, C

    2016-01-01

    In the era of large astronomical surveys, photometric classification of supernovae (SNe) has become an important research field due to limited spectroscopic resources for candidate follow-up and classification. In this work, we present a method to photometrically classify type Ia supernovae based on machine learning with redshifts that are derived from the SN light-curves. This method is implemented on real data from the SNLS deferred pipeline, a purely photometric pipeline that identifies SNe Ia at high-redshifts ($0.2redshift from photometry and estimating light-curve shape parameters) and machine learning classification. We study the performance of different algorithms such as Random Forest and Boosted Decision Trees. We evaluate the performance using SN simulations and real data from the first 3 years of the Supernova Legacy Survey (SNLS), which contains large spectroscopically and photometrically classified type Ia sa...

  8. Spectra of High-Redshift Type Ia Supernovae and a Comparison withtheir Low-Redshift Counterparts

    Energy Technology Data Exchange (ETDEWEB)

    Hook, I.M.; Howell, D.A.; Aldering, G.; Amanullah, R.; Burns,M.S.; Conley, A.; Deustua, S.E.; Ellis, R.; Fabbro, S.; Fadeyev, V.; Folatelli, G.; Garavini, G.; Gibbons, R.; Goldhaber, G.; Goobar, A.; Groom, D.E.; Kim, A.G.; Knop, R.A.; Kowalski, M.; Lidman, C.; Nobili, S.; Nugent, P.E.; Pain, R.; Pennypacker, C.R.; Perlmutter, S.; Ruiz-Lapuente,P.; Sainton, G.; Schaefer, B.E.; Smith, E.; Spadafora, A.L.; Stanishev,V.; Thomas, R.C.; Walton, N.A.; Wang, L.; Wood-Vasey, W.M.

    2005-07-20

    We present spectra for 14 high-redshift (0.17 < z < 0.83) supernovae, which were discovered by the Supernova Cosmology Project as part of a campaign to measure cosmological parameters. The spectra are used to determine the redshift and classify the supernova type, essential information if the supernovae are to be used for cosmological studies. Redshifts were derived either from the spectrum of the host galaxy or from the spectrum of the supernova itself. We present evidence that these supernovae are of Type Ia by matching to spectra of nearby supernovae. We find that the dates of the spectra relative to maximum light determined from this fitting process are consistent with the dates determined from the photometric light curves, and moreover the spectral time-sequence for SNe Type Ia at low and high redshift is indistinguishable. We also show that the expansion velocities measured from blueshifted Ca H&K are consistent with those measured for low-redshift Type Ia supernovae. From these first-level quantitative comparisons we find no evidence for evolution in SNIa properties between these low- and high-redshift samples. Thus even though our samples may not be complete, we conclude that there is a population of SNe Ia at high redshift whose spectral properties match those at low redshift.

  9. Probing the bias of radio sources at high redshift

    CERN Document Server

    Passmoor, Sean; Faltenbacher, Andreas; Johnston, Russell; Smith, Mathew; Ratsimbazafy, Ando; Hoyle, Ben

    2012-01-01

    The relationship between the clustering of dark matter and that of luminous matter is often described using the bias parameter. Here, we provide a new method to probe the bias of intermediate to high-redshift radio continuum sources for which no redshift information is available. We matched radio sources from the Faint Images of the Radio Sky at Twenty centimetres (FIRST) survey data to their optical counterparts in the Sloan Digital Sky Survey (SDSS) to obtain photometric redshifts for the matched radio sources. We then use the publicly available semi-empirical simulation of extragalactic radio continuum sources (S3) to infer the redshift distribution for all FIRST sources and estimate the redshift distribution of unmatched sources by subtracting the matched distribution from the distribution of all sources. We infer that the majority of unmatched sources are at higher redshifts than the optically matched sources and demonstrate how the angular scales of the angular two-point correlation function can be used...

  10. Catastrophic Crop Insurance

    OpenAIRE

    Edwards, William M.

    2003-01-01

    Beginning in 1995 farmers were offered the chance to carry a minimum level of Multiple Peril Crop Insurance (MPCI) coverage at very little cost. This catastrophic or CAT insurance coverage replaces the protection offered to crop producers under federal disaster programs in recent years.

  11. Catastrophic Medical Expenditure Risk

    NARCIS (Netherlands)

    G. Flores (Gabriela); O.A. O'Donnell (Owen)

    2012-01-01

    textabstractMedical expenditure risk can pose a major threat to living standards. We derive decomposable measures of catastrophic medical expenditure risk from reference-dependent utility with loss aversion. We propose a quantile regression based method of estimating risk exposure from cross-section

  12. Dusty Quasars at High Redshifts

    CERN Document Server

    Weedman, Daniel

    2016-01-01

    A population of quasars at z ~ 2 is determined based on dust luminosities vLv(7.8 um) that includes unobscured, partially obscured, and obscured quasars. Quasars are classified by the ratio vLv(0.25 um)/vLv(7.8 um) = UV/IR, assumed to measure obscuration of UV luminosity by the dust which produces IR luminosity. Quasar counts at rest frame 7.8 um are determined for quasars in the Bootes field of the NOAO Deep Wide Field Survey using 24 um sources with optical redshifts from the AGN and Galaxy Evolution Survey (AGES) or infrared redshifts from the Spitzer Infrared Spectrograph. Spectral energy distributions are extended to far infrared wavelengths using observations from the Herschel Space Observatory Spectral and Photometric Imaging Receiver (SPIRE), and new SPIRE photometry is presented for 77 high redshift quasars from the Sloan Digital Sky Survey. It is found that unobscured and obscured quasars have similar space densities at rest frame 7.8 um, but the ratio Lv(100 um)/Lv(7.8 um) is about three times high...

  13. SDSS DR6 Data for Photometric Redshift Calculations

    Data.gov (United States)

    National Aeronautics and Space Administration — Subject Area: Astronomical data Description: The Sloan Digital Sky Survey (SDSS) is a multi-organization effort to gather deep, multi-color images covering more...

  14. Optimising Spectroscopic and Photometric Galaxy Surveys: Same-sky Benefits for Dark Energy and Modified Gravity

    CERN Document Server

    Kirk, Donnacha; Bridle, Sarah; Jouvel, Stephanie; Abdalla, Filipe B; Frieman, Joshua A

    2013-01-01

    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...

  15. A model of the anisotropic correlation function xi(rp, pi) in redshift space including redshift errors

    CERN Document Server

    Schlagenhaufer, Holger A; Sanchez, Ariel G

    2012-01-01

    With the advent of very large volume, wide-angle photometric redshift surveys like e.g. Pan-STARRS, DES, or PAU, which aim at using the spatial distribution of galaxies as a means to constrain the equation of state parameter of dark energy, w_DE, it has become extremely important to understand the influence of redshift inaccuracies on the measurement. We have developed a new model for the anisotropic two point large-scale (r > 64 h^-1 Mpc) correlation function xi(rp,pi), in which nonlinear structure growth and nonlinear coherent infall velocities are taken into account, and photometric redshift errors can easily be incorporated. In order to test its validity and investigate the effects of photometric redshifts, we compare our model with the correlation function computed from a suite of 50 large-volume, moderate-resolution numerical N-body simulation boxes, where we can perform the analysis not only in real- and redshift space, but also simulate the influence of a gaussian redshift error distribution with an a...

  16. The angular power spectra of photometric Sloan Digital Sky Survey luminous red galaxies

    Science.gov (United States)

    Thomas, Shaun A.; Abdalla, Filipe B.; Lahav, Ofer

    2011-04-01

    We construct new galaxy angular power spectra Cℓ based on the extended, updated and final Sloan Digital Sky Survey (SDSS) II luminous red galaxy (LRG) photometric redshift survey - MegaZ (DR7). Encapsulating 7746 deg2 we utilize 723 556 photometrically determined LRGs between 0.45 preliminary parameter constraints of fb≡Ωb/Ωm= 0.173 ± 0.046 and Ωm= 0.260 ± 0.035 assuming H0= 75 km s-1 Mpc-1, ns= 1 and Ωk= 0. These limits are consistent with the cosmic microwave background and the previous data release (DR4). The Cℓ are sensitive to redshift space distortions and therefore we also recast our constraints into a measurement of β≈Ω0.55m/b in different redshift shells. The robustness of these power spectra with respect to a number of potential systematics such as extinction, photometric redshift and ANNz training set extrapolation are examined. The latter includes a cosmological comparison of available photometric redshift estimation codes where we find excellent agreement between template and empirical estimation methods. MegaZ DR7 represents a methodological prototype to next generation surveys such as the Dark Energy Survey and, furthermore, is a photometric precursor to the spectroscopic BOSS survey. Our galaxy catalogue and all power spectra data can be found at .

  17. Catastrophic primary antiphospholipid syndrome

    International Nuclear Information System (INIS)

    Catastrophic antiphospholipid syndrome (CAPLS) was diagnosed in a 64-year-old male who was admitted to our hospital with dyspnea. The clinical and radiological examinations showed pulmonary thromboembolism, and so thromboembolectomy was performed. Abdominal distension rapidly developed several days later, and the abdominal computed tomography (CT) abdominal scan revealed thrombus within the superior mesenteric artery with small bowel and gall bladder distension. Cholecystectomy and jejunoileostomy were performed, and gall bladder necrosis and small bowel infarction were confirmed. The anticardiolipin antibody was positive. Anticoagulant agents and steroids were administered, but the patient expired 4 weeks after surgery due to acute respiratory distress syndrome (ARDS). We report here on a case of catastrophic APLS with manifestations of pulmonary thromboembolism, rapidly progressing GB necrosis and bowel infarction

  18. Catastrophic primary antiphospholipid syndrome

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Dong Hun; Byun, Joo Nam [Chosun University Hospital, Gwangju (Korea, Republic of); Ryu, Sang Wan [Miraero21 Medical Center, Gwangju (Korea, Republic of)

    2006-09-15

    Catastrophic antiphospholipid syndrome (CAPLS) was diagnosed in a 64-year-old male who was admitted to our hospital with dyspnea. The clinical and radiological examinations showed pulmonary thromboembolism, and so thromboembolectomy was performed. Abdominal distension rapidly developed several days later, and the abdominal computed tomography (CT) abdominal scan revealed thrombus within the superior mesenteric artery with small bowel and gall bladder distension. Cholecystectomy and jejunoileostomy were performed, and gall bladder necrosis and small bowel infarction were confirmed. The anticardiolipin antibody was positive. Anticoagulant agents and steroids were administered, but the patient expired 4 weeks after surgery due to acute respiratory distress syndrome (ARDS). We report here on a case of catastrophic APLS with manifestations of pulmonary thromboembolism, rapidly progressing GB necrosis and bowel infarction.

  19. Catastrophic Medical Expenditure Risk

    OpenAIRE

    O'Donnell, Owen; Flores, Gabriela

    2012-01-01

    textabstractMedical expenditure risk can pose a major threat to living standards. We derive decomposable measures of catastrophic medical expenditure risk from reference-dependent utility with loss aversion. We propose a quantile regression based method of estimating risk exposure from cross-section data containing information on the means of financing health payments. We estimate medical expenditure risk in seven Asian countries and find it is highest in Laos and China, and is lowest in Mala...

  20. Valuing Catastrophic Citrus Losses

    OpenAIRE

    Adams, Damian C.; Kilmer, Richard L.; Moss, Charles B.; Schmitz, Andrew

    2004-01-01

    Courts are often required to estimate changes in welfare to agricultural operations from catastrophic events. For example, courts must assign damages in lawsuits, such as with pesticide drift cases, or determine "just compensation" when the government takes private land for public use, as with the removal of dairy farms from environmentally sensitive land or destruction of canker-contaminated citrus trees. In economics, the traditional method of quantifying producer losses is estimating chang...

  1. The limits of catastrophe aversion.

    Science.gov (United States)

    Peterson, Martin

    2002-06-01

    We discuss the management of catastrophe-risks from a theoretical point of view. The concept of a catastrophe is informally and formally defined, and a number of desiderata for catastrophe-averse decision rules are introduced. However, the proposed desiderata turn out to be mutually inconsistent. As a consequence of this result, it is argued that the "rigid" form of catastrophe aversion articulated by, for example, the maximin rule, the maximum probable loss rule, (some versions of) the precautionary principle, and the rule proposed in Ekenberg et al. (1997, 2000) should be given up. An alternative form of "non-rigid" catastrophe aversion is considered. PMID:12088231

  2. Predicting the Quasar Photometric Reshift with the Sloan Digital Sky Survey Filter System

    Science.gov (United States)

    Laubacher, Emily M.; York, Donald G.

    1999-10-01

    Photometric data were obtained for a set of known quasars (QSOs) in five bands with the Sloan Digital Sky Survey (SDSS) filter system for the purpose of testing the ability of the SDSS system to accurately predict the photometric redshift of QSOs. The initial plot of the SDSS photometric redshift versus the measured redshift shows a good relationship, but a lot of scatter. A literature search was conducted on a selected sampling of 49 QSOs, 26 with redshift z advertised redshifts. This search revealed 10 rejected QSOs which were not QSOs but rather Seyfert galaxies or Narrow Line Objects. Additionally, 11 QSOs were either Broad Absorption Line Systems or had spectra that were in some way incomplete, and therefore, their QSO identification could not be confirmed. The revised plot, with the rejected and unconfirmed QSOs removed, gives an excellent straight line with very little scatter. Although these results are preliminary and for only a small sampling of QSOs, they show that further study of the relationship is warranted and that eventually the SDSS method may be used to accurately predict the photometric redshift of QSOs.

  3. Breaking the "Redshift Deadlock" -- II The redshift distribution for the submillimetre population of galaxies

    CERN Document Server

    Aretxaga, I; Chapin, E L; Gaztañaga, E; Dunlop, J S

    2003-01-01

    In this paper we apply our Monte-Carlo photometric-redshift technique, introduced in paper I (Hughes et al. 2002), to the multi-wavelength data available for 77 galaxies selected at 850um and 1.25mm. Unlike earlier redshift estimates, we calculate a probability distribution for the redshift of each galaxy. These estimates include a detailed treatment of the observational errors and uncertainties in the evolutionary model. The cumulative redshift distribution of the sub-mm galaxy population that we present in this paper, based on 47 galaxies with a S/N >3.5 at 850um found in wide-area SCUBA surveys, is asymmetric, and broader than those published elsewhere, with a significant high-z tail. Approximately 40 to 90 per cent of the sub-mm population is expected to have redshifts in the interval 2 4. Spectroscopic confirmation of the redshifts, through the detection of rest-frame FIR--mm wavelength molecular transition-lines, will ultimately calibrate the accuracy of this technique. We use the redshift probability ...

  4. The ALHAMBRA survey: Accurate photometric merger fractions from PDF analysis

    Science.gov (United States)

    López-Sanjuan, C.; Cenarro, A. J..; Varela, J.; Viironen, K.; ALHAMBRA Team

    2015-05-01

    The estimation of the merger fraction in photometric surveys is limited by the large uncertainty in the photometric redshift compared with the velocity difference in kinematical close pairs (less than 500 km s^{-1}). Several efforts have conducted to deal with this limitation and we present the latest improvements. Our new method (i) provides a robust estimation of the merger fraction by using full probability distribution functions (PDFs) instead of Gaussian distributions, as in previous work; (ii) takes into account the dependence of the luminosity on redshift in both the selection of the samples and the definition of major/minor mergers; and (iii) deals with partial PDFs to define ``red" (E/S0 templates) and ``blue" (spiral/starburst templates) samples without apply any colour selection. We highlight our new method with the estimation of the merger fraction at z SHARDS, J-PAS, or LSST.

  5. CATASTROPHIC EVENTS MODELING

    Directory of Open Access Journals (Sweden)

    Ciumas Cristina

    2013-07-01

    Full Text Available This paper presents the emergence and evolution of catastrophe models (cat models. Starting with the present context of extreme weather events and features of catastrophic risk (cat risk we’ll make a chronological illustration from a theoretical point of view of the main steps taken for building such models. In this way the importance of interdisciplinary can be observed. The first cat model considered contains three modules. For each of these indentified modules: hazard, vulnerability and financial losses a detailed overview and also an exemplification of a potential case of an earthquake that measures more than 7 on Richter scale occurring nowadays in Bucharest will be provided. The key areas exposed to earthquake in Romania will be identified. Then, based on past catastrophe data and taking into account present conditions of housing stock, insurance coverage and the population of Bucharest the impact will be quantified by determining potential losses. In order to accomplish this work we consider a scenario with data representing average values for: dwelling’s surface, location, finishing works. On each step we’ll make a reference to the earthquake on March 4 1977 to see what would happen today if a similar event occurred. The value of Bucharest housing stock will be determined taking firstly the market value, then the replacement value and ultimately the real value to quantify potential damages. Through this approach we can find the insurance coverage of potential losses and also the uncovered gap. A solution that may be taken into account by public authorities, for example by Bucharest City Hall will be offered: in case such an event occurs the impossibility of paying compensations to insured people, rebuilding infrastructure and public buildings and helping the suffering persons should be avoided. An actively public-private partnership should be created between government authorities, the Natural Disaster Insurance Pool, private

  6. Abdominal Vascular Catastrophes.

    Science.gov (United States)

    Singh, Manpreet; Koyfman, Alex; Martinez, Joseph P

    2016-05-01

    Abdominal vascular catastrophes are among the most challenging and time sensitive for emergency practitioners to recognize. Mesenteric ischemia remains a highly lethal entity for which the history and physical examination can be misleading. Laboratory tests are often unhelpful, and appropriate imaging must be quickly obtained. A multidisciplinary approach is required to have a positive impact on mortality rates. Ruptured abdominal aortic aneurysm likewise may present in a cryptic fashion. A specific type of ruptured aneurysm, the aortoenteric fistula, often masquerades as the more common routine gastrointestinal bleed. The astute clinician recognizes that this is a more lethal variant of gastrointestinal hemorrhage. PMID:27133247

  7. Cosmic impacts, cosmic catastrophes. II

    Science.gov (United States)

    Chapman, Clark R.; Morrison, David

    1990-01-01

    The role of extraterrestrial impacts in shaping the earth's history is discussed, arguing that cosmic impacts represent just one example of a general shift in thinking that has made the idea of catastrophes respectable in science. The origins of this view are presented and current catastrophic theory is discussed in the context of modern debate on the geological formation of the earth. Various conflicting theories are reviewed and prominent participants in the ongoing scientific controversy concerning catastrophism are introduced.

  8. Puzzlement about thermal redshift

    OpenAIRE

    Dimitrov, Vesselin I.

    1997-01-01

    Discussed is the classical theoretical description of the experimentally established thermal redshift of spectral lines. Straightforward calculation of the observable spectrum from a canonical ensamble of monochromatic radiators yileds overall blueshift rather than redshift. It is concluded that the customary explanation of the thermal redshift as a second order Doppler effect does not bear closer examination, and that in fact, the phenomenon ''thermal redshift'' is not yet fully uderstood in...

  9. New Neutrino Mass Bounds from Sloan Digital Sky Survey III Data Release 8 Photometric Luminous Galaxies

    CERN Document Server

    de Putter, Roland; Giusarma, Elena; Ho, Shirley; Cuesta, Antonio; Seo, Hee-Jong; Ross, Ashley; White, Martin; Bizyaev, Dmitry; Brewington, Howard; Kirkby, David; Malanushenko, Elena; Malanushenko, Viktor; Oravetz, Daniel; Pan, Kaike; Percival, Will J; Ross, Nicholas P; Schneider, Donald P; Shelden, Alaina; Simmons, Audrey; Snedden, Stephanie

    2012-01-01

    We present neutrino mass bounds using 900,000 luminous galaxies with photometric redshifts measured from Sloan Digital Sky Survey III Data Release Eight (SDSS DR8). The galaxies have photometric redshifts between $z = 0.45$ and $z = 0.65$, and cover 10,000 square degrees and thus probe a volume of 3$h^{-3}$Gpc$^3$, enabling tight constraints to be derived on the amount of dark matter in the form of massive neutrinos. A new bound on the sum of neutrino masses $\\sum m_\

  10. RECONSTRUCTING REDSHIFT DISTRIBUTIONS WITH CROSS-CORRELATIONS: TESTS AND AN OPTIMIZED RECIPE

    International Nuclear Information System (INIS)

    Many of the cosmological tests to be performed by planned dark energy experiments will require extremely well-characterized photometric redshift measurements. Current estimates for cosmic shear are that the true mean redshift of the objects in each photo-z bin must be known to better than 0.002(1 + z), and the width of the bin must be known to ∼0.003(1 + z) if errors in cosmological measurements are not to be degraded significantly. A conventional approach is to calibrate these photometric redshifts with large sets of spectroscopic redshifts. However, at the depths probed by Stage III surveys (such as DES), let alone Stage IV (LSST, JDEM, and Euclid), existing large redshift samples have all been highly (25%-60%) incomplete, with a strong dependence of success rate on both redshift and galaxy properties. A powerful alternative approach is to exploit the clustering of galaxies to perform photometric redshift calibrations. Measuring the two-point angular cross-correlation between objects in some photometric redshift bin and objects with known spectroscopic redshift, as a function of the spectroscopic z, allows the true redshift distribution of a photometric sample to be reconstructed in detail, even if it includes objects too faint for spectroscopy or if spectroscopic samples are highly incomplete. We test this technique using mock DEEP2 Galaxy Redshift survey light cones constructed from the Millennium Simulation semi-analytic galaxy catalogs. From this realistic test, which incorporates the effects of galaxy bias evolution and cosmic variance, we find that the true redshift distribution of a photometric sample can, in fact, be determined accurately with cross-correlation techniques. We also compare the empirical error in the reconstruction of redshift distributions to previous analytic predictions, finding that additional components must be included in error budgets to match the simulation results. This extra error contribution is small for surveys that sample

  11. Catastrophic medical expenditure risk.

    Science.gov (United States)

    Flores, Gabriela; O'Donnell, Owen

    2016-03-01

    We propose a measure of household exposure to particularly onerous medical expenses. The measure can be decomposed into the probability that medical expenditure exceeds a threshold, the loss due to predictably low consumption of other goods if it does and the further loss arising from the volatility of medical expenses above the threshold. Depending on the choice of threshold, the measure is consistent with a model of reference-dependent utility with loss aversion. Unlike the risk premium, the measure is only sensitive to particularly high expenses, and can identify households that expect to incur such expenses and would benefit from subsidised, but not actuarially fair, insurance. An empirical illustration using data from seven Asian countries demonstrates the importance of taking account of informal insurance and reveals clear differences in catastrophic medical expenditure risk across and within countries. In general, risk is higher among poorer, rural and chronically ill populations. PMID:26812650

  12. Presidential Address: Catastrophe Theory and Catastrophes in China's Civil Service Examinations (Part 1).

    Science.gov (United States)

    D'Costa, Ayres

    1991-01-01

    Introduces Rene Thom's catastrophe theory, which is based upon complex theorems in multidimensional geometry. Catastrophe theory analysis begins by identifying the occurrence of major discontinuities, or catastrophes, in a system such as civil service exams, resulting in catastrophic change. (KS)

  13. Volcanoes and global catastrophes

    Science.gov (United States)

    Simkin, Tom

    1988-01-01

    The search for a single explanation for global mass extinctions has let to polarization and the controversies that are often fueled by widespread media attention. The historic record shows a roughly linear log-log relation between the frequency of explosive volcanic eruptions and the volume of their products. Eruptions such as Mt. St. Helens 1980 produce on the order of 1 cu km of tephra, destroying life over areas in the 10 to 100 sq km range, and take place, on the average, once or twice a decade. Eruptions producing 10 cu km take place several times a century and, like Krakatau 1883, destroy life over 100 to 1000 sq km areas while producing clear global atmospheric effects. Eruptions producting 10,000 cu km are known from the Quaternary record, and extrapolation from the historic record suggests that they occur perhaps once in 20,000 years, but none has occurred in historic time and little is known of their biologic effects. Even larger eruptions must also exist in the geologic record, but documentation of their volume becomes increasingly difficult as their age increases. The conclusion is inescapable that prehistoric eruptions have produced catastrophes on a global scale: only the magnitude of the associated mortality is in question. Differentiation of large magma chambers is on a time scale of thousands to millions of years, and explosive volcanoes are clearly concentrated in narrow belts near converging plate margins. Volcanism cannot be dismissed as a producer of global catastrophes. Its role in major extinctions is likely to be at least contributory and may well be large. More attention should be paid to global effects of the many huge eruptions in the geologic record that dwarf those known in historic time.

  14. Optimal Redshift Weighting For Redshift Space Distortions

    CERN Document Server

    Ruggeri, Rossana; Gil-Marín, Héctor; Zhu, Fangzhou; Zhao, Gongbo; Wang, Yuting

    2016-01-01

    The low statistical errors on cosmological parameters promised by future galaxy surveys will only be realised with the development of new, fast, analysis methods that reduce potential systematic problems to low levels. We present an efficient method for measuring the evolution of the growth of structure using Redshift Space Distortions (RSD), that removes the need to make measurements in redshift shells. We provide sets of galaxy-weights that cover a wide range in redshift, but are optimised to provide differential information about cosmological evolution. These are derived to optimally measure the coefficients of a parameterisation of the redshift-dependent matter density, which provides a framework to measure deviations from the concordance $\\Lambda$CDM cosmology, allowing for deviations in both geometric and/or growth. We test the robustness of the weights by comparing with alternative schemes and investigate the impact of galaxy bias. We extend the results to measure the combined anisotropic Baryon Acoust...

  15. THE LOW-REDSHIFT CARNEGIE SUPERNOVA PROJECT

    Directory of Open Access Journals (Sweden)

    G. Folatelli

    2009-01-01

    Full Text Available We present the low-redshift Carnegie Supernova Project (CSP, an undergoing program to follow up about 250 nearby supernovae (SNe of all types. We brie y describe the observations which yield well-sampled, highly precise optical and near-infrared light curves in a well-understood photometric system, complemented with optical spectroscopy. As one of the main goals of the CSP, we preliminarily present the rst Hubble diagram using a sample of 30 Type-Ia SNe (SNe Ia.

  16. An extended galaxy redshift survey: Pt. 1

    International Nuclear Information System (INIS)

    Redshifts and blue magnitudes are presented for a sample of 264 'field' galaxies virtually complete to a limiting magnitude of bj ∼ 16.80 mag. The galaxies were selected by sampling one galaxy in every three in order of apparent magnitude on each of nine high-latitude UK Schmidt (UKST) fields. Photometric data were provided by COSMOS machine measures of UKST plates, zero-pointed with CCD photometry. The spectral data came from observations with the 1.9-m telescope at the South African Astronomical Observatory (SAAO), and the resulting radial velocities have a precision of ∼ ± 130 km s-1. This survey augments substantially the Durham/AAT redshift survey. (author)

  17. Photometric and Spectroscopic Study of Abell 0671

    CERN Document Server

    Pan, Zhizheng; Kong, Xu; Fan, Dongxin; Zhou, Xu; Lin, Xuanbin

    2011-01-01

    In this paper we present a photometric and spectroscopic study of the nearby galaxy cluster Abell 0671 (A671) with 15 intermediate-band filters in the Beijing-Arizona-Taiwan-Connecticut (BATC) system and the Sloan Digital Sky Survey (SDSS) data. The photometric redshift technique is applied to the galaxy sample for further membership determination. After the color-magnitude relation is taken into account, 97 galaxies brighter than h_batc=19.5 mag are selected as new member galaxies. Based on the enlarged sample of cluster galaxies, spatial distribution, dynamics of A671 are investigated. The substructures of A671 are well shown by the sample of bright members, but it appears less significant based on the enlarged sample, which is mainly due to larger uncertainties in the light-of-sight velocities of the newly-selected faint members. The SDSS r-band luminosity function of A671 is flat at faint magnitudes, with the faint end slope parameter alpha=-1.12. The SDSS spectra allow us to investigate the star formatio...

  18. Subpixel photometric stereo.

    Science.gov (United States)

    Tan, Ping; Lin, Stephen; Quan, Long

    2008-08-01

    Conventional photometric stereo recovers one normal direction per pixel of the input image. This fundamentally limits the scale of recovered geometry to the resolution of the input image, and cannot model surfaces with subpixel geometric structures. In this paper, we propose a method to recover subpixel surface geometry by studying the relationship between the subpixel geometry and the reflectance properties of a surface. We first describe a generalized physically-based reflectance model that relates the distribution of surface normals inside each pixel area to its reflectance function. The distribution of surface normals can be computed from the reflectance functions recorded in photometric stereo images. A convexity measure of subpixel geometry structure is also recovered at each pixel, through an analysis of the shadowing attenuation. Then, we use the recovered distribution of surface normals and the surface convexity to infer subpixel geometric structures on a surface of homogeneous material by spatially arranging the normals among pixels at a higher resolution than that of the input image. Finally, we optimize the arrangement of normals using a combination of belief propagation and MCMC based on a minimum description length criterion on 3D textons over the surface. The experiments demonstrate the validity of our approach and show superior geometric resolution for the recovered surfaces. PMID:18566498

  19. Supernova Photometric Lightcurve Classification

    Science.gov (United States)

    Zaidi, Tayeb; Narayan, Gautham

    2016-01-01

    This is a preliminary report on photometric supernova classification. We first explore the properties of supernova light curves, and attempt to restructure the unevenly sampled and sparse data from assorted datasets to allow for processing and classification. The data was primarily drawn from the Dark Energy Survey (DES) simulated data, created for the Supernova Photometric Classification Challenge. This poster shows a method for producing a non-parametric representation of the light curve data, and applying a Random Forest classifier algorithm to distinguish between supernovae types. We examine the impact of Principal Component Analysis to reduce the dimensionality of the dataset, for future classification work. The classification code will be used in a stage of the ANTARES pipeline, created for use on the Large Synoptic Survey Telescope alert data and other wide-field surveys. The final figure-of-merit for the DES data in the r band was 60% for binary classification (Type I vs II).Zaidi was supported by the NOAO/KPNO Research Experiences for Undergraduates (REU) Program which is funded by the National Science Foundation Research Experiences for Undergraduates Program (AST-1262829).

  20. Galaxies at High Redshifts

    CERN Document Server

    Yahil, A; Fernández-Soto, A

    1998-01-01

    Several conclusions have been reached over the last few years concerning high-redshift galaxies: (1) The excess of faint blue galaxies is due to dwarf galaxies. (2) Star formation peaks at redshifts z ~1-2. (3) It appears to occur piecemeal in any given galaxy and there is no evidence for starbursting throughout a large ~10 kpc galaxy. (4) There is significant and sharp diminution in the number of L* spiral galaxies at redshifts 1redshifts 2.5redshift galaxies in universes with larger volumes per unit redshift, i.e., open or lambda models, which have lower deceleration parameters.

  1. Galaxies at High Redshifts

    OpenAIRE

    Yahil, A.; Lanzetta, K. M.; Fernandez-Soto, A.

    1998-01-01

    Several conclusions have been reached over the last few years concerning high-redshift galaxies: (1) The excess of faint blue galaxies is due to dwarf galaxies. (2) Star formation peaks at redshifts z ~1-2. (3) It appears to occur piecemeal in any given galaxy and there is no evidence for starbursting throughout a large ~10 kpc galaxy. (4) There is significant and sharp diminution in the number of L* spiral galaxies at redshifts 1

  2. Catastrophic antiphospholipid Syndrome

    International Nuclear Information System (INIS)

    The antiphospholipid syndrome (APS) is characterized by venous, arterial thrombosis and miscarriages along with lupic anticoagulant and antibodies against anticardiolipin. The catastrophic antiphospholipid syndrome (CAPS) has been described since 1992 like a multiple organic dysfunction caused by multiple vascular thrombosis in three or more organs. The patients who suffer from this syndrome may have or not history of APS. There are two or three mechanisms that may cause the CAPS, alone or in combination: These are: 1. The multisystemic thrombotic disease with emphasis in microvasculature occlusion of the organs and occlusion of big arterial or veins 2. The disseminated intravascular coagulation (DIC) superimpose in 15% to 50% of the patients that, of course, conducted to an occlusive disease of arterioles, veins or capillaries. 3. A systemic inflammatory response syndrome (SIRS) induced by citoquines. In this review it is described clinical and laboratory features, pathogenesis and treatment of CAPS. For this purpose, it was searched for Medline from 1993 to 2000 and revised the most significant issues obtained by this medium

  3. A Fourteen-Band Photometric Study of A2443

    Institute of Scientific and Technical Information of China (English)

    Zhong-Lue Wen; Yan-Bin Yang; Qi-Rong Yuan; Xu Zhou; Jun Ma; Zhao-Ji Jiang

    2007-01-01

    We present a multi-color photometric study of the galaxy cluster A2443 (z = 0.108) with the Beijing-Arizona-Taiwan-Connecticut (BATC) system. The spectral energy distributions (SEDs) in 14 intermediate bands are obtained for 5975 detected from ~1deg2 of the BATC images. Color-color diagrams are used for star-galaxy separation, then a photometric redshift technique is applied to the galaxy sample for cluster membership determination. There are 301 galaxies with photometric redshifts between 0.08 and 0.14 determined as member candidates of A2443, including 289 new ones. Based on this enlarged sample, the luminosity function and color magnitude relation of the cluster are studied. With an evolutionary synthesis model, we find that the fainter galaxies tend to have longer time scales of star formation than the brighter ones. Morphologically, we show an elongated spatial distribution associating with the galaxy cluster ZwCl 2224.2+ 1651, which contains more blue galaxies. This result indicates that galaxy cluster ZwCl 2224.2+1651 may be falling into A2443, and cluster-cluster interaction could have triggered star formation activities in ZwCl 2224.2+1651.

  4. The Photometric Classification Server for Pan-STARRS1

    CERN Document Server

    Saglia, R P; Bender, R; Greisel, N; Seitz, S; Senger, R; Snigula, J; Phleps, S; Wilman, D; Bailer-Jones, C A L; Klement, R J; Rix, H -W; Smith, K; Green, P J; Burgett, W S; Chambers, K C; Heasley, J N; Kaiser, N; Magnier, E A; Morgan, J S; Price, P A; Stubbs, C W; Wainscoat, R J

    2011-01-01

    The Pan-STARRS1 survey is obtaining multi-epoch imaging in 5 bands (gps rps ips zps yps) over the entire sky North of declination -30deg. We describe here the implementation of the Photometric Classification Server (PCS) for Pan-STARRS1. PCS will allow the automatic classification of objects into star/galaxy/quasar classes based on colors, the measurement of photometric redshifts for extragalactic objects, and constrain stellar parameters for stellar objects, working at the catalog level. We present tests of the system based on high signal-to-noise photometry derived from the Medium Deep Fields of Pan-STARRS1, using available spectroscopic surveys as training and/or verification sets. We show that the Pan-STARRS1 photometry delivers classifications and photometric redshifts as good as the Sloan Digital Sky Survey (SDSS) photometry to the same magnitude limits. In particular, our preliminary results, based on this relatively limited dataset down to the SDSS spectroscopic limits and therefore potentially improv...

  5. Combining spectroscopic and photometric surveys: Same or different sky?

    Science.gov (United States)

    Eriksen, Martin; Gaztañaga, Enrique

    2015-08-01

    This paper looks at the combined constraints from a photometric and spectroscopic survey. These surveys will measure cosmology using weak lensing (WL), galaxy clustering, baryon acoustic oscillations (BAO) and redshift space distortions (RSD). We find, contrary to some findings in the recent literature, that overlapping surveys can give important benefits when measuring dark energy. We therefore try to clarify the status of this issue with a full forecast of two stage-IV surveys using a new approach to properly account for covariance between the different probes in the overlapping samples. The benefit of the overlapping survey can be traced back to two factors: additional observables and sample variance cancellation. Both needs to be taken into account and contribute equally when combining 3D power spectrum and 2D correlations for lensing. With an analytic example we also illustrate that for optimal constraints, one should minimize the (Pearson) correlation coefficient between cosmological and nuisance parameters and maximize the one among nuisance parameters (e.g. galaxy bias) in the two samples. This can be achieved by increasing the overlap between the spectroscopic and photometric surveys. We show how BAO, WL and RSD contribute to this benefit and also look at some other survey designs, such as photometric redshift errors and spectroscopic density.

  6. Photometric Selection of a Luminous Red Galaxy Catalog with $z\\geq0.55$

    CERN Document Server

    Núñez, Carolina; Ho, Shirley

    2016-01-01

    We present the development of a photometrically selected Luminous Red Galaxy (LRG) catalog at redshift $z\\geq 0.55$. LRG candidates are selected using infrared/optical color-color cuts, optimized using ROC curve analysis, with optical data from Sloan Digital Sky Survey (SDSS) and infrared data from "unWISE" forced photometry derived from the Wide-field Infrared Survey Explorer (WISE). The catalog contains 16,191,145 objects, selected over the full SDSS DR10 footprint. The redshift distribution of the resulting catalogs is estimated using spectroscopic redshifts from the DEEP2 Galaxy Redshift Survey and photometric redshifts from COSMOS. Restframe $U-B$ colors from DEEP2 are used to estimate LRG selection efficiency. In DEEP2, the resulting catalog has average redshift $z=0.65$, with standard deviation $\\sigma = 2.0$, and average restframe $U-B=1.0$, with $\\sigma=0.27$. In COSMOS, the resulting catalog has average redshift $z=0.60$, with standard deviation $\\sigma = 1.8$. We allow for 35% contamination from bl...

  7. High Redshift Supernovae in the Hubble Deep Field

    OpenAIRE

    Gilliland, Ronald L.; Nugent, Peter E.; Phillips, M. M.

    1999-01-01

    Two supernovae detected in the Hubble Deep Field using the original December 1995 epoch and data from a shorter (63000 s in F814W) December 1997 visit with HST are discussed. The supernovae (SNe) are both associated with distinct galaxies at redshifts of 0.95 (spectroscopic) from Cohen etal. (1996) and 1.32 (photometric) from the work of Fernandez-Soto, Lanzetta, and Yahil (1998). These redshifts are near, in the case of 0.95, and well beyond for 1.32 the greatest distance reported previously...

  8. Should Governments Provide Catastrophe Insurance?

    OpenAIRE

    Jaffee, Dwight; Russell, Thomas

    2005-01-01

    Hurricane Katrina and the terrorist attacks of 9/11 2001 have focused attention on the appropriate role of government in providing insurance against catastrophes. This paper argues that wherever possible governments should follow policies which enable the continuation of a private insurance market. In the event that government must itself provide catastrophe insurance it should follow the same actuarially based pricing and reserving rules that would be followed by a competitive private market.

  9. Women, catastrophe and mental health.

    Science.gov (United States)

    Raphael, Beverley; Taylor, Mel; McAndrew, Virginia

    2008-01-01

    This paper examines the concept of catastrophic experience, its relationship to the range of acute and prolonged stressors to which women may be exposed and the broad impacts on their mental health and well-being. It identifies catastrophe in terms of multiple accumulated stresses including death, loss, victimization, demoralization, shame, stigmatization, helplessness and identity. Catastrophic experiences include personal violence in domestic circumstances of intimate partner abuse, sexual assault and child physical and sexual abuse. Women's experiences of loss through the violent deaths of children and loved ones may also have such enduring impacts. Terrorism victimizes men and women in this way, with the enduring impacts for women in terms of threat of ongoing attacks as well as acute effects and their aftermath. The catastrophes of war, conflict, genocide, sexual exploitation and refugee status differentially affect large numbers of women, directly and through their concerns for the care of their children and loved ones. Ultimate catastrophes such as Hiroshima and the Holocaust are discussed but with recognition of the very large numbers of women currently experiencing catastrophe in ongoing ways that may be silent and unrecognized. This is significant for clinical care and population impacts, and in the losses for women across such contexts. PMID:18058439

  10. Measuring galaxy environment with the synergy of future photometric and spectroscopic surveys

    CERN Document Server

    Cucciati, O; Cimatti, A; Merson, A I; Norberg, P; Pozzetti, L; Baugh, C M; Branchini, E

    2016-01-01

    [Abridged] We exploit the synergy between low-resolution spectroscopy and photometric redshifts to study environmental effects on galaxy evolution in slitless spectroscopic surveys from space. As a test case, we consider the future Euclid Deep survey (~40deg$^2$), which combines a slitless spectroscopic survey limited at H$\\alpha$ flux $\\leq5\\times 10^{-17}$ erg cm$^{-2}$ s$^{-1}$ and a photometric survey limited in H-band ($H\\leq26$). To test the power of the method, we use Euclid-like galaxy mock catalogues, in which we anchor the photometric redshifts to the 3D galaxy distribution of the available spectroscopic redshifts. We then estimate the local density contrast by counting objects in cylindrical cells with radius ranging from 1 to 10 h$^{-1}$Mpc over the redshift range 0.9redshift measurement errors. We find that our method is successful in separating hi...

  11. Estimating Redshifts for Long Gamma-Ray Bursts

    CERN Document Server

    Xiao, Limin

    2009-01-01

    We are constructing a program to estimate the redshifts for GRBs from the original Swift light curves and spectra, aiming to get redshifts for the Swift bursts \\textit{without} spectroscopic or photometric redshifts. We derive the luminosity indicators from the light curves and spectra of each burst, including the lag time between low and high photon energy light curves, the variability of the light curve, the peak energy of the spectrum, the number of peaks in the light curve, and the minimum rise time of the peaks. These luminosity indicators can each be related directly to the luminosity, and we combine their independent luminosities into one weighted average. Then with our combined luminosity value, the observed burst peak brightness, and the concordance redshift-distance relation, we can derive the redshift for each burst. In this paper, we test the accuracy of our method on 107 bursts with known spectroscopic redshift. The reduced $\\chi^2$ of our best redshifts ($z_{best}$) compared with known spectrosc...

  12. The number density of quiescent compact galaxies at intermediate redshift

    Energy Technology Data Exchange (ETDEWEB)

    Damjanov, Ivana [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States); Hwang, Ho Seong; Geller, Margaret J.; Chilingarian, Igor, E-mail: idamjanov@cfa.harvard.edu [Smithsonian Astrophysical Observatory, 60 Garden St., Cambridge, MA 02138 (United States)

    2014-09-20

    Massive compact systems at 0.2 < z < 0.6 are the missing link between the predominantly compact population of massive quiescent galaxies at high redshift and their analogs and relics in the local volume. The evolution in number density of these extreme objects over cosmic time is the crucial constraining factor for the models of massive galaxy assembly. We select a large sample of ∼200 intermediate-redshift massive compacts from the Baryon Oscillation Spectroscopic Survey (BOSS) spectroscopy by identifying point-like Sloan Digital Sky Survey photometric sources with spectroscopic signatures of evolved redshifted galaxies. A subset of our targets have publicly available high-resolution ground-based images that we use to augment the dynamical and stellar population properties of these systems by their structural parameters. We confirm that all BOSS compact candidates are as compact as their high-redshift massive counterparts and less than half the size of similarly massive systems at z ∼ 0. We use the completeness-corrected numbers of BOSS compacts to compute lower limits on their number densities in narrow redshift bins spanning the range of our sample. The abundance of extremely dense quiescent galaxies at 0.2 < z < 0.6 is in excellent agreement with the number densities of these systems at high redshift. Our lower limits support the models of massive galaxy assembly through a series of minor mergers over the redshift range 0 < z < 2.

  13. Discovery of Nine Intermediate Redshift Compact Quiescent Galaxies in the Sloan Digital Sky Survey

    CERN Document Server

    Damjanov, Ivana; Hwang, Ho Seong; Geller, Margaret J

    2013-01-01

    We identify nine galaxies with dynamical masses of M_dyn>10^10 M_sol as photometric point sources, but with redshifts between z=0.2 and z=0.6, in the Sloan Digital Sky Survey (SDSS) spectro-photometric database. All nine galaxies have archival Hubble Space Telescope (HST) images. Surface brightness profile fitting confirms that all nine galaxies are extremely compact (with circularized half-light radii between 0.4 and 6.6 kpc and the median value of 0.74 kpc) for their velocity dispersion (1101 galaxies and the other eight objects follow the high-redshift dynamical size-mass relation.

  14. GTC Photometric Calibration

    Science.gov (United States)

    di Cesare, M. A.; Hammersley, P. L.; Rodriguez Espinosa, J. M.

    2006-06-01

    We are currently developing the calibration programme for GTC using techniques similar to the ones use for the space telescope calibration (Hammersley et al. 1998, A&AS, 128, 207; Cohen et al. 1999, AJ, 117, 1864). We are planning to produce a catalogue with calibration stars which are suitable for a 10-m telescope. These sources will be not variable, non binary and do not have infrared excesses if they are to be used in the infrared. The GTC science instruments require photometric calibration between 0.35 and 2.5 microns. The instruments are: OSIRIS (Optical System for Imaging low Resolution Integrated Spectroscopy), ELMER and EMIR (Espectrógrafo Multiobjeto Infrarrojo) and the Acquisition and Guiding boxes (Di Césare, Hammersley, & Rodriguez Espinosa 2005, RevMexAA Ser. Conf., 24, 231). The catalogue will consist of 30 star fields distributed in all of North Hemisphere. We will use fields containing sources over the range 12 to 22 magnitude, and spanning a wide range of spectral types (A to M) for the visible and near infrared. In the poster we will show the method used for selecting these fields and we will present the analysis of the data on the first calibration fields observed.

  15. Redshift estimation from low-resolution prism SEDs with an NGST MOS

    OpenAIRE

    Teplitz, Harry I.; Malumuth, Eliot; Woodgate, Bruce E.; Moseley, S. Harvey; Gardner, Jonathan P.; Kimble, Randy A.; Bowers, Charles W.; Kutyrev, Alexander S.; Fettig, Rainer K.; Wesenberg, Richard P.; Mentzell, John E.

    2000-01-01

    We discuss the utility of a low resolution prism as a component of a Multi-Object Spectrometer for NASA's proposed Next Generation Space Telescope (NGST). Low resolution prism spectroscopy permits simultaneous observation of the 0.6-5micron wavelength regime at R~50. To such data we can apply the modern techniques in spectral energy distribution (SED) fitting to determine source redshifts, sometimes called ``photometric redshifts''. Low resolution prism observations of galaxy SED's provide a ...

  16. Sudden stratospheric warmings as catastrophes

    Science.gov (United States)

    Chao, W. C.

    1985-01-01

    The sudden stratospheric warming (SSW) process is qualitatively studied using a conceptual and numerical approach guided by catastrophe theory. A simple example of a catastrophe taken from nonlinear dynamics is given, and results from previous modelling studies of SSW are interpreted in light of catastrophe theory. Properties of this theory such as hysteresis, cusp, and triggering essential to SSW are numerically demonstrated using the truncated quasi-geostrophic beta-plane model of Holton and Mass (1976). A qualitative explanation of the transition from the steady regime to the vacillation regime is given for the Holton and Mass model in terms of the topographically induced barotropic Rossby wave instability. Some implications for the simulation and prediction of SSW are discussed.

  17. Photometric Selection of Emission Line Galaxies, Clustering Analysis and a Search for the ISW effect

    CERN Document Server

    Bielby, Rich; Sawangwit, U; Croom, S M; Ross, Nicholas P; Wake, D A

    2009-01-01

    We investigate the use of simple colour cuts applied to the SDSS optical imaging to perform photometric selections of emission line galaxies out to z<1. From colour-cuts using the SDSS g, r and i bands, we obtain mean photometric redshifts of z=0.32+-0.08, z=0.44+-0.12 and z=0.65+-0.21. We further calibrate our high redshift selection using spectroscopic observations with the AAOmega spectrograph on the 4m Anglo-Australian Telescope (AAT), observing ~50-200 galaxy candidates in 4 separate fields. With just 1-hour of integration time and with seeing of ~1.6", we successfully determined redshifts for ~65% of the targeted candidates. We calculate the angular correlation functions of the samples and find correlation lengths of r0=2.64 h-1 Mpc, r0=3.62 h-1 Mpc and r0=5.88 h-1 Mpc for the low, mid and high redshift samples respectively. Comparing these results with predicted dark matter clustering, we estimate the bias parameter for each sample to be b=0.70, b=0.92 and b=1.46. We calculate the 2-point redshift-s...

  18. Photometric Supernova Classification with Machine Learning

    Science.gov (United States)

    Lochner, Michelle; McEwen, Jason D.; Peiris, Hiranya V.; Lahav, Ofer; Winter, Max K.

    2016-08-01

    Automated photometric supernova classification has become an active area of research in recent years in light of current and upcoming imaging surveys such as the Dark Energy Survey (DES) and the Large Synoptic Survey Telescope, given that spectroscopic confirmation of type for all supernovae discovered will be impossible. Here, we develop a multi-faceted classification pipeline, combining existing and new approaches. Our pipeline consists of two stages: extracting descriptive features from the light curves and classification using a machine learning algorithm. Our feature extraction methods vary from model-dependent techniques, namely SALT2 fits, to more independent techniques that fit parametric models to curves, to a completely model-independent wavelet approach. We cover a range of representative machine learning algorithms, including naive Bayes, k-nearest neighbors, support vector machines, artificial neural networks, and boosted decision trees (BDTs). We test the pipeline on simulated multi-band DES light curves from the Supernova Photometric Classification Challenge. Using the commonly used area under the curve (AUC) of the Receiver Operating Characteristic as a metric, we find that the SALT2 fits and the wavelet approach, with the BDTs algorithm, each achieve an AUC of 0.98, where 1 represents perfect classification. We find that a representative training set is essential for good classification, whatever the feature set or algorithm, with implications for spectroscopic follow-up. Importantly, we find that by using either the SALT2 or the wavelet feature sets with a BDT algorithm, accurate classification is possible purely from light curve data, without the need for any redshift information.

  19. A New Redshift Interpretation

    CERN Document Server

    Gentry, R V

    1997-01-01

    A nonhomogeneous universe with vacuum energy, but without spacetime expansion, is utilized together with gravitational and Doppler redshifts as the basis for proposing a new interpretation of the Hubble relation and the 2.7K Cosmic Blackbody Radiation.

  20. MARZ: Redshifting Program

    Science.gov (United States)

    Hinton, Samuel

    2016-05-01

    MARZ analyzes objects and produces high quality spectroscopic redshift measurements. Spectra not matched correctly by the automatic algorithm can be redshifted manually by cycling automatic results, manual template comparison, or marking spectral features. The software has an intuitive interface and powerful automatic matching capabilities on spectra, and can be run interactively or from the command line, and runs as a Web application. MARZ can be run on a local server; it is also available for use on a public server.

  1. Redshift and Energy Conservation

    OpenAIRE

    Macleod, Alasdair

    2004-01-01

    It has always been considered a serious error to treat the cosmological redshift as a Doppler velocity effect rather than the result of space expansion. It is demonstrated here that in practical terms this is not the case, and that the apparent distance - redshift relation derived from a Doppler interpretation is reasonably consistent with supernova data (though not as good as the standard model with dark energy). The normal Doppler effect is examined in detail and shown to conserve energy as...

  2. The K20 survey. III. Photometric and spectroscopic properties of the sample

    CERN Document Server

    Cimatti, A; Daddi, E; Pozzetti, L; Fontana, A; Saracco, P; Poli, F; Renzini, A; Zamorani, G; Broadhurst, T J; Cristiani, S; D'Odorico, S; Giallongo, E; Gilmozzi, R; Menci, N

    2002-01-01

    The K20 survey is an ESO VLT optical and near-infrared spectroscopic survey aimed at obtaining spectral information and redshifts of a complete sample of about 550 objects to K_s\\leq20.0 over two independent fields with a total area of 52 arcmin^2. In this paper we discuss the scientific motivation of such a survey, we describe the photometric and spectroscopic properties of the sample, and we release the $K_s$-band photometric catalog. Extensive simulations showed that the sample is photometrically highly complete to K_s=20. The observed galaxy counts and the R-K_s color distribution are consistent with literature results. We observed spectroscopically 94% of the sample, reaching a spectroscopic redshift identification completeness of 92% to K_s\\leq20.0 for the observed targets, and of 87% for the whole sample (i.e. counting also the unobserved targets). Deep spectroscopy was complemented with multi-band deep imaging in order to derive tested and reliable photometric redshifts for the galaxies lacking spectr...

  3. Radio-loud high-redshift protogalaxy canidates in Bootes

    Energy Technology Data Exchange (ETDEWEB)

    Croft, S; van Breugel, W; Brown, M J; de Vries, W; Dey, A; Eisenhardt, P; Jannuzi, B; Rottgering, H; Stanford, S A; Stern, D; Willner, S P

    2007-07-20

    We used the Near Infrared Camera (NIRC) on Keck I to obtain K{sub s}-band images of four candidate high-redshift radio galaxies selected using optical and radio data in the NOAO Deep Wide-Field Survey in Bootes. Our targets have 1.4 GHz radio flux densities greater than 1 mJy, but are undetected in the optical. Spectral energy distribution fitting suggests that three of these objects are at z > 3, with radio luminosities near the FR-I/FR-II break. The other has photometric redshift z{sub phot} = 1.2, but may in fact be at higher redshift. Two of the four objects exhibit diffuse morphologies in K{sub s}-band, suggesting that they are still in the process of forming.

  4. On the Number of Galaxies at High Redshift

    Directory of Open Access Journals (Sweden)

    Lorenzo Zaninetti

    2015-09-01

    Full Text Available The number of galaxies at a given flux as a function of the redshift, z, is derived when the z-distance relation is non-standard. In order to compare different models, the same formalism is also applied to the standard cosmology. The observed luminosity function for galaxies of the zCOSMOS catalog at different redshifts is modeled by a new luminosity function for galaxies, which is derived by the truncated beta probability density function. Three astronomical tests, which are the photometric maximum as a function of the redshift for a fixed flux, the mean value of the redshift for a fixed flux, and the luminosity function for galaxies as a function of the redshift, compare the theoretical values of the standard and non-standard model with the observed value. The tests are performed on the FORS Deep Field (FDF catalog up to redshift z = 1.5 and on the zCOSMOS catalog extending beyond z = 4. These three tests show minimal differences between the standard and the non-standard models.

  5. The Climate Catastrophe as Blockbuster

    DEFF Research Database (Denmark)

    Eskjær, Mikkel Fugl

    2013-01-01

    Modern disaster films constitute a specific cultural form that speaks to the anxieties of the “risk society.” This essay looks at how risks like climate change is presented and constructed in popular culture. It regards blockbuster representations as part of a wider discourse of “catastrophism...

  6. Constructive criterion of catastrophe inevitability

    International Nuclear Information System (INIS)

    A mathematical procedure is proposed for the constructive criteria of nuclear catastrophe inevitability. It was concluded that the procedure can fulfill the objective set, and it allows to make a full formal safety classification of object states. (N.T.). 1 ref., 1 fig

  7. High-Redshift Quasars Found in Sloan Digital Sky Survey Commissioning Data

    OpenAIRE

    SDSS Collaboration; Fan, X

    1999-01-01

    We present photometric and spectroscopic observations of 15 high-redshift quasars (z > 3.6) discovered from ~140 deg^2 of five-color (u'g'r'i'z') imaging data taken by the Sloan Digital Sky Survey (SDSS) during its commissioning phase. The quasars are selected by their distinctive colors in SDSS multicolor space. Four of the quasars have redshifts higher than 4.6 (z=4.63, 4.75, 4.90 and 5.00, the latter being the highest redshift quasar yet known). In addition, two previously known z > 4 obje...

  8. On the gravitational redshift

    CERN Document Server

    Wilhelm, Klaus

    2013-01-01

    The study of the gravitational redshift -- a relative wavelength increase of $\\approx 2 \\times 10^{-6}$ was predicted for solar radiation by Einstein in 1908 -- is still an important subject in modern physics. In a dispute whether or not atom interferometry experiments can be employed for gravitational redshift measurements, two research teams have recently disagreed on the physical cause of the shift. Regardless of any discussion on the interferometer aspect -- we find that both groups of authors miss the important point that the ratio of gravitational to the electrostatic forces is generally very small. For instance, the gravitational force acting on an electron in a hydrogen atom situated in the Sun's photosphere to the electrostatic force between the proton and the electron is approximately $3 \\times 10^{-21}$. A comparison of this ratio with the predicted and observed solar redshift indicates a discrepancy of many orders of magnitude. Here we show, with Einstein's early assumption of the frequency of spe...

  9. Sky Mining - Application to Photomorphic Redshift Estimation

    Science.gov (United States)

    Nayak, Pragyansmita

    The field of astronomy has evolved from the ancient craft of observing the sky. In it's present form, astronomers explore the cosmos not just by observing through the tiny visible window used by our eyes, but also by exploiting the electromagnetic spectrum from radio waves to gamma rays. The domain is undoubtedly at the forefront of data-driven science. The data growth rate is expected to be around 50%--100% per year. This data explosion is attributed largely to the large-scale wide and deep surveys of the different regions of the sky at multiple wavelengths (both ground and space-based surveys). This dissertation describes the application of machine learning methods to the estimation of galaxy redshifts leveraging such a survey data. Galaxy is a large system of stars held together by mutual gravitation and isolated from similar systems by vast regions of space. Our view of the universe is closely tied to our understanding of galaxy formation. Thus, a better understanding of the relative location of the multitudes of galaxies is crucial. The position of each galaxy can be characterized using three coordinates. Right Ascension (ra) and Declination (dec) are the two coordinates that locate the galaxy in two dimensions on the plane of the sky. It is relatively straightforward to measure them. In contrast, fixing the third coordinate that is the galaxy's distance from the observer along the line of sight (redshift 'z') is considerably more challenging. "Spectroscopic redshift" method gives us accurate and precise measurements of z. However, it is extremely time-intensive and unusable for faint objects. Additionally, the rate at which objects are being identified via photometric surveys far exceeds the rate at which the spectroscopic redshift measurements can keep pace in determining their distance. As the surveys go deeper into the sky, the proportion of faint objects being identified also continues to increase. In order to tackle both these drawbacks increasing in

  10. Redshift and Shear Calibration: Impact on Cosmic Shear Studies and Survey Design

    CERN Document Server

    Waerbeke, V

    2006-01-01

    The cosmological interpretation of weak lensing by large-scale structures requires knowledge of the redshift distribution of the source galaxies. Current lensing surveys are often calibrated using external redshift samples which span a significantly smaller sky area in comparison to the lensing survey, and are thus subject to sample variance. Some future lensing surveys are expected to be calibrated in the same way, in particular the fainter galaxy populations where the entire color coverage, and hence photometric redshift estimate, could be challenging to obtain. Using N-body simulations, we study the impact of this sample variance on cosmic shear analysis and show that, to first approximation, it behaves like a shear calibration error 1+/-epsilon. Using the Hubble Deep Field as a redshift calibration survey could therefore be a problem for current lensing surveys. We discuss the impact of the redshift distribution sampling error and a shear calibration error on the design of future lensing surveys, and find...

  11. Redshift Measurement and Spectral Classification for eBOSS Galaxies with the Redmonster Software

    CERN Document Server

    Hutchinson, Timothy A; Dawson, Kyle S; Prieto, Carlos Allende; Bailey, Stephen; Bautista, Julian E; Brownstein, Joel R; Conroy, Charlie; Guy, Julien; Myers, Adam D; Newman, Jeffrey A; Prakash, Abhishek; Carnero-Rosell, Aurelio; Seo, Hee-Jong; Vivek, M; Zhu, Guangtun Ben

    2016-01-01

    We describe the redmonster automated redshift measurement and spectral classification software designed for the extended Baryon Oscillation Spectroscopic Survey (eBOSS) of the Sloan Digital Sky Survey IV (SDSS-IV). We describe the algorithms, the template standard and requirements, and the newly developed galaxy templates to be used on eBOSS spectra. We present results from testing on early data from eBOSS, where we have found a 90.5% automated redshift and spectral classification success rate for the luminous red galaxy sample (redshifts 0.6 $\\lesssim$ $z$ $\\lesssim$ 1.0). The \\texttt{redmonster} performance meets the eBOSS cosmology requirements for redshift classification and catastrophic failures, and represents a significant improvement over the previous pipeline. We describe the empirical processes used to determine the optimum number of additive polynomial terms in our models and an acceptable $\\Delta\\chi_r^2$ threshold for declaring statistical confidence. Statistical errors on redshift measurement du...

  12. The DEEP2 Galaxy Redshift Survey: Design, Observations, Data Reduction, and Redshifts

    Science.gov (United States)

    Newman, Jeffrey A.; Cooper, Michael C.; Davis, Marc; Faber, S. M.; Coil, Alison L; Guhathakurta, Puraga; Koo, David C.; Phillips, Andrew C.; Conroy, Charlie; Dutton, Aaron A.; Finkbeiner, Douglas P.; Gerke, Brian F.; Rosario, David J.; Weiner, Benjamin J.; Wilmer, C. N. A.; Yan, Renbin; Harker, Justin J.; Kassin, Susan A.; Konidaris, N. P.; Lai, Kamson; Madgwick, Darren S.; Noeske, K. G.; Wirth, Gregory D.; Kirby, Evan N.; Lotz, Jennifer M.

    2013-01-01

    We describe the design and data analysis of the DEEP2 Galaxy Redshift Survey, the densest and largest high-precision redshift survey of galaxies at z approx. 1 completed to date. The survey was designed to conduct a comprehensive census of massive galaxies, their properties, environments, and large-scale structure down to absolute magnitude MB = -20 at z approx. 1 via approx.90 nights of observation on the Keck telescope. The survey covers an area of 2.8 Sq. deg divided into four separate fields observed to a limiting apparent magnitude of R(sub AB) = 24.1. Objects with z approx. galaxies with z > 0.7 to be targeted approx. 2.5 times more efficiently than in a purely magnitude-limited sample. Approximately 60% of eligible targets are chosen for spectroscopy, yielding nearly 53,000 spectra and more than 38,000 reliable redshift measurements. Most of the targets that fail to yield secure redshifts are blue objects that lie beyond z approx. 1.45, where the [O ii] 3727 Ang. doublet lies in the infrared. The DEIMOS 1200 line mm(exp -1) grating used for the survey delivers high spectral resolution (R approx. 6000), accurate and secure redshifts, and unique internal kinematic information. Extensive ancillary data are available in the DEEP2 fields, particularly in the Extended Groth Strip, which has evolved into one of the richest multiwavelength regions on the sky. This paper is intended as a handbook for users of the DEEP2 Data Release 4, which includes all DEEP2 spectra and redshifts, as well as for the DEEP2 DEIMOS data reduction pipelines. Extensive details are provided on object selection, mask design, biases in target selection and redshift measurements, the spec2d two-dimensional data-reduction pipeline, the spec1d automated redshift pipeline, and the zspec visual redshift verification process, along with examples of instrumental signatures or other artifacts that in some cases remain after data reduction. Redshift errors and catastrophic failure rates are assessed

  13. Redshift evolution of clustering

    CERN Document Server

    Matarrese, S; Lucchin, F; Moscardini, L; Matarrese, Sabino; Coles, Peter; Lucchin, Francesco; Moscardini, Lauro

    1996-01-01

    We discuss how the redshift dependence of the observed two-point correlation function of various classes of objects can be related to theoretical predictions. This relation involves first a calculation of the redshift evolution of the underlying matter correlations. The next step is to relate fluctuations in mass to those of any particular class of cosmic objects; in general terms, this means a model for the bias and how it evolves with cosmic epoch. Only after these two effects have been quantified can one perform an appropriate convolution of the non-linearly evolved two-point correlation function of the objects with their redshift distribution to obtain the `observed' correlation function for a given sample. This convolution in itself tends to mask the effect of evolution by mixing amplitudes at different redshifts. We develop a formalism which incorporates these requirements and, in particular, a set of plausible models for the evolution of the bias factor. We apply this formalism to the spatial, angular ...

  14. Coping with ecological catastrophe: crossing major thresholds

    Directory of Open Access Journals (Sweden)

    John Cairns, Jr.

    2004-08-01

    Full Text Available The combination of human population growth and resource depletion makes catastrophes highly probable. No long-term solutions to the problems of humankind will be discovered unless sustainable use of the planet is achieved. The essential first step toward this goal is avoiding or coping with global catastrophes that result from crossing major ecological thresholds. Decreasing the number of global catastrophes will reduce the risks associated with destabilizing ecological systems, which could, in turn, destabilize societal systems. Many catastrophes will be local, regional, or national, but even these upheavals will have global consequences. Catastrophes will be the result of unsustainable practices and the misuse of technology. However, avoiding ecological catastrophes will depend on the development of eco-ethics, which is subject to progressive maturation, comments, and criticism. Some illustrative catastrophes have been selected to display some preliminary issues of eco-ethics.

  15. The high redshift Integrated Sachs-Wolfe effect

    International Nuclear Information System (INIS)

    In this paper we rely on the quasar (QSO) catalog of the Sloan Digital Sky Survey Data Release Six (SDSS DR6) of about one million photometrically selected QSOs to compute the Integrated Sachs-Wolfe (ISW) effect at high redshift, aiming at constraining the behavior of the expansion rate and thus the behaviour of dark energy at those epochs. This unique sample significantly extends previous catalogs to higher redshifts while retaining high efficiency in the selection algorithm. We compute the auto-correlation function (ACF) of QSO number density from which we extract the bias and the stellar contamination. We then calculate the cross-correlation function (CCF) between QSO number density and Cosmic Microwave Background (CMB) temperature fluctuations in different subsamples: at high z > 1.5 and low z 1.5. We focus on the capabilities of the ISW to constrain the behaviour of the dark energy component at high redshift both in the Λ CDM and Early Dark Energy cosmologies, when the dark energy is substantially unconstrained by observations. At present, the inclusion of the ISW data results in a poor improvement compared to the obtained constraints from other cosmological datasets. We study the capabilities of future high-redshift QSO survey and find that the ISW signal can improve the constraints on the most important cosmological parameters derived from Planck CMB data, including the high redshift dark energy abundance, by a factor ∼ 1.5

  16. Using Morphology to Identify Galaxy Mergers at High Redshift

    Science.gov (United States)

    Blancato, Kirsten; Kartaltepe, J. S.; CANDELS Collaboration

    2014-01-01

    We analyzed a set of 22,003 galaxies in three of the five CANDELS fields: COSMOS, UDS, and GOODS-S, in order to determine how well automated image statistics did with classifying galaxy morphology and mergers at high redshifts (z > 1). For each galaxy in our set, we have multi-wavelength data, photometric redshifts from SED fitting, visual classifications from the CANDELS structure and morphology group, and automated image statistics. The redshifts of our sample range from z = .01 to 4 with = 1.33. We constructed a conservative set of 1,914 galaxies that we believe to be mergers and interactions. Of this set of merging galaxies, 1,343 were at a redshift greater than z = 1. We also identified a conservative set of 535 spheroids and a set of 2,902 disks. Several different quantitative methods were then used to attempt an automated classification of these visually classified samples. Of the different image statistics, we found M20 and Gini to be the most successful at picking out high redshift mergers and morphological characteristics. Blancato was supported by the NOAO/KPNO Research Experiences for Undergraduates (REU) Program which is funded by the National Science Foundation Research Experiences for Undergraduates Program (AST-1262829).

  17. Catastrophic events and older adults.

    Science.gov (United States)

    Cloyd, Elizabeth; Dyer, Carmel B

    2010-12-01

    The plight of older adults during catastrophic events is a societal concern. Older persons have an increased prevalence of cognitive disorders, chronic illnesses, and mobility problems that limit their ability to cope. These disorders may result in a lack of mental capacity and the ability to discern when they should evacuate or resolve problems encountered during a catastrophe. Some older persons may have limited transportation options, and many of the elderly survivors are at increased risk for abuse, neglect, and exploitation. Recommendations for future catastrophic events include the development of a federal tracking system for elders and other vulnerable adults, the designation of separate shelter areas for elders and other vulnerable adults, and involvement of gerontological professionals in all aspects of emergency preparedness and care delivery, including training of frontline workers. Preparation through preevent planning that includes region-specific social services, medical and public health resources, volunteers, and facilities for elders and vulnerable adults is critical. Elders need to be protected from abuse and fraud during catastrophic events. A public health triage system for elders and other vulnerable populations in pre- and postdisaster situations is useful, and disaster preparedness is paramount. Communities and members of safety and rescue teams must address ethical issues before an event. When older adults are involved, consideration needs to be given to triage decision making, transporting those who are immobile, the care of older adults who receive palliative care, and the equitable distribution of resources. Nurses are perfectly equipped with the skills, knowledge, and training needed to plan and implement disaster preparedness programs. In keeping with the tradition of Florence Nightingale, nurses can assume several crucial roles in disaster preparedness for older adults. Nurses possess the ability to participate and lead community

  18. The ALHAMBRA survey: accurate merger fractions derived by PDF analysis of photometrically close pairs

    Science.gov (United States)

    López-Sanjuan, C.; Cenarro, A. J.; Varela, J.; Viironen, K.; Molino, A.; Benítez, N.; Arnalte-Mur, P.; Ascaso, B.; Díaz-García, L. A.; Fernández-Soto, A.; Jiménez-Teja, Y.; Márquez, I.; Masegosa, J.; Moles, M.; Pović, M.; Aguerri, J. A. L.; Alfaro, E.; Aparicio-Villegas, T.; Broadhurst, T.; Cabrera-Caño, J.; Castander, F. J.; Cepa, J.; Cerviño, M.; Cristóbal-Hornillos, D.; Del Olmo, A.; González Delgado, R. M.; Husillos, C.; Infante, L.; Martínez, V. J.; Perea, J.; Prada, F.; Quintana, J. M.

    2015-04-01

    Aims: Our goal is to develop and test a novel methodology to compute accurate close-pair fractions with photometric redshifts. Methods: We improved the currently used methodologies to estimate the merger fraction fm from photometric redshifts by (i) using the full probability distribution functions (PDFs) of the sources in redshift space; (ii) including the variation in the luminosity of the sources with z in both the sample selection and the luminosity ratio constrain; and (iii) splitting individual PDFs into red and blue spectral templates to reliably work with colour selections. We tested the performance of our new methodology with the PDFs provided by the ALHAMBRA photometric survey. Results: The merger fractions and rates from the ALHAMBRA survey agree excellently well with those from spectroscopic work for both the general population and red and blue galaxies. With the merger rate of bright (MB ≤ -20-1.1z) galaxies evolving as (1 + z)n, the power-law index n is higher for blue galaxies (n = 2.7 ± 0.5) than for red galaxies (n = 1.3 ± 0.4), confirming previous results. Integrating the merger rate over cosmic time, we find that the average number of mergers per galaxy since z = 1 is Nmred = 0.57 ± 0.05 for red galaxies and Nmblue = 0.26 ± 0.02 for blue galaxies. Conclusions: Our new methodology statistically exploits all the available information provided by photometric redshift codes and yields accurate measurements of the merger fraction by close pairs from using photometric redshifts alone. Current and future photometric surveys will benefit from this new methodology. Based on observations collected at the German-Spanish Astronomical Center, Calar Alto, jointly operated by the Max-Planck-Institut für Astronomie (MPIA) at Heidelberg and the Instituto de Astrofísica de Andalucía (CSIC).The catalogues, probabilities, and figures of the ALHAMBRA close pairs detected in Sect. 5.1 are available at http://https://cloud.iaa.csic.es/alhambra/catalogues/ClosePairs

  19. Low X-Ray Luminosity Galaxy Clusters: Main Goals, Sample Selection, Photometric and Spectroscopic Observations

    Science.gov (United States)

    Nilo Castellón, José Luis; Alonso, M. Victoria; García Lambas, Diego; Valotto, Carlos; O’ Mill, Ana Laura; Cuevas, Héctor; Carrasco, Eleazar R.; Ramírez, Amelia; Astudillo, José M.; Ramos, Felipe; Jaque Arancibia, Marcelo; Ulloa, Natalie; Órdenes, Yasna

    2016-06-01

    We present our study of 19 low X-ray luminosity galaxy clusters (L{}X ∼ 0.5–45 × 1043 erg s‑1), selected from the ROSAT Position Sensitive Proportional Counters Pointed Observations and the revised version of Mullis et al. in the redshift range of 0.16–0.7. This is the introductory paper of a series presenting the sample selection, photometric and spectroscopic observations, and data reduction. Photometric data in different passbands were taken for eight galaxy clusters at Las Campanas Observatory; three clusters at Cerro Tololo Interamerican Observatory; and eight clusters at the Gemini Observatory. Spectroscopic data were collected for only four galaxy clusters using Gemini telescopes. Using the photometry, the galaxies were defined based on the star-galaxy separation taking into account photometric parameters. For each galaxy cluster, the catalogs contain the point-spread function and aperture magnitudes of galaxies within the 90% completeness limit. They are used together with structural parameters to study the galaxy morphology and to estimate photometric redshifts. With the spectroscopy, the derived galaxy velocity dispersion of our clusters ranged from 507 km s‑1 for [VMF98]022 to 775 km s‑1 for [VMF98]097 with signs of substructure. Cluster membership has been extensively discussed taking into account spectroscopic and photometric redshift estimates. In this sense, members are the galaxies within a projected radius of 0.75 Mpc from the X-ray emission peak and with clustercentric velocities smaller than the cluster velocity dispersion or 6000 km s‑1, respectively. These results will be used in forthcoming papers to study, among the main topics, the red cluster sequence, blue cloud and green populations, the galaxy luminosity function, and cluster dynamics.

  20. Low X-Ray Luminosity Galaxy Clusters: Main goals, sample selection, photometric and spectroscopic observations

    CERN Document Server

    Castellón, J L Nilo; Lambas, D García; Valotto, Carlos; Mill, A L O'; Cuevas, H; Carrasco, E R; Ramírez, A; Astudillo, J M; Ramos, F; Jaque, M; Ulloa, N; Órdenes, Y

    2016-01-01

    We present the study of nineteen low X-ray luminosity galaxy clusters (L$_X \\sim$ 0.5--45 $\\times$ $10^{43}$ erg s$^{-1}$), selected from the ROSAT Position Sensitive Proportional Counters (PSPC) Pointed Observations (Vikhlinin et al. 1998) and the revised version of Mullis et al. (2003) in the redshift range of 0.16 to 0.7. This is the introductory paper of a series presenting the sample selection, photometric and spectroscopic observations and data reduction. Photometric data in different passbands were taken for eight galaxy clusters at Las Campanas Observatory; three clusters at Cerro Tololo Interamerican Observatory; and eight clusters at the Gemini Observatory. Spectroscopic data were collected for only four galaxy clusters using Gemini telescopes. With the photometry, the galaxies were defined based on the star-galaxy separation taking into account photometric parameters. For each galaxy cluster, the catalogues contain the PSF and aperture magnitudes of galaxies within the 90\\% completeness limit. They...

  1. The ALHAMBRA survey: Accurate merger fractions by PDF analysis of photometric close pairs

    CERN Document Server

    López-Sanjuan, C; Varela, J; Viironen, K; Molino, A; Benítez, N; Arnalte-Mur, P; Ascaso, B; Díaz-García, L A; Fernández-Soto, A; Jiménez-Teja, Y; Márquez, I; Masegosa, J; Moles, M; Pović, M; Aguerri, J A L; Alfaro, E; Aparicio-Villegas, T; Broadhurst, T; Cabrera-Caño, J; Castander, J F; Cepa, J; Cerviño, M; Cristóbal-Hornillos, D; Del Olmo, A; Delgado, R M González; Husillos, C; Infante, L; Martínez, V J; Perea, J; Prada, F; Quintana, J M

    2014-01-01

    Our goal is to develop and test a novel methodology to compute accurate close pair fractions with photometric redshifts. We improve the current methodologies to estimate the merger fraction f_m from photometric redshifts by (i) using the full probability distribution functions (PDFs) of the sources in redshift space, (ii) including the variation in the luminosity of the sources with z in both the selection of the samples and in the luminosity ratio constrain, and (iii) splitting individual PDFs into red and blue spectral templates to deal robustly with colour selections. We test the performance of our new methodology with the PDFs provided by the ALHAMBRA photometric survey. The merger fractions and rates from the ALHAMBRA survey are in excellent agreement with those from spectroscopic work, both for the general population and for red and blue galaxies. With the merger rate of bright (M_B <= -20 - 1.1z) galaxies evolving as (1+z)^n, the power-law index n is larger for blue galaxies (n = 2.7 +- 0.5) than fo...

  2. High redshift detection of the integrated Sachs-Wolfe effect

    International Nuclear Information System (INIS)

    We present evidence of a large angle correlation between the cosmic microwave background measured by WMAP and a catalog of photometrically detected quasars from the SDSS. The observed cross correlation is 0.30±0.14 μK at zero lag, with a shape consistent with that expected for correlations arising from the integrated Sachs-Wolfe effect. The photometric redshifts of the quasars are centered at z∼1.5, making this the deepest survey in which such a correlation has been observed. Assuming this correlation is due to the ISW effect, this constitutes the earliest evidence yet for dark energy and it can be used to constrain exotic dark energy models

  3. Is Geothermal Simulation a "Catastrophe"?

    Energy Technology Data Exchange (ETDEWEB)

    Nguyen, V.V.; Pinder, George F.

    1980-12-16

    All numerical simulators of geothermal reservoirs depend upon an accurate representation of the thermodynamics of steam-water systems. These relationships are required to render tractable the system of balance equations derived from the physics of flow through porous media. While it is generally recognized that the steam-water system (i.e. two phase) is not in thermodynamic equilibrium, equihbrium thermodynamics are employed in its description. In this paper, we present an alternative view based on non-equilibrium thermodynamics. The underpinnings of this approach are found in a branch of topology generally referred to as "catastrophe theory". [Thom, 1975

  4. Is geothermal simulation a catastrophe

    Energy Technology Data Exchange (ETDEWEB)

    Nguyen, V.V.; Pinder, G.F.

    1980-01-01

    All numerical simulators of geothermal reservoirs depend upon an accurate representation of the thermodynamics of steam-water systems. These relationships are required to render tractable the system of balance equations derived from the physics of flow through porous media. While it is generally recognized that the steam-water system (i.e., two phase) is not in thermodynamic equilibrium, equilibrium thermodynamics are employed in its description. An alternative view based on non-equilibrium thermodynamics is presented. The underpinnings of this approach are found in a branch of topology generally referred to as catastrophe theory.

  5. A catastrophe in quantum mechanics

    International Nuclear Information System (INIS)

    The standard scattering theory (SST) in nonrelativistic quantum mechanics (QM) is analyzed. Self-contradictions of SST are deconstructed. A direct way to calculate scattering probability without introduction of a finite volume is discussed. Substantiation of SST in textbooks with the help of wave packets is shown to be incomplete. A complete theory of wave packet scattering on a fixed center is presented, and its similarity to the plane wave scattering is demonstrated. The neutron scattering on a monatomic gas is investigated, and several problems are pointed out. A catastrophic ambiguity of the cross section is revealed, and a way to resolve this ambiguity is discussed

  6. The Diseconomies of Environmental Catastrophes

    OpenAIRE

    Cairns, John

    2006-01-01

    Four factors are almost certain to lead to one or more catastrophes unless major remedial measures are taken. (1) China has replaced the United States as the world s leading consumer of resources, except for oil (Brown, 2006a), but China is already a major factor in the world market in this area also. Together, China and the United States consume approximately half the world s resources and the global population is still increasing on a finite planet. (2) The over 20% global ecological oversh...

  7. Catastrophic models of materials destruction

    Science.gov (United States)

    Kupchishin, A. I.; Taipova, B. G.; Kupchishin, A. A.; Voronova, N. A.; Kirdyashkin, V. I.; Fursa, T. V.

    2016-02-01

    The effect of concentration and type of fillers on mechanical properties of composite material based on polyimide were studied. Polyethylene terephthalate (PET, polyester), polycarbonate (PCAR) and montmorillonite (MM) were used as the fillers. The samples were prepared by mechanically blending the polyimide-based lacquer solutions with different concentrations of the second component. The concentration of filler and its class, especially their internal structure and technology of synthesis determine features of physical and mechanical properties of obtained materials. Models of catastrophic failure of material satisfactorily describe the main features depending on tension ct from deformation e.

  8. Photometric Variability in Earthshine Observations

    CERN Document Server

    Langford, Sally V; Turner, Edwin L

    2009-01-01

    The identification of an extrasolar planet as Earth-like will depend on the detection of atmospheric signatures or surface non-uniformities. In this paper we present spatially unresolved flux light curves of Earth for the purpose of studying a prototype extrasolar terrestrial planet. Our monitoring of the photometric variability of earthshine revealed changes of up to 23 % per hour in the brightness of Earth's scattered light at around 600 nm, due to the removal of specular reflection from the view of the Moon. This variability is accompanied by reddening of the spectrum, and results from a change in surface properties across the continental boundary between the Indian Ocean and Africa's east coast. Our results based on earthshine monitoring indicate that specular reflection should provide a useful tool in determining the presence of liquid water on extrasolar planets via photometric observations.

  9. Photometric Science Alerts from Gaia

    CERN Document Server

    Wyrzykowski, Lukasz; Blogorodnova, Nadejda; Koposov, Sergey; Burgon, Ross

    2012-01-01

    Gaia is the cornerstone mission of the European Space Agency. From late 2013 it will start collecting superb astrometric, photometric and spectroscopic data for around a billion of stars of our Galaxy. While surveying the whole sky down to V=20mag Gaia will be detecting transients and anomalous behaviour of objects, providing near-real-time alerts to the entire astronomical community. Gaia should detected about 6000 supernovae, 1000 microlensing events and many other interesting types of transients. Thanks to its on-board low-dispersion spectrograph the classification of transients will be robust, assuring low false-alert rate. We describe the operation of the Photometric Science Alerts system, outline the scientific possibilities and conclude with an invitation to collaborate in the ground-based follow-up Gaia alerts during the early months of the mission when the outcome of the alerting pipeline needs to be verified.

  10. Photometric study of IC 2156

    CERN Document Server

    Tadross, A L

    2015-01-01

    The optical UBVRI photometric analysis has been established using SLOAN DIGITAL SKY SURVEY (SDSS database) in order to estimate the astrophysical parameters of poorly studied open star cluster IC 2156. The results of the present study are compared with a previous one of ours, which relied on the 2MASS JHK infrared photometry. The stellar density distributions and color-magnitude diagrams of the cluster are used to determine the geometrical structure; limited radius, core and tidal radii, the distances from the Sun, from the Galactic plane and from the Galactic center. Also, the main photometric parameters; age, distance modulus, color excesses, membership, total mass, luminosity, mass functions and relaxation time; have been estimated.

  11. Photometrics at Sandia National Laboratories

    Energy Technology Data Exchange (ETDEWEB)

    McWilliams, J.Y.; Hill, R.A.; Hughes, R.L. (eds.)

    1990-07-01

    This report highlights Sandia National Laboratories' work in the following areas: photometrics and optical development; still and time-lapse photography; real-time motion photography; high-speed photography; image-motion photography; schlieren photography; ultra-high-speed photography; electronic imaging; shuttered video and high-speed video; infrared imaging radiometry; exoatmospheric photography and videography; microdensitometry and image analysis; and optical system design and development.

  12. Extensional rheometer based on viscoelastic catastrophes outline

    DEFF Research Database (Denmark)

    2014-01-01

    The present invention relates to a method and a device for determining viscoelastic properties of a fluid. The invention resides inter alia in the generation of viscoelastic catastrophes in confined systems for use in the context of extensional rheology. The viscoelastic catastrophe is according to...... the invention generated in a bistable fluid system, and the flow conditions for which the catastrophe occurs can be used as a fingerprint of the fluid's viscoelastic properties in extensional flow....

  13. Galaxy Redshifts from Discrete Optimization of Correlation Functions

    CERN Document Server

    Lee, Benjamin C G; Basu, Amitabh

    2016-01-01

    We propose a new method of constraining the redshifts of individual extragalactic sources based on their celestial coordinates. Techniques from integer linear programming are utilized to optimize simultaneously for the angular two-point cross- and autocorrelation functions. Our novel formalism introduced here not only transforms the otherwise hopelessly expensive, brute-force combinatorial search into a linear system with integer constraints but is also readily implementable in off-the-shelf solvers. We adopt Gurobi and use Python to dynamically build the cost function. The preliminary results on simulated data show great promise for future applications to sky surveys by complementing and enhancing photometric redshift estimators. Our approach is the first use of linear programming in astronomy.

  14. Catastrophe mechanism & classification of discontinuity behavior in thermal science (Ⅰ) --Fold catastrophe

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    The mechanism of discontinuity behavior has important significance in the study of thermal science,such as fire,combustion,explosion and heat transfer.This sort of discontinuity behavior and the catastrophe caused by system nonlinearity may be equivalently classified according to the catastrophe model promulgated by catastrophe theory.Under the conditions of uniform temperature and thermal isolation,the self-ignition behavior of a Semenov System can be viewed as a result of the fold catastrophe of the system.

  15. Combining Spectroscopic and Photometric Surveys: Same or different sky?

    CERN Document Server

    Eriksen, Martin

    2014-01-01

    This article looks at the combined constraints from a photometric and spectroscopic survey. These surveys will measure cosmology using weak lensing (WL), galaxy cluster- ing, baryon acoustic oscillations (BAO) and redshift space distortions (RSD). We find, contrary to some findings in the recent literature, that overlapping surveys can give important benefits when measuring dark energy. We therefore try to clarify the status of this issue with a full forecast of two stage-IV surveys using a new approach to prop- erly account for covariance between the different probes in the overlapping samples. The benefit of the overlapping survey can be traced back to two factors: additional observables and sample variance cancellation. Both needs to be taken into account and contribute equally when combining 3D power spectrum and 2D correlations for lensing. With an analytic example we also illustrate that for optimal constraints, one should minimize the (Pearson) correlation coefficient between cosmological and nui- sanc...

  16. Identifying high-redshift gamma-ray bursts with RATIR

    Energy Technology Data Exchange (ETDEWEB)

    Littlejohns, O. M.; Butler, N. R. [School of Earth and Space Exploration, Arizona State University, AZ 85287 (United States); Cucchiara, A. [Goddard Space Flight Center, Greenbelt, MD 20771 (United States); Watson, A. M.; Lee, W. H.; Richer, M. G.; De Diego, J. A.; Georgiev, L.; González, J.; Román-Zúñiga, C. G. [Instituto de Astronomía, Universidad Nacional Autónoma de México, Apartado Postal 70-264, 04510 México, D. F. (Mexico); Kutyrev, A. S.; Troja, E.; Gehrels, N.; Moseley, H. [NASA, Goddard Space Flight Center, Greenbelt, MD 20771 (United States); Klein, C. R.; Fox, O. D.; Bloom, J. S. [Astronomy Department, University of California, Berkeley, CA 94720-7450 (United States); Prochaska, J. X.; Ramirez-Ruiz, E. [Department of Astronomy and Astrophysics, UCO/Lick Observatory, University of California, 1156 High Street, Santa Cruz, CA 95064 (United States)

    2014-07-01

    We present a template-fitting algorithm for determining photometric redshifts, z {sub phot}, of candidate high-redshift gamma-ray bursts (GRBs). Using afterglow photometry, obtained by the Reionization and Transients InfraRed (RATIR) camera, this algorithm accounts for the intrinsic GRB afterglow spectral energy distribution, host dust extinction, and the effect of neutral hydrogen (local and cosmological) along the line of sight. We present the results obtained by this algorithm and the RATIR photometry of GRB 130606A, finding a range of best-fit solutions, 5.6 < z {sub phot} < 6.0, for models of several host dust extinction laws (none, the Milky Way, Large Magellanic Clouds, and Small Magellanic Clouds), consistent with spectroscopic measurements of the redshift of this GRB. Using simulated RATIR photometry, we find that our algorithm provides precise measures of z {sub phot} in the ranges of 4 < z {sub phot} ≲ 8 and 9 < z {sub phot} < 10 and can robustly determine when z {sub phot} > 4. Further testing highlights the required caution in cases of highly dust-extincted host galaxies. These tests also show that our algorithm does not erroneously find z {sub phot} < 4 when z {sub sim} > 4, thereby minimizing false negatives and allowing us to rapidly identify all potential high-redshift events.

  17. High-Redshift Supernovae in the Hubble Deep Field

    Energy Technology Data Exchange (ETDEWEB)

    Gilliland, R.L. [Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218 (United States); Nugent, P.E. [E.O. Lawrence Berkeley National Laboratory, 1 Cyclotron Road, MS 50-232, Berkeley, CA 94720 (United States); Phillips, M.M. [Carnegie Institution of Washington, Las Campanas Observatory, Casilla 601, La Serena (Chile)

    1999-08-01

    Two supernovae detected in the Hubble Deep Field (HDF) using the original 1995 December epoch and data from a shorter (63,000 s in F814W) 1997 December visit with {ital HST} are discussed. The supernovae (SNe) are both associated with distinct galaxies at redshifts of 0.95 (spectroscopic) from Cohen et al. and 1.32 (photometric) from the work of Fern{acute a}ndez-Soto, Lanzetta, & Yahil. These redshifts are near, in the case of 0.95, and well beyond, for 1.32, the greatest distance reported previously for SNe. We show that our observations are sensitive to supernovae to z{approx_lt}1.8 in either epoch for an event near peak brightness. Detailed simulations are discussed that quantify the level at which false events from our search phase would start to arise and the completeness of our search as a function of both SN brightness and host galaxy redshift. The number of Type Ia and Type II SNe expected as a function of redshift in the two HDF epochs are discussed in relation to several published predictions and our own detailed calculations. A mean detection frequency of one SN per epoch for the small HDF area is consistent with expectations from current theory. {copyright} {ital {copyright} 1999.} {ital The American Astronomical Society}

  18. High Redshift Supernovae in the Hubble Deep Field

    CERN Document Server

    Gilliland, R L; Phillips, M M; Gilliland, Ronald L.; Nugent, Peter E.

    1999-01-01

    Two supernovae detected in the Hubble Deep Field using the original December 1995 epoch and data from a shorter (63000 s in F814W) December 1997 visit with HST are discussed. The supernovae (SNe) are both associated with distinct galaxies at redshifts of 0.95 (spectroscopic) from Cohen etal. (1996) and 1.32 (photometric) from the work of Fernandez-Soto, Lanzetta, and Yahil (1998). These redshifts are near, in the case of 0.95, and well beyond for 1.32 the greatest distance reported previously for SNe. We show that our observations are sensitive to SNe to z < 1.8 in either epoch for an event near peak brightness. Detailed simulations are discussed that quantify the level at which false events from our search phase would start to to arise, and the completeness of our search as a function of both SN brightness and host galaxy redshift. The number of Type Ia and Type II SNe expected as a function of redshift in the two HDF epochs are discussed in relation to several published predictions and our own detailed c...

  19. High-Redshift Supernovae in the Hubble Deep Field

    International Nuclear Information System (INIS)

    Two supernovae detected in the Hubble Deep Field (HDF) using the original 1995 December epoch and data from a shorter (63,000 s in F814W) 1997 December visit with HST are discussed. The supernovae (SNe) are both associated with distinct galaxies at redshifts of 0.95 (spectroscopic) from Cohen et al. and 1.32 (photometric) from the work of Fernacute andez-Soto, Lanzetta, and Yahil. These redshifts are near, in the case of 0.95, and well beyond, for 1.32, the greatest distance reported previously for SNe. We show that our observations are sensitive to supernovae to z approx-lt 1.8 in either epoch for an event near peak brightness. Detailed simulations are discussed that quantify the level at which false events from our search phase would start to arise and the completeness of our search as a function of both SN brightness and host galaxy redshift. The number of Type Ia and Type II SNe expected as a function of redshift in the two HDF epochs are discussed in relation to several published predictions and our own detailed calculations. A mean detection frequency of one SN per epoch for the small HDF area is consistent with expectations from current theory. copyright copyright 1999. The American Astronomical Society

  20. Redshifts and Killing Vectors

    CERN Document Server

    Harvey, A; Surowitz, E J; Harvey, Alex; Schucking, Engelbert L.; Surowitz, Eugene J.

    2005-01-01

    Courses in introductory special and general relativity have increasingly become part of the curriculum for upper-level undergraduate physics majors and master's degree candidates. One of the topics rarely discussed is symmetry, particularly in the theory of general relativity. The principal tool for its study is the Killing vector. We provide an elementary introduction to the concept of a Killing vector field, its properties, and as an example of its utility apply these ideas to the rigorous determination of gravitational and cosmological redshifts.

  1. Academic Training: Predicting Natural Catastrophes

    CERN Multimedia

    Françoise Benz

    2005-01-01

    2005-2006 ACADEMIC TRAINING PROGRAMME LECTURE SERIES 12, 13, 14, 15, 16 December from 11:00 to 12:00 - Main Auditorium, bldg. 500 Predicting Natural Catastrophes E. OKAL / Northwestern University, Evanston, USA 1. Tsunamis -- Introduction Definition of phenomenon - basic properties of the waves Propagation and dispersion Interaction with coasts - Geological and societal effects Origin of tsunamis - natural sources Scientific activities in connection with tsunamis. Ideas about simulations 2. Tsunami generation The earthquake source - conventional theory The earthquake source - normal mode theory The landslide source Near-field observation - The Plafker index Far-field observation - Directivity 3. Tsunami warning General ideas - History of efforts Mantle magnitudes and TREMOR algorithms The challenge of 'tsunami earthquakes' Energy-moment ratios and slow earthquakes Implementation and the components of warning centers 4. Tsunami surveys Principles and methodologies Fifteen years of field surveys and re...

  2. Catastrophe Finance: An Emerging Discipline

    Science.gov (United States)

    Elsner, James B.; Burch, R. King; Jagger, Thomas H.

    2009-08-01

    While the recent disasters in the world's financial markets demonstrate that finance theory remains far from perfected, science also faces steep challenges in the quest to predict and manage the effects of natural disasters. Worldwide, as many as half a million people have died in disasters such as earthquakes, tsunamis, and tropical cyclones since the turn of the 21st century [Wirtz, 2008]. Further, natural disasters can lead to extreme financial losses, and independent financial collapses can be exacerbated by natural disasters. In financial cost, 2008 was the second most expensive year on record for such catastrophes and for financial market declines. These extreme events in the natural and financial realms push the issue of risk management to the fore, expose the deficiencies of existing knowledge and practice, and suggest that progress requires further research and training at the graduate level.

  3. Catastrophic disruption experiments: Recent results

    Science.gov (United States)

    Martelli, G.; Ryan, E. V.; Nakamura, A. M.; Giblin, I.

    1994-01-01

    This paper presents a review of the progress in the field of catastrophic disruption experiments over the past 4 years, since the publication of the review paper by Fujiwara et al. (1989). We describe the development of new techniques to produce shattering impacts relevant to the study of the collisional evolution of the asteroids, and summarize the results from numerous experiments which have been performed to date, using a variety of materials for both the impactor and the targets. Some of these, such as ice-on-ice, loose aggregates and pressurized targets, are quite new and have provided novel and exciting results. Some of the gaps existing previously in the data on fragment ejection-angle distributions, as well as translational and rotational velocity fields (including fine fragments) have been filled, and these new results will be surveyed.

  4. A Study of Selection Methods for H alpha Emitting Galaxies at z~1.3 for the Subaru/FMOS Galaxy Redshift Survey for Cosmology (FastSound)

    OpenAIRE

    Tonegawa, Motonari; Totani, Tomonori; Akiyama, Masayuki; Dalton, Gavin; Glazebrook, Karl; Iwamuro, Fumihide; Sumiyoshi, Masanao; Tamura, Naoyuki; Yabe, Kiyoto; Coupon, Jean; Goto, Tomotsugu; Spitler, Lee R.

    2013-01-01

    The efficient selection of high-redshift emission galaxies is important for future large galaxy redshift surveys for cosmology. Here we describe the target selection methods for the FastSound project, a redshift survey for H alpha emitting galaxies at z=1.2-1.5 using Subaru/FMOS to measure the linear growth rate f\\sigma 8 via Redshift Space Distortion (RSD) and constrain the theory of gravity. To select ~400 target galaxies in the 0.2 deg^2 FMOS field-of-view from photometric data of CFHTLS-W...

  5. High-redshift standard candles

    DEFF Research Database (Denmark)

    King, Anthea L.; Davis, Tamara M.; Denney, K. D.; Vestergaard, M.; Watson, D.

    2014-01-01

    dark energy equation of state, $w(z)$, and assess the optimal redshift distribution a high-redshift standard-candle survey could take to constrain these models. The more general the form of the dark energy equation of state $w(z)$ being tested, the more useful high-redshift standard candles become. For......We investigate whether future measurements of high redshift standard candles (HzSCs) will be a powerful probe of dark energy, when compared to other types of planned dark energy measurements. Active galactic nuclei and gamma ray bursts have both been proposed as potential HzSC candidates. Due to...... a linear parameterization of $w(z)$, HzSCs give only small improvements over planned supernova and baryon acoustic oscillation measurements; a wide redshift range with many low redshift points is optimal to constrain this linear model. However to constrain a general, and thus potentially more...

  6. Climate Catastrophe - The Giant Swindle

    International Nuclear Information System (INIS)

    Energy is the life-blood of civilization. More than 80% of global energy is supplied by fossil fuels. And this will continue for the foreseeable future - if an implementation of the Kyoto Protocol does not lead to a dramatic decrease of these fuels causing worldwide turmoil of unprecedented dimensions. However, the scaremongering with a 'climate catastrophe' allegedly caused by 'greenhouse gas' emissions from the burning of fossil fuels is a huge hoax. Its only 'scientific' base is the IPCC management's enigmatic assessment: 'The balance of evidence suggests a discernable human influence on climate'. But even IPCC had to admit at the World Energy Conference in Tokyo in 1996: 'We have no evidence'. And all the scaremongering assertions of the protagonists of 'global warming' have been convincingly refuted by the world elite of scientists. This paper will: - show how the whole anti-CO2 campaign has been manipulated from the very beginning till today; - give great many scientific and logical reason why the arguments of the scaremongers are incorrect; - outline the catastrophic economic and social consequences of the proposed anti-CO2 measures - without any benefit for the environment of climate; - name the driving forces behind this campaign and their interests. The witchhunt against CO2 is an incredible scientific and political scandal, CO2 does not damage the environment at all, and labelling it a 'climate killer' is absurd. On the contrary, this gas is vital for the life on our plant, and a stronger concentration of CO2 will be beneficial by doubling plant growth and with this combatting global famine. And to pretend that we could influence - with a CO2 tax - the climate, is insane arrogance. Man is absolutely helpless when confronted with the forces of nature. The squandering of multimillions USD of taxpayer's money for the travelling circus of 'Climate summits' and the stultification of the population must stop. The 'global warming' lie is the biggest

  7. Catastrophe theory with application in nuclear technology

    International Nuclear Information System (INIS)

    The monograph is structured on the following seven chapters: 1. Correlation of risk, catastrophe and chaos at the level of polyfunctional systems with nuclear injection; 1.1 Approaching the risk at the level of power systems; 1.2 Modelling the chaos-catastrophe-risk correlation in the structure of integrated classical and nuclear processes; 2. Catastrophe theory applied in ecosystems models and applications; 2.1 Posing the problems in catastrophe theory; 2.2 Application of catastrophe theory in the engineering of the power ecosystems with nuclear injection; 4.. Decision of abatement of the catastrophic risk based on minimal costs; 4.1 The nuclear power systems sensitive to risk-catastrophe-chaos in the structure of minimal costs; 4.2 Evaluating the market structure on the basis of power minimal costs; 4.3 Decisions in power systems built on minimal costs; 5. Models of computing the minimal costs in classical and nuclear power systems; 5.1 Calculation methodologies of power minimal cost; 5.2 Calculation methods of minimal costs in nuclear power sector; 6. Expert and neuro expert systems for supervising the risk-catastrophe-chaos correlation; 6.1 The structure of expert systems; 6.2 Application of the neuro expert program; 7. Conclusions and operational proposals; 7.1 A synthesis of the problems presented in this work; 7.2 Highlighting the novel aspects applicable in the power systems with nuclear injection

  8. Adaptation to and Recovery from Global Catastrophe

    Directory of Open Access Journals (Sweden)

    Seth D. Baum

    2013-03-01

    Full Text Available Global catastrophes, such as nuclear war, pandemics and ecological collapse threaten the sustainability of human civilization. To date, most work on global catastrophes has focused on preventing the catastrophes, neglecting what happens to any catastrophe survivors. To address this gap in the literature, this paper discusses adaptation to and recovery from global catastrophe. The paper begins by discussing the importance of global catastrophe adaptation and recovery, noting that successful adaptation/recovery could have value on even astronomical scales. The paper then discusses how the adaptation/recovery could proceed and makes connections to several lines of research. Research on resilience theory is considered in detail and used to develop a new method for analyzing the environmental and social stressors that global catastrophe survivors would face. This method can help identify options for increasing survivor resilience and promoting successful adaptation and recovery. A key point is that survivors may exist in small isolated communities disconnected from global trade and, thus, must be able to survive and rebuild on their own. Understanding the conditions facing isolated survivors can help promote successful adaptation and recovery. That said, the processes of global catastrophe adaptation and recovery are highly complex and uncertain; further research would be of great value.

  9. Fracto—emissions in Catastrophic Cleavage Process

    Institute of Scientific and Technical Information of China (English)

    HonglaiTAN; WeiYANG

    1996-01-01

    Fracto-emissions accompanying crack propagation are observed in the recent experiments.The energy impulses during and after fracture stimulate the fracto-emissions.Model concerning atomic scale cleavage processes is proposed to formulate a catastrophic fracure theory relevant to these phenomena.A criterion for catastrophic jump of the cleavage potential is applied to representative crystals.

  10. 76 FR 50929 - Catastrophic Risk Protection Endorsement

    Science.gov (United States)

    2011-08-17

    ..., published at 48 FR 29115, June 24, 1983. Executive Order 12988 This proposed rule has been reviewed in...; ] DEPARTMENT OF AGRICULTURE Federal Crop Insurance Corporation 7 CFR Part 402 RIN 0563-AC31 Catastrophic Risk... Federal Crop Insurance Corporation (FCIC) proposes to amend the Catastrophic Risk Protection...

  11. Environmental Catastrophes Under Time-inconsistent Preferences

    NARCIS (Netherlands)

    Michielsen, T.O.

    2013-01-01

    Abstract I analyze optimal natural resource use in an intergenerational model with the risk of a catastrophe. Each generation maximizes a weighted sum of discounted utility (positive) and the probability that a catastrophe will occur at any point in the future (negative). The model generates time-in

  12. Catastrophe mechanism and classification of discontinuity behavior in thermal science (Ⅱ) -- Cusp catastrophe

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    The catastrophe mechanisms of thermal performance characteristics of the firebox gas combustion system were analyzed from the viewpoint of catastrophe theory. The mathematical models of cusp catastrophe were established. The relationship between the thermal performance characteristics and the changing of system control variables was studied. The cusp catastrophe mechanisms of typical performance characteristics, such as kicking and lagging, and those of transition from quenching to igniting were explained. It was illustrated that discontinuity behavior of thermal systems with an "S" motion feature curve and lagging feature may be equivalently classified according to the topology of cusp catastrophe, influenced by two groups of independent control variables.

  13. High redshift blazars

    CERN Document Server

    Ghisellini, G

    2013-01-01

    Blazars are sources whose jet is pointing to us. Since their jets are relativistic, the flux is greatly amplified in the direction of motion, making blazars the most powerful persistent objects in the Universe. This is true at all frequencies, but especially where their spectrum peaks. Although the spectrum of moderate powerful sources peaks in the ~GeV range, extremely powerful sources at high redshifts peak in the ~MeV band. This implies that the hard X-ray band is the optimal one to find powerful blazars beyond a redshift of ~4. First indications strongly suggest that powerful high-z blazars harbor the most massive and active early black holes, exceeding a billion solar masses. Since for each detected blazars there must exist hundreds of similar, but misaligned, sources, the search for high-z blazars is becoming competitive with the search of early massive black holes using radio-quiet quasars. Finding how the two populations of black holes (one in jetted sources, the other in radio-quiet objects) evolve i...

  14. Colour Dynamic Photometric Stereo for Textured Surfaces

    OpenAIRE

    Janko, Zsolt; Delaunoy, Amael; Prados, Emmanuel

    2010-01-01

    International audience In this paper we present a novel method to apply photometric stereo on textured dynamic surfaces. We aim at exploiting the high accuracy of photometric stereo and reconstruct local surface orientation from illumination changes. The main difficulty derives from the fact that photometric stereo requires varying illumination while the object remains still, which makes it quite impractical to use for dynamic surfaces. Using coloured lights gives a clear solution to this ...

  15. Sloan Digital Sky Survey Photometric Calibration Revisited

    Energy Technology Data Exchange (ETDEWEB)

    Marriner, John; /Fermilab

    2012-06-29

    The Sloan Digital Sky Survey calibration is revisited to obtain the most accurate photometric calibration. A small but significant error is found in the flat-fielding of the Photometric telescope used for calibration. Two SDSS star catalogs are compared and the average difference in magnitude as a function of right ascension and declination exhibits small systematic errors in relative calibration. The photometric transformation from the SDSS Photometric Telescope to the 2.5 m telescope is recomputed and compared to synthetic magnitudes computed from measured filter bandpasses.

  16. Superresolution under Photometric Diversity of Images

    Directory of Open Access Journals (Sweden)

    Gevrekci Murat

    2007-01-01

    Full Text Available Superresolution (SR is a well-known technique to increase the quality of an image using multiple overlapping pictures of a scene. SR requires accurate registration of the images, both geometrically and photometrically. Most of the SR articles in the literature have considered geometric registration only, assuming that images are captured under the same photometric conditions. This is not necessarily true as external illumination conditions and/or camera parameters (such as exposure time, aperture size, and white balancing may vary for different input images. Therefore, photometric modeling is a necessary task for superresolution. In this paper, we investigate superresolution image reconstruction when there is photometric variation among input images.

  17. Sloan Digital Sky Survey Photometric Calibration Revisited

    Science.gov (United States)

    Marriner, J.

    2016-05-01

    The Sloan Digital Sky Survey calibration is revisited to obtain the most accurate photometric calibration. A small but significant error is found in the flat-fielding of the Photometric telescope used for calibration. Two SDSS star catalogs are compared and the average difference in magnitude as a function of right ascension and declination exhibits small systematic errors in relative calibration. The photometric transformation from the SDSS Photometric Telescope to the 2.5 m telescope is recomputed and compared to synthetic magnitudes computed from measured filter bandpasses.

  18. High-Redshift Quasars Found in Sloan Digital Sky Survey Commissioning Data

    CERN Document Server

    Fan, X

    1999-01-01

    We present photometric and spectroscopic observations of 15 high-redshift quasars (z > 3.6) discovered from ~140 deg^2 of five-color (u'g'r'i'z') imaging data taken by the Sloan Digital Sky Survey (SDSS) during its commissioning phase. The quasars are selected by their distinctive colors in SDSS multicolor space. Four of the quasars have redshifts higher than 4.6 (z=4.63, 4.75, 4.90 and 5.00, the latter being the highest redshift quasar yet known). In addition, two previously known z > 4 objects were recovered from the data. The quasars all have i* < 20 and have luminosities comparable to that of 3C273. The spectra of the quasars have similar features (strong, broad emission lines and substantial absorption blueward of the Ly alpha emission line) seen in previously known high-redshift quasars. Although the photometric accuracy and image quality fail to meet the final survey requirements, our success rate for identifying high-redshift quasars (17 quasars from 27 candidates) is much higher than that of previ...

  19. Improved Linear Algebra Methods for Redshift Computation from Limited Spectrum Data - II

    Science.gov (United States)

    Foster, Leslie; Waagen, Alex; Aijaz, Nabella; Hurley, Michael; Luis, Apolo; Rinsky, Joel; Satyavolu, Chandrika; Gazis, Paul; Srivastava, Ashok; Way, Michael

    2008-01-01

    Given photometric broadband measurements of a galaxy, Gaussian processes may be used with a training set to solve the regression problem of approximating the redshift of this galaxy. However, in practice solving the traditional Gaussian processes equation is too slow and requires too much memory. We employed several methods to avoid this difficulty using algebraic manipulation and low-rank approximation, and were able to quickly approximate the redshifts in our testing data within 17 percent of the known true values using limited computational resources. The accuracy of one method, the V Formulation, is comparable to the accuracy of the best methods currently used for this problem.

  20. Stacking for machine learning redshifts applied to SDSS galaxies

    Science.gov (United States)

    Zitlau, Roman; Hoyle, Ben; Paech, Kerstin; Weller, Jochen; Rau, Markus Michael; Seitz, Stella

    2016-08-01

    We present an analysis of a general machine learning technique called `stacking' for the estimation of photometric redshifts. Stacking techniques can feed the photometric redshift estimate, as output by a base algorithm, back into the same algorithm as an additional input feature in a subsequent learning round. We show how all tested base algorithms benefit from at least one additional stacking round (or layer). To demonstrate the benefit of stacking, we apply the method to both unsupervised machine learning techniques based on self-organizing maps (SOMs), and supervised machine learning methods based on decision trees. We explore a range of stacking architectures, such as the number of layers and the number of base learners per layer. Finally we explore the effectiveness of stacking even when using a successful algorithm such as AdaBoost. We observe a significant improvement of between 1.9 per cent and 21 per cent on all computed metrics when stacking is applied to weak learners (such as SOMs and decision trees). When applied to strong learning algorithms (such as AdaBoost) the ratio of improvement shrinks, but still remains positive and is between 0.4 per cent and 2.5 per cent for the explored metrics and comes at almost no additional computational cost.

  1. Stacking for machine learning redshifts applied to SDSS galaxies

    CERN Document Server

    Zitlau, Roman; Paech, Kerstin; Weller, Jochen; Rau, Markus Michael; Seitz, Stella

    2016-01-01

    We present an analysis of a general machine learning technique called 'stacking' for the estimation of photometric redshifts. Stacking techniques can feed the photometric redshift estimate, as output by a base algorithm, back into the same algorithm as an additional input feature in a subsequent learning round. We shown how all tested base algorithms benefit from at least one additional stacking round (or layer). To demonstrate the benefit of stacking, we apply the method to both unsupervised machine learning techniques based on self-organising maps (SOMs), and supervised machine learning methods based on decision trees. We explore a range of stacking architectures, such as the number of layers and the number of base learners per layer. Finally we explore the effectiveness of stacking even when using a successful algorithm such as AdaBoost. We observe a significant improvement of between 1.9% and 21% on all computed metrics when stacking is applied to weak learners (such as SOMs and decision trees). When appl...

  2. Stacking for machine learning redshifts applied to SDSS galaxies

    Science.gov (United States)

    Zitlau, Roman; Hoyle, Ben; Paech, Kerstin; Weller, Jochen; Rau, Markus Michael; Seitz, Stella

    2016-08-01

    We present an analysis of a general machine learning technique called 'stacking' for the estimation of photometric redshifts. Stacking techniques can feed the photometric redshift estimate, as output by a base algorithm, back into the same algorithm as an additional input feature in a subsequent learning round. We shown how all tested base algorithms benefit from at least one additional stacking round (or layer). To demonstrate the benefit of stacking, we apply the method to both unsupervised machine learning techniques based on self-organising maps (SOMs), and supervised machine learning methods based on decision trees. We explore a range of stacking architectures, such as the number of layers and the number of base learners per layer. Finally we explore the effectiveness of stacking even when using a successful algorithm such as AdaBoost. We observe a significant improvement of between 1.9% and 21% on all computed metrics when stacking is applied to weak learners (such as SOMs and decision trees). When applied to strong learning algorithms (such as AdaBoost) the ratio of improvement shrinks, but still remains positive and is between 0.4% and 2.5% for the explored metrics and comes at almost no additional computational cost.

  3. Photometric type Ia supernova surveys in narrow band filters

    CERN Document Server

    Xavier, Henrique S; Sako, Masao; Benítez, Narciso; Calvão, Maurício O; Ederoclite, Alessandro; Marín-Franch, Antonio; Molino, Alberto; Reis, Ribamar R R; Siffert, Beatriz B; Sodré, Laerte

    2013-01-01

    We study the characteristics of a narrow band type Ia supernova survey through simulations based on the upcoming Javalambre Physics of the accelerating universe Astrophysical Survey (J-PAS). This unique survey has the capabilities of obtaining distances, redshifts, and the SN type from a single experiment thereby circumventing the challenges faced by the resource-intensive spectroscopic follow-up observations. We analyse the flux measurements signal-to-noise ratio and bias, the supernova typing performance, the ability to recover light curve parameters given by the SALT2 model, the photometric redshift precision from type Ia supernova light curves and the effects of systematic errors on the data. We show that such a survey is not only feasible but may yield large type Ia supernova samples (up to 300 supernovae at $z<0.5$ per month of search) with low core collapse contamination ($\\sim 3$ per cent), good precision on the SALT2 parameters (average $\\sigma_{m_B}=0.063$, $\\sigma_{x_1}=0.47$ and $\\sigma_c=0.040...

  4. J-PLUS: The Javalambre Photometric Local Universe Survey

    Science.gov (United States)

    Cenarro, Javier; Marin-Franch, Antonio; Moles, Mariano; Cristobal-Hornillos, David; Mendes de Oliveira, Claudia; Sodre, Laerte

    2015-08-01

    The Javalambre-Photometric Local Universe Survey, J-PLUS (www.j-plus.es), is defined to observe 8500 deg2 of the sky visible from the Javalambre Observatory (Teruel, Spain) with the panoramic camera T80Cam at the JAST/T80 telescope, using a set of 12 broad, intermediate and narrow band optical filters. The Project is particularly designed to carry out the photometric calibration of J-PAS (http://j-pas.org). For this reason, some J-PLUS filters are located at key stellar spectral features that allow to retrieve very accurate spectral energy distributions for more than 5 millions of stars in our Galaxy. Beyond the calibration goals, the unusually large FOV of T80Cam, 2deg2, together with the unique width and location of some filters, turn the J-PLUS Project into a powerful 3D view of the nearby Universe, mapping more than 20 millions of galaxies with reliable distance determinations and a similar number of stars of the Milky Way halo. At a rate of 100 gigabytes of data per night, J-PLUS will provide unprecedented multi-color images of the Universe to address a wide variety of astrophysical questions related with cosmology, large scale structure, galaxy clusters, 2D stellar populations and star formation studies in galaxies, the discovery of high redshift galaxies at specific redshift slices, quasars, supernovae, Milky Way science and structure, and minor bodies in the Solar System. In addition, the repetition of the whole area over time in certain filters will allow to face variability studies in the time domain.Complementing J-PLUS, a replica of the JAST/T80 telescope, T80Cam and the J-PLUS filters have been installed at the CTIO, allowing to extend the project to the Southern Hemisphere. J-PLUS together with the southern extension, S-PLUS, constitute an All-sky Photometric Local Universe Survey whose details and scientific applications are the bulk of the present talk.

  5. Redshift Survey Strategies

    Science.gov (United States)

    Jones, A. W.; Bland-Hawthorn, J.; Kaiser, N.

    1994-12-01

    In the first half of 1995, the Anglo-Australian Observatory is due to commission a wide field (2.1(deg) ), 400-fiber, double spectrograph system (2dF) at the f/3.3 prime focus of the AAT 3.9m bi-national facility. The instrument should be able to measure ~ 4000 galaxy redshifts (assuming a magnitude limit of b_J ~\\ 20) in a single dark night and is therefore ideally suited to studies of large-scale structure. We have carried out simple 3D numerical simulations to judge the relative merits of sparse surveys and contiguous surveys. We generate a survey volume and fill it randomly with particles according to a selection function which mimics a magnitude-limited survey at b_J = 19.7. Each of the particles is perturbed by a gaussian random field according to the dimensionless power spectrum k(3) P(k) / 2pi (2) determined by Feldman, Kaiser & Peacock (1994) from the IRAS QDOT survey. We introduce some redshift-space distortion as described by Kaiser (1987), a `thermal' component measured from pairwise velocities (Davis & Peebles 1983), and `fingers of god' due to rich clusters at random density enhancements. Our particular concern is to understand how the window function W(2(k)) of the survey geometry compromises the accuracy of statistical measures [e.g., P(k), xi (r), xi (r_sigma ,r_pi )] commonly used in the study of large-scale structure. We also examine the reliability of various tools (e.g. genus) for describing the topological structure within a contiguous region of the survey.

  6. An Efficient Approach to Obtaining Large Numbers of Distant Supernova Host Galaxy Redshifts

    CERN Document Server

    Lidman, C; Sullivan, M; Myzska, J; Dobbie, P; Glazebrook, K; Mould, J; Astier, P; Balland, C; Betoule, M; Carlberg, R; Conley, A; Fouchez, D; Guy, J; Hardin, D; Hook, I; Howell, D A; Pain, R; Palanque-Delabrouille, N; Perrett, K; Pritchet, C; Regnault, N; Rich, J

    2012-01-01

    We use the wide-field capabilities of the 2dF fibre positioner and the AAOmega spectrograph on the Anglo-Australian Telescope (AAT) to obtain redshifts of galaxies that hosted supernovae during the first three years of the Supernova Legacy Survey (SNLS). With exposure times ranging from 10 to 60 ksec per galaxy, we were able to obtain redshifts for 400 host galaxies in two SNLS fields, thereby substantially increasing the total number of SNLS supernovae with host galaxy redshifts. The median redshift of the galaxies in our sample that hosted photometrically classified Type Ia supernovae (SNe Ia) is 0.77, which is 25% higher than the median redshift of spectroscopically confirmed SNe Ia in the three-year sample of the SNLS. Our results demonstrate that one can use wide-field fibre-fed multi-object spectrographs on 4m telescopes to efficiently obtain redshifts for large numbers of supernova host galaxies over the large areas of sky that will be covered by future high-redshift supernova surveys, such as the Dark...

  7. The Team Keck Treasury Redshift Survey of the GOODS-North Field

    CERN Document Server

    Wirth, G D; Amico, P; Chaffee, F H; Goodrich, R W; Kwok, S; Lyke, J E; Mader, J A; Tran, H D; Barger, A J; Cowie, L L; Capak, P; Cooper, M C; Conrad, A; Davis, M; Faber, S M; Hu, E M; Koo, D C; Le Mignant, D; Newman, J A; Songaila, A; Wirth, Gregory D.; Willmer, Christopher N. A.; Amico, Paola; Chaffee, Frederic H.; Goodrich, Robert W.; Kwok, Shui; Lyke, James E.; Mader, Jeff A.; Tran, Hien D.; Barger, Amy J.; Cowie, Lennox L.; Capak, Peter; Cooper, Michael C.; Conrad, Al; Davis, Marc; Hu, Esther M.; Koo, David C.; Mignant, David Le; Newman, Jeffrey A.; Songaila, Antoinette

    2004-01-01

    We report the results of an extensive imaging and spectroscopic survey in the GOODS-North field completed using DEIMOS on the Keck II telescope. Observations of 2018 targets in a magnitude-limited sample of 2911 objects to R=24.4 yield secure redshifts for a sample of 1440 galaxies and AGN plus 96 stars. In addition to redshifts and associated quality assessments, our catalog also includes photometric and astrometric measurements for all targets detected in our R-band imaging survey of the GOODS-North region. We investigate various sources of incompleteness and find the redshift catalog to be 53% complete at its limiting magnitude. The median redshift of z=0.65 is lower than in similar deep surveys because we did not select against low-redshift targets. Comparison with other redshift surveys in the same field, including a complementary Hawaii-led DEIMOS survey, establishes that our velocity uncertainties are as low as 40 km/s for red galaxies and that our redshift confidence assessments are accurate. The dist...

  8. Quantum catastrophes: a case study

    Science.gov (United States)

    Znojil, Miloslav

    2012-11-01

    The bound-state spectrum of a Hamiltonian H is assumed real in a non-empty domain D of physical values of parameters. This means that for these parameters, H may be called crypto-Hermitian, i.e. made Hermitian via an ad hoc choice of the inner product in the physical Hilbert space of quantum bound states (i.e. via an ad hoc construction of the operator Θ called the metric). The name quantum catastrophe is then assigned to the N-tuple-exceptional-point crossing, i.e. to the scenario in which we leave the domain D along such a path that at the boundary of D, an N-plet of bound-state energies degenerates and, subsequently, complexifies. At any fixed N ⩾ 2, this process is simulated via an N × N benchmark effective matrix Hamiltonian H. It is being assigned such a closed-form metric which is made unique via an N-extrapolation-friendliness requirement. This article is part of a special issue of Journal of Physics A: Mathematical and Theoretical devoted to ‘Quantum physics with non-Hermitian operators’.

  9. Quantum catastrophes: a case study

    International Nuclear Information System (INIS)

    The bound-state spectrum of a Hamiltonian H is assumed real in a non-empty domain D of physical values of parameters. This means that for these parameters, H may be called crypto-Hermitian, i.e. made Hermitian via an ad hoc choice of the inner product in the physical Hilbert space of quantum bound states (i.e. via an ad hoc construction of the operator Θ called the metric). The name quantum catastrophe is then assigned to the N-tuple-exceptional-point crossing, i.e. to the scenario in which we leave the domain D along such a path that at the boundary of D, an N-plet of bound-state energies degenerates and, subsequently, complexifies. At any fixed N ⩾ 2, this process is simulated via an N × N benchmark effective matrix Hamiltonian H. It is being assigned such a closed-form metric which is made unique via an N-extrapolation-friendliness requirement. This article is part of a special issue of Journal of Physics A: Mathematical and Theoretical devoted to ‘Quantum physics with non-Hermitian operators’. (paper)

  10. A story of transformation following catastrophic loss.

    Science.gov (United States)

    Rateau, Margaret R

    2010-08-01

    The emotional impact following catastrophic loss is a highly individualized and personal experience. Such an experience may be life transforming and can significantly influence the course of one's emotional recovery. Through the gathering of story, a clearer understanding of the transformational experience may lead to more appropriate mental health support for those most in need. The purposes of this article are to share the author's 4-year autobiographical story following catastrophic loss from a house explosion and fire, to discuss the transpersonal perspective on transformation, and to offer the use of story for practice and research applications for persons experiencing catastrophic loss. PMID:20650371

  11. The Compared Number Density of High-Redshift Galaxies and Lyman \\alpha Clouds

    OpenAIRE

    Fernandez-Soto, A.; Lanzetta, K. M.; Yahil, A.; Chen, H. -W.

    1997-01-01

    We use our catalog of photometric redshifts in the Hubble Deep Field (HDF) to estimate the Luminosity Function (LF) of galaxies up to z=2. Using the obtained LF and a relationship between luminosity and halo size, we calculate the expected density of galactic halo crossings for any arbitrary line of sight. This density is then compared with the known one of Lyman \\alpha lines, showing that the observed density of galaxies is enough to account for the observed absorption lines.

  12. A Spectroscopically Identified Galaxy of Probable Redshift z = 6.68

    OpenAIRE

    Chen, Hsiao-Wen; Lanzetta, Kenneth M.; Pascarelle, Sebastian

    1999-01-01

    The detection and identification of distant galaxies is a prominent goal of observational cosmology because distant galaxies are seen as they were in the distant past and hence probe early galaxy formation, due to the cosmologically significant light travel time. We have sought to identify distant galaxies in very deep spectroscopy by combining a new spectrum extraction technique with photometric and spectroscopic analysis techniques. Here we report the identification of a galaxy of redshift ...

  13. The Compared Number Density of High-Redshift Galaxies and Lyman $\\alpha$ Clouds

    CERN Document Server

    Fernández-Soto, A; Chen, A Y

    1997-01-01

    We use our catalog of photometric redshifts in the Hubble Deep Field (HDF) to estimate the Luminosity Function (LF) of galaxies up to z=2. Using the obtained LF and a relationship between luminosity and halo size, we calculate the expected density of galactic halo crossings for any arbitrary line of sight. This density is then compared with the known one of Lyman \\alpha lines, showing that the observed density of galaxies is enough to account for the observed absorption lines.

  14. Insuring catastrophes and the role of governments

    Science.gov (United States)

    Boyer, M. M.; Nyce, C. M.

    2013-08-01

    In this paper we model the cost of providing insurance coverage against natural and man-made hazards. We propose an insurance market model that explains (1) the use of reinsurance to help finance the cost of catastrophic events and (2) the implicit (or explicit) presence of government entities acting as (re)insurers of last resort. Using an economic model, we show how insurance programmes should be designed to cover the losses due to a possible catastrophic natural hazard. Our results show that the optimal structure of a reinsurance programme minimizes the cost of offering insurance protection. We also show how government intervention can reduce the cost of insurance against natural catastrophes and increase policyholders' welfare. Our paper therefore offers public policy implications as to the role and presence of government as an insurer of last resort and the minimum insurance premium necessary to cover the cost of catastrophic events.

  15. Catastrophes in Scale-Free Networks

    Institute of Scientific and Technical Information of China (English)

    ZHOU Tao; WANG Bing-Hong

    2005-01-01

    @@ An alternative model about cascading occurrences caused by perturbation is established to search the mechanism because catastrophes in networks occur. We investigate the avalanche dynamics of our model on two-dimensional Euclidean lattices and scale-free networks and find that the avalanche dynamic behaviour is sensitive to the topological structure of networks. The simulation results show that the catastrophes occur much more frequently in scale-free networks than those in Euclidean lattices, and the greatest catastrophe in scale-free networks is much more serious than that in Euclidean lattices. Furthermore, we have studied how to reduce the catastrophes'degree, and have schemed out an effective strategy, called the targeted safeguard strategy for scale-free networks.

  16. Catastrophic event modeling. [lithium thionyl chloride batteries

    Science.gov (United States)

    Frank, H. A.

    1981-01-01

    A mathematical model for the catastrophic failures (venting or explosion of the cell) in lithium thionyl chloride batteries is presented. The phenomenology of the various processes leading to cell failure is reviewed.

  17. Insuring catastrophes and the role of governments

    Directory of Open Access Journals (Sweden)

    M. M. Boyer

    2013-08-01

    Full Text Available In this paper we model the cost of providing insurance coverage against natural and man-made hazards. We propose an insurance market model that explains (1 the use of reinsurance to help finance the cost of catastrophic events and (2 the implicit (or explicit presence of government entities acting as (reinsurers of last resort. Using an economic model, we show how insurance programmes should be designed to cover the losses due to a possible catastrophic natural hazard. Our results show that the optimal structure of a reinsurance programme minimizes the cost of offering insurance protection. We also show how government intervention can reduce the cost of insurance against natural catastrophes and increase policyholders' welfare. Our paper therefore offers public policy implications as to the role and presence of government as an insurer of last resort and the minimum insurance premium necessary to cover the cost of catastrophic events.

  18. Microtubule dynamics: Caps, catastrophes, and coupled hydrolysis

    DEFF Research Database (Denmark)

    Flyvbjerg, H.; Holy, T.E.; Leibler, S.

    1996-01-01

    probability distributions relating to available experimental data are derived. Caps are found to be short and the total rate of hydrolysis at a microtubule end is found to be dynamically coupled to growth. The so-called catastrophe rate is a simple function of the microtubule growth rare and fits experimental...... data. A constant nonzero catastrophe rare, identical for both microtubule ends, is predicted at large growth rates. The delay time for dilution-induced catastrophes is stochastic with a simple distribution that fits the experimental one and, like the experimental one, does not depend on the rate of...... unified description of several apparently contradictory experimental data. Experimental results for the catastrophe rate at different concentrations of magnesium ions and of microtubule associated proteins are discussed in terms of the model. Feasible experiments are suggested that can provide decisive...

  19. Valuing Catastrophe Bonds Involving Credit Risks

    OpenAIRE

    Jian Liu; Jihong Xiao; Lizhao Yan; Fenghua Wen

    2014-01-01

    Catastrophe bonds are the most important products in catastrophe risk securitization market. For the operating mechanism, CAT bonds may have a credit risk, so in this paper we consider the influence of the credit risk on CAT bonds pricing that is different from the other literature. We employ the Jarrow and Turnbull method to model the credit risks and get access to the general pricing formula using the Extreme Value Theory. Furthermore, we present an empirical pricing study of the Property C...

  20. Catastrophic avalanches and methods of their control

    Directory of Open Access Journals (Sweden)

    N. A. Volodicheva

    2014-01-01

    Full Text Available Definition of such phenomenon as “catastrophic avalanche” is presented in this arti-cle. Several situations with releases of catastrophic avalanches in mountains of Caucasus, Alps, and Central Asia are investigated. Materials of snow-avalanche ob-servations performed since 1960s at the Elbrus station of the Lomonosov Moscow State University (Central Caucasus were used for this work. Complex-valued measures of engineering protection demonstrating different efficiencies are consid-ered.

  1. Mindfulness, Acceptance and Catastrophizing in Chronic Pain

    OpenAIRE

    de Boer, Maaike J.; Steinhagen, Hannemike E.; Versteegen, Gerbrig J.; Struys, Michel M.R.F.; Sanderman, Robbert

    2014-01-01

    Objectives: Catastrophizing is often the primary target of the cognitive-behavioral treatment of chronic pain. Recent literature on acceptance and commitment therapy (ACT) suggests an important role in the pain experience for the concepts mindfulness and acceptance. The aim of this study is to examine the influence of mindfulness and general psychological acceptance on pain-related catastrophizing in patients with chronic pain. Methods: A cross-sectional survey was conducted, including 87 chr...

  2. Catastrophizing and Causal Beliefs in Whiplash

    OpenAIRE

    Buitenhuis, J.; de Jong, P J; Jaspers, J. P. C.; Groothoff, J. W.

    2008-01-01

    Study Design. Prospective cohort study. Objective. This study investigates the role of pain catastrophizing and causal beliefs with regard to severity and persistence of neck complaints after motor vehicle accidents. Summary of Background Data. In previous research on low back pain, somatoform disorders and chronic fatigue syndrome, pain catastrophizing and causal beliefs were found to be related to perceived disability and prognosis. Furthermore, it has been argued with respect to whiplash t...

  3. The Economic and Policy Consequences of Catastrophes

    OpenAIRE

    Robert S. Pindyck; Neng Wang

    2013-01-01

    How likely is a catastrophic event that would substantially reduce the capital stock, GDP, and wealth? How much should society be willing to pay to reduce the probability or impact of a catastrophe? We answer these questions and provide a framework for policy analysis using a general equilibrium model of production, capital accumulation, and household preferences. Calibrating the model to economic and financial data, we estimate the mean arrival rate of shocks and their size distribution, the...

  4. Bayesian redshift-space distortions correction from galaxy redshift surveys

    CERN Document Server

    Kitaura, Francisco-Shu; Angulo, Raul E; Chuang, Chia-Hsun; Rodriguez-Torres, Sergio; Monteagudo, Carlos Hernandez; Prada, Francisco; Yepes, Gustavo

    2015-01-01

    We present a Bayesian reconstruction method which maps a galaxy distribution from redshift-space to real-space inferring the distances of the individual galaxies. The method is based on sampling density fields assuming a lognormal prior with a likelihood given by the negative binomial distribution function modelling stochastic bias. We assume a deterministic bias given by a power law relating the dark matter density field to the expected halo or galaxy field. Coherent redshift-space distortions are corrected in a Gibbs-sampling procedure by moving the galaxies from redshift-space to real-space according to the peculiar motions derived from the recovered density field using linear theory with the option to include tidal field corrections from second order Lagrangian perturbation theory. The virialised distortions are corrected by sampling candidate real-space positions (being in the neighbourhood of the observations along the line of sight), which are compatible with the bulk flow corrected redshift-space posi...

  5. Mindfulness, acceptance and catastrophizing in chronic pain.

    Directory of Open Access Journals (Sweden)

    Maaike J de Boer

    Full Text Available OBJECTIVES: Catastrophizing is often the primary target of the cognitive-behavioral treatment of chronic pain. Recent literature on acceptance and commitment therapy (ACT suggests an important role in the pain experience for the concepts mindfulness and acceptance. The aim of this study is to examine the influence of mindfulness and general psychological acceptance on pain-related catastrophizing in patients with chronic pain. METHODS: A cross-sectional survey was conducted, including 87 chronic pain patients from an academic outpatient pain center. RESULTS: The results show that general psychological acceptance (measured with the AAQ-II is a strong predictor of pain-related catastrophizing, independent of gender, age and pain intensity. Mindfulness (measured with the MAAS did not predict levels of pain-related catastrophizing. DISCUSSION: Acceptance of psychological experiences outside of pain itself is related to catastrophizing. Thus, acceptance seems to play a role in the pain experience and should be part of the treatment of chronic pain. The focus of the ACT treatment of chronic pain does not necessarily have to be on acceptance of pain per se, but may be aimed at acceptance of unwanted experiences in general. Mindfulness in the sense of "acting with awareness" is however not related to catastrophizing. Based on our research findings in comparisons with those of other authors, we recommend a broader conceptualization of mindfulness and the use of a multifaceted questionnaire for mindfulness instead of the unidimensional MAAS.

  6. Morphological Number Counts and Redshift Distributions to I = 25 from the Hubble Deep Fields: Constraints on Cosmological Models from Early Type Galaxies

    OpenAIRE

    Phillipps, S.; Driver, S. P.; Couch, W. J.; Fernandez-Soto, A.; Bristow, P. D.; Odewahn, S. C.; Windhorst, R. A.; Lanzetta, K.

    2000-01-01

    We combine magnitude and photometric redshift data on galaxies in the Hubble Deep Fields with morphological classifications in order to separate out the distributions for early type galaxies. The updated morphological galaxy number counts down to I = 25 and the corresponding redshift distributions are used as joint constraints on cosmological models, in particular on the values of the density parameter Omega_{0} and normalised cosmological constant Lambda_{0}. We find that an Einstein - de Si...

  7. Non-Doppler Redshift and Redshifts of QSOs

    OpenAIRE

    Zheng, Yi-Jia

    2013-01-01

    Quasars have reigned as the most luminous and distant objects in the Universe. These concepts were based on the hypothesis that the redshifts of quasars are obeying the Hubble low. This hypothesis has little serious competition today, but has met some difficulties when using it to determine the distances of quasars. However, the majority of the redshifts of quasars can be explained by the soft photon process proposed by Zheng (2013), then quasars are not located at the distances as that calcu...

  8. Combining spectroscopic and photometric surveys using angular cross-correlations II: Parameter constraints from different physical effects

    OpenAIRE

    Eriksen, Martin; Gaztanaga, Enrique

    2015-01-01

    Future spectroscopic and photometric surveys will measure accurate positions and shapes of an increasing number of galaxies. In the previous paper of this series we studied the effects of Redshift Space Distortions (RSD), baryon acoustic oscillations (BAO) and Weak gravitational Lensing (WL) using angular cross-correlation. Here, we provide a new forecast that explores the contribution of including different observables, physical effects (galaxy bias, WL, RSD, BAO) and approximations (non-lin...

  9. THE FIRST HIGH-REDSHIFT QUASAR FROM Pan-STARRS

    International Nuclear Information System (INIS)

    We present the discovery of the first high-redshift (z > 5.7) quasar from the Panoramic Survey Telescope and Rapid Response System 1 (Pan-STARRS1 or PS1). This quasar was initially detected as an iP1 dropout in PS1, confirmed photometrically with the SAO Wide-field InfraRed Camera at Arizona's Multiple Mirror Telescope (MMT) and the Gamma-Ray Burst Optical/Near-Infrared Detector at the MPG 2.2 m telescope in La Silla. The quasar was verified spectroscopically with the MMT Spectrograph, Red Channel and the Cassegrain Twin Spectrograph at the Calar Alto 3.5 m telescope. Its near-infrared spectrum was taken at the Large Binocular Telescope Observatory (LBT) with the LBT Near-Infrared Spectroscopic Utility with Camera and Integral Field Unit for Extragalactic Research. It has a redshift of 5.73, an AB zP1 magnitude of 19.4, a luminosity of 3.8 × 1047 erg s–1, and a black hole mass of 6.9 × 109 M☉. It is a broad absorption line quasar with a prominent Lyβ peak and a very blue continuum spectrum. This quasar is the first result from the PS1 high-redshift quasar search that is projected to discover more than 100 iP1 dropout quasars and could potentially find more than 10 zP1 dropout (z > 6.8) quasars.

  10. The High Redshift Integrated Sachs-Wolfe Effect

    CERN Document Server

    Xia, Jun-Qing; Baccigalupi, Carlo; Matarrese, Sabino

    2009-01-01

    In this paper we rely on the quasar (QSO) catalog of the Sloan Digital Sky Survey Data Release Six (SDSS DR6) of about one million photometrically selected QSOs to compute the Integrated Sachs-Wolfe (ISW) effect at high redshift, aiming at constraining the behavior of the expansion rate and thus the behaviour of dark energy at those epochs. This unique sample significantly extends previous catalogs to higher redshifts while retaining high efficiency in the selection algorithm. We compute the auto-correlation function (ACF) of QSO number density from which we extract the bias and the stellar contamination. We then calculate the cross-correlation function (CCF) between QSO number density and Cosmic Microwave Background (CMB) temperature fluctuations in different subsamples: at high z>1.5 and low z1.5. We focus on the capabilities of the ISW to constrain the behaviour of the dark energy component at high redshift both in the \\LambdaCDM and Early Dark Energy cosmologies, when the dark energy is substantially unco...

  11. Death rate of massive stars at redshift ~0.3

    CERN Document Server

    Cappellaro, E; Altavilla, G; Botticella, M T; Benetti, S; Clocchiatti, A; Danziger, J I; Mazzali, P A; Pastorello, A; Patat, F; Salvo, M; Turatto, M; Valenti, S

    2004-01-01

    We report the first result of a supernova search program designed to measure the evolution of the supernova rate with redshift. To make the comparison with local rates more significant we copied, as much as possible, the same computation recepies as for the measurements of local rates. Moreover, we exploited the multicolor images and the photometric redshift technique to characterize the galaxy sample and accurately estimate the detection efficiency. Combining our data with the recently published meaurements of the SN Ia rate at different redshifts, we derived the first, direct measurement of the core collapse supernova rate at z = 0.26 as r_cc = 1.45 [+0.55, -0.45] h^2 SNu [h=H_0/75]. This is a factor three larger than the local estimate. The increase for a look back time of "only" 2.8 Gyr is more rapid than predicted by most of the published models of the SN rate evolution. Core-collapse SN rates measure the death rate of massive star and, because of the short time scale of evolution, can be translated in a...

  12. The First High Redshift Quasar from Pan-STARRS

    CERN Document Server

    Morganson, Eric; Decarli, Roberto; Walter, Fabian; Chambers, Ken; McGreer, Ian; Fan, Xiaohui; Burgett, William; Flewelling, Heather; Hodapp, Klaus; Kaiser, Nick; Magnier, Eugene; Price, Paul; Rix, Hans-Walter; Sweeney, Bill; Waters, Christopher

    2011-01-01

    We present the discovery of the first high redshift (z > 5.7) quasar from the Panoramic Survey Telescope and Rapid Response System 1 (Pan-STARRS1 or PS1). This quasar was initially detected as an i dropoutout in PS1, confirmed photometrically with the SAO Widefield InfraRed Camera (SWIRC) at Arizona's Multiple Mirror Telescope (MMT) and the Gamma-Ray Burst Optical/Near-Infrared Detector (GROND) at the MPG 2.2 m telescope in La Silla. The quasar was verified spectroscopically with the the MMT Spectrograph, Red Channel and the Cassegrain Twin Spectrograph (TWIN) at the Calar Alto 3.5 m telescope. It has a redshift of 5.73, an AB z magnitude of 19.4, a luminosity of 3.8 x 10^47 erg/s and a black hole mass of 6.9 x 10^9 solar masses. It is a Broad Absorption Line quasar with a prominent Ly-beta peak and a very blue continuum spectrum. This quasar is the first result from the PS1 high redshift quasar search that is projected to discover more than a hundred i dropout quasars, and could potentially find more than 10...

  13. A WFC3 Grism Emission Line Redshift Catalog in the GOODS-South Field

    Science.gov (United States)

    Morris, Aaron M.; Kocevski, Dale D.; Trump, Jonathan R.; Weiner, Benjamin J.; Hathi, Nimish P.; Barro, Guillermo; Dahlen, Tomas; Faber, Sandra M.; Finkelstein, Steven L.; Fontana, Adriano; Ferguson, Henry C.; Grogin, Norman A.; Grützbauch, Ruth; Guo, Yicheng; Hsu, Li-Ting; Koekemoer, Anton M.; Koo, David C.; Mobasher, Bahram; Pforr, Janine; Salvato, Mara; Wiklind, Tommy; Wuyts, Stijn

    2015-06-01

    We combine Hubble Space Telescope (HST)/Wide Field Camera3 (WFC3) imaging and G141 grism observations from the Cosmic Assembly Near-infrared Deep Extragalactic Legacy Survey (CANDELS) and 3D-HST surveys to produce a catalog of grism spectroscopic redshifts for galaxies in the CANDELS/GOODS-South field. The WFC3/G141 grism spectra cover a wavelength range of 1.1≤slant λ ≤slant 1.7 μm with a resolving power of R∼ 130 for point sources, thus providing rest-frame optical spectra for galaxies out to z∼ 3.5. The catalog is selected in the H-band (F160W) and includes both galaxies with and without previously published spectroscopic redshifts. Grism spectra are extracted for all H-band detected galaxies with H ≤slant 24 and a CANDELS photometric redshift {{z}phot}≥slant 0.6. The resulting spectra are visually inspected to identify emission lines, and redshifts are determined using cross-correlation with empirical spectral templates. To establish the accuracy of our redshifts, we compare our results against high-quality spectroscopic redshifts from the literature. Using a sample of 411 control galaxies, this analysis yields a precision of {{σ }NMAD}=0.0028 for the grism-derived redshifts, which is consistent with the accuracy reported by the 3D-HST team. Our final catalog covers an area of 153 arcmin2 and contains 1019 redshifts for galaxies in GOODS-S. Roughly 60% (608/1019) of these redshifts are for galaxies with no previously published spectroscopic redshift. These new redshifts span a range of 0.677≤slant z≤slant 3.456 and have a median redshift of z = 1.282. The catalog contains a total of 234 new redshifts for galaxies at z\\gt 1.5. In addition, we present 20 galaxy pair candidates identified for the first time using the grism redshifts in our catalog, including four new galaxy pairs at z∼ 2, nearly doubling the number of such pairs previously identified.

  14. Intrinsic Redshifts in QSOs Near NGC 6212

    CERN Document Server

    Bell, M B

    2003-01-01

    The high number of QSOs around NGC 6212 allows a correlation analysis to be carried out between their redshift distribution and the redshift distributions predicted by intrinsic redshift models. We find no correlation between the QSO redshift distribution and the intrinsic redshifts predicted by Karlsson's log(1+z) = 0.089 relation. However, we find that the QSO redshift distribution is correlated with the intrinsic redshifts predicted by the relation z_{iQ} = 0.62[N-0.1M_{N}], for N = 3. We also find evidence that the observed redshifts of the QSOs contain a small cosmological redshift component similar to that of NGC 6212. The same correlation analysis carried out on the distribution of 574 quasar redshifts discussed by Karlsson also gave a negative result for the log(1+z)= 0.089 relation, and a positive result for the z_{iQ} intrinsic redshifts.

  15. 22 CFR 71.7 - Reports on catastrophes abroad.

    Science.gov (United States)

    2010-04-01

    ... 22 Foreign Relations 1 2010-04-01 2010-04-01 false Reports on catastrophes abroad. 71.7 Section 71... catastrophes abroad. Whenever a great catastrophe occurs abroad, either on land or on sea, the officer within whose district the catastrophe takes place or into whose district the survivors are brought shall...

  16. Effects of Interstellar Dust on the Photometric Properties of Faint Disk Galaxies

    Science.gov (United States)

    Bruzual, G. A.; Magris, C.

    1986-02-01

    We compute the effects of interstellar dust on the photometric properties of disk galaxies in several photographic and photoelectric bands. The solution to the radiative transfer problem including absorption and multiple scattering 0+ light by dust grains is taken from a previous paper by the authors (Magris and Bruzual, this conference). We present magnitudes and colors V. redshift for galaxies seen at different inclination angles and with different values of the optical depth through the plane of the galaxy. The results are compared with those obtained from a straightforward application of the galactic extinction law. It is concluded that in order to properly take into account the effects of dust in the photometric properties of distant galaxies of cosmological interest it is necessary to use correction factors such as those of Magris and Bruzual.

  17. Exploiting the full potential of photometric quasar surveys: Optimal power spectra through blind mitigation of systematics

    CERN Document Server

    Leistedt, Boris

    2014-01-01

    We present optimal measurements of the angular power spectrum of the XDQSOz catalogue of photometric quasars from the Sloan Digital Sky Survey. These measurements rely on a quadratic maximum likelihood estimator that simultaneously measures the auto- and cross-power spectra of four redshift samples, and provides minimum-variance, unbiased estimates even at the largest angular scales. Since photometric quasars are known to be strongly affected by systematics such as spatially-varying depth and stellar contamination, we introduce a new framework of extended mode projection to robustly mitigate the impact of systematics on the power spectrum measurements. This technique involves constructing template maps of potential systematics, decorrelating them on the sky, and projecting out modes which are significantly correlated with the data. Our method is able to simultaneously process several thousands of nonlinearly-correlated systematics, and mode projection is performed in a blind fashion. Using our final power spe...

  18. Research on catastrophe control in 1-D system

    Institute of Scientific and Technical Information of China (English)

    SUN Yao; TANG Li-ping; LI Xue-lian

    2003-01-01

    A new method of catastrophe control is described in one dimension nonlinear system. Catastrophe control based on catastrophe theory is a brand new area for control theory. A certain catastrophe is created at a desired location by appropriate control, which has preferred properties. Washout filter is presented and applied to preserve the original equilibrium of a system. Washout filter aided dynamic feedback controller is developed for the creation of catastrophe, and an example is given to illustrate the process. Catastrophe control may provide a new way of designing warning signals of impending collapse or catastrophe for monitoring and control purposes.

  19. Photometric Studies of GEO Debris

    Science.gov (United States)

    Seitzer, Patrick; Cowardin, Heather M.; Barker, Edwin; Abercromby, Kira J.; Foreman, Gary; Horstman, Matt

    2009-01-01

    The photometric signature of a debris object can be useful in determining what the physical characteristics of a piece of debris are. We report on optical observations in multiple filters of debris at geosynchronous Earth orbit (GEO). Our sample is taken from GEO objects discovered in a survey with the University of Michigan's 0.6-m aperture Schmidt telescope MODEST (for Michigan Orbital DEbris Survey Telescope), and then followed up in real-time with the SMARTS (Small and Medium Aperture Research Telescope System) 0.9-m at CTIO for orbits and photometry. Our goal is to determine 6 parameter orbits and measure colors for all objects fainter than R = 15 th magnitude that are discovered in the MODEST survey. At this magnitude the distribution of observed angular rates changes significantly from that of brighter objects. There are two objectives: 1. Estimate the orbital distribution of objects selected on the basis of two observational criteria: brightness (magnitude) and angular rates. 2. Obtain magnitudes and colors in standard astronomical filters (BVRI) for comparison with reflectance spectra of likely spacecraft materials. What is the faint debris likely to be? In this paper we report on the photometric results. For a sample of 50 objects, more than 90 calibrated sequences of R-B-V-I-R magnitudes have been obtained with the CTIO 0.9-m. For objects that do not show large brightness variations, the colors are largely redder than solar in both B-R and R-I. The width of the color distribution may be intrinsic to the nature of the surfaces, but also could be that we are seeing irregularly shaped objects and measuring the colors at different times with just one telescope. For a smaller sample of objects we have observed with synchronized CCD cameras on the two telescopes. The CTIO 0.9-m observes in B, and MODEST in R. The CCD cameras are electronically linked together so that the start time and duration of observations are the same to better than 50 milliseconds. Thus

  20. Gravitational redshift in Kerr field

    International Nuclear Information System (INIS)

    Generally gravitational redshift has been calculated without consideration of rotation of a body. Neglecting the rotation, the geometry of space time can be described by using the well-known spherically symmetric Schwarzschild geometry. Rotation has great effect on general relativity, which gives new challenges on gravitational redshift. When rotation is taken into consideration spherical symmetry lost and off diagonal terms appears in the metric and the geometry of space time can be described by using the Kerr solution, which is the exact solution of the Einstein's field equations known at present. In this paper we will derive the expression for gravitational redshift for rotating source in Kerr field, and also apply the derived expression to calculate the gravitational redshift in case of Sun under Newtonian approximation of angular momentum

  1. Pricing for Catastrophe Bonds Based on Expected-value Model

    Directory of Open Access Journals (Sweden)

    Junfei Chen

    2013-02-01

    Full Text Available As the catastrophes cannot be avoided and result in huge economic losses, therefore the compensation issue for catastrophe losses become an important research topic. Catastrophe bonds can effectively disperse the catastrophe risks which mainly undertaken by the government and the insurance companies currently and focus on capital more effectively in broad capital market, therefore to be an ideal catastrophe securities product. This study adopts Expectancy Theory to supplement and improve the pricing of catastrophe bonds based on Value Theory. A model of expected utility is established to determine the conditions of the expected revenue R of catastrophe bonds. The pricing model of the value function is used to get the psychological value of R,U (R-R‾, for catastrophe bonds. Finally, the psychological value is improved by the value according to expected utility and this can more accurately evaluate catastrophe bonds at a reasonable price. This research can provide decision-making for the pricing of catastrophe bonds.

  2. Atom gravimeters and gravitational redshift

    CERN Document Server

    Wolf, Peter; Borde, Christian J; Reynaud, Serge; Salomon, Christophe; Cohen-Tannoudji, Claude; 10.1038/nature09340

    2010-01-01

    In a recent paper, H. Mueller, A. Peters and S. Chu [A precision measurement of the gravitational redshift by the interference of matter waves, Nature 463, 926-929 (2010)] argued that atom interferometry experiments published a decade ago did in fact measure the gravitational redshift on the quantum clock operating at the very high Compton frequency associated with the rest mass of the Caesium atom. In the present Communication we show that this interpretation is incorrect.

  3. Redshift distributions of galaxies in the DES Science Verification shear catalogue and implications for weak lensing

    CERN Document Server

    Bonnett, C; Amara, A; Leistedt, B; Becker, M R; Bernstein, G M; Bridle, S; Bruderer, C; Busha, M T; Kind, M Carrasco; Childress, M J; Castander, F J; Chang, C; Crocce, M; Davis, T M; Eifler, T F; Frieman, J; Gangkofner, C; Gaztanaga, E; Glazebrook, K; Gruen, D; Kacprzak, T; King, A; Kwan, J; Lahav, O; Lewis, G; Lidman, C; Lin, H; MacCrann, N; Miquel, R; O'Neill, C R; Palmese, A; Peiris, H V; Refregier, A; Rozo, E; Rykoff, E S; Sadeh, I; Sánchez, C; Sheldon, E; Uddin, S; Wechsler, R H; Zuntz, J; Abbott, T; Abdalla, F B; Allam, S; Armstrong, R; Banerji, M; Bauer, A H; Benoit-Lévy, A; Bertin, E; Brooks, D; Buckley-Geer, E; Burke, D L; Capozzi, D; Rosell, A Carnero; Carretero, J; Cunha, C E; D'Andrea, C B; da Costa, L N; DePoy, D L; Desai, S; Diehl, H T; Dietrich, J P; Doel, P; Neto, A Fausti; Fernandez, E; Flaugher, B; Fosalba, P; Gerdes, D W; Gruendl, R A; Honscheid, K; Jain, B; James, D J; Jarvis, M; Kim, A G; Kuehn, K; Kuropatkin, N; Li, T S; Lima, M; Maia, M A G; March, M; Marshall, J L; Martini, P; Melchior, P; Miller, C J; Neilsen, E; Nichol, R C; Nord, B; Ogando, R; Plazas, A A; Reil, K; Romer, A K; Roodman, A; Sako, M; Sanchez, E; Santiago, B; Smith, R C; Soares-Santos, M; Sobreira, F; Suchyta, E; Swanson, M E C; Tarle, G; Thaler, J; Thomas, D; Vikram, V; Walker, A R

    2015-01-01

    We present photometric redshift estimates for galaxies used in the weak lensing analysis of the Dark Energy Survey Science Verification (DES SV) data. Four model- or machine learning-based photometric redshift methods -- ANNZ2, BPZ calibrated against BCC-Ufig simulations, SkyNet, and TPZ -- are analysed. For training, calibration, and testing of these methods, we construct a catalogue of spectroscopically confirmed galaxies matched against DES SV data. The performance of the methods is evaluated against the matched spectroscopic catalogue, focusing on metrics relevant for weak lensing analyses, with additional validation against COSMOS photo-zs. From the galaxies in the DES SV shear catalogue, which have mean redshift $0.72\\pm0.01$ over the range $0.3redshift distributi...

  4. Downward Catastrophe of Solar Magnetic Flux Ropes

    Science.gov (United States)

    Zhang, Quanhao; Wang, Yuming; Hu, Youqiu; Liu, Rui

    2016-07-01

    2.5-dimensional time-dependent ideal magnetohydrodynamic (MHD) models in Cartesian coordinates were used in previous studies to seek MHD equilibria involving a magnetic flux rope embedded in a bipolar, partially open background field. As demonstrated by these studies, the equilibrium solutions of the system are separated into two branches: the flux rope sticks to the photosphere for solutions at the lower branch but is suspended in the corona for those at the upper branch. Moreover, a solution originally at the lower branch jumps to the upper, as the related control parameter increases and reaches a critical value, and the associated jump is here referred to as an upward catastrophe. The present paper advances these studies in three aspects. First, the magnetic field is changed to be force-free; the system still experiences an upward catastrophe with an increase in each control parameter. Second, under the force-free approximation, there also exists a downward catastrophe, characterized by the jump of a solution from the upper branch to the lower. Both catastrophes are irreversible processes connecting the two branches of equilibrium solutions so as to form a cycle. Finally, the magnetic energy in the numerical domain is calculated. It is found that there exists a magnetic energy release for both catastrophes. The Ampère's force, which vanishes everywhere for force-free fields, appears only during the catastrophes and does positive work, which serves as a major mechanism for the energy release. The implications of the downward catastrophe and its relevance to solar activities are briefly discussed.

  5. Galaxies Associated with z~4 Damped Lya Systems: I. Imaging and Photometric Selection

    OpenAIRE

    Prochaska, Jason X.; Gawiser, Eric; Wolfe, Arthur M.; Quirrenbach, Andreas; Lanzetta, Kenneth M.; Chen, Hsiao-Wen; Cooke, Jeff; Yahata, Noriaki

    2002-01-01

    This paper describes the acquisition and analysis of imaging data for the identification of galaxies associated with z~4 damped Lya systems. We present deep BRI images of three fields known to contain four z~4 damped systems. We discuss the reduction and calibration of the data, detail the color criteria used to identify z~4 galaxies, and present a photometric redshift analysis to complement the color selection. We have found no galaxy candidates closer to the QSO than 7'' which could be resp...

  6. Galaxy And Mass Assembly (GAMA): Curation and reanalysis of 17.5k redshifts in the G10/COSMOS region

    CERN Document Server

    Davies, L J M; Robotham, A S G; Baldry, I K; Lange, R; Liske, J; Meyer, M; Popping, A; Wright, A H; Wilkins, S M

    2014-01-01

    We discuss the construction of the Galaxy And Mass Assembly (GAMA) 10h region (G10) using publicly available data in the Cosmic Evolution Survey region (COSMOS) in order to extend the GAMA survey to z~1 in a single ~1deg$^2$. In order to obtain the maximum number of high precision spectroscopic redshifts we re-reduce all archival zCOSMOS-bright data and use the GAMA automatic cross-correlation redshift fitting code autoz. We combine autoz redshifts with all other available redshift information (zCOSMOS-bright 10k, PRIMUS, VVDS, SDSS and photometric redshifts) to calculate robust best-fit redshifts for all galaxies and visually inspect all 1D and 2D spectra to confirm automatically assigned redshifts. In total, we obtain 17,466 robust redshifts in the full COSMOS region. We then define the G10 region to be the central ~1deg$^2$ of COSMOS, which has relatively high spectroscopic completeness, and encompasses the CHILES VLA region. We define a combined r < 23.0 mag & i < 22.0 mag G10 sample (selected t...

  7. Environmental catastrophes under time-inconsistent preference

    Energy Technology Data Exchange (ETDEWEB)

    Michielsen, T.

    2013-02-15

    I analyze optimal natural resource use in an intergenerational model with the risk of a catastrophe. Each generation maximizes a weighted sum of discounted utility (positive) and the probability that a catastrophe will occur at any point in the future (negative). The model generates time inconsistency as generations disagree on the relative weights on utility and catastrophe prevention. As a consequence, future generations emit too much from the current generation's perspective and a dynamic game ensues. I consider a sequence of models. When the environmental problem is related to a scarce exhaustible resource, early generations have an incentive to reduce emissions in Markov equilibrium in order to enhance the ecosystem's resilience to future emissions. When the pollutant is expected to become obsolete in the near future, early generations may however increase their emissions if this reduces future emissions. When polluting inputs are abundant and expected to remain essential, the catastrophe becomes a self-fulfilling prophecy and the degree of concern for catastrophe prevention has limited or even no effect on equilibrium behaviour.

  8. Severe catastrophes and public reactions

    International Nuclear Information System (INIS)

    nuclear opposition. Economical basis of nuclear energy stagnation is in not very successful competition of nuclear engineering with fossil energy production technologies. Much money has been spent for improvement of safety of NPPs. Social roots of the opposition are linked with a bad experience of the public with demonstration of the nuclear energy- The explosion of atomic bombs, some contamination of the territories after nuclear arm tests, misfortunes with TMI-2 and Chernobyl have created a stable enmity and non-acceptance of the all connected with 'atom'. The mass media have strongly promoted the dissemination of the fear of radiation exposures. There is also an influence on that attitude the radiation protection regulation via the declaration of the linear no-threshold dependence of the radiation detriments and dose of exposure. Such concept ignores the adoptive features of all living. But modem studies have showed that protracted irradiation at the same dose is much less dangerous compared with sharp one. It could change public attitude to nuclear energy in the society. Role of nuclear communication for public informing: The reactions of public on various technological and man-made events differ significantly and are being determined not scales of catastrophes but the mental impression and a multiplication of psychological stresses in the society by mass -media. In present situation a nuclear community has to improve the contacts with the pubic, to launch more effective campaign for explanation of real adventures of nuclear power. It needs to compare the risks of climate warming and health detriments from different electricity production technologies and to show that nuclear power is a single alternative all fossil burning techniques of electricity production. It's the truth the nuclear power is a real method of fight for suppression of emission the greenhouse gases, isn't it? (author)

  9. Machine learning techniques for astrophysical modelling and photometric redshift estimation of quasars in optical sky surveys

    OpenAIRE

    Kumar, N. Daniel

    2008-01-01

    Machine learning techniques are utilised in several areas of astrophysical research today. This dissertation addresses the application of ML techniques to two classes of problems in astrophysics, namely, the analysis of individual astronomical phenomena over time and the automated, simultaneous analysis of thousands of objects in large optical sky surveys. Specifically investigated are (1) techniques to approximate the precise orbits of the satellites of Jupiter and Saturn given Earth-based o...

  10. A photometric redshift of z = 6.39 +/- 0.12 for GRB 050904

    Czech Academy of Sciences Publication Activity Database

    Haislip, J.B.; Nysewander, M.C.; Reichart, D. E.; Levan, A.; Tanvir, N. R.; Cenko, S.B.; Fox, D.B.; Price, P.A.; Castro-Tirado, A.J.; Gorosabel, J.; Evans, C.R.; Figueredo, E.; MacLeod, C.L.; Kirschbrown, J.R.; Jelínek, M.; Guziy, S.; de Ugarte Postigo, A.; Cypriano, E.S.; LaCluyze, A.; Graham, J.; Priddey, R.; Chapman, R.; Rhoads, J.; Fruchter, A.S.; Lamb, D.Q.; Kouveliotou, C.; Wijers, R. A. M. J.; Bayliss, M.B.; Schmidt, B.P.; Soderberg, A.M.; Kulkarni, S.R.; Harrison, F.A.; Moon, D.S.; Gal-Yam, A.; Kasliwal, M.M.; Hudec, René; Vítek,, S.; Kubánek, Petr; Crain, J.A.; Foster, A.C.; Clemens, J.C.; Bartelme, J.W.; Canterna, R.; Hartmann, D.H.; Henden, A. A.; Klose, S.; Park, H.-S.; Williams, G.G.; Rol, E.; O'Brien, P.; Bersier, D.; Prada, F.; Pizzaro, S.; Maturana, D.; Ugarte, P.; Alvarez, A.; Fernandez, A.J.M.; Jarvis, M.J.; Moles, M.; Alfaro, E.; Ivarsen, K.M.; Kumar, N.D.; Mack, C.E.; Zdarowicz, C.M.; Gehrels, N.; Barthelmy, S. D.; Burrows, D.N.

    2006-01-01

    Roč. 440, č. 7081 (2006), s. 181-183. ISSN 0028-0836 R&D Projects: GA AV ČR IAA3003206 Institutional research plan: CEZ:AV0Z10030501 Keywords : gamma-ray astrophysics * gamma-ray bursts * optical transients Subject RIV: BN - Astronomy, Celestial Mechanics, Astrophysics Impact factor: 26.681, year: 2006

  11. Machine learning techniques for astrophysical modelling and photometric redshift estimation of quasars in optical sky surveys

    CERN Document Server

    Kumar, N Daniel

    2008-01-01

    Machine learning techniques are utilised in several areas of astrophysical research today. This dissertation addresses the application of ML techniques to two classes of problems in astrophysics, namely, the analysis of individual astronomical phenomena over time and the automated, simultaneous analysis of thousands of objects in large optical sky surveys. Specifically investigated are (1) techniques to approximate the precise orbits of the satellites of Jupiter and Saturn given Earth-based observations as well as (2) techniques to quickly estimate the distances of quasars observed in the Sloan Digital Sky Survey. Learning methods considered include genetic algorithms, particle swarm optimisation, artificial neural networks, and radial basis function networks. The first part of this dissertation demonstrates that GAs and PSOs can both be efficiently used to model functions that are highly non-linear in several dimensions. It is subsequently demonstrated in the second part that ANNs and RBFNs can be used as ef...

  12. The Redshift Distribution of the TOUGH Survey

    OpenAIRE

    Jakobsson, P.; Chapman, R; Hjorth, J.; Malesani, D.; Fynbo, J. P. U.; Milvang-Jensen, B.; Kruhler, T.; Tanvir, N. R.

    2013-01-01

    We present the redshift results from a Very Large Telescope program aimed at optimizing the legacy value of the Swift mission: to characterize a homogeneous, X-ray selected, sample of 69 GRB host galaxies. 19 new redshifts have been secured, resulting in a 83% (57/69) redshift completion, making the survey the most comprehensive in terms of redshift completeness of any sample to the full Swift depth, available to date. We present the cumulative redshift distribution and derive a conservative,...

  13. Valuing Catastrophe Bonds Involving Credit Risks

    Directory of Open Access Journals (Sweden)

    Jian Liu

    2014-01-01

    Full Text Available Catastrophe bonds are the most important products in catastrophe risk securitization market. For the operating mechanism, CAT bonds may have a credit risk, so in this paper we consider the influence of the credit risk on CAT bonds pricing that is different from the other literature. We employ the Jarrow and Turnbull method to model the credit risks and get access to the general pricing formula using the Extreme Value Theory. Furthermore, we present an empirical pricing study of the Property Claim Services data, where the parameters in the loss function distribution are estimated by the MLE method and the default probabilities are deduced by the US financial market data. Then we get the catastrophe bonds value by the Monte Carlo method.

  14. Relativistic Transverse Gravitational Redshift

    Science.gov (United States)

    Mayer, A. F.

    2012-12-01

    symmetric energy potential exists between the frames that is quantified by the instantaneous Δ {v} = v\\cdot{d}φ between them; in order for either frame to become indistinguishable from the other, such that their respective velocity and acceleration vectors are parallel, a change in velocity is required. While the qualitative features of general relativity imply this phenomenon (i.e., a symmetric potential difference between two points on a Newtonian `equipotential surface' that is similar to a friction effect), it is not predicted by the field equations due to a modeling error concerning time. This is an error of omission; time has fundamental geometric properties implied by the principles of relativity that are not reflected in the field equations. Where b is the radius and g is the gravitational acceleration characterizing a spherical geoid S of an ideal point-source gravitational field, an elegant derivation that rests on first principles shows that for two points at rest on S separated by a distance d << b, a symmetric relativistic redshift exists between these points of magnitude z = gd2/bc^2, which over 1 km at Earth sea level yields z ˜{10-17}. It can be tested with a variety of methods, in particular laser interferometry. A more sophisticated derivation yields a considerably more complex predictive formula for any two points in a gravitational field.

  15. Effective Theory of Dark Energy at Redshift Survey Scales

    CERN Document Server

    Gleyzes, Jérôme; Mancarella, Michele; Vernizzi, Filippo

    2016-01-01

    We explore the phenomenological consequences of general late-time modifications of gravity in the quasi-static approximation, in the case where cold dark matter is non-minimally coupled to the gravitational sector. Assuming spectroscopic and photometric surveys with configuration parameters similar to those of the Euclid mission, we derive constraints on our effective description from three observables: the galaxy power spectrum in redshift space, tomographic weak-lensing shear power spectrum and the correlation spectrum between the integrated Sachs-Wolfe effect and the galaxy distribution. In particular, with $\\Lambda$CDM as fiducial model and a specific choice for the time dependence of our effective functions, we perform a Fisher matrix analysis and find that the unmarginalized $68\\%$ CL errors on the parameters describing the modifications of gravity are of order $\\sigma\\sim10^{-2}$--$10^{-3}$. We also consider two other fiducial models. A nonminimal coupling of CDM enhances the effects of modified gravit...

  16. Three-dimensional stereo by photometric ratios

    International Nuclear Information System (INIS)

    We present a methodology for corresponding a dense set of points on an object surface from photometric values for three-dimensional stereo computation of depth. The methodology utilizes multiple stereo pairs of images, with each stereo pair being taken of the identical scene but under different illumination. With just two stereo pairs of images taken under two different illumination conditions, a stereo pair of ratio images can be produced, one for the ratio of left-hand images and one for the ratio of right-hand images. We demonstrate how the photometric ratios composing these images can be used for accurate correspondence of object points. Object points having the same photometric ratio with respect to two different illumination conditions constitute a well-defined equivalence class of physical constraints defined by local surface orientation relative to illumination conditions. We formally show that for diffuse reflection the photometric ratio is invariant to varying camera characteristics, surface albedo, and viewpoint and that therefore the same photometric ratio in both images of a stereo pair implies the same equivalence class of physical constraints. The correspondence of photometric ratios along epipolar lines in a stereo pair of images under different illumination conditions is a correspondence of equivalent physical constraints, and the determination of depth from stereo can be performed. Whereas illumination planning is required, our photometric-based stereo methodology does not require knowledge of illumination conditions in the actual computation of three-dimensional depth and is applicable to perspective views. This technique extends the stereo determination of three-dimensional depth to smooth featureless surfaces without the use of precisely calibrated lighting. We demonstrate experimental depth maps from a dense set of points on smooth objects of known ground-truth shape, determined to within 1% depth accuracy

  17. Direct determination of quasar redshifts

    CERN Document Server

    De Bruijne, J H J; Perryman, M; Peacock, A; Favata, F; Rando, N; Martin, D; Verhoeve, P; Christlieb, N; Bruijne, Jos de; Reynolds, Alastair P; Perryman, Michael; Peacock, Anthony; Favata, Fabio; Rando, Nicola; Martin, Didier; Verhoeve, Peter; Christlieb, Norbert

    2001-01-01

    We present observations of 11 quasars, selected in the range z = 2.2-4.1, obtained with ESA's Superconducting Tunnel Junction (STJ) camera on the WHT. Using a single template quasar spectrum, we show that we can determine the redshifts of these objects to about 1%. A follow-up spectroscopic observation of one QSO for which our best-fit redshift (z = 2.976) differs significantly from the tentative literature value (z ~ 2.30) confirms that the latter was incorrect.

  18. Are GRBs the same at high redshift and low redshift?

    CERN Document Server

    Littlejohns, O M; Willingale, R; Evans, P A; O'Brien, P T; Levan, A J

    2013-01-01

    The majority of Swift gamma-ray bursts (GRBs) observed at z > 6 have prompt durations of T90 < 30s, which, at first sight, is surprising given that cosmological time-dilation means this corresponds to < 5s in their rest frames. We have tested whether these high-redshift GRBs are consistent with being drawn from the same population as those observed at low-redshift by comparing them to an artificially red-shifted sample of 114 z < 4 bursts. This is accomplished using two methods to produce realistic high-z simulations of light curves based on the observed characteristics of the low-z sample. In Method 1 we use the Swift/BAT data directly, taking the photons detected in the harder bands to predict what would be seen in the softest energy band if the burst were seen at higher-z. In Method 2 we fit the light curves with a model, and use that to extrapolate the expected behaviour over the whole BAT energy range at any redshift. Based on the results of Method 2, a K-S test of their durations finds a ~1% pr...

  19. On a new global catastrophic ICT model

    DEFF Research Database (Denmark)

    Riaz, M. Tahir; Bhalerao, Dipashree M.; Madsen, Ole Brun;

    2011-01-01

    Many parts of India are prone to natural disasters, particularly caused by earthquakes and floods because of its geographical location. The Catastrophic areas can be rural, remote or urban anywhere in the world. It has been understood that earthquakes directly do not cause causalities but instead...

  20. 78 FR 52832 - Catastrophic Risk Protection Endorsement

    Science.gov (United States)

    2013-08-27

    .... See the Notice related to 7 CFR part 3015, subpart V, published at 48 FR 29115, June 24, 1983... the Federal Register at 76 FR 50929-50931. The public was afforded 60 days to submit written comments... Federal Crop Insurance Corporation 7 CFR Part 402 RIN 0563-AC31 Catastrophic Risk Protection...

  1. The redshift distribution of the TOUGH survey

    DEFF Research Database (Denmark)

    Jakobsson, P.; Hjorth, J.; Malesani, D.;

    2013-01-01

    We present the redshift results from a Very Large Telescope (VLT) program aimed at optimizing the legacy value of the Swift mission: to characterize a homogeneous, X-ray selected, sample of 69 GRB host galaxies. Fifteen new redshifts have been secured, resulting in a 77% (53/69) redshift completion......, making the survey the most comprehensive in terms of redshift completeness of any sample to the full Swift depth, available to date. We present the cumulative redshift distribution and derive a conservative, yet small, associated uncertainty. We constrain the fraction of Swift GRBs at high redshift to a...

  2. Photometric Study of Kepler Asteroseismic Targets

    CERN Document Server

    Molenda-Zakowicz, J; Frasca, A

    2009-01-01

    Reported are UBV and uvbybeta observations of 15 candidates for Kepler primary astero- seismic targets and 14 other stars in the Kepler field, carried out at the M.G. Fracastoro station of the Catania Astrophysical Observatory. These data serve to plot the 29 stars in two-parameter diagrams with the photometric indices (such as B-V or delta m1 and the atmospheric parameters (such as the MK type or [Fe/H]) as coordinates. The two-parameter diagrams show no evidence of interstellar reddening. The photometric indices B-V and beta are then used to derive photometric effective temperatures, Teff(B-V) and Teff(beta). For Teff(B-V) > 6400 K, the photometric effective temperatures turn out to be systematically higher than spectroscopic effective temperatures by 311 +/- 34 K and 346 +/- 91 K for Teff(B-V) and Teff(beta), respectively. For T_eff(B-V) < 6250 K, the agreement between Teff(B-V) and the spectroscopic effective temperatures is very good. The photometric surface gravities, derived from c_1 and beta, show ...

  3. An ALMA Survey of Submillimeter Galaxies in the Extended Chandra Deep Field South: The Redshift Distribution and Evolution of Submillimeter Galaxies

    CERN Document Server

    Simpson, James; Smail, Ian; Alexander, Dave; Brandt, Niel; Bertoldi, Frank; de Breuck, Carlos; Chapman, Scott; Coppin, Kristen; da Cunha, Elisabete; Danielson, Alice; Dannerbauer, Helmut; Greve, Thomas; Hodge, Jackie; Ivison, Rob; Karim, Alex; Knudsen, Kirsten; Poggianti, Bianca; Schinnerer, Eva; Thomson, Alasdair; Walter, Fabian; Wardlow, Julie; Weiss, Axel; van der Werf, Paul

    2013-01-01

    We present the first photometric redshift distribution for a large unbiased sample of 870um selected submillimeter galaxies (SMGs) with robust identifications based on observations with the Atacama Large Millimeter Array (ALMA). In our analysis we consider 96 SMGs in the Extended Chandra Deep Field South, 77 of which have 4-19 band, optical-near-infrared, photometry. We model the Spectral Energy Distributions (SEDs) for these 77 SMGs, deriving a median photometric redshift of z=2.3+/-0.1. The remaining 19 SMGs have insufficient optical or near-infrared photometry to derive photometric redshifts, but a stacking analysis of IRAC and Herschel observations confirms they are not spurious. Assuming these sources have an absolute H-band magnitude distribution comparable to that of a complete sample of z~1-2 SMGs, we demonstrate that the undetected SMGs lie at higher redshifts, raising the median redshift for SMGs to z=2.5+/-0.2. More critically we show that the proportion of galaxies undergoing an SMG phase at z>3 i...

  4. First Measurement of the Clustering Evolution of Photometrically-Classified Quasars

    CERN Document Server

    Myers, A D; Richards, G T; Nichol, R C; Schneider, D P; Vanden Berk, Daniel E; Scranton, R; Gray, A G; Brinkmann, J; Myers, Adam D.; Brunner, Robert J.; Richards, Gordon T.; Nichol, Robert C.; Schneider, Donald P.; Berk, Daniel E. Vanden; Scranton, Ryan; Gray, Alexander G.; Brinkmann, Jon

    2006-01-01

    We present new measurements of the quasar autocorrelation from a sample of \\~80,000 photometrically-classified quasars taken from SDSS DR1. We find a best-fit model of $\\omega(\\theta) = (0.066\\pm^{0.026}_{0.024})\\theta^{-(0.98\\pm0.15)}$ for the angular autocorrelation, consistent with estimates from spectroscopic quasar surveys. We show that only models with little or no evolution in the clustering of quasars in comoving coordinates since z~1.4 can recover a scale-length consistent with local galaxies and Active Galactic Nuclei (AGNs). A model with little evolution of quasar clustering in comoving coordinates is best explained in the current cosmological paradigm by rapid evolution in quasar bias. We show that quasar biasing must have changed from b_Q~3 at a (photometric) redshift of z=2.2 to b_Q~1.2-1.3 by z=0.75. Such a rapid increase with redshift in biasing implies that quasars at z~2 cannot be the progenitors of modern L* objects, rather they must now reside in dense environments, such as clusters. Simil...

  5. INCORPORATING CATASTROPHES INTO INTEGRATED ASSESSMENT: SCIENCE, IMPACTS, AND ADAPTATION

    Science.gov (United States)

    Incorporating potential catastrophic consequences into integrated assessment models of climate change has been a top priority of policymakers and modelers alike. We review the current state of scientific understanding regarding three frequently mentioned geophysical catastrophes,...

  6. The VLT LBG Redshift Survey - V. Characterising the z = 3.1 Lyman Alpha Emitter Population

    CERN Document Server

    Bielby, R M; Shanks, T; Francke, H; Crighton, N H M; Bañados, E; González-López, Jorge; Infante, L; Orsi, A

    2016-01-01

    We present a survey of Ly$\\alpha$ emitting galaxies in the fields of the VLT LBG Redshift Survey, incorporating the analysis of narrow band number counts, the rest frame UV luminosity function and the two-point correlation function of Ly$\\alpha$ emitters at $z\\approx3.1$. Our photometric sample consists of 750 LAE candidates, over an area of 1.07 deg$^2$, with estimated equivalent widths of $\\gtrsim65$ \\AA, from 5 fields based on deep Subaru Suprime-Cam imaging data. Added to this we have obtained spectroscopic follow-up observations, which successfully detected Ly$\\alpha$ emission in 35 galaxies. Based on the spectroscopic results, we refined our photometric selection constraints, with the resulting sample having a success rate of $78\\pm18\\%$. We calculate the narrow band number counts for our photometric sample and find these to be consistent with previous studies of LAEs at this redshift. We find the $R$-band continuum luminosity function to be $\\sim10\\times$ lower than the equivalent luminosity function o...

  7. Defining photometric peculiar type Ia supernovae

    International Nuclear Information System (INIS)

    We present a new photometric identification technique for SN 1991bg-like type Ia supernovae (SNe Ia), i.e., objects with light curve characteristics such as later primary maxima and the absence of a secondary peak in redder filters. This method is capable of selecting this sub-group from the normal type Ia population. Furthermore, we find that recently identified peculiar sub-types such as SNe Iax and super-Chandrasekhar SNe Ia have photometric characteristics similar to 91bg-like SNe Ia, namely, the absence of secondary maxima and shoulders at longer wavelengths, and can also be classified with our technique. The similarity of these different SN Ia sub-groups perhaps suggests common physical conditions. This typing methodology permits the photometric identification of peculiar SNe Ia in large upcoming wide-field surveys either to study them further or to obtain a pure sample of normal SNe Ia for cosmological studies.

  8. Zernike polynomials for photometric characterization of LEDs

    International Nuclear Information System (INIS)

    We propose a method based on Zernike polynomials to characterize photometric quantities and descriptors of light emitting diodes (LEDs) from measurements of the angular distribution of the luminous intensity, such as total luminous flux, BA, inhomogeneity, anisotropy, direction of the optical axis and Lambertianity of the source. The performance of this method was experimentally tested for 18 high-power LEDs from different manufacturers and with different photometric characteristics. A small set of Zernike coefficients can be used to calculate all the mentioned photometric quantities and descriptors. For applications not requiring a great accuracy such as those of lighting design, the angular distribution of the luminous intensity of most of the studied LEDs can be interpolated with only two Zernike polynomials. (paper)

  9. Defining photometric peculiar type Ia supernovae

    Energy Technology Data Exchange (ETDEWEB)

    González-Gaitán, S.; Pignata, G.; Förster, F.; Gutiérrez, C. P.; Bufano, F.; Galbany, L.; Hamuy, M.; De Jaeger, T. [Millennium Institute of Astrophysics, Casilla 36-D, Santiago (Chile); Hsiao, E. Y.; Phillips, M. M. [Carnegie Observatories, Las Campanas Observatory, Casilla 601, La Serena (Chile); Folatelli, G. [Kavli Institute for the Physics and Mathematics of the Universe, the University of Tokyo, Kashiwa 277-8583 (Kavli IPMU, WPI) (Japan); Anderson, J. P., E-mail: sgonzale@das.uchile.cl [European Southern Observatory, Alonso de Córdova 3107, Casilla 19, Santiago (Chile)

    2014-11-10

    We present a new photometric identification technique for SN 1991bg-like type Ia supernovae (SNe Ia), i.e., objects with light curve characteristics such as later primary maxima and the absence of a secondary peak in redder filters. This method is capable of selecting this sub-group from the normal type Ia population. Furthermore, we find that recently identified peculiar sub-types such as SNe Iax and super-Chandrasekhar SNe Ia have photometric characteristics similar to 91bg-like SNe Ia, namely, the absence of secondary maxima and shoulders at longer wavelengths, and can also be classified with our technique. The similarity of these different SN Ia sub-groups perhaps suggests common physical conditions. This typing methodology permits the photometric identification of peculiar SNe Ia in large upcoming wide-field surveys either to study them further or to obtain a pure sample of normal SNe Ia for cosmological studies.

  10. Defining Photometric Peculiar Type Ia Supernovae

    CERN Document Server

    Gonzalez-Gaitan, S; Pignata, G; Forster, F; Gutierrez, C P; Bufano, F; Galbany, L; Folatelli, G; Phillips, M M; Hamuy, M; Anderson, J P; de Jaeger, T

    2014-01-01

    We present a new photometric identification technique for SN 1991bg-like type Ia supernovae (SNe Ia), i.e. objects with light-curve characteristics such as later primary maxima and absence of secondary peak in redder filters. This method is capable of selecting out this sub-group from the normal type Ia population. Furthermore, we find that recently identified peculiar sub-types such as SNe Iax and super-Chandrasekhar SNe Ia have similar photometric characteristics as 91bg-like SNe Ia, namely the absence of secondary maxima and shoulders at longer wavelengths, and can also be classified with our technique. The similarity of these different SN Ia sub-groups perhaps suggests common physical conditions. This typing methodology permits the photometric identification of peculiar SNe Ia in large up-coming wide field surveys either to study them further or to obtain a pure sample of normal SNe Ia for cosmological studies.

  11. GRB 070714B-DISCOVERY OF THE HIGHEST SPECTROSCOPICALLY CONFIRMED SHORT BURST REDSHIFT

    International Nuclear Information System (INIS)

    We detect the optical afterglow and host galaxy of GRB 070714B. Our observations of the afterglow show an initial plateau in the light curve for approximately the first 5-25 minutes, and then steepening to a power-law decay with index α = 0.86 ± 0.10 for the period between 1 and 24 hr postburst. This is consistent with the X-ray light curve which shows an initial plateau followed by a similar subsequent decay. At late time, we detect a host galaxy at the location of the optical transient. Gemini Nod and Shuffle spectroscopic observations of the host show a single emission line at 7167 A which, based on a griz JHK photometric redshift, we conclude is the 3727 A [O II] line. We therefore find a redshift of z = 0.923. This redshift, as well as a subsequent probable spectroscopic redshift determination of GRB 070429B at z = 0.904 by two other groups significantly exceeds the previous highest spectroscopically confirmed short burst redshift of z = 0.546 for GRB 051221. This dramatically moves back the time at which we know short bursts were being formed and suggests that the present evidence for an old progenitor population may be observationally biased.

  12. A New Modification of Photometric Method

    Directory of Open Access Journals (Sweden)

    M. Chrenek

    1993-11-01

    Full Text Available For the digital 1D-image processing we go out from the so-called photometric method. For the concrete applications of the introduced method its accuracy lowers, owing to that the form of an output video signal of linear CCD sensor is not smooth and not symmetrical. In some cases the output video signal of linear CCD sensor is devalued by the certain disperse of pixel sensitivity, respectively also that a measured object and its background are not uniform. Therefore we introduce a new modification of photometric method. The obtained results show, that introduced method gives a possibility to raise the measurement accuracy of the object dimension considerably.

  13. CATASTROPHE FRACTURE OF THIN-WALL PRESSURE TUBES

    Institute of Scientific and Technical Information of China (English)

    魏德敏; 杨桂通

    2002-01-01

    Catastrophe theory was used to investigate the fracture behavior of thin-wall cylindrical tubes subjected to nternal explosive pressure. Based on the energy theory and catastrophe theory, a cusp catastrophe model for the fracture was established, and a critical condition associated with the model is given.

  14. Axial and focal-plane diffraction catastrophe integrals

    Energy Technology Data Exchange (ETDEWEB)

    Berry, M V [H H Wills Physics Laboratory, Tyndall Avenue, Bristol BS8 1TL (United Kingdom); Howls, C J [School of Mathematics, University of Southampton, Southampton, SO17 1BJ (United Kingdom)

    2010-09-17

    Exact expressions in terms of Bessel functions are found for some of the diffraction catastrophe integrals that decorate caustics in optics and mechanics. These are the axial and focal-plane sections of the elliptic and hyperbolic umbilic diffraction catastrophes, and symmetric elliptic and hyperbolic unfoldings of the X{sub 9} diffraction catastrophes. These representations reveal unexpected relations between the integrals.

  15. Probing the dark ages: Observations of the high-redshift universe

    Science.gov (United States)

    Stevens, Daniel Keith

    This thesis attempts to describe some of the earliest phases in the collapse of galaxies from an observational standpoint. The work is composed of an assortment of projects which sample objects at very high redshift, probing the Universe 1-3 Gyr after the Big Bang. The first section of the thesis concerns high-redshift galaxies. Search techniques for identifying distant galaxies are extensively reviewed. Radio selection was once the primary vehicle to targeting the early Universe. Keck spectroscopy of high-redshift radio galaxies from the MIT-Greenbank radio catalog (S5GHz >~ 50 mJy) are discussed. We synthesize a composite radio galaxy spectrum, which we compare with other composite active galaxy spectra. Our data suggests a correlation between radio power and ionization state in high-redshift radio galaxies. The following three chapters detail individual galaxies confirmed at z > 5. These galaxies are among the half-dozen most distant sources known at the close of the 20th Century. Two of the galaxies were photometrically-selected from the Hubble Deep Field (HDF 4-473.0 at z = 5.60 and HDF 3-951.0 at z = 5.34 +/- 0.01). The third is TN J0924-2201, a radio galaxy at z = 5.19 selected on the basis of steep radio spectral index and faint K-band brightness. This source contains the most distant active galactic nucleus currently known, requiring early formation of supermassive blackholes within a Gyr after the Big Bang. The second section of the thesis concerns searches for high-redshift Lyα emission, identified either from deep, narrow-band imaging surveys or deep slit spectra. We discuss in detail one faint, high equivalent width line-emitter. Conventional wisdom would suggest identifying the 9185 Å line with Lyα at z = 6.55. We argue [O II] λ3727 at z = 1.46 is the more likely identification and discuss observational tests to distinguish Lyα-emitters at high redshift from foreground (active) sources. The final section of the thesis concerns high-redshift

  16. Large-scale analysis of the SDSS-III DR8 photometric luminous galaxies angular correlation function

    CERN Document Server

    de Simoni, Fernando; Carnero, Aurelio; Ross, Ashley J; Camacho, Hugo O; Rosenfeld, Rogerio; Lima, Marcos; da Costa, Luiz A N; Maia, Marcio A G

    2013-01-01

    We analyze the large-scale angular correlation function (ACF) of the CMASS Luminous Galaxies (LGs), a photometric-redshift catalog based on the 8th data release (DR8) of the SDSS-III. This catalog contains over 600,000 LGs in the range $0.45 \\leq z \\leq 0.65$, which was split into four redshift shells of constant width. First, we estimate the constraints on the redshift space distortion (RSD) parameters $b\\sigma_8$ and $f\\sigma_8$, where $b$ is the galaxy bias, $f$ the growth rate and $\\sigma_8$ is the normalization of the perturbations, finding that they vary appreciably among different redshift shells, in agreement with previous results using DR7 data. When assuming constant RSD parameters over the survey redshift range, we obtain $f\\sigma_8 = 0.69 \\pm 0.21$, which agrees at the $1.5\\sigma$ level with BOSS DR9 spectroscopic results. Next, we performed two cosmological analyses, where relevant parameters not fitted were kept fixed at their fiducial values. In the first analysis, we extracted the BAO peak pos...

  17. On Catastrophe and Cavitation for Spherical Cavity

    Institute of Scientific and Technical Information of China (English)

    MingJIN; KefuHUANG; 等

    1999-01-01

    This work deals with catastrophe of a spherical cavity and cavitation of a spherical cavity for Hooke material with 1/2 Poisson's ratio.A nonlinear problem.which is the Cauchy traction problem,is solved analytically.The governing equations are written on the deformed region or on the present configuration.And the conditions are described on moving boundary.A closed form solution is found.Furthermore,a bifurcation solution in closed form is given from the trivial homogeneous solution of a solid sphere.The results indicate that there is a tangent bifurcation on the displacement-load curve for a sphere with a cavity.On the tangent bifurcation point,the cavity grows up suddenly,which is a kind of catastrophe,And there is a pitchfork bifurcation on the displacement-load curve for a solid sphere.On the pitchfork bifurcation point.there is a cavitation in the solid sphere.

  18. Microtubule dynamics: Caps, catastrophes, and coupled hydrolysis

    DEFF Research Database (Denmark)

    Flyvbjerg, H.; Holy, T.E.; Leibler, S.

    1996-01-01

    An effective theory is formulated for the dynamics of the guanosine triphosphate (GTP) cap believed to stabilize growing microtubules. The theory provides a ''coarse-grained'' description of the cap's dynamics. ''Microscopic'' details, such as the microtubule lattice structure and the fate of its...... data. A constant nonzero catastrophe rare, identical for both microtubule ends, is predicted at large growth rates. The delay time for dilution-induced catastrophes is stochastic with a simple distribution that fits the experimental one and, like the experimental one, does not depend on the rate of....... A recent experimental result for the size of the minimal cap that can stabilize a microtubule is shown to agree with the result predicted by the cap model, after its parameters have been extracted from previous experimental results. Thus the effective theory and cap model presented here provide a...

  19. Nonlinear physics: Catastrophe, chaos and complexity

    International Nuclear Information System (INIS)

    Currently in the world of physics, there is open debate on the role of the three C's - catastrophe, chaos and complexity. Seen as new ideas or paradigms, incapable of being harmonized within the realm of traditional physics, these terms seem to be creating turmoil in the classical physics establishment whose foundations date back to the early seventeenth century. This paper first defines catastrophe, chaos and complexity and shows how these terms are all connected to nonlinear dynamics and how they have long since been present within scientific treatises. It also evidences the relationship of the three C's with the concept of organization, inappropriately called self-organization, and with recognition and decisional strategies of cognitive systems. Relevant to natural science, the development of these considerations is necessitating the re-examination of the role and capabilities of human knowledge and a return to inter-disciplinary scientific-philosophical debate

  20. Valuing Catastrophic Losses for Perennial Agricultural Crops

    OpenAIRE

    Adams, Damian C.; Kilmer, Richard L.; Moss, Charles B.; Schmitz, Andrew

    2003-01-01

    Courts are often required to estimate changes in welfare to agricultural operations from catastrophic events. For example, courts must assign damages in lawsuits, such as with pesticide drift cases, or determine 'just compensation' when the government takes private land for public use, as with the removal of dairy farms from environmentally sensitive land or destruction of canker-contaminated citrus trees. In economics, the traditional method of estimating changes in producer welfare is the c...

  1. Catastrophic health expenditure and impoverishment in Mongolia

    OpenAIRE

    Dorjdagva, Javkhlanbayar; Batbaatar, Enkhjargal; Svensson, Mikael; Dorjsuren, Bayarsaikhan; Kauhanen, Jussi

    2016-01-01

    Background The social health insurance coverage is relatively high in Mongolia; however, escalation of out-of-pocket payments for health care, which reached 41 % of the total health expenditure in 2011, is a policy concern. The aim of this study is to analyse the incidence of catastrophic health expenditures and to measure the rate of impoverishment from health care payments under the social health insurance scheme in Mongolia. Methods We used the data from the Household Socio-Economic Survey...

  2. Recent catastrophic landslides and mitigation in China

    Institute of Scientific and Technical Information of China (English)

    2011-01-01

    Increasing population density and development of mountainous terrain have brought human settlements within reach of landslide hazards.In recent years,due to the shortening of return period for severe natural events such as heavy rainfall,snowline retreating,great earthquake together with human activities,catastrophic landslides happened more frequently than before,resulting in large-scale casualties due to the increasing occurrences of rapid long-runout rock avalanches,especially in China.This paper present...

  3. Catastrophic Consequences of Kicking the Chameleon

    OpenAIRE

    Erickcek, Adrienne L.; Barnaby, Neil; Burrage, Clare; Huang, Zhiqi

    2013-01-01

    The physics of the "dark energy" that drives the current cosmological acceleration remains mysterious, and the dark sector may involve new light dynamical fields. If these light scalars couple to matter, a screening mechanism must prevent them from mediating an unacceptably strong fifth force locally. Here we consider a concrete example: the chameleon mechanism. We show that the same coupling between the chameleon field and matter employed by the screening mechanism also has catastrophic cons...

  4. Catastrophic Natural Disasters and Economic Growth

    OpenAIRE

    Cavallo, Eduardo; Galiani, Sebastian; Noy, Ilan; Pantano, Juan

    2010-01-01

    We examine the short and long run average causal impact of catastrophic natural disasters on economic growth by combining information from comparative case studies. We assess the counterfactual of the cases studied by constructing synthetic control groups taking advantage of the fact that the timing of large sudden natural disasters is an exogenous event. We find that only extremely large disasters have a negative effect on output both in the short and long run. However, we also show that thi...

  5. Fitting the Cusp Catastrophe in R: A cusp Package Primer

    Directory of Open Access Journals (Sweden)

    Raoul P. P. P. Grasman

    2009-11-01

    Full Text Available Of the seven elementary catastrophes in catastrophe theory, the “cusp” model is the most widely applied. Most applications are however qualitative. Quantitative techniques for catastrophe modeling have been developed, but so far the limited availability of flexible software has hindered quantitative assessment. We present a package that implements and extends the method of Cobb (Cobb and Watson 1980; Cobb, Koppstein, and Chen 1983, and makes it easy to quantitatively fit and compare different cusp catastrophe models in a statistically principled way. After a short introduction to the cusp catastrophe, we demonstrate the package with two instructive examples.

  6. Paleomagnetic study of the Tunguska catastrophe epicenter

    Science.gov (United States)

    Gladysheva, O. G.; Popov, V. V.

    2016-03-01

    The Tunguska catastrophe occurred in the area of the East Siberian magnetic anomaly on June 30, 1908. The epicenter of the explosive destruction of the Tunguska cosmic body (TCB) was above the central neck of a paleovolcano (Mt. Stoikovich). According to the paleomagnetic data available, the bedrocks on the top of Mt. Stoikovich carry remanent magnetization, which is substantially higher than that in rocks from neighboring mountains. Analysis of the results of paleomagnetic measurements of rock samples collected in the vicinity of the Tunguska catastrophe epicenter showed that the destruction of the cosmic body was accompanied by the formation of multidirectional magnetic fields, which provide disturbances spreading over a distance of 25 km from the epicenter. The chaotic distribution pattern of magnetization vectors measured in the soil in the vicinity of the Tunguska catastrophe epicenter confirms the previously expressed assumption that destruction of the TCB was accompanied with multiple discharges. According to this, we can conclude that the matter of the Tunguska cosmic body was dispersed around the epicenter in a zone approximately 25 km in diameter.

  7. A critical look at catastrophe risk assessments

    CERN Document Server

    Kent, A

    2004-01-01

    Recent papers by Busza et al. (BJSW) and Dar et al. (DDH) argue that astrophysical data can be used to establish bounds on the risk of a catastrophe in forthcoming collider experiments. The safety case set out by BJSW does not rely on these bounds, but on theoretical arguments, which BJSW find sufficiently compelling. However, DDH and other commentators (initially including BJSW) have suggested that the astrophysical bounds alone do give sufficient reassurance. This seems unsupportable when the bounds are expressed in terms of expected cost. For example, DDH's main bound, $p_{\\rm catastrophe} < 2 \\times 10^{-8}$, implies only that the expectation value of the number of deaths is bounded by 120. We thus reappraise the DDH and BJSW risk bounds by comparing risk policy in other areas. We find that requiring a catastrophe risk of no higher than 10^{-15} is necessary to be consistent with established policy for risk optimisation from radiation hazards, even if highly risk tolerant assumptions are made. A respec...

  8. Catastrophic fragmentation of asteroids: Evidence from meteorites

    Science.gov (United States)

    Keil, K.; Haack, H.; Scott, E. R. D.

    1994-01-01

    Meteorites are impact-derived fragments from approximately 85 parent bodies. For seven of these bodies, the meteorites record evidence suggesting that they may have been catastrophically fragmented. We identify three types of catastrophic events: (1) impact and reassemble events greater than 4.4 Gy ago, involving molten or very hot parent bodies (greater than 1200 C); this affected the parent bodies of the ureilites, Shallowater, and the mesosiderites. In each case, the fragments cooled rapidly (approximately 1-1000 C/day) and then reassembled. (2) Later impacts involving cold bodies which, in some cases, reassembled; this occurred on the H and L ordinary chondrite parent bodies. The L parent body probably suffered another catastrophic event about 500 My ago. (3) Recent impacts of cold, multi-kilometer-sized bodies that generated meter-sized meteoroids; this occurred on the parent bodies of the IIIAB irons (650 My ago), the IVA irons (400 My ago), and the H ordinary chondrite (7 My ago).

  9. Downward catastrophe of solar magnetic flux ropes

    CERN Document Server

    Zhang, Quanhao; Hu, Youqiu; Liu, Rui

    2016-01-01

    2.5D time-dependent ideal magnetohydrodynamic (MHD) models in Cartesian coordinates were used in previous studies to seek MHD equilibria involving a magnetic flux rope embedded in a bipolar, partially open background field. As demonstrated by these studies, the equilibrium solutions of the system are separated into two branches: the flux rope sticks to the photosphere for solutions at the lower branch but is suspended in the corona for those at the upper branch. Moreover, a solution originally at the lower branch jumps to the upper, as the related control parameter increases and reaches a critical value, and the associated jump is here referred to as upward catastrophe. The present paper advances these studies in three aspects. First, the magnetic field is changed to be force-free. The system still experiences an upward catastrophe with an increase in each control parameter. Secondly, under the force-free approximation, there also exists a downward catastrophe, characterized by a jump of a solution from the u...

  10. Philosophy and updating of the asteroid photometric catalogue

    Science.gov (United States)

    Magnusson, Per; Barucci, M. Antonietta; Capria, M. T.; Dahlgren, Mats; Fulchignoni, Marcello; Lagerkvist, C. I.

    1992-01-01

    The Asteroid Photometric Catalogue now contains photometric lightcurves for 584 asteroids. We discuss some of the guiding principles behind it. This concerns both observers who offer input to it and users of the product.

  11. Probing obscured, high redshift galaxies using deep P-band continuum imaging with GMRT

    CERN Document Server

    Wadadekar, Yogesh; Ishwara-Chandra, C H; Singh, Veeresh; Beelen, Alexandre; Omont, Alain

    2014-01-01

    We have carried out a deep (150 micro Jy rms) P-band, continuum imaging survey of about 40 square degrees of sky in the XMM-LSS, Lockman Hole and ELAIS-N1 fields with the GMRT. Our deep radio data, combined with deep archival observations in the X-ray (XMM/Chandra), optical (SDSS, CFHTLS), near-infrared (UKIDSS, VISTA/VIDEO), mid-infrared (Spitzer/SWIRE, Spitzer/SERVS) and far-infrared (Spitzer/SWIRE, Herschel/HerMES) will enable us to obtain an accurate census of star-forming and active galaxies out to z~2. This panchromatic coverage enables accurate determination of photometric redshifts and accurate modeling of the spectral energy distribution. We are using our large, merged photometric catalog of over 10000 galaxies to pursue a number of science goals.

  12. DISCOVERING BRIGHT QUASARS AT INTERMEDIATE REDSHIFTS BASED ON OPTICAL/NEAR-INFRARED COLORS

    International Nuclear Information System (INIS)

    The identification of quasars at intermediate redshifts (2.2 < z < 3.5) has been inefficient in most previous quasar surveys since the optical colors of quasars are similar to those of stars. The near-IR K-band excess technique has been suggested to overcome this difficulty. Our recent study also proposed to use optical/near-IR colors for selecting z < 4 quasars. To verify the effectiveness of this method, we selected a list of 105 unidentified bright targets with i ≤ 18.5 from the quasar candidates of SDSS DR6 with both SDSS ugriz optical and UKIDSS YJHK near-IR photometric data, which satisfy our proposed Y – K/g – z criterion and have photometric redshifts between 2.2 and 3.5 estimated from the nine-band SDSS-UKIDSS data. We observed 43 targets with the BFOSC instrument on the 2.16 m optical telescope at Xinglong station of the National Astronomical Observatory of China in the spring of 2012. We spectroscopically identified 36 targets as quasars with redshifts between 2.1 and 3.4. The high success rate of discovering these quasars in the SDSS spectroscopic surveyed area further demonstrates the robustness of both the Y – K/g – z selection criterion and the photometric redshift estimation technique. We also used the above criterion to investigate the possible stellar contamination rate among the quasar candidates of SDSS DR6, and found that the rate is much higher when selecting 3 < z < 3.5 quasar candidates than when selecting lower redshift candidates (z < 2.2). The significant improvement in the photometric redshift estimation when using the nine-band SDSS-UKIDSS data over the five-band SDSS data is demonstrated and a catalog of 7727 unidentified quasar candidates in SDSS DR6 selected with optical/near-IR colors and having photometric redshifts between 2.2 and 3.5 is provided. We also tested the Y – K/g – z selection criterion with the recently released SDSS-III/DR9 quasar catalog and found that 96.2% of 17,999 DR9 quasars with UKIDSS Y- and K

  13. Discovery of six high-redshift quasars with the Lijiang 2.4 m telescope and the Multiple Mirror Telescope

    International Nuclear Information System (INIS)

    Quasars with redshifts greater than 4 are rare, and can be used to probe the structure and evolution of the early universe. Here we report the discovery of six new quasars with i-band magnitudes brighter than 19.5 and redshifts between 2.4 and 4.6 from spectroscopy with the Yunnan Faint Object Spectrograph and Camera (YFOSC) at the Lijiang 2.4 m telescope in February, 2012. These quasars are in the list of z > 3.6 quasar candidates selected by using our proposed J — K/i — Y criterion and the photometric redshift estimations from the SDSS optical and UKIDSS near-IR photometric data. Nine candidates were observed by YFOSC, and five among six new quasars were identified as z > 3.6 quasars. One of the other three objects was identified as a star and the other two were unidentified due to the lower signal-to-noise ratio of their spectra. This is the first time that z > 4 quasars have been discovered using a telescope in China. Thanks to the Chinese Telescope Access Program (TAP), the redshift of 4.6 for one of these quasars was confirmed by the Multiple Mirror Telescope (MMT) Red Channel spectroscopy. The continuum and emission line properties of these six quasars, as well as their central black hole masses and Eddington ratios, were obtained. (letters)

  14. Discovery of six high-redshift quasars with the Lijiang 2.4 m telescope and the Multiple Mirror Telescope

    Institute of Scientific and Technical Information of China (English)

    Xue-Bing Wu; Wen-Wen Zuo; Qian Yang; Wei-Min Yi; Chen-Wei Yang; Wen-Juan Liu; Peng Jiang; Xin-Wen Shu; Hong-Yan Zhou

    2012-01-01

    Quasars with redshifts greater than 4 are rare,and can be used to probe the structure and evolution of the early universe.Here we report the discovery of six new quasars with i-band magnitudes brighter than 19.5 and redshifts between 2.4 and 4.6 from spectroscopy with the Yunnan Faint Object Spectrograph and Camera (YFOSC) at the Lijiang 2.4m telescope in February,2012.These quasars are in the list of z > 3.6 quasar candidates selected by using our proposed J - K/i - Y criterion and the photometric redshift estimations from the SDSS optical and UKIDSS near-IR photometric data.Nine candidates were observed by YFOSC,and five among six new quasars were identified as z > 3.6 quasars.One of the other three objects was identified as a star and the other two were unidentified due to the lower signal-to-noise ratio of their spectra.This is the first time that z > 4 quasars have been discovered using a telescope in China.Thanks to the Chinese Telescope Access Program (TAP),the redshift of 4.6 for one of these quasars was confirmed by the Multiple Mirror Telescope (MMT) Red Channel spectroscopy.The continuum and emission line properties of these six quasars,as well as their central black hole masses and Eddington ratios,were obtained.

  15. Supernovae in the Subaru Deep Field: An Initial Sample, and Type Ia Rate, out to Redshift 1.6

    CERN Document Server

    Poznanski, Dovi; Yasuda, Naoki; Foley, Ryan J; Doi, Mamoru; Filippenko, Alexei V; Fukugita, Masataka; Gal-Yam, Avishay; Jannuzi, Buell T; Morokuma, Tomoki; Oda, Takeshi; Schweiker, Heidi; Sharon, Keren; Silverman, Jeffrey M; Totani, Tomonori

    2007-01-01

    Large samples of high-redshift supernovae (SNe) are potentially powerful probes of cosmic star formation, metal enrichment, and SN physics. We present initial results from a new deep SN survey, based on re-imaging in the R, i', z' bands, of the 0.25 deg2 Subaru Deep Field (SDF), with the 8.2-m Subaru telescope and Suprime-Cam. In a single new epoch consisting of two nights of observations, we have discovered 33 SNe, down to a z'-band magnitude of 26.3 (AB). We have measured the photometric redshifts of the SN host galaxies, obtained Keck spectroscopic redshifts for 17 of the host galaxies, and classified the SNe using the Bayesian photometric algorithm of Poznanski et al. (2007) that relies on template matching. After correcting for biases in the classification, 55% of our sample consists of Type Ia supernovae and 45% of core-collapse SNe. The redshift distribution of the SNe Ia reaches z ~ 1.6, with a median of z ~ 1.2. The core-collapse SNe reach z ~ 1.0, with a median of z ~ 0.5. Our SN sample is comparabl...

  16. The Accelerated Build-up of the Red Sequence in High Redshift Galaxy Clusters

    CERN Document Server

    Cerulo, P; Lidman, C; Demarco, R; Huertas-Company, M; Mei, S; Sánchez-Janssen, R; Barrientos, L F; Muñoz, R P

    2016-01-01

    We analyse the evolution of the red sequence in a sample of galaxy clusters at redshifts $0.8 11.5$) red sequence galaxies in the WINGS clusters, which do not include only the brightest cluster galaxies and which are not present in the HCS clusters, suggesting that they formed at epochs later than $z=0.8$. The comparison with the luminosity distribution of a sample of passive red sequence galaxies drawn from the COSMOS/UltraVISTA field in the photometric redshift range $0.8

  17. The VIMOS Ultra-Deep Survey: ~10,000 galaxies with spectroscopic redshifts to study galaxy assembly at early epochs 2

    CERN Document Server

    Fevre, O Le; Cassata, P; Garilli, B; Brun, V Le; Maccagni, D; Pentericci, L; Thomas, R; Vanzella, E; Zamorani, G; Zucca, E; Amorin, R; Bardelli, S; Capak, P; Cassara, L; Castellano, M; Cimatti, A; Cuby, J G; Cucciati, O; de la Torre, S; Durkalec, A; Fontana, A; Giavalisco, M; Grazian, A; Hathi, N P; Ilbert, O; Lemaux, B C; Moreau, C; Paltani, S; Ribeiro, B; Salvato, M; Schaerer, D; Scodeggio, M; Sommariva, V; Talia, M; Taniguchi, Y; Tresse, L; Vergani, D; Wang, P W; Charlot, S; Contini, T; Fotopoulo, S; Lopez-Sanjuan, C; Mellier, Y; Scoville, N

    2014-01-01

    We present the VIMOS Ultra Deep Survey (VUDS), a spectroscopic redshift survey of ~10.000 very faint galaxies to study the major phase of galaxy assembly 2photometric redshifts and color properties. Spectra covering 3650redshift measurement process, emphasizing the specific methods adapted to this high redshift range. The spectra quality and redshift reliability are discussed, and we derive a completeness in redshift measurement of 91%, or 74% for the most reliable measurements, down to i_AB=25, and measurements are performed all the way down to i_AB=27. The redshift distribution of the main sample peaks at z=3-4 and extends over a large redshift range mainly in 2 < z < 6. A...

  18. Redshifts, Sample Purity, and BCG Positions for the Galaxy Cluster Catalog from the first 720 Square Degrees of the South Pole Telescope Survey

    CERN Document Server

    Song, J; Stalder, B; Desai, S; Bleem, L E; Aird, K A; Armstrong, R; Ashby, M L N; Bayliss, M; Bazin, G; Benson, B A; Bertin, E; Brodwin, M; Carlstrom, J E; Chang, C L; Cho, H M; Clocchiatti, A; Crawford, T M; Crites, A T; de Haan, T; Dobbs, M A; Dudley, J P; Foley, R J; George, E M; Gettings, D; Gladders, M D; Gonzalez, A H; Halverson, N W; Harrington, N L; High, F W; Holder, G P; Holzapfel, W L; Hoover, S; Hrubes, J D; Joy, M; Keisler, R; Knox, L; Lee, A T; Leitch, E M; Liu, J; Lueker, M; Luong-Van, D; Marrone, D P; McDonald, M; McMahon, J J; Mehl, J; Meyer, S S; Mocanu, L; Mohr, J J; Montroy, T E; Natoli, T; Nurgaliev, D; Padin, S; Plagge, T; Pryke, C; Reichardt, C L; Rest, A; Ruel, J; Ruhl, J E; Saliwanchik, B R; Saro, A; Sayre, J T; Schaffer, K K; Shaw, L; Shirokoff, E; Suhada, R; Spieler, H G; Stanford, S A; Staniszewski, Z; Stark, A A; Story, K; Stubbs, C W; van Engelen, A; Vanderlinde, K; Vieira, J D; Williamson, R; Zahn, O

    2012-01-01

    We present the results of the ground- and space-based optical and near-infrared (NIR) follow-up of 224 galaxy cluster candidates detected with the Sunyaev-Zel'dovich (SZ) effect in the 720 deg^2 of the South Pole Telescope (SPT) survey completed in the 2008 and 2009 observing seasons. We use the optical/NIR data to establish whether each candidate is associated with an overdensity of galaxies and to estimate the cluster redshift. Most photometric redshifts are derived through a combination of three different cluster redshift estimators using red-sequence galaxies, resulting in an accuracy of \\Delta z/(1+z)=0.017, determined through comparison with a subsample of 57 clusters for which we have spectroscopic redshifts. We successfully measure redshifts for 158 systems and present redshift lower limits for the remaining candidates. The redshift distribution of the confirmed clusters extends to z=1.35 with a median of z_{med}=0.57. Approximately 18% of the sample with measured redshifts lies at z>0.8. We estimate ...

  19. Redshift Distributions of Galaxies in the DES Science Verification Shear Catalogue and Implications for Weak Lensing

    Energy Technology Data Exchange (ETDEWEB)

    Bonnett, C. [Universitat Autonoma de Barcelona (Spain). et al.

    2015-07-21

    We present photometric redshift estimates for galaxies used in the weak lensing analysis of the Dark Energy Survey Science Verification (DES SV) data. Four model- or machine learning-based photometric redshift methods { annz2, bpz calibrated against BCC-U fig simulations, skynet, and tpz { are analysed. For training, calibration, and testing of these methods, we also construct a catalogue of spectroscopically confirmed galaxies matched against DES SV data. The performance of the methods is evalu-ated against the matched spectroscopic catalogue, focusing on metrics relevant for weak lensing analyses, with additional validation against COSMOS photo-zs. From the galaxies in the DES SV shear catalogue, which have mean redshift 0.72 ±0.01 over the range 0:3 < z < 1:3, we construct three tomographic bins with means of z = {0.45; 0.67,1.00g}. These bins each have systematic uncertainties δz ≲ 0.05 in the mean of the fiducial skynet photo-z n(z). We propagate the errors in the redshift distributions through to their impact on cosmological parameters estimated with cosmic shear, and find that they cause shifts in the value of σ8 of approx. 3%. This shift is within the one sigma statistical errors on σ8 for the DES SV shear catalog. We also found that further study of the potential impact of systematic differences on the critical surface density, Σcrit, contained levels of bias safely less than the statistical power of DES SV data. We recommend a final Gaussian prior for the photo-z bias in the mean of n(z) of width 0:05 for each of the three tomographic bins, and show that this is a sufficient bias model for the corresponding cosmology analysis.

  20. QUEST FOR COSMOS SUBMILLIMETER GALAXY COUNTERPARTS USING CARMA AND VLA: IDENTIFYING THREE HIGH-REDSHIFT STARBURST GALAXIES

    Energy Technology Data Exchange (ETDEWEB)

    Smolcic, V. [European Southern Observatory, Karl-Schwarzschild-Strasse 2, D-85748 Garching b. Muenchen (Germany); Navarrete, F.; Bertoldi, F. [Argelander Institut for Astronomy, Auf dem Huegel 71, Bonn D-53121 (Germany); Aravena, M.; Sheth, K. [National Radio Astronomy Observatory, 520 Edgemont Road, Charlottesville, VA 22903 (United States); Ilbert, O. [Laboratoire d' Astrophysique de Marseille, Universite de Provence, CNRS, BP 8, Traverse du Siphon, F-13376 Marseille Cedex 12 (France); Yun, M. S. [Department of Astronomy, University of Massachusetts, Amherst, MA 01003 (United States); Salvato, M.; Finoguenov, A. [Max-Planck-Institut fuer Extraterrestrische Physik, Giessenbachstrasse, D-85748 Garching (Germany); McCracken, H. J. [Institut d' Astrophysique de Paris, UMR7095 CNRS, Universit Pierre et Marie Curie, 98 bis Boulevard Arago, F-75014 Paris (France); Diener, C. [Institute for Astronomy, ETH Zrich, Wolfgang-Pauli-strasse 27, 8093 Zurich (Switzerland); Aretxaga, I.; Hughes, D.; Wilson, G. [Instituto Nacional de Astrofisica, Optica y Electronica (INAOE), Aptdo. Postal 51 y 216, 72000 Puebla, Pue. (Mexico); Riechers, D. A.; Capak, P.; Scoville, N. Z. [Astronomy Department, California Institute of Technology, MC 249-17, 1200 East California Boulevard, Pasadena, CA 91125 (United States); Karim, A.; Schinnerer, E. [Max Planck Institut fuer Astronomie, Koenigstuhl 17, Heidelberg D-69117 (Germany)

    2012-05-01

    We report on interferometric observations at 1.3 mm at 2''-3'' resolution using the Combined Array for Research in Millimeter-wave Astronomy. We identify multi-wavelength counterparts of three submillimeter galaxies (SMGs; F{sub 1m} > 5.5 mJy) in the COSMOS field, initially detected with MAMBO and AzTEC bolometers at low, {approx}10''-30'', resolution. All three sources-AzTEC/C1, Cosbo-3, and Cosbo-8-are identified to coincide with positions of 20 cm radio sources. Cosbo-3, however, is not associated with the most likely radio counterpart, closest to the MAMBO source position, but with that farther away from it. This illustrates the need for intermediate-resolution ({approx}2'') mm-observations to identify the correct counterparts of single-dish-detected SMGs. All of our three sources become prominent only at NIR wavelengths, and their mm-to-radio flux based redshifts suggest that they lie at redshifts z {approx}> 2. As a proof of concept, we show that photometric redshifts can be well determined for SMGs, and we find photometric redshifts of 5.6 {+-} 1.2, 1.9{sup +0.9}{sub -0.5}, and {approx}4 for AzTEC/C1, Cosbo-3, and Cosbo-8, respectively. Using these we infer that these galaxies have radio-based star formation rates of {approx}> 1000 M{sub Sun} yr{sup -1}and IR luminosities of {approx}10{sup 13} L{sub Sun} consistent with properties of high-redshift SMGs. In summary, our sources reflect a variety of SMG properties in terms of redshift and clustering, consistent with the framework that SMGs are progenitors of z {approx} 2 and today's passive galaxies.

  1. QUEST FOR COSMOS SUBMILLIMETER GALAXY COUNTERPARTS USING CARMA AND VLA: IDENTIFYING THREE HIGH-REDSHIFT STARBURST GALAXIES

    International Nuclear Information System (INIS)

    We report on interferometric observations at 1.3 mm at 2''-3'' resolution using the Combined Array for Research in Millimeter-wave Astronomy. We identify multi-wavelength counterparts of three submillimeter galaxies (SMGs; F1m > 5.5 mJy) in the COSMOS field, initially detected with MAMBO and AzTEC bolometers at low, ∼10''-30'', resolution. All three sources—AzTEC/C1, Cosbo-3, and Cosbo-8—are identified to coincide with positions of 20 cm radio sources. Cosbo-3, however, is not associated with the most likely radio counterpart, closest to the MAMBO source position, but with that farther away from it. This illustrates the need for intermediate-resolution (∼2'') mm-observations to identify the correct counterparts of single-dish-detected SMGs. All of our three sources become prominent only at NIR wavelengths, and their mm-to-radio flux based redshifts suggest that they lie at redshifts z ∼> 2. As a proof of concept, we show that photometric redshifts can be well determined for SMGs, and we find photometric redshifts of 5.6 ± 1.2, 1.9+0.9–0.5, and ∼4 for AzTEC/C1, Cosbo-3, and Cosbo-8, respectively. Using these we infer that these galaxies have radio-based star formation rates of ∼> 1000 M☉ yr–1and IR luminosities of ∼1013 L☉ consistent with properties of high-redshift SMGs. In summary, our sources reflect a variety of SMG properties in terms of redshift and clustering, consistent with the framework that SMGs are progenitors of z ∼ 2 and today's passive galaxies.

  2. Catastrophic Fires in the Russian Federation

    Science.gov (United States)

    Sukhinin, A. I.; Soja, A. J.; McRae, D. J.; Cahoon, D. R.; Stocks, B. J.; Dubrovskaya, O. A.; Ji-Zhong, J.; Flannigan, M.; DeGroot, B.; Westberg, D.; Stackhouse, P. W.; Conard, S. G.; Hao, W. M.

    2011-12-01

    Impacts of climate change on the severity of wildfires and the implications for carbon emissions in the boreal zone are globally significant because Russia contains two-thirds of the world's boreal forest and peat lands. Wildfires in Russia burn from 2 to 20 million ha annually, depending on burning conditions, yet quantification of trends in fire patterns is hampered by the lack of accurate historic fire data. Official Russian wildfire records greatly underestimate burned areas. However, satellite data for Russia have become easily available for assessing area burned since 1980, and we are in the process of analyzing these data to map historic burned area and fire patterns. Catastrophic fire refers to large, uncontrollable fires that are associated with extreme weather conditions. In Russia, major catastrophic fire events are associated with stable anticyclonic systems, which lead to severe drought that supports extreme fire behavior. These forest fires result in large areas burned and high consumption of vegetation and organic soil horizons. Additionally, thick smoke can reduce visibility, which often paralyzes suppression efforts. In recent years, there have been several large and often economically devastating fire complexes across Russia (European Russia, Tyva, Sakha, Chita and the Far East). We present evidence of the association of these large fires with very high or extreme fire weather danger. We assert that these large fire systems have increased in severity in response to current changes in weather and climate, and we argue that catastrophic fires are likely to increase in the future, as climate warms in the northern hemisphere upper latitudes of Russia.

  3. A unified approach of catastrophic events

    Directory of Open Access Journals (Sweden)

    S. Nikolopoulos

    2004-01-01

    Full Text Available Although there is an accumulated charge of theoretical, computational, and numerical work, like catastrophe theory, bifurcation theory, stochastic and deterministic chaos theory, there is an important feeling that these matters do not completely cover the physics of real catastrophic events. Recent studies have suggested that a large variety of complex processes, including earthquakes, heartbeats, and neuronal dynamics, exhibits statistical similarities. Here we are studying in terms of complexity and non linear techniques whether isomorphic signatures emerged indicating the transition from the normal state to the both geological and biological shocks. In the last 15 years, the study of Complex Systems has emerged as a recognized field in its own right, although a good definition of what a complex system is, actually is eluded. A basic reason for our interest in complexity is the striking similarity in behaviour close to irreversible phase transitions among systems that are otherwise quite different in nature. It is by now recognized that the pre-seismic electromagnetic time-series contain valuable information about the earthquake preparation process, which cannot be extracted without the use of important computational power, probably in connection with computer Algebra techniques. This paper presents an analysis, the aim of which is to indicate the approach of the global instability in the pre-focal area. Non-linear characteristics are studied by applying two techniques, namely the Correlation Dimension Estimation and the Approximate Entropy. These two non-linear techniques present coherent conclusions, and could cooperate with an independent fractal spectral analysis to provide a detection concerning the emergence of the nucleation phase of the impending catastrophic event. In the context of similar mathematical background, it would be interesting to augment this description of pre-seismic electromagnetic anomalies in order to cover biological

  4. Photometric and spectroscopic investigation of TW Draconis

    CERN Document Server

    Zejda, M; Harmanec, P; Slechta, M; Mikulasek, Z; Zverko, J; Svoboda, P; Krticka, J

    2010-01-01

    Context. TW Draconis is one of the best studied Algol-type eclipsing binaries. There is significant evidence for miscellaneous physical processes between interacting binary components manifesting themselves by period and light curve changes. Aims. Obtaining new set of photometric and spectroscopic observations, we analysed them together with the older spectroscopic and photometric data to build model of this eclipsing system with respect to observed changes of O-C diagram and light curve. Methods. Reduction of new spectra was carried out in the IRAF and SPEFO programs. Radial velocities were determined manually using SPEFO, by CCF using the Zverko's code and from the program KOREL. Orbital elements were derived with the FOTEL program and via disentangling with KOREL. The final combined solution was obtained with the programs PHOEBE and FOTEL. Results. Photometry shows small irregularities in light curves as a results of pulsating of one component and spot activity. Using net of KOREL outputs we found the mass...

  5. Stellar physics with the ALHAMBRA photometric system

    International Nuclear Information System (INIS)

    The ALHAMBRA photometric system was specifically designed to perform a tomography of the Universe in some selected areas. Although mainly designed for extragalactic purposes, its 20 contiguous, equal-width, medium-band photometric system in the optical wavelength range, shows a great capacity for stellar classification. In this contribution we propose a methodology for stellar classification and physical parameter estimation (Teff, log g, [Fe/H], and color excess E(B – V)) based on 18 independent reddening-free Q-values from the ALHAMBRA photometry. Based on the theoretical Spectral library BaSeL 2.2, and applied to 288 stars from the Next Generation spectral Library (NGSL), we discuss the reliability of the method and its dependence on the extinction law used.

  6. Photometric Variability of Four Coronally Active Stars

    Indian Academy of Sciences (India)

    J. C. Pandey; K. P. Singh; R. Sagar; S. A. Drake

    2002-03-01

    We present photometric observations of four stars that are optical counterparts of soft X-ray/EUV sources, namely 1ES 0829+15.9, 1ES0920-13.6, 2RE J110159+223509 and 1ES 1737+61.2. We have discovered periodic variability in two of the stars, viz., MCC 527 (1ES 0829+15.9; Period = 0.828 ± 0.0047) and HD 81032 (1ES 0920-13.6; Period = ∼ 57.02 ± 0.560 days). HD 95559 (2RE J110159+223509) is found to show a period of 3. HD 160934 (1ES1737+61.2) also shows photometric variability but needs to be monitored further for finding its period. These stars most likely belong to the class of chromospherically active stars.

  7. Photometric Standards for Non-Standard Filters

    Science.gov (United States)

    Hoot, John E.

    2015-05-01

    The AAVSO, professional collaborators, and research consortiums are increasingly requesting that photometric observations be submitted after they have been transformed onto 'standard' photometric systems. This greatly reduces the burden on the principal investigators in managing and merging data from many disparate contributors, but discourages many potential contributors who are unaware that their present equipment can make a valuable contribution. Many potential observers, amateurs, students and instructors are confused over what filters are required and what standards are best. This paper focuses on the best standards and observation methods for observers with one shot color cameras and those possessing monochrome CCD cameras with LRGB filter sets, the two most common configurations used in amateur and educational observatories. This paper examines which current standards best match common equipment and present effective ways for amateurs and students to reduce data to standard systems with common tools and a minimum of mathematical rigor.

  8. Dust Formation, Evolution, and Obscuration Effects in the Very High-Redshift Universe

    Science.gov (United States)

    Dwek, Eli; Staguhn, Johannes; Arendt, Richard G.; Kovacs, Attila; Su, Ting; Benford, Dominic J.

    2014-01-01

    The evolution of dust at redshifts z > or approx. 9, and consequently the dust properties, differs greatly from that in the local universe. In contrast to the local universe, core collapse supernovae (CCSNe) are the only source of thermally-condensed dust. Because of the low initial dust-to-gas mass ratio, grain destruction rates are low, so that CCSNe are net producers of interstellar dust. Galaxies with large initial gas mass or high mass infall rate will therefore have a more rapid net rate of dust production comported to galaxies with lower gas mass, even at the same star formation rate. The dust composition is dominated by silicates, which exhibit a strong rise in the UV opacity near the Lyman break. This "silicate-UV break" may be confused with the Lyman break, resulting in a misidentification of a galaxies' photometric redshift. In this paper we demonstrate these effects by analyzing the spectral energy distribution (SED) of MACS1149-JD, a lensed galaxy at z = 9.6. A potential 2mm counterpart of MACS1149-JD has been identified with GISMO. While additional observations are required to corroborate this identification, we use this possible association to illustrate the physical processes and the observational effects of dust in the very high redshift universe. Subject headings: galaxies: high-redshift - galaxies: evolution - galaxies: individual (MACS1149- JD) - Interstellar medium (ISM), nebulae: dust, extinction - physical data and processes: nuclear reactions, nucleosynthesis, abundances.

  9. The evolution of quiescent galaxies at high redshift (z > 1.4)

    CERN Document Server

    Pozzi, F; Cimatti, A; Ilbert, O; Pozzetti, L; McCracken, H; Capak, P; Floch, E Le; Salvato, M; Zamorani, G; Carollo, C M; Contini, T; Kneib, J P; Févre, O Le; Lilly, S J; Mainieri, V; Renzini, A; Scodeggio, M; Bardelli, S; Bolzonella, M; Bongiorno, A; Caputi, K; Coppa, G; Cucciati, O; de la Torre, S; de Ravel, L; Franzetti, P; Garilli, B; Iovino, A; Kampczyk, P; Knobel, C; Kovac, K; Lamareille, F; Borgne, J F Le; Brun, V Le; Maier, C; Mignoli, M; Pelló, R; Peng, Y; Pérez-Montero, E; Ricciardelli, E; Silverman, J D; Tanaka, M; Tasca, L A M; Tresse, L; Vergani, D; Zucca, E

    2011-01-01

    We have studied the evolution of high redshift quiescent galaxies over an effective area of ~1.7 deg^2 in the COSMOS field. Galaxies have been divided according to their star-formation activity and the evolution of the different populations has been investigated in detail. We have studied an IRAC (mag_3.6 1.4 with multi-wavelength coverage. We have derived accurate photometric redshifts (sigma=0.06) and other important physical parameters through a SED-fitting procedure. We have divided our sample into actively star-forming, intermediate and quiescent galaxies depending on their specific star formation rate. We have computed the galaxy stellar mass function of the total sample and the different populations at z=1.4-3.0. We have studied the properties of high redshift quiescent galaxies finding that they are old (1-4 Gyr), massive (log(M/M_sun)~10.65), weakly star forming stellar populations with low dust extinction (E(B-V) 11, while the quiescent population increases from 10% to 50% at the same redshift and...

  10. The redshift distribution of dusty star forming galaxies from the SPT survey

    CERN Document Server

    Strandet, M L; Vieira, J D; de Breuck, C; Aguirre, J E; Aravena, M; Ashby, M L N; Béthermin, M; Bradford, C M; Carlstrom, J E; Chapman, S C; Crawford, T M; Everett, W; Fassnacht, C D; Furstenau, R M; Gonzalez, A H; Greve, T R; Gullberg, B; Hezaveh, Y; Kamenetzky, J R; Litke, K; Ma, J; Malkan, M; Marrone, D P; Menten, K M; Murphy, E J; Nadolski, A; Rotermund, K M; Spilker, J S; Stark, A A; Welikala, N

    2016-01-01

    We use the Atacama Large Millimeter/submillimeter Array (ALMA) in Cycle 1 to determine spectroscopic redshifts of high-redshift dusty star-forming galaxies (DSFGs) selected by their 1.4mm continuum emission in the South Pole Telescope (SPT) survey. We present ALMA 3mm spectral scans between 84-114GHz for 15 galaxies and targeted ALMA 1mm observations for an additional eight sources. Our observations yield 30 new line detections from CO, [CI] , [NII] , H_2O and NH_3. We further present APEX [CII] and CO mid-J observations for seven sources for which only a single line was detected in spectral-scan data from ALMA Cycle 0 or Cycle 1. We combine the new observations with previously published and new mm/submm line and photometric data of the SPT-selected DSFGs to study their redshift distribution. The combined data yield 39 spectroscopic redshifts from molecular lines, a success rate of >85%. Our sample represents the largest data set of its kind today and has the highest spectroscopic completeness among all redsh...

  11. Improving LSST Photometric Calibration with Gaia Data

    CERN Document Server

    Axelrod, Tim

    2014-01-01

    We consider the possibility that the Gaia mission can supply data which will improve the photometric calibration of LSST. After outlining the LSST calibra- tion process and the information that will be available from Gaia, we explore two options for using Gaia data. The first is to use Gaia G-band photometry of selected stars, in conjunction with knowledge of the stellar parameters Teff, log g, and AV, and in some cases Z, to create photometric standards in the LSST u, g, r, i, z, and y bands. The accuracies of the resulting standard magnitudes are found to be insufficient to satisfy LSST requirements when generated from main sequence (MS) stars, but generally adequate from DA white dwarfs (WD). The second option is combine the LSST bandpasses into a synthetic Gaia G band, which is a close approximation to the real Gaia G band. This allows synthetic Gaia G photometry to be directly compared with actual Gaia G photometry at a level of accuracy which is useful for both verifying and improving LSST photometric c...

  12. Morphological number-count and redshift distributions to I < 26 from the Hubble Deep Field Implications for the evolution of Ellipticals, Spirals and Irregulars

    CERN Document Server

    Driver, S P; Couch, W J; Odewahn, S C; Windhorst, R A; Phillipps, S; Lanzetta, K; Yahil, A

    1998-01-01

    We combine the photometric redshift data of Fernandez-Soto et al. (1997) with the morphological data of Odewahn et al. (1996) for all galaxies with I 24. (2) Spiral galaxies are present in numbers consistent with zero- evolution predictions to I = 22. Beyond this magnitude some net- positive evolution is required. Although the number-counts are consistent with the passive-evolution predictions to I=26.0 the redshift distributions favor number AND luminosity evolution. (3) There is no obvious explanation for the late-type/irregular class and this category requires further subdivision. While a small fraction of the population lies at low redshift (i.e. true irregulars), the majority lie at redshifts, 1 1.5 mergers are frequent and, taken in conjunction with the absence of normal spirals at z > 2, the logical inference is that they represent the progenitors of normal spirals forming via hierarchical merging.

  13. Morphological Number Counts and Redshift Distributions to I = 25 from the Hubble Deep Fields Constraints on Cosmological Models from Early Type Galaxies

    CERN Document Server

    Phillipps, S; Couch, W J; Fernández-Soto, A; Bristow, P D; Odewahn, S C; Windhorst, R A; Lanzetta, K

    2000-01-01

    We combine magnitude and photometric redshift data on galaxies in the Hubble Deep Fields with morphological classifications in order to separate out the distributions for early type galaxies. The updated morphological galaxy number counts down to I = 25 and the corresponding redshift distributions are used as joint constraints on cosmological models, in particular on the values of the density parameter Omega_{0} and normalised cosmological constant Lambda_{0}. We find that an Einstein - de Sitter universe with simple passive evolution gives an excellent fit to the counts and redshift data at all magnitudes. An open, low Omega_{0}, model with no net evolution (and conservation of the number of ellipticals), which fits the counts equally well, is somewhat less successful, predicting slightly lower mean redshifts and, more significantly, the lack of a high--z tail. A number conserving model with a dominant contribution from Lambda_{0}, on the other hand, is far less successful, predicting a much narrower distrib...

  14. Bankruptcy by catastrophes for major multi-nationals: stock exchange sensitivity for three catastrophes

    NARCIS (Netherlands)

    Van Gulijk, C.; Ale, B.J.M.

    2012-01-01

    This paper investigates the effect of major catastrophes have on stock exchange values for the major multi-nationals. The paper demonstrates that the Sharpe analysis is more sensitive in identifying effects than just following the daily stock values for assessing market response. It was found that m

  15. Catastrophizing and Parental Response to Child Symptom Complaints

    OpenAIRE

    Langer, Shelby L.; Romano, Joan M.; Levy, Rona L; Walker, Lynn S.; Whitehead, William E.

    2009-01-01

    This study investigated whether catastrophic thinking about pain by children with functional abdominal pain or by their parents is associated with health outcomes in the child. Subjects were 132 parent-child dyads. Child catastrophizing predicted child depression, anxiety and functional disability. Parents’ catastrophizing cognitions about their own pain predicted self-reported protective responses to their children’s abdominal pain (responding in ways that encourage illness behavior). Protec...

  16. Averting Catastrophes: The Strange Economics of Scylla and Charybdis

    OpenAIRE

    Martin, Ian; Pindyck, R. S.

    2014-01-01

    How should we evaluate public policies or projects to avert, or reduce the likelihood of, a catastrophic event? Examples might include inspection and surveillance programs to avert nuclear terrorism, investments in vaccine technologies to help respond to a "mega-virus," or the construction of levees to avert major flooding. A policy to avert a particular catastrophe considered in isolation might be evaluated in a cost-benefit framework. But because society faces multiple potential catastrophe...

  17. Mutation accumulation and the catastrophic senescence of Pacific salmon

    CERN Document Server

    Penna, T J P; Stauffer, D; Stauffer, Dietrich

    1995-01-01

    The bit-string model of biological aging is used to simulate the catastrophic senescence of Pacific Salmon. We have shown that reproduction occuring only once and at a fixed age is the only ingredient needed to explain the catastrophic senescence according the mutation accumulation theory. Several results are presented, some of them with up to 10^8 fishes, showing how the survival rates in catastrophic senescence are affected by changes in the parameters of the model.

  18. Optimal Redshift Weighting For Baryon Acoustic Oscillations

    OpenAIRE

    Zhu, Fangzhou; Padmanabhan, Nikhil; White, Martin

    2014-01-01

    Future baryon acoustic oscillation (BAO) surveys will survey very large volumes, covering wide ranges in redshift. We derive a set of redshift weights to compress the information in the redshift direction to a small number of modes. We suggest that such a compression preserves almost all of the signal for most cosmologies, while giving high signal-to-noise measurements for each combination. We present some toy models and simple worked examples. As an intermediate step, we give a precise meani...

  19. Death, Catastrophe, and the Significance of Tragedy

    Directory of Open Access Journals (Sweden)

    Jennifer Ballengee

    2014-05-01

    Full Text Available This NANO note will examine the tension between representation, memorial, and the catastrophe of death that emerges in the space of tragedy, as the problem arises in two quite different works: Oedipus at Colonus, a fairly typical fifth-century Greek tragedy, and Falling Man, Don DeLillo’s novel that, in its attempt to address the events of 9/11, reflects in form and subject matter many of Aristotle’s terms of tragic representation. It is not the intent of this note to engage with the recent proliferation of work in “performance theory.” Rather than being concerned with an imagined exchange between audience and actor, this study examines how the supplementary relationship of gesture and speech in tragedy disrupts the public/private distinction, and how this articulation effects and enables the public memorialization of death. Thus, this paper will consider the representation of death as an event whose catastrophic, and somewhat mysterious, collision of the public and the private lends it its tragic significance.

  20. Inside Money, Procyclical Leverage, and Banking Catastrophes

    Science.gov (United States)

    Brummitt, Charles D.; Sethi, Rajiv; Watts, Duncan J.

    2014-01-01

    We explore a model of the interaction between banks and outside investors in which the ability of banks to issue inside money (short-term liabilities believed to be convertible into currency at par) can generate a collapse in asset prices and widespread bank insolvency. The banks and investors share a common belief about the future value of certain long-term assets, but they have different objective functions; changes to this common belief result in portfolio adjustments and trade. Positive belief shocks induce banks to buy risky assets from investors, and the banks finance those purchases by issuing new short-term liabilities. Negative belief shocks induce banks to sell assets in order to reduce their chance of insolvency to a tolerably low level, and they supply more assets at lower prices, which can result in multiple market-clearing prices. A sufficiently severe negative shock causes the set of equilibrium prices to contract (in a manner given by a cusp catastrophe), causing prices to plummet discontinuously and banks to become insolvent. Successive positive and negative shocks of equal magnitude do not cancel; rather, a banking catastrophe can occur even if beliefs simply return to their initial state. Capital requirements can prevent crises by curtailing the expansion of balance sheets when beliefs become more optimistic, but they can also force larger price declines. Emergency asset price supports can be understood as attempts by a central bank to coordinate expectations on an equilibrium with solvency. PMID:25136959

  1. Inside money, procyclical leverage, and banking catastrophes.

    Science.gov (United States)

    Brummitt, Charles D; Sethi, Rajiv; Watts, Duncan J

    2014-01-01

    We explore a model of the interaction between banks and outside investors in which the ability of banks to issue inside money (short-term liabilities believed to be convertible into currency at par) can generate a collapse in asset prices and widespread bank insolvency. The banks and investors share a common belief about the future value of certain long-term assets, but they have different objective functions; changes to this common belief result in portfolio adjustments and trade. Positive belief shocks induce banks to buy risky assets from investors, and the banks finance those purchases by issuing new short-term liabilities. Negative belief shocks induce banks to sell assets in order to reduce their chance of insolvency to a tolerably low level, and they supply more assets at lower prices, which can result in multiple market-clearing prices. A sufficiently severe negative shock causes the set of equilibrium prices to contract (in a manner given by a cusp catastrophe), causing prices to plummet discontinuously and banks to become insolvent. Successive positive and negative shocks of equal magnitude do not cancel; rather, a banking catastrophe can occur even if beliefs simply return to their initial state. Capital requirements can prevent crises by curtailing the expansion of balance sheets when beliefs become more optimistic, but they can also force larger price declines. Emergency asset price supports can be understood as attempts by a central bank to coordinate expectations on an equilibrium with solvency. PMID:25136959

  2. Gradient catastrophe and flutter in vortex filament dynamics

    CERN Document Server

    Konopelchenko, B G

    2011-01-01

    Gradient catastrophe and flutter instability in the motion of vortex filament within the localized induction approximation are analyzed. It is shown that the origin if this phenomenon is in the gradient catastrophe for the dispersionless Da Rios system which describes motion of filament with slow varying curvature and torsion. Geometrically this catastrophe manifests as a rapid oscillation of a filament curve in a point that resembles the flutter of airfoils. Analytically it is the elliptic umbilic singularity in the terminology of the catastrophe theory. It is demonstrated that its double scaling regularization is governed by the Painlev\\'e-I equation.

  3. Gradient catastrophe and flutter in vortex filament dynamics

    International Nuclear Information System (INIS)

    Gradient catastrophe and flutter instability in the motion of a vortex filament within the localized induction approximation are analyzed. It is shown that the origin of this phenomenon is in the gradient catastrophe for the dispersionless Da Rios system which describes the motion of a filament with slow varying curvature and torsion. Geometrically, this catastrophe manifests as a rapid oscillation of a filament curve in a point that resembles the flutter of airfoils. Analytically, it is the elliptic umbilic singularity in the terminology of the catastrophe theory. It is demonstrated that its double scaling regularization is governed by the Painleve-I equation. (fast track communication)

  4. Gradient catastrophe and flutter in vortex filament dynamics

    Energy Technology Data Exchange (ETDEWEB)

    Konopelchenko, B G [Dipartimento di Fisica, Universita del Salento and INFN, Sezione di Lecce, 73100 Lecce (Italy); Ortenzi, G, E-mail: giovanni.ortenzi@unimib.it [Dipartimento di Matematica Pura ed Applicazioni, Universita di Milano Bicocca, 20125 Milano (Italy)

    2011-10-28

    Gradient catastrophe and flutter instability in the motion of a vortex filament within the localized induction approximation are analyzed. It is shown that the origin of this phenomenon is in the gradient catastrophe for the dispersionless Da Rios system which describes the motion of a filament with slow varying curvature and torsion. Geometrically, this catastrophe manifests as a rapid oscillation of a filament curve in a point that resembles the flutter of airfoils. Analytically, it is the elliptic umbilic singularity in the terminology of the catastrophe theory. It is demonstrated that its double scaling regularization is governed by the Painleve-I equation. (fast track communication)

  5. Corporate Demand for Insurance: An Empirical Analysis of the U.S. Market for Catastrophe and Non-Catastrophe Risks

    OpenAIRE

    Michel-Kerjan, Erwann; Raschky, Paul A.; Kunreuther, Howard C.

    2009-01-01

    This paper tests some existing theories developed over the past 25 years on corporate demand for insurance. Using a unique dataset of 1,809 large U.S. corporations it provides the first empirical analysis that compares corporate demand for standard property insurance and for catastrophe coverage (here, terrorism). We find that larger companies are more likely to have some catastrophe coverage. Corporate demand for catastrophe insurance is found to be more price inelastic than insurance for no...

  6. Galaxies Associated with z~4 Damped Lya Systems I. Imaging and Photometric Selection

    CERN Document Server

    Prochaska, J X; Wolfe, A M; Quirrenbach, Andreas G; Lanzetta, K M; Chen, H W; Cooke, J; Yahata, N; Prochaska, Jason X.; Gawiser, Eric; Wolfe, Arthur M.; Quirrenbach, Andreas; Lanzetta, Kenneth M.; Chen, Hsiao-Wen; Cooke, Jeff; Yahata, Noriaki

    2002-01-01

    This paper describes the acquisition and analysis of imaging data for the identification of galaxies associated with z~4 damped Lya systems. We present deep BRI images of three fields known to contain four z~4 damped systems. We discuss the reduction and calibration of the data, detail the color criteria used to identify z~4 galaxies, and present a photometric redshift analysis to complement the color selection. We have found no galaxy candidates closer to the QSO than 7'' which could be responsible for the damped Lya systems. Assuming that at least one of the galaxies is not directly beneath the QSO, we set an upper limit on this damped Lya system of L < L*/4. Finally, we have established a web site to release these imaging data to the public.

  7. Madame Bovary and Catastrophism: Revolving narratives

    Directory of Open Access Journals (Sweden)

    Ruth Morris

    2011-07-01

    Full Text Available Cet article relie Madame Bovary au contexte scientifique français des années 1850, en lisant le roman de Flaubert à la lumière des théories de Cuvier. Le savant français Georges Cuvier, avec nombre de ses contemporains, explique les origines du monde à l’aide de la théorie des catastrophes. D’après cette théorie, le monde est divisé en périodes très courtes ponctuées de grandes catastrophes ou, en termes cuviériens, de « révolutions » qui ont éradiqué toute vie et ont permis au monde d’être entièrement repeuplé. Une telle conception affecte l’idée même du « temps ». Cuvier pense que la formation de la Terre est relativement récente, l’époque présente n’étant vieille que de cinq mille ans. Cette compression temporelle peut être rapportée à Madame Bovary dont le « tempo » s’accroît au fur et à mesure qu’on se rapproche du dénouement. Dans la théorie des catastrophes comme dans le roman, le temps ne suit pas une ligne chronologique. Les « révolutions » viennent briser le fil continu du temps et Emma est souvent incapable de distinguer entre le passé, le présent et le futur. Les « révolutions » servent aussi à ponctuer et à perturber le cours de la vie sur Terre en produisant des événements majeurs dans l’histoire du globe. Il en est de même dans la vie d’Emma. Son existence est marquée par des événements majeurs, comme le bal, qui créent un éclatement et une fragmentation de la temporalité, comme dans la théorie de Cuvier. Je défendrai aussi l’idée d’un lien entre la soudaineté et la violence des « révolutions » et les crises nerveuses d’Emma, qui surviennent brusquement et relèvent de l’hystérie. La conception cuviérienne de la temporalité doit enfin être envisagée au regard des théories de l’évolution, ce qui implique de réévaluer les notions d’adaptation, d’hérédité et de mort dans le roman de Flaubert.This paper locates Madame

  8. DISCOVERY OF NINE INTERMEDIATE-REDSHIFT COMPACT QUIESCENT GALAXIES IN THE SLOAN DIGITAL SKY SURVEY

    International Nuclear Information System (INIS)

    We identify nine galaxies with dynamical masses of M dyn ∼> 1010 M ☉ as photometric point sources, but with redshifts between z = 0.2 and z = 0.6, in the Sloan Digital Sky Survey (SDSS) spectro-photometric database. All nine galaxies have archival Hubble Space Telescope images. Surface brightness profile fitting confirms that all nine galaxies are extremely compact (0.4 e,c e,c = 0.74 kpc) for their velocity dispersion (110 –1; median σ = 178 km s–1). From the SDSS spectra, three systems are dominated by very young stars; the other six are older than ∼1 Gyr (two are E+A galaxies). The three young galaxies have disturbed morphologies and the older systems have smooth profiles consistent with a single-Sérsic function. All nine lie below the z ∼ 0 velocity dispersion-half-light radius relation. The most massive system—SDSSJ123657.44+631115.4—lies right within the locus for massive compact z > 1 galaxies and the other eight objects follow the high-redshift dynamical size-mass relation

  9. Quasar Probabilities and Redshifts from WISE mid-IR through GALEX UV Photometry

    CERN Document Server

    DiPompeo, M A; Myers, A D; Lang, D

    2015-01-01

    Extreme deconvolution (XD) of broad-band photometric data can both separate stars from quasars and generate probability density functions for quasar redshifts, while incorporating flux uncertainties and missing data. Mid-infrared photometric colors are now widely used to identify hot dust intrinsic to quasars, and the release of all-sky WISE data has led to a dramatic increase in the number of IR-selected quasars. Using forced-photometry on public WISE data at the locations of SDSS point sources, we incorporate this all-sky data into the training of the XDQSOz models originally developed to select quasars from optical photometry. The combination of WISE and SDSS information is far more powerful than SDSS alone, particularly at $z>2$. The use of SDSS$+$WISE photometry is comparable to the use of SDSS$+$ultraviolet$+$near-IR data. We release a new public catalogue of 5,537,436 (total; 3,874,639 weighted by probability) potential quasars with probability $P_{\\textrm{QSO}} > 0.2$. The catalogue includes redshift ...

  10. Photometric quantities for solar irradiance modeling

    Science.gov (United States)

    Preminger, D. G.; Walton, S. R.; Chapman, G. A.

    2002-11-01

    We analyze photometric quantities for the modeling of the total solar irradiance, S. These quantities are derived from full-disk solar images taken at the San Fernando Observatory. We introduce a new quantity, the photometric sum, Σ, which is the sum over an entire image of each pixel's contribution to the irradiance in that image. Σ combines both bright and dark features; and because the sum is over the entire image, it will include low contrast features that cannot be identified directly. Specifically, we examine Σr, Σb, and ΣK, the photometric sums over broadband red, broadband blue, and 1-nm bandpass Ca II K images, respectively. Σr and Σb measure the effects of solar features on the variability in S at two different continuum wavelengths. ΣK measures the variability in spectral lines due to solar features. We find that Σr and Σb have no long-term trend. ΣK, however, varies in phase with the solar cycle. We carry out several multiple linear regressions on the value of S from cycle 22; the best fit uses Σr and ΣK and reproduces the observed composite S with a multiple regression coefficient R = 0.96. We conclude that the long-term change in S over the solar cycle can be accounted for by the variability in the spectral lines as measured by ΣK, assuming no change in the quiet Sun; the contribution of the continuum to the variations in S is only on active region timescales.

  11. Intergalactic shells at large redshift

    Science.gov (United States)

    Shull, J. M.; Silk, J.

    1981-01-01

    The intergalactic shells produced by galactic explosions at large redshift, whose interiors cool by inverse Compton scattering off the cosmic background radiation, have a characteristic angular size of about 1 arcmin at peak brightness. At z values lower than 2, the shells typically have a radius of 0.5 Mpc, a velocity of about 50 km/sec, a metal abundance of about 0.0001 of cosmic values, and strong radiation in H I(Lyman-alpha), He II 304 A, and the IR fine-structure lines of C II and Si II. The predicted extragalactic background emission from many shells, strongly peaked toward the UV, sets an upper limit to the number of exploding sources at z values of about 10. Shell absorption lines of H I, C II, Si II, and Fe II, which may be seen at more recent epochs in quasar spectra, may probe otherwise invisible explosions in the early universe.

  12. Catastrophic Consequences of Kicking the Chameleon

    CERN Document Server

    Erickcek, Adrienne L; Burrage, Clare; Huang, Zhiqi

    2013-01-01

    The physics of the "dark energy" that drives the current cosmological acceleration remains mysterious, and the dark sector may involve new light dynamical fields. If these light scalars couple to matter, a screening mechanism must prevent them from mediating an unacceptably strong fifth force locally. Here we consider a concrete example: the chameleon mechanism. We show that the same coupling between the chameleon field and matter employed by the screening mechanism also has catastrophic consequences for the chameleon during the Universe's first minutes. The chameleon couples to the trace of the stress-energy tensor, which is temporarily non-zero in a radiation-dominated universe whenever a particle species becomes non-relativistic. These "kicks" impart a significant velocity to the chameleon field, causing its effective mass to vary non-adiabatically and resulting in the copious production of quantum fluctuations. Dissipative effects strongly modify the background evolution of the chameleon field, invalidati...

  13. Application of catastrophe theory to nuclear structure

    International Nuclear Information System (INIS)

    Three two-parameter models, one describing an A-body system (the atomic nucleus) and two describing many-body systems (the van der Waals gas and the ferroelectric (perovskite) system) are compared within the framework of catastrophe theory. It is shown that each has a critical point (second-order phase transition) when the two counteracting forces controlling it are in balance; further, each undergoes a first-order phase transition when one of the forces vanishes (the deforming force for the nucleus, the attractive force for the van der Waals gas, and the dielectric constant for the perovskite). Finally, when both parameters are kept constant, a kind of phase transition may occur at a critical angular momentum, critical pressure, and critical electric field. 3 figures, 1 table

  14. The Redshift Distribution of the TOUGH Survey

    CERN Document Server

    Jakobsson, P; Malesani, D; Chapman, R; Fynbo, J P U; Milvang-Jensen, B; Kruhler, T; Tanvir, N R

    2013-01-01

    We present the redshift results from a Very Large Telescope program aimed at optimizing the legacy value of the Swift mission: to characterize a homogeneous, X-ray selected, sample of 69 GRB host galaxies. 19 new redshifts have been secured, resulting in a 83% (57/69) redshift completion, making the survey the most comprehensive in terms of redshift completeness of any sample to the full Swift depth, available to date. We present the cumulative redshift distribution and derive a conservative, yet small, associated uncertainty. We constrain the fraction of Swift GRBs at high redshift to a maximum of 10% (5%) for z > 6 (z > 7). The mean redshift of the host sample is assessed to be > 2.2. Using this more complete sample, we confirm previous findings that the GRB rate at high redshift (z > 3) appears to be in excess of predictions based on assumptions that it should follow conventional determinations of the star formation history of the universe, combined with an estimate of its likely metallicity dependence. T...

  15. Sirius B and the gravitational redshift

    International Nuclear Information System (INIS)

    An historical account is given of studies of the spectrum of Sirius B; in particular of the measurements reported by Adams, by Moore and by later workers, of the differences between the redshifts of Sirius and Sirius B. The measurements are discussed in the context of the search for the gravitational redshift predicted by Einstein from relativity theory. (U.K.)

  16. A New Modification of Photometric Method

    OpenAIRE

    M. Chrenek; J. Misun; P. Kulla; Sevcik, P

    1993-01-01

    For the digital 1D-image processing we go out from the so-called photometric method. For the concrete applications of the introduced method its accuracy lowers, owing to that the form of an output video signal of linear CCD sensor is not smooth and not symmetrical. In some cases the output video signal of linear CCD sensor is devalued by the certain disperse of pixel sensitivity, respectively also that a measured object and its background are not uniform. Therefore we introduce a new modifica...

  17. Experiments on Mixotrophic Protists and Catastrophic Darkness

    Science.gov (United States)

    Jones, Harriet; Cockell, Charles S.; Goodson, Claire; Price, Nicola; Simpson, Annika; Thomas, Benjamin

    2009-08-01

    Catastrophically darkened photic zone conditions in water bodies are postulated to be induced by a diversity of mechanisms that are recorded in the geological record, including asteroid and comet impacts and large-scale volcanic eruptions. Giant wildfires, such as those that followed the great fires in Siberia in 1915, have been directly shown to cause large reductions in sunlight penetrating to the ground. Previous studies on the response of phototrophs to s udden prolonged darkness have focused on the survival of axenic strains. In this paper, we describe laboratory experiments to investigate the survival and growth of isolated and mixed cultures of freshwater and marine mixotrophs after 6 months of darkness and in the low light that would follow these events. Mixotrophs could survive 6 months of darkness. Some species used dissolved organic carbon, which can be released from dead biomass after loss of light and was shown to improve feeding rates. Mixotrophs also improved the survival and subsequent growth of obligate phototrophs at low light levels when grown in mixed cultures. The ability of mixotrophs to switch from photosynthesis to heterotrophy following sudden darkening would not only allow them to survive but to grow and contribute to active food chains. The experiments suggest that, following the return of light, resumption of photosynthesis can be rapid. These experiments improve our understanding of the collapse of photosynthesis following catastrophic darkening and emphasize the important role of mixotrophy in the resilience of the photosynthetic biosphere during such periods. We speculate on the implications for the Cretaceous-Tertiary impact event and periods of global freezing.

  18. Grasshopper Population Ecology: Catastrophe, Criticality, and Critique

    Directory of Open Access Journals (Sweden)

    Jeffrey A. Lockwood

    2008-06-01

    Full Text Available Grasshopper population dynamics are an important part of the North American rangeland ecosystem and an important factor in the economies that derive from the rangeland. Outbreak dynamics have plagued management strategies in the rangeland, and attempts to find simple, linear and mechanistic solutions to both understanding and predicting the dynamics have proved fruitless. These efforts to ground theory in a correspondence with the “real” world, including whether the population dynamics are ultimately density dependent or density independent, have generated abundant heat but little light. We suggest that a pragmatic approach, in which theories are taken to be “tools” rather than competing claims of truth, has greater promise to move ecological research in a constructive direction. Two recent non-linear approaches exploiting the tools of complexity science provide insights relevant to explaining and forecasting population dynamics. Observation and data collection were used to structure models derived from catastrophe theory and self-organized criticality. These models indicate that nonlinear processes are important in the dynamics of the outbreaks. And the conceptual structures of these approaches provide clear, albeit constrained or contingent, implications for pest managers. We show that, although these two frameworks, catastrophe theory and self-organized criticality, are very different, the frequency distributions of time series from both systems result in power law relationships. Further, we show that a simple lattice-based model, similar to SOC but structured on the biology of the grasshoppers gives a spatial time series similar to data over a 50-year span and the frequency distribution is also a power law relationship. This demonstration exemplifies how a “both–and” rather than an “either–or” approach to ecological modeling, in which the useful elements of particular theories or conceptual structures are extracted, may

  19. Determinants of Catastrophic Health Expenditure in Iran

    Directory of Open Access Journals (Sweden)

    M Ramezanian

    2013-01-01

    Full Text Available Background: This study will provide detailed specification of those variables and determinants of unpredictable health expenditure in Iran, and the requirements to reduce extensive effects of the factors affecting households’ payments for health and other goods and services inappropriately.Method: This study aims to identify measures of fair financing of health services and determinants of fair financing contribution, regarding the required share of households that prevents their catastrophic payments. In this regard, analysis of shares of households’ expenditures on main groups of goods and services in urban and rural areas and in groups of deciles in the statistics from households’ expenditure surveys was applied.Results: The growth of spending in nominal values within the years 2002-2008 was considerably high and the rate for out-of-pocket payments is nearly the same or greater than the rate for total health expenditure. In 2008, urban and rural households in average pay 6.4% and 6.35% of their total expenditure on health services. Finally three categories of determinants of unfair and catastrophic payments by households were recognized in terms of households’ socio-economic status, equality/inequality conditions of the distribution of risk of financing, and economic aspects of health expenditure distribution.Conclusion: While extending the total share of government and prepayment sources of financing health services are considered as the simplest policy for limiting out-of-pocket payments, indicators and policies introduced in this study could also be considered important and useful for the development of health sector and easing access to health services, irrespective of health financing fairness

  20. Unsupervised self-organised mapping: a versatile empirical tool for object selection, classification and redshift estimation in large surveys

    CERN Document Server

    Geach, James E

    2011-01-01

    We present an application of unsupervised machine learning - the self-organised map (SOM) - as a tool for visualising, exploring and mining the catalogues of large astronomical surveys. Self-organisation culminates in a low-resolution representation of the 'topology' of a parameter volume, and this can be exploited in various ways pertinent to astronomy. Using data from the Cosmological Evolution Survey (COSMOS), we demonstrate two key astronomical applications of the SOM: (i) object classification and selection, using the example of galaxies with active galactic nuclei as a demonstration, and (ii) photometric redshift estimation, illustrating how SOMs can be used as totally empirical predictive tools. With a training set of ~3800 galaxies with z_spec<1, we achieve photometric redshift accuracies competitive with other (mainly template fitting) techniques that use a similar number of photometric bands (sigma(Dz)=0.03 with a ~2% outlier rate when using u*-band to 8um photometry). We also test the SOM as a p...