WorldWideScience

Sample records for catastrophic photometric redshift

  1. 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...

  2. Photometric Redshifts of Galaxies in COSMOS

    CERN Document Server

    Mobasher, B; Scoville, N Z; Dahlen, T; Salvato, M; Aussel, H; Thompson, D J; Feldmann, R; Tasca, L; Lefèvre, O; Lilly, S; Carollo, C M; Kartaltepe, J S; McCracken, H; Mould, J; Renzini, A; Sanders, D B; Shopbell, P L; Taniguchi, Y; Ajiki, M; Shioya, Y; Contini, T; Giavalisco, M; Ilbert, O; Iovino, A; Le Brun, V; Mainieri, V; Mignoli, M; Scodeggio, M

    2006-01-01

    We measure photometric redshifts and spectral types for galaxies in the COSMOS survey. We use template fitting technique combined with luminosity function priors and with the option to simultaneously estimate dust extinction (i.e. E(B-V)) for each galaxy.Our estimated redshifts are accurate to i<25 and z~1.2. Using simulations with sampling and noise characteristics similar to those in COSMOS, the accuracy and reliability is estimated for the photometric redshifts as a function of the magnitude limits of the sample, S/N ratios and the number of bands used. From the simulations we find that the ratio of derived 95% confidence interval in the redshift probability distribution to the estimated photometric redshift (D95) can be used to identify and exclude the catastrophic failures in the photometric redshift estimates. We compare the derived redshifts with high-reliability spectroscopic redshifts for a sample of 868 normal galaxies with z < 1.2 from zCOSMOS. Considering different scenarios, depending on us...

  3. Photometric redshifts for the NGVS

    Science.gov (United States)

    Raichoor, A.; Mei, S.; Erben, T.; Hildebrandt, H.; Huertas-Company, M.; Ilbert, O.; Licitra, R.; Ball, N. M.; Boissier, S.; Boselli, A.; Chen, Y.-T.; Côté, P.; Cuillandre, J.-C.; Duc, P. A.; Durrell, P. R.; Ferrarese, L.; Guhathakurta, P.; Gwyn, S. D. J.; Kavelaars, J. J.; Lancon, A.; Liu, C.; MacArthur, L. A.; Muller, M.; Muñoz, R. P.; Peng, E. W.; Puzia, T. H.; Sawicki, M.; Toloba, E.; Van Waerbeke, L.; Woods, D.; Zhang, H.

    2014-12-01

    We present the photometric redshift catalog for the Next Generation Virgo Cluster Survey (NGVS), a 104 deg^2 optical imaging survey centered on the Virgo cluster in the u^*, g, r ,i, z bandpasses at point source depth of 25-26 ABmag. It already is the new optical reference survey for the study of the Virgo cluster, and will be also used for multiple ancillary programs. To obtain photometric redshifts, we perform accurate photometry, through the PSF-homogenization of our data. We then estimate the photometric redshifts using Le Phare and BPZ codes, adding a new prior extended down to i_{AB}=12.5 mag. We assess the accuracy of our photometric redshifts as a function of magnitude and redshift using ˜80,000 spectroscopic redshifts from public surveys. For i_{AB} outliers.

  4. 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.

  5. Calibrating Photometric Redshifts of Luminous Red Galaxies

    CERN Document Server

    Padmanabhan, N; Schlegel, D J; Bridges, T J; Brinkmann, J; Cannon, R; Connolly, A J; Croom, S M; Csabai, I; Drinkwater, M; Eisenstein, D J; Hewett, P C; Loveday, J; Nichol, R C; Pimbblet, K A; De Propris, R; Schneider, D P; Scranton, R; Seljak, U; Shanks, T; Szapudi, I; Szalay, A S; Wake, D; Padmanabhan, Nikhil; Budavari, Tamas; Schlegel, David J.; Bridges, Terry; Brinkmann, Jonathan; Cannon, Russell; Connolly, Andrew J.; Croom, Scott M.; Csabai, Istvan; Drinkwater, Michael; Eisenstein, Daniel J.; Hewett, Paul C.; Loveday, Jon; Nichol, Robert C.; Pimbblet, Kevin A.; Propris, Roberto De; Schneider, Donald P.; Scranton, Ryan; Seljak, Uros; Shanks, Tom; Szapudi, Istvan; Szalay, Alexander S.; Wake, David

    2004-01-01

    We discuss the construction of a photometric redshift catalogue of Luminous Red Galaxies (LRGs) from the Sloan Digital Sky Survey (SDSS), emphasizing the principal steps necessary for constructing such a catalogue -- (i) photometrically selecting the sample, (ii) measuring photometric redshifts and their error distributions, (iii) and estimating the true redshift distribution. We compare two photometric redshift algorithms for these data and find that they give comparable results. Calibrating against the SDSS and SDSS-2dF spectroscopic surveys, we find that the photometric redshift accuracy is $\\sigma \\sim 0.03$ for redshifts less than 0.55 and worsens at higher redshift ($\\sim 0.06$). These errors are caused by photometric scatter, as well as systematic errors in the templates, filter curves, and photometric zeropoints. We also parametrize the photometric redshift error distribution with a sum of Gaussians, and use this model to deconvolve the errors from the measured photometric redshift distribution to est...

  6. Photometric redshifts in the SWIRE Survey

    CERN Document Server

    Rowan-Robinson, Michael; Oliver, Seb; Trichas, Markos; Berta, Stefano; Lonsdale, Carol; Smith, Gene; Shupe, David; Surace, Jason; Arnouts, Stephane; LeFevre, Olivier; Afonso-Luis, Alejandro; Perez-Fournon, Ismael; Hatziminaoglou, Evanthia; Polletta, Maria; Farrah, Duncan; Vaccari, Mattia

    2008-01-01

    We present the SWIRE Photometric Redshift Catalogue, 1024750 redshifts of unprecedented reliability and accuracy. Our method is based on fixed galaxy and QSO templates applied to data at 0.36-4.5 mu, and on a set of 4 infrared emission templates fitted to infrared excess data at 3.6-170 mu. The code involves two passes through the data, to try to optimize recognition of AGN dust tori. A few carefully justified priors are used and are the key to supression of outliers. Extinction, A_V, is allowed as a free parameter. We use a set of 5982 spectroscopic redshifts, taken from the literature and from our own spectroscopic surveys, to analyze the performance of our method as a function of the number of photometric bands used in the solution and the reduced chi^2. For 7 photometric bands the rms value of (z_{phot}-z_{spec})/(1+z_{spec}) is 3.5%, and the percentage of catastrophic outliers is ~1%. We discuss the redshift distributions at 3.6 and 24 mu. In individual fields, structure in the redshift distribution corr...

  7. 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...

  8. Photometric redshifts for supernovae Ia in the Supernova Legacy Survey

    CERN Document Server

    Palanque-Delabrouille, Nathalie; Pascal, S; Rich, J; Guy, J; Bazin, G; Astier, P; Balland, C; Basa, S; Carlberg, R G; Conley, A; Fouchez, D; Hardin, D; Hook, I M; Howell, D A; Pain, R; Perrett, K; Pritchet, C J; Regnault, N; Sullivan, M

    2009-01-01

    We present a method using the SALT2 light curve fitter to determine the redshift of Type Ia supernovae in the Supernova Legacy Survey (SNLS) based on their photometry in g', r', i' and z'. On 289 supernovae of the first three years of SNLS data, we obtain a precision $\\sigma_{\\Delta z/(1+z)} = 0.022$ on average up to a redshift of 1.0, with a higher precision of 0.016 for z0.45. The rate of events with $|\\Delta z|/(1+z)>0.15$ (catastrophic errors) is 1.4%. Both the precision and the rate of catastrophic errors are better than what can be currently obtained using host galaxy photometric redshifts. Photometric redshifts of this precision may be useful for future experiments which aim to discover up to millions of supernovae Ia but without spectroscopy for most of them.

  9. CuBANz: Photometric redshift estimator

    Science.gov (United States)

    Samui, Saumyadip; Pal, Shanoli Samui

    2016-09-01

    CuBANz is a photometric redshift estimator code for high redshift galaxies that uses the back propagation neural network along with clustering of the training set, making it very efficient. 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. The clustering method enables accurate determination of the redshifts. CuBANz considers uncertainty in the photometric measurements as well as uncertainty in the neural network training. The code is written in C.

  10. Photometric redshifts for the CFHTLS-Wide

    CERN Document Server

    Brimioulle, Fabrice; Seitz, Stella; Bender, Ralf; Snigula, Jan

    2008-01-01

    We want to derive bias free, accurate photometric redshifts for those fields of the CFHTLS-Wide data which are covered in the u*, g', r', i' and z' filters and are public on January 2008. These are 37 square degrees in the W1, W3 and W4 fields with photometric data for a total of 2.597.239 galaxies. We use the photometric redshift code PHOTO-z of Bender et al. (2001). We compare our redshifts for the W1, W3 and W4 fields to about 7500 spectroscopic redshifts from the VVDS therein. For galaxies with 17.5 <= i' AB <= 22.5 the accuracies and outlier rates become sigma=0.033, eta~2 % for W1, sigma=0.037, eta~2% for W3 and sigma=0.035, eta~2.5 % outliers for W4 fields. For the total galaxy sample with about 9000 spectroscopic redshifts from VVDS, DEEP2 or SDSS we obtain a sigma=0.04 and eta~5.7% for the PHOTO-z redshifts. We consider the photometric redshifts of Erben et al. (2008) which were obtained with exactly the same photometric catalog using the BPZ-redshift code and compare them with our computed red...

  11. 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...

  12. 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.

  13. Photometric Redshifts for the SDSS Early Data Release

    CERN Document Server

    Csabai, I; Connolly, A J; Szalay, A S; Györy, Z; Benítez, N; Annis, J; Brinkmann, J; Eisenstein, D J; Fukugita, M; Gunn, J; Kent, S; Lupton, R; Nichol, R C; Stoughton, C; Csabai, Istvan; Budavari, Tamas; Connolly, Andrew J.; Szalay, Alexander S.; Gyory, Zsuzsanna; Benitez, Narciso; Annis, Jim; Brinkmann, Jon; Eisenstein, Daniel; Fukugita, Masataka; Gunn, Jim; Kent, Stephen; Lupton, Robert; Nichol, Robert C.; Stoughton, Chris

    2003-01-01

    The Early Data Release from the Sloan Digital Sky survey provides one of the largest multicolor photometric catalogs currently available to the astronomical community. In this paper we present the first application of photometric redshifts to the $\\sim 6$ million extended sources within these data (with 1.8 million sources having $r' < 21$). Utilizing a range of photometric redshift techniques, from empirical to template and hybrid techniques, we investigate the statistical and systematic uncertainties present within the redshift estimates for the EDR data. For $r'<21$ we find that the redshift estimates provide realistic redshift histograms with an rms uncertainty in the photometric redshift relation of 0.035 at $r'<18$ and rising to 0.1 at $r'<21$. We conclude by describing how these photometric redshifts and derived quantities, such as spectral type, restframe colors and absolute magnitudes, are stored within the SDSS database. We provide sample queries for searching on photometric redshifts an...

  14. Improving Estimation Accuracy of Quasars’ Photometric Redshifts by Integration of KNN and SVM

    Science.gov (United States)

    Han, Bo; Ding, Hongpeng; Zhang, Yanxia; Zhao, Yongheng

    2015-08-01

    The massive photometric data collected from multiple large-scale sky surveys offers significant opportunities for measuring distances of many celestial objects by photometric redshifts zphot in a wide coverage of the sky. However, catastrophic failure, an unsolved problem for a long time, 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 zphot. By analysis, we observe two dense regions with catastrophic failure, one in the range of zphot [0.1,1.1], the other in the range of zphot [1.5,2.5]. In the second stage, we map the photometric multiband input pattern of points falling into the two ranges from original attribute space into high dimensional feature space by Gaussian kernel function in SVM. In the high dimensional feature space, many bad estimation points resulted from catastrophic failure by using simple Euclidean distance computation in KNN can be identified by classification hyperplane SVM and further be applied correction. Experimental results based on SDSS data for quasars showed that the two-stage fusion approach can significantly mitigate catastrophic failure and improve the estimation accuracy of photometric redshift.

  15. 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...

  16. New insights on the accuracy of photometric redshift measurements

    CERN Document Server

    Massarotti, M; Buzzoni, A; Valls-Gabaud, D

    2001-01-01

    We use the deepest and most complete redshift catalog currently available (the Hubble Deep Field (HDF) North supplemented by new HDF South redshift data) to minimize residuals between photometric and spectroscopic redshift estimates. The good agreement at z_spec 2.0, the systematic shift between photometric and spectroscopic redshifts decreases when the modeling of the absorption by the interstellar and intergalactic media is refined. As a result, in the entire redshift range 0 < z < 6, residuals between photometric and spectroscopic redshifts are roughly halved. For objects fainter than the spectroscopic limit, the main source of uncertainty in photometric redshifts is related to photometric errors, and can be assessed with Monte Carlo simulations.

  17. Photometric Redshift Estimation Using Spectral Connectivity Analysis

    CERN Document Server

    Freeman, P E; Lee, A B; Richards, J W; Schafer, C M

    2009-01-01

    The development of fast and accurate methods of photometric redshift estimation is a vital step towards being able to fully utilize the data of next-generation surveys within precision cosmology. In this paper we apply a specific approach to spectral connectivity analysis (SCA; Lee & Wasserman 2009) called diffusion map. SCA is a class of non-linear techniques for transforming observed data (e.g., photometric colours for each galaxy, where the data lie on a complex subset of p-dimensional space) to a simpler, more natural coordinate system wherein we apply regression to make redshift predictions. As SCA relies upon eigen-decomposition, our training set size is limited to ~ 10,000 galaxies; we use the Nystrom extension to quickly estimate diffusion coordinates for objects not in the training set. We apply our method to 350,738 SDSS main sample galaxies, 29,816 SDSS luminous red galaxies, and 5,223 galaxies from DEEP2 with CFHTLS ugriz photometry. For all three datasets, we achieve prediction accuracies on ...

  18. Accurate photometric redshift probability density estimation - method comparison and application

    CERN Document Server

    Rau, Markus Michael; Brimioulle, Fabrice; Frank, Eibe; Friedrich, Oliver; Gruen, Daniel; Hoyle, Ben

    2015-01-01

    We introduce an ordinal classification algorithm for photometric redshift estimation, which vastly improves the reconstruction of photometric redshift probability density functions (PDFs) for individual galaxies and galaxy samples. As a use case we apply our method to CFHTLS galaxies. The ordinal classification algorithm treats distinct redshift bins as ordered values, which improves the quality of photometric redshift PDFs, compared with non-ordinal classification architectures. We also propose a new single value point estimate of the galaxy redshift, that can be used to estimate the full redshift PDF of a galaxy sample. This method is competitive in terms of accuracy with contemporary algorithms, which stack the full redshift PDFs of all galaxies in the sample, but requires orders of magnitudes less storage space. The methods described in this paper greatly improve the log-likelihood of individual object redshift PDFs, when compared with a popular Neural Network code (ANNz). In our use case, this improvemen...

  19. 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.

  20. 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).

  1. 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...

  2. 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.

  3. 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.

  4. 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

  5. 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,...

  6. Leveraging 3D-HST Grism Redshifts to Quantify Photometric Redshift Performance

    CERN Document Server

    Bezanson, Rachel; Brammer, Gabriel B; van Dokkum, Pieter G; Franx, Marijn; Labbé, Ivo; Leja, Joel; Momcheva, Ivelina G; Nelson, Erica J; Quadri, Ryan F; Skelton, Rosalind E; Weiner, Benjamin J; Whitaker, Katherine E

    2015-01-01

    We present a study of photometric redshift accuracy in the 3D-HST photometric catalogs, using 3D-HST grism redshifts to quantify and dissect trends in redshift accuracy for galaxies brighter than $H_{F140W} 2$), dusty star-forming galaxies for which the scatter increases to $\\sim0.1(1+z)$. Although the overall photometric redshift accuracy for quiescent galaxies is better than for star-forming galaxies, scatter depends more strongly on magnitude and redshift than on galaxy type. We verify these trends using the redshift distributions of close pairs and extend the analysis to fainter objects, where photometric redshift errors further increase to $\\sim0.046(1+z)$ at $H_{F160W}=26$. We demonstrate that photometric redshift accuracy is strongly filter-dependent and quantify the contribution of multiple filter combinations. We evaluate the widths of redshift probability distribution functions and find that error estimates are underestimated by a factor of $\\sim1.1-1.6$, but that uniformly broadening the distributi...

  7. Calibrating photometric redshift distributions with cross-correlations

    CERN Document Server

    Schulz, A E

    2009-01-01

    The next generation of proposed galaxy surveys will increase the number of galaxies with photometric redshifts by two orders of magnitude, drastically expanding both redshift range and detection threshold from the current state of the art. Obtaining spectra for a fair sub-sample of this new data could be cumbersome and expensive. However, adequate calibration of the true redshift distribution of galaxies is vital to tapping the potential of these surveys. We examine a promising alternative to direct spectroscopic follow up: calibration of the redshift distribution of photometric galaxies via cross-correlation with an overlapping spectroscopic survey whose members trace the same density field. We review the theory, develop a pipeline, apply it to mock data from N-body simulations, and examine the properties of this redshift distribution estimator. We demonstrate that the method is effective, but the estimator is weakened by two factors. 1) The correlation function of the spectroscopic sample must be measured i...

  8. Galaxy clustering with photometric surveys using PDF redshift information

    CERN Document Server

    Asorey, J; Sevilla-Noarbe, I; Brunner, R J; Thaler, J

    2016-01-01

    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 colors, that are obtained through multi-band 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 $\\Delta z=0.1$, the use of the entire PDF reduces the typical measurement bias from 5%, when using single point estimates, to 3%.

  9. Photometric redshifts of galaxies from SDSS and 2MASS

    Institute of Scientific and Technical Information of China (English)

    Tao Wang; Jia-Sheng Huang; Qiu-Sheng Gu

    2009-01-01

    In order to find the physical parameters which determine the accuracy of pho- tometric redshifts, we compare the spectroscopic and photometric redshifts (photo-z's) for a large sample of ~ 80 000 SDSS-2MASS galaxies. Photo-z's in this paper are es- timated by using the artificial neural network photometric redshift method (ANNz). For a subset of~40000 randomly selected galaxies, we find that the photometric redshift recovers the spectroscopic redshifi distribution very well with rms of 0.016. Our main results are as follows: (1) Using magnitudes directly as input parameters produces more accurate photo-z's than using colors; (2) The inclusion of 2MASS (3, H, Ks) bands does not improve photo-z's significantly, which indicates that near infrared data might not be important for the low-redshift sample; (3) Adding the concentration index (essentially the steepness of the galaxy brightness profile) as an extra input can improve the photo-z's estimation up to~10 percent; (4) Dividing the sample into early- and late-type galaxies by using the concentration index, normal and abnormal galaxies by using the emission line flux ratios, and red and blue galaxies by using color index (g - r), we can improve the accuracy of photo-z's significantly; (5) Our analysis shows that the outliers (where there is a big difference between the spectroscopic and photometric redshifts) are mainly correlated with galaxy types, e.g., most outliers are late-type (blue) galaxies.

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

    Institute of Scientific and Technical Information of China (English)

    Xue-Bing Wu; Wei Zhang; Xu Zhou

    2004-01-01

    With a recently constructed composite quasar spectrum and the χ2 minimization technique, we describe a general method for estimating the photometric redshifts of a large sample of quasars by deriving 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 compared them with their spectroscopic redshifts. The difference is less than 0.1 for 47% of the quasars and less than 0.2for 68%. Based on the calculation of the theoretical color-color diagrams of stars,galaxies and quasars both on the SDSS system and on the BATC system, we expect that we would be able to select candidates of high redshift quasars more efficaciously with the latter than with the former, provided the BATC survey can detect objects with magnitudes fainter than 21.

  11. 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...

  12. 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.

  13. 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.

  14. Gamma photometric redshifts for long gamma-ray bursts

    CERN Document Server

    Bagoly, Z; Mészáros, A; Mészáros, P; Horváth, I; Balázs, L G; Vavrek, R

    2003-01-01

    It is known that the soft tail of the gamma-ray bursts' spectra show excesses from the exact power-law dependence. In this article we show that this departure can be detected in the peak flux ratios of different BATSE DISCSC energy channels. This effect allows to estimate the redshift of the bright long gamma-ray bursts in the BATSE Catalog. A verification of these redshifts is obtained for the 8 GRB which have both BATSE DISCSC data and measured optical spectroscopic redshifts. There is good correlation between the measured and esti redshifts, and the average error is $\\Delta z \\approx 0.33$. The method is similar to the photometric redshift estimation of galaxies in the optical range, hence it can be called as "gamma photometric redshift estimation". The estimated redshifts for the long bright gamma-ray bursts are up to $z \\simeq 4$. For the the faint long bursts - which should be up to $z \\simeq 20$ - the redshifts cannot be determined unambiguously with this method.

  15. Cosmological parameters from a million photometric redshifts of SDSS LRGs

    CERN Document Server

    Blake, C; Bridle, S; Lahav, O; Blake, Chris; Collister, Adrian; Bridle, Sarah; Lahav, Ofer

    2006-01-01

    We analyze MegaZ-LRG, a new photometric-redshift catalogue of Luminous Red Galaxies (LRGs) based on the imaging data of the Sloan Digital Sky Survey (SDSS) 4th Data Release. MegaZ-LRG, presented in a companion paper, contains > 10^6 photometric redshifts derived with ANNz, an Artificial Neural Network method, constrained by a spectroscopic sub-sample of ~13,000 galaxies obtained by the 2dF-SDSS LRG and Quasar (2SLAQ) survey. The catalogue spans the redshift range 0.4redshift error ~ 0.03(1+z). We present the first cosmological parameter fits to galaxy angular power spectra from a photometric redshift survey. Combining the redshift slices with appropriate covariances, we determine the matter density Omega_m and baryon density Omega_b in the combinations Omega_m h = 0.20+/-0.03 and Omega_b/Omega_m = 0.14+/-0.04. These results are in agreement with and independent of the latest studies of the Cosmic Microwave Background radiation, and their precision is comparable to analyses of conte...

  16. 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)

  17. Precision Cosmology with a New Probabilistic Photometric Redshifts Approach

    Science.gov (United States)

    Carrasco Kind, Matias; Brunner, R. J.

    2013-06-01

    A complete understanding of both dark energy and dark matter remains one of most important challenges in astrophysics today. Recent theoretical and numerical computations have made important progress in quantifying the role of these dark components on the formation and evolution of galaxies through cosmic time, but observational verification of these predictions and the development of new, more stringent constraints has not kept pace. It is in this context that, photometric redshifts have become more important with the growth of large imaging surveys, such as DES and LSST, that have been designed to address this issue. But their basic implementation has not changed significantly from their original development, as most techniques provide a single photometric redshift estimate and an associated error for the an extragalactic source. In this work, we present a unique and powerful solution that leverages the full information contained in the photometric data to address this cosmological challenge with a new approach that provides accurate photometric redshift probability density functions (PDF) for galaxies. This new approach, which scales efficiently to massive data, efficiently combines standard template fitting techniques with powerful machine learning methods. Included in this framework is our recently developed technique entitled Trees for PhotoZ (TPZ); a new, robust, parallel photometric redshift code that uses prediction trees and random forests to generate photo-z PDFs in a reliable and fast manner. In addition, our approach also provides ancillary information about the internal structure of the data, including the relative importance of variables used during the redshift estimation, an identification of areas in the training sample that provide poor predictions, and an accurate outlier rejection method. We will also present current results of this approach on a variety of datasets and discuss, by using specific examples, how the full photo-z PDF can be

  18. 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.

  19. A cooperative approach among methods for photometric redshifts estimation: an application to KiDS data

    Science.gov (United States)

    Cavuoti, S.; Tortora, C.; Brescia, M.; Longo, G.; Radovich, M.; Napolitano, N. R.; Amaro, V.; Vellucci, C.; La Barbera, F.; Getman, F.; Grado, A.

    2017-04-01

    Photometric redshifts (photo-z) are fundamental in galaxy surveys to address different topics, from gravitational lensing and dark matter distribution to galaxy evolution. The Kilo Degree Survey (KiDS), i.e. the European Southern Observatory (ESO) public survey on the VLT Survey Telescope (VST), provides the unprecedented opportunity to exploit a large galaxy data set with an exceptional image quality and depth in the optical wavebands. Using a KiDS subset of about 25000 galaxies with measured spectroscopic redshifts, we have derived photo-z using (i) three different empirical methods based on supervised machine learning; (ii) the Bayesian photometric redshift model (or BPZ); and (iii) a classical spectral energy distribution (SED) template fitting procedure (LE PHARE). We confirm that, in the regions of the photometric parameter space properly sampled by the spectroscopic templates, machine learning methods provide better redshift estimates, with a lower scatter and a smaller fraction of outliers. SED fitting techniques, however, provide useful information on the galaxy spectral type, which can be effectively used to constrain systematic errors and to better characterize potential catastrophic outliers. Such classification is then used to specialize the training of regression machine learning models, by demonstrating that a hybrid approach, involving SED fitting and machine learning in a single collaborative framework, can be effectively used to improve the accuracy of photo-z estimates.

  20. A catalogue of photometric redshifts for the SDSS-DR9 galaxies

    CERN Document Server

    Brescia, M; Longo, G; De Stefano, V

    2014-01-01

    Accurate photometric redshifts for large samples of galaxies are among the main products of modern multiband digital surveys. Over the last decade, the Sloan Digital Sky Survey (SDSS) has become a sort of benchmark against which to test the various methods. We present an application of a new method to the estimation of photometric redshifts for the galaxies in the SDSS Data Release 9 (SDSS-DR9). Photometric redshifts for more than 143 million galaxies were produced and made available at the URL: http://dame.dsf.unina.it/catalog/DR9PHOTOZ/. The MLPQNA (Multi Layer Perceptron with Quasi Newton Algorithm) model provided within the framework of the DAMEWARE (DAta Mining and Exploration Web Application REsource) is an interpolative method derived from machine learning models. The obtained redshifts have an overall uncertainty of sigma=0.023 with a very small average bias of about 3x10^-5, and a fraction of catastrophic outliers of about 5%. This result is slightly better than what was already available in the lite...

  1. Comparison of Approaches to Photometric Redshift Estimation of Quasars

    Science.gov (United States)

    Tu, Yang; Zhang, Yan-Xia; Zhao, Yong-Heng; Tian, Hai-Jun

    We probe many kinds of approaches used for photometric redshift estimation of quasars, including KNN (K-nearest neighbor algorithm), Lasso (Least Absolute Shrinkage and Selection Operator), PLS (Partial Least Square regression), ridge regression, SGD (Stochastic Gradient Descent) and Extra-Trees.

  2. Photometric Redshift and Classification for the XMM-COSMOS Sources

    NARCIS (Netherlands)

    Salvato, M.; Hasinger, G.; Ilbert, O.; Zamorani, G.; Brusa, M.; Scoville, N. Z.; Rau, A.; Capak, P.; Arnouts, S.; Aussel, H.; Bolzonella, M.; Buongiorno, A.; Cappelluti, N.; Caputi, K.; Civano, F.; Cook, R.; Elvis, M.; Gilli, R.; Jahnke, K.; Kartaltepe, J. S.; Impey, C. D.; Lamareille, F.; Le Floch, E.; Lilly, S.; Mainieri, V.; McCarthy, P.; McCracken, H.; Mignoli, M.; Mobasher, B.; Murayama, T.; Sasaki, S.; Sanders, D. B.; Schiminovich, D.; Shioya, Y.; Shopbell, P.; Silverman, J.; Smolcic, V.; Surace, J.; Taniguchi, Y.; Thompson, D.; Trump, J. R.; Urry, M.; Zamojski, M.

    2009-01-01

    We present photometric redshifts and spectral energy distribution (SED) classifications for a sample of 1542 optically identified sources detected with XMM in the COSMOS field. Our template fitting classifies 46 sources as stars and 464 as nonactive galaxies, while the remaining 1032 require templat

  3. 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...

  4. 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...

  5. 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...

  6. Photometric redshift and classification for the XMM-COSMOS sources

    CERN Document Server

    Salvato, M; Ilbert, O; Zamorani, G; Brusa, M; Scoville, N; Rau, A; Capak, P; Arnouts, S; Aussel, H; Bolzonella, M; Buongiorno, A; Cappelluti, N; Caputi, K; Civano, F; Cook, R; Elvis, M; Gilli, R; Jahnke, K; Kartaltepe, J S; Impey, C D; Lamareille, F; Le Floc'h, E; Lilly, S; Mainieri, V; McCarthy, P; McCracken, H; Mignoli, M; Mobasher, B; Murayama, T; Sasaki, S; Sanders, D B; Schiminovich, D; Shioya, Y; Shopbell, P; Silvermann, J; Smolcic, V; Surace, J; Taniguchi, Y; Thompson, D; Trump, J R; Urry, M; Zamojski, M

    2008-01-01

    We present photometric redshifts and spectral energy distribution (SED) classifications for a sample of 1542 optically identified sources detected with XMM in the COSMOS field. Our template fitting classifies 46 sources as stars and 464 as non-active galaxies, while the remaining 1032 require templates with an AGN contribution. High accuracy in the derived photometric redshifts was accomplished as the result of 1) photometry in up to 30 bands with high significance detections, 2) a new set of SED templates including 18 hybrids covering the far-UV to mid-infrared, which have been constructed by the combination of AGN and non-active galaxies templates, and 3) multi-epoch observations that have been used to correct for variability (most important for type 1 AGN). The reliability of the photometric redshifts is evaluated using the sub-sample of 442 sources with measured spectroscopic redshifts. We achieved an accuracy of $\\sigma_{\\Delta z/(1+z_{spec})} = 0.014$ for i$_{AB}^*<$22.5 ($\\sigma_{\\Delta z/(1+z_{spec...

  7. Comparision of approaches to photometric redshift estimation of quasars

    Science.gov (United States)

    Tu, Yang; Zhang, Yanxia; Zhao, Yongheng; Tian, Haijun

    2015-08-01

    Based on databases from various different band photometric surveys (optical from SDSS, infrared from UKIDSS and WISE), we compare k-nearest neighbor regression based on KD-tree and Ball-tree, LASSO, PLS (Partial Least Squares), SDG, ridge regression and kernel ridge regression applied for photometric redshift estimation of quasars. The experimental result shows that the perfomance order of these methods is KD-tree kNN, Ball-tree kNN, kernal ridge regression, ridge regression, PLS, SGD, LASSO.

  8. 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...

  9. 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...

  10. Spectroscopic Needs for Calibration of LSST Photometric Redshifts

    CERN Document Server

    Schmidt, Samuel J; Abate, Alexandra

    2014-01-01

    This white paper summarizes the conclusions of the Snowmass White Paper "Spectroscopic Needs for Imaging Dark Energy Experiments" (arXiv:1309.5384) which are relevant to the calibration of LSST photometric redshifts; i.e., the accurate characterization of biases and uncertainties in photo-z's. Any significant miscalibration will lead to systematic errors in photo-z's, impacting nearly all extragalactic science with LSST. As existing deep redshift samples have failed to yield highly-secure redshifts for a systematic 20%-60% of their targets, it is a strong possibility that future deep spectroscopic samples will not solve the calibration problem on their own. The best options in this scenario are provided by cross-correlation methods that utilize clustering with objects from spectroscopic surveys (which need not be fully representative) to trace the redshift distribution of the full sample. For spectroscopy, the eBOSS survey would enable a basic calibration of LSST photometric redshifts, while the expected LSST...

  11. 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...

  12. DNF - Galaxy photometric redshift by Directional Neighbourhood Fitting

    Science.gov (United States)

    De Vicente, J.; Sánchez, E.; Sevilla-Noarbe, I.

    2016-07-01

    Wide field images taken in several photometric bands allow simultaneous measurement of redshifts for thousands of galaxies. A variety of algorithms to make this measurement have appeared in the last few years, the majority of which can be classified as either template- or training-based methods. Among the latter, nearest neighbour estimators stand out as one of the most successful, in terms of both precision and the quality of error estimation. In this paper we describe the Directional Neighbourhood Fitting (DNF) algorithm based on the following: a new neighbourhood metric (Directional Neighbourhood), a photo-z estimation strategy (Neighbourhood Fitting) and a method for generating the photo-z probability distribution function. We compare DNF with other well-known empirical photometric redshift tools using different public data sets (Sloan Digital Sky Survey, VIMOS VLT Deep Survey and Photo-z Accuracy Testing). DNF achieves high-quality results with reliable error.

  13. MAPPING THE GALAXY COLOR–REDSHIFT RELATION: OPTIMAL PHOTOMETRIC REDSHIFT CALIBRATION STRATEGIES FOR COSMOLOGY SURVEYS

    Energy Technology Data Exchange (ETDEWEB)

    Masters, Daniel; Steinhardt, Charles; Faisst, Andreas [Infrared Processing and Analysis Center, California Institute of Technology, Pasadena, CA 91125 (United States); Capak, Peter [Spitzer Science Center, California Institute of Technology, Pasadena, CA 91125 (United States); Stern, Daniel; Rhodes, Jason [Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA 91109 (United States); Ilbert, Olivier [Aix Marseille Universite, CNRS, LAM (Laboratoire dAstrophysique de Marseille) UMR 7326, F-13388, Marseille (France); Salvato, Mara [Max-Planck-Institut für extraterrestrische Physik, Giessenbachstrasse, D-85748 Garching (Germany); Schmidt, Samuel [Department of Physics, University of California, Davis, CA 95616 (United States); Longo, Giuseppe [Department of Physics, University Federico II, via Cinthia 6, I-80126 Napoli (Italy); Paltani, Stephane; Coupon, Jean [Department of Astronomy, University of Geneva ch. dcogia 16, CH-1290 Versoix (Switzerland); Mobasher, Bahram [Department of Physics and Astronomy, University of California, Riverside, CA 92521 (United States); Hoekstra, Henk [Leiden Observatory, Leiden University, P.O. Box 9513, 2300 RA, Leiden (Netherlands); Hildebrandt, Hendrik [Argelander-Institut für Astronomie, Universität Bonn, Auf dem H’´ugel 71, D-53121 Bonn (Germany); Speagle, Josh [Department of Astronomy, Harvard University, 60 Garden Street, MS 46, Cambridge, MA 02138 (United States); Kalinich, Adam [Massachusetts Institute of Technology, Cambridge, MA 02139 (United States); Brodwin, Mark [Department of Physics and Astronomy, University of Missouri, Kansas City, MO 64110 (United States); Brescia, Massimo; Cavuoti, Stefano [Astronomical Observatory of Capodimonte—INAF, via Moiariello 16, I-80131, Napoli (Italy)

    2015-11-01

    Calibrating the photometric redshifts of ≳10{sup 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 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.

  14. Astroinformatics of galaxies and quasars: a new general method for photometric redshifts estimation

    CERN Document Server

    Laurino, Omar; Longo, Giuseppe; Riccio, Giuseppe

    2011-01-01

    With the availability of the huge amounts of data produced by current and future large multi-band photometric surveys, photometric redshifts have become a crucial tool for extragalactic astronomy and cosmology. In this paper we present a novel method, called Weak Gated Experts (WGE), which allows to derive photometric redshifts through a combination of data mining techniques. \

  15. 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.

  16. 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.

  17. 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...

  18. Photometric Properties of the Most Massive High-Redshift Galaxies

    Science.gov (United States)

    Robertson, Brant; Li, Yuexing; Cox, Thomas J.; Hernquist, Lars; Hopkins, Philip F.

    2007-09-01

    We calculate the observable properties of the most massive high-redshift galaxies in the hierarchical formation scenario where stellar spheroid and supermassive black hole growth are fueled by gas-rich mergers. Combining high-resolution hydrodynamical simulations of the hierarchical formation of a z~6 quasar, stellar population synthesis models, template active galactic nucleus (AGN) spectra, prescriptions for interstellar and intergalactic absorption, and the response of modern telescopes, the photometric evolution of galaxies destined to host z~6 quasars is modeled at redshifts z~4-14. These massive galaxies, with enormous stellar masses of M*~1011.5-1012 Msolar and star formation rates of SFR~103-104 Msolar yr-1 at z>~7, satisfy a variety of photometric selection criteria based on Lyman break techniques, including V-band dropouts at z>~5, i-band dropouts at z>~6, and z-band dropouts at z>~7. The observability of the most massive high-redshift galaxies is assessed and compared with a wide range of existing and proposed photometric surveys, including the Sloan Digital Sky Survey (SDSS), Great Observatories Origins Deep Survey (GOODS)/Hubble Ultra Deep Field (HUDF), National Optical Astronomy Observatory Deep Wide-Field Survey (NDWFS), UKIRT Infared Deep Sky Survey (UKIDSS), Infrared Array Camera (IRAC) Shallow Survey, Ultradeep Visible and Infrared Survey Telescope for Astronomy (VISTA), Dark Universe Explorer (DUNE), Panoramic Survey Telescope and Rapid Response System (Pan-STARRS), Large Synoptic Survey Telescope (LSST), and Supernova/Acceleration Probe (SNAP). Massive stellar spheroids descended from z~6 quasars will likely be detected at z~4 by existing surveys, but owing to their low number densities the discovery of quasar progenitor galaxies at z>7 will likely require future surveys of large portions of the sky (>~0.5%) at wavelengths λ>~1 μm. The detection of rare, starbursting, massive galaxies at redshifts z>~6 would provide support for the

  19. 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...

  20. A Photometric redshift galaxy catalog from the Red-Sequence Cluster Survey

    Energy Technology Data Exchange (ETDEWEB)

    Hsieh, Bau-Ching; /Taiwan, Natl. Central U. /Taipei, Inst. Astron. Astrophys.; Yee, H.K.C.; /Toronto U., Astron. Dept.; Lin, H.; /Fermilab; Gladders, M.D.; /Carnegie Inst.

    2005-02-01

    The Red-Sequence Cluster Survey (RCS) provides a large and deep photometric catalog of galaxies in the z' and R{sub c} bands for 90 square degrees of sky, and supplemental V and B data have been obtained for 33.6 deg{sup 2}. They 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{sub c} < 24, giving an rms scatter {delta}({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. They describe the empirical quadratic polynomial photometric redshift fitting technique which they use to determine the relation between red-shift and photometry. A kd-tree algorithm is used to divide up the sample to improve the accuracy of the catalog. They also present a method for estimating the photometric redshift error for individual galaxies. They show that the redshift distribution of the sample is in excellent agreement with smaller and much deeper photometric and spectroscopic redshift surveys.

  1. 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.

  2. Dissecting Photometric Redshift for Active Galactic Nucleus Using XMM- and Chandra-COSMOS Samples

    NARCIS (Netherlands)

    Salvato, M.; Ilbert, O.; Hasinger, G.; Rau, A.; Civano, F.; Zamorani, G.; Brusa, M.; Elvis, M.; Vignali, C.; Aussel, H.; Comastri, A.; Fiore, F.; Le Floc'h, E.; 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.; Le Fevre, O.; Lamareille, F.; Lanzuisi, G.; Le Borgne, J. -F.; Le Brun, V.; Lilly, S.; Maier, C.; Manohar, S.; Masters, D.; McCracken, H.; Messias, H.; Mignoli, M.; Mobasher, B.; Nagao, T.; Pello, R.; Puccetti, S.; Perez-Montero, E.; Renzini, 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

    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 redsh

  3. 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...

  4. Sparse Representation of Photometric Redshift PDFs: Preparing for Petascale Astronomy

    CERN Document Server

    Kind, M Carrasco

    2014-01-01

    One of the consequences of entering the era of precision cosmology is the widespread adoption of photometric redshift probability density functions (PDFs). Both current and future photometric surveys are expected to obtain images of billions of distinct galaxies. As a result, storing and analyzing all of these PDFs will be non-trivial and even more severe if a survey plans to compute and store multiple different PDFs. In this paper we propose the use of a sparse basis representation to fully represent individual photo-$z$ PDFs. By using an Orthogonal Matching Pursuit algorithm and a combination of Gaussian and Voigt basis functions, we demonstrate how our approach is superior to a multi-Gaussian fitting, as we require approximately half of the parameters for the same fitting accuracy with the additional advantage that an entire PDF can be stored by using a 4-byte integer per basis function, and we can achieve better accuracy by increasing the number of bases. By using data from the CFHTLenS, we demonstrate th...

  5. Photometric Properties of Low-Redshift Galaxy Clusters (LOCOS)

    CERN Document Server

    López-Cruz, O

    2000-01-01

    A comprehensive multicolor survey was undertaken to investigate global optical properties of Abell clusters of galaxies. This survey was christened the "Low-Redshift Cluster Optical Survey" (LOCOS). LOCOS was devised to search for patterns of galaxy evolution induced by the environment. The generated data base contains accurate deep CCD photometric measurements (Kron-Cousins R,,B and I) for a sample of 46 low-redshift (0.04 <= z <= 0.18) Abell clusters. This is one of the few large surveys that included the contribution due to dwarf galaxies (about 5.5 mag deeper than the R characteristic magnitude (M*); Ho=50 km/s/Mpc, qo=0). Due to space restrictions only the main results concerning the variations at the bright-end of the luminosity function (LF) are presented here. Other results are presented elsewhere (Lopez-Cruz & Yee 2000a,b). We have detected clear variations at both the bright end and the faint end of the LF. The nature of the variations at the bright end revealed that poor cD clusters have ...

  6. 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.

  7. EXTENDED PHOTOMETRY FOR THE DEEP2 GALAXY REDSHIFT SURVEY: A TESTBED FOR PHOTOMETRIC REDSHIFT EXPERIMENTS

    Energy Technology Data Exchange (ETDEWEB)

    Matthews, Daniel J.; Newman, Jeffrey A. [Department of Physics and Astronomy, University of Pittsburgh, 3941 O' Hara Street, Pittsburgh, PA 15260 (United States); Coil, Alison L. [Department of Physics, University of California San Diego, 9500 Gilman Drive, La Jolla, CA 92093 (United States); Cooper, Michael C. [Center for Galaxy Evolution, Department of Physics and Astronomy, University of California, Irvine, 4129 Frederick Reines Hall, Irvine, CA 92697 (United States); Gwyn, Stephen D. J., E-mail: djm70@pitt.edu, E-mail: janewman@pitt.edu, E-mail: acoil@ucsd.edu, E-mail: m.cooper@uci.edu, E-mail: Stephen.Gwyn@nrc-cnrc.gc.ca [Canadian Astronomical Data Centre, Herzberg Institute of Astrophysics, 5071 West Saanich Road, Victoria, British Columbia V9E 2E7 (Canada)

    2013-02-15

    This paper describes a new catalog that supplements the existing DEEP2 Galaxy Redshift Survey photometric and spectroscopic catalogs with ugriz photometry from two other surveys: the Canada-France-Hawaii Legacy Survey (CFHTLS) and the Sloan Digital Sky Survey (SDSS). Each catalog is cross-matched by position on the sky in order to assign ugriz photometry to objects in the DEEP2 catalogs. We have recalibrated the CFHTLS photometry where it overlaps DEEP2 in order to provide a more uniform data set. We have also used this improved photometry to predict DEEP2 BRI photometry in regions where only poorer measurements were available previously. In addition, we have included improved astrometry tied to SDSS rather than USNO-A2.0 for all DEEP2 objects. In total this catalog contains {approx}27, 000 objects with full ugriz photometry as well as robust spectroscopic redshift measurements, 64% of which have r > 23. By combining the secure and accurate redshifts of the DEEP2 Galaxy Redshift Survey with ugriz photometry, we have created a catalog that can be used as an excellent testbed for future photo-z studies, including tests of algorithms for surveys such as LSST and DES.

  8. The Next Generation Virgo Cluster Survey. XV. The Photometric Redshift Estimation for Background Sources

    Science.gov (United States)

    Raichoor, A.; Mei, S.; Erben, T.; Hildebrandt, H.; Huertas-Company, M.; Ilbert, O.; Licitra, R.; Ball, N. M.; Boissier, S.; Boselli, A.; Chen, Y.-T.; Côté, P.; Cuillandre, J.-C.; Duc, P. A.; Durrell, P. R.; Ferrarese, L.; Guhathakurta, P.; Gwyn, S. D. J.; Kavelaars, J. J.; Lançon, A.; Liu, C.; MacArthur, L. A.; Muller, M.; Muñoz, R. P.; Peng, E. W.; Puzia, T. H.; Sawicki, M.; Toloba, E.; Van Waerbeke, L.; Woods, D.; Zhang, H.

    2014-12-01

    The Next Generation Virgo Cluster Survey (NGVS) is an optical imaging survey covering 104 deg2 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 AB = 12.5 mag. When using the u* griz bands, our photometric redshifts for 15.5 mag outliers, a scatter σoutl.rej., and an individual error on z 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 outliers, and z 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.

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

    Energy Technology Data Exchange (ETDEWEB)

    Bovy, Jo; Hogg, David W.; Weaver, Benjamin A. [Center for Cosmology and Particle Physics, Department of Physics, New York University, 4 Washington Place, New York, NY 10003 (United States); Myers, Adam D. [Department of Physics and Astronomy, University of Wyoming, Laramie, WY 82071 (United States); Hennawi, Joseph F. [Max-Planck-Institut fuer Astronomie, Koenigstuhl 17, D-69117 Heidelberg (Germany); McMahon, Richard G. [Institute of Astronomy, University of Cambridge, Madingley Road, Cambridge CB3 0HA (United Kingdom); Schiminovich, David [Department of Astronomy, Columbia University, New York, NY 10027 (United States); Sheldon, Erin S. [Brookhaven National Laboratory, Upton, NY 11973 (United States); Brinkmann, Jon [Apache Point Observatory, P.O. Box 59, Sunspot, NM 88349 (United States); Schneider, Donald P., E-mail: jo.bovy@nyu.edu [Department of Astronomy and Astrophysics, Pennsylvania State University, 525 Davey Laboratory, University Park, PA 16802 (United States)

    2012-04-10

    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.

  10. Photometric redshifts and quasar probabilities from a single, data-driven generative model

    Energy Technology Data Exchange (ETDEWEB)

    Bovy, Jo [New York Univ. (NYU), NY (United States); Myers, Adam D. [Univ. of Wyoming, Laramie, WY (United States); Max Planck Inst. for Medical Research, Heidelberg (Germany); Hennawi, Joseph F. [Max Planck Inst. for Medical Research, Heidelberg (Germany); Hogg, David W. [Max Planck Inst. for Medical Research, Heidelberg (Germany); New York Univ. (NYU), NY (United States); McMahon, Richard G. [Univ. of Cambridge (United Kingdom); Schiminovich, David [Columbia Univ., New York, NY (United States); Sheldon, Erin S. [Brookhaven National Lab. (BNL), Upton, NY (United States); Brinkmann, Jon [Apache Point Observatory and New Mexico State Univ., Sunspot, NM (United States); Schneider, Donald P. [Pennsylvania State Univ., University Park, PA (United States); Weaver, Benjamin A. [New York Univ. (NYU), NY (United States)

    2012-03-20

    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.

  11. Photometric redshifts and cluster tomography in the ESO Distant Cluster Survey

    CERN Document Server

    Pellò, R; De Lucia, G; Simard, L; Clowe, D I; Jablonka, P; Milvang-Jensen, B; Saglia, R P; White, S D M; Aragón-Salamanca, A; Halliday, C; Poggianti, B; Best, P; Dalcanton, J; Dantel-Fort, M; Fort, B; Von der Linden, A; Mellier, Y; Rottgering, H; Zaritsky, D

    2009-01-01

    This paper reports the results obtained on the photometric redshifts measurement and accuracy, and cluster tomography in the ESO Distant Cluster Survey (EDisCS) fields. Photometric redshifts were computed using two independent codes (Hyperz and G. Rudnick's code). The accuracy of photometric redshifts was assessed by comparing our estimates with the spectroscopic redshifts of ~1400 galaxies in the 0.3photometric catalog for the spectroscopic sample. The accuracy of photometric redshifts is typically sigma(Delta z/(1+z)) ~ 0.05+/-0.01, depending on the field, the filter set, and the spectral type of the galaxies. The quality of the photometric redshifts degrades by a factor of two in sigma(Delta z/(1+z)) between the brightest (I~22) and the faintest (I~24-24.5) galaxies in the EDisCS sample. The photometric determination of cluster redshifts in the EDisCS fields using a sim...

  12. Estimating Luminosities and Stellar Masses of Galaxies Photometrically without Determining Redshifts

    CERN Document Server

    Hsieh, B C

    2014-01-01

    Large direct-imaging surveys usually use a template-fitting technique to estimate photometric redshifts for galaxies, which are then applied to derive important galaxy properties such as luminosities and stellar masses. These estimates can be noisy and suffer from systematic biases because of the possible mis-selection of templates and the propagation of the photometric redshift uncertainty. We introduce an algorithm, the Direct Empirical Photometric method (DEmP), which can be used to directly estimate these quantities using training sets, bypassing photometric redshift determination. DEmP also applies two techniques to minimize the effects arising from the non-uniform distribution of training-set galaxy redshifts from a flux-limited sample. First, for each input galaxy, fitting is performed using a subset of the training-set galaxies with photometry and colors closest to those of the input galaxy. Second, the training set is artificially resampled to produce a flat distribution in redshift, or other propert...

  13. Data-driven, Interpretable Photometric Redshifts Trained on Heterogeneous and Unrepresentative Data

    Science.gov (United States)

    Leistedt, Boris; Hogg, David W.

    2017-03-01

    We present a new method for inferring photometric redshifts in deep galaxy and quasar surveys, based on a data-driven model of latent spectral energy distributions (SEDs) and a physical model of photometric fluxes as a function of redshift. This conceptually novel approach combines the advantages of both machine learning methods and template fitting methods by building template SEDs directly from the spectroscopic training data. This is made computationally tractable with Gaussian processes operating in flux–redshift space, encoding the physics of redshifts and the projection of galaxy SEDs onto photometric bandpasses. This method alleviates the need to acquire representative training data or to construct detailed galaxy SED models; it requires only that the photometric bandpasses and calibrations be known or have parameterized unknowns. The training data can consist of a combination of spectroscopic and deep many-band photometric data with reliable redshifts, which do not need to entirely spatially overlap with the target survey of interest or even involve the same photometric bands. We showcase the method on the i-magnitude-selected, spectroscopically confirmed galaxies in the COSMOS field. The model is trained on the deepest bands (from SUBARU and HST) and photometric redshifts are derived using the shallower SDSS optical bands only. We demonstrate that we obtain accurate redshift point estimates and probability distributions despite the training and target sets having very different redshift distributions, noise properties, and even photometric bands. Our model can also be used to predict missing photometric fluxes or to simulate populations of galaxies with realistic fluxes and redshifts, for example.

  14. 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.

  15. 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...

  16. The effects of UV photometry and binary interactions on photometric redshift and galaxy morphology

    CERN Document Server

    Zhang, F; Li, L; Shan, H; Zhang, Y

    2010-01-01

    Using the Hyperz code and a template spectral library which consists of 4 observed galaxy spectra from Coleman, Wu & Weedman (CWW, 1980) and 8 spectral families built with evolutionary population synthesis models, we present photometric redshift estimates (photo-z) for a spectroscopic sample of 6,531 galaxies, and morphologies for a morphological sample of 1,502 bright galaxies. All galaxies are matched with the SDSS DR7 and GALEX DR4. The inclusion of Fuv or Nuv or both photometry decreases the number of catastrophic identifications (CIs, |z_phot -z_spec| > 1.0). If CIs are removed, the inclusion of both Fuv and Nuv photometry mainly increases the number of non-CIs in the low redshift, g-r 14 regions. Moreover, BIs mainly affect the determinations of E and S0 types. Nuv -u = 1.94 and 5.77-1.47(u-r) = Fuv discriminators can be used as morphology selection indicators. These two criteria have comparable reliability and completeness for selecting early- and late-type galaxies to C=2.6 criterion and higher c...

  17. 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...

  18. The overlooked potential of Generalized Linear Models in astronomy-II: Gamma regression and photometric redshifts

    Science.gov (United States)

    Elliott, J.; de Souza, R. S.; Krone-Martins, A.; Cameron, E.; Ishida, E. E. O.; Hilbe, J.

    2015-04-01

    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 real data. Moreover, we can easily obtain such levels of precision within a matter of seconds on a normal desktop computer and with training sets that contain merely thousands of galaxies. Our software is made publicly available as a user-friendly package developed in Python, R and via an interactive web application. This software allows users to apply a set of GLMs to their own photometric catalogues and generates publication quality plots with minimum effort. By facilitating their ease of use to the astronomical community, this paper series aims to make GLMs widely known and to encourage their implementation in future large-scale projects, such as the Large Synoptic Survey Telescope.

  19. 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...

  20. Spectroscopic failures in photometric redshift calibration: cosmological biases and survey requirements

    Energy Technology Data Exchange (ETDEWEB)

    Cunha, Carlos E. [KIPAC, Menlo Park; Huterer, Dragan [Michigan U.; Lin, Huan [Fermilab; Busha, Michael T. [Zurich U.; Wechsler, Risa H. [SLAC

    2014-10-11

    We use N-body-spectro-photometric simulations to investigate the impact of incompleteness and incorrect redshifts in spectroscopic surveys to photometric redshift training and calibration and the resulting effects on cosmological parameter estimation from weak lensing shear-shear correlations. The photometry of the simulations is modeled after the upcoming Dark Energy Survey and the spectroscopy is based on a low/intermediate resolution spectrograph with wavelength coverage of 5500{\\AA} < {\\lambda} < 9500{\\AA}. The principal systematic errors that such a spectroscopic follow-up encounters are incompleteness (inability to obtain spectroscopic redshifts for certain galaxies) and wrong redshifts. Encouragingly, we find that a neural network-based approach can effectively describe the spectroscopic incompleteness in terms of the galaxies' colors, so that the spectroscopic selection can be applied to the photometric sample. Hence, we find that spectroscopic incompleteness yields no appreciable biases to cosmology, although the statistical constraints degrade somewhat because the photometric survey has to be culled to match the spectroscopic selection. Unfortunately, wrong redshifts have a more severe impact: the cosmological biases are intolerable if more than a percent of the spectroscopic redshifts are incorrect. Moreover, we find that incorrect redshifts can also substantially degrade the accuracy of training set based photo-z estimators. The main problem is the difficulty of obtaining redshifts, either spectroscopically or photometrically, for objects at z > 1.3. We discuss several approaches for reducing the cosmological biases, in particular finding that photo-z error estimators can reduce biases appreciably.

  1. METAPHOR: A machine learning based method for the probability density estimation of photometric redshifts

    CERN Document Server

    Cavuoti, Stefano; Brescia, Massimo; Vellucci, Civita; Tortora, Crescenzo; Longo, Giuseppe

    2016-01-01

    A variety of fundamental astrophysical science topics require the determination of very accurate photometric redshifts (photo-z's). A wide plethora of methods have been developed, based either on template models fitting or on empirical explorations of the photometric parameter space. Machine learning based techniques are not explicitly dependent on the physical priors and able to produce accurate photo-z estimations within the photometric ranges derived from the spectroscopic training set. These estimates, however, are not easy to characterize in terms of a photo-z Probability Density Function (PDF), due to the fact that the analytical relation mapping the photometric parameters onto the redshift space is virtually unknown. We present METAPHOR (Machine-learning Estimation Tool for Accurate PHOtometric Redshifts), a method designed to provide a reliable PDF of the error distribution for empirical techniques. The method is implemented as a modular workflow, whose internal engine for photo-z estimation makes use...

  2. 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...

  3. Photometric redshifts for the Dark Energy Survey and VISTA and implications for large-scale structure

    Science.gov (United States)

    Banerji, Manda; Abdalla, Filipe B.; Lahav, Ofer; Lin, Huan

    2008-05-01

    We conduct a detailed analysis of the photometric redshift requirements for the proposed Dark Energy Survey (DES) using two sets of mock galaxy simulations and an artificial neural network code - ANNZ. In particular, we examine how optical photometry in the DES grizY bands can be complemented with near-infrared photometry from the planned VISTA Hemisphere Survey (VHS) in the JHKs bands. We find that the rms scatter on the photometric redshift estimate over 1 neural network code, calculate the extinction, Av for these reddened galaxies. We also look at the impact of using different training sets when calculating photometric redshifts. In particular, we find that using the ongoing DEEP2 and VVDS-Deep spectroscopic surveys to calibrate photometric redshifts for DES, will prove effective. However, we need to be aware of uncertainties in the photometric redshift bias that arise when using different training sets as these will translate into errors in the dark energy equation of state parameter, w. Furthermore, we show that the neural network error estimate on the photometric redshift may be used to remove outliers from our samples before any kind of cosmological analysis, in particular for large-scale structure experiments. By removing all galaxies with a neural network photo-z error estimate of greater than 0.1 from our DES + VHS sample, we can constrain the galaxy power spectrum out to a redshift of 2 and reduce the fractional error on this power spectrum by ~15-20 per cent compared to using the entire catalogue. Output tables of spectroscopic redshift versus photometric redshift used to produce the results in this paper can be found at http://www.star.ucl.ac.uk/~mbanerji/DESdata.

  4. MegaZ-LRG: A photometric redshift catalogue of one million SDSS Luminous Red Galaxies

    CERN Document Server

    Collister, A A; Blake, C; Cannon, R; Croom, S; Drinkwater, M; Edge, A; Eisenstein, D; Loveday, J; Nichol, R; Pimbblet, K; De Propris, R; Roseboom, I; Ross, N; Schneider, D P; Shanks, T; Wake, D; Collister, Adrian; Lahav, Ofer; Blake, Chris; Cannon, Russell; Croom, Scott; Drinkwater, Michael; Edge, Alastair; Eisenstein, Daniel; Loveday, Jon; Nichol, Robert; Pimbblet, Kevin; Propris, Roberto De; Roseboom, Isaac; Ross, Nic; Schneider, Donald P.; Shanks, Tom; Wake, David

    2006-01-01

    We describe the construction of MegaZ-LRG, a photometric redshift catalogue of over one million luminous red galaxies (LRGs) in the redshift range 0.4 < z < 0.7 with limiting magnitude i < 20. The catalogue is selected from the imaging data of the Sloan Digital Sky Survey Data Release 4. The 2dF-SDSS LRG and Quasar (2SLAQ) spectroscopic redshift catalogue of 13,000 intermediate-redshift LRGs provides a photometric redshift training set, allowing use of ANNz, a neural network-based photometric-redshift estimator. The rms photometric redshift accuracy obtained for an evaluation set selected from the 2SLAQ sample is sigma_z = 0.049 averaged over all galaxies, and sigma_z = 0.040 for a brighter subsample (i < 19.0). The catalogue is expected to contain ~5 per cent stellar contamination. The ANNz code is used to compute a refined star/galaxy probability based on a range of photometric parameters; this allows the contamination fraction to be reduced to 2 per cent with negligible loss of genuine galaxies...

  5. 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

  6. A critical appraisal of the SED fitting method to estimate photometric redshifts

    CERN Document Server

    Massarotti, M; Buzzoni, A

    2001-01-01

    We discuss the stability of the photometric redshift estimate obtained with the SED fitting method with respect to the choice of the galaxy templates. Within the observational uncertainty and photometric errors, we find satisfactory agreement among different sets of theoretical and empirical templates using the Hubble Deep Field North as a target galaxy sample. Our results suggest that, especially at high redshift, the description of the physical processes of photon absorption in the interstellar and intergalactic medium plays a dominant role in the redshift estimate. The specific choice of the template set, as long as this includes both normal and starburst galaxies, is in comparison a minor issue.

  7. 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...

  8. Photo-z-SQL: integrated, flexible photometric redshift computation in a database

    CERN Document Server

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

    2016-01-01

    We present a flexible template-based photometric redshift estimation framework, implemented in C#, that can be seamlessly integrated into a SQL database (or DB) server and executed on-demand in SQL. The DB integration eliminates the need to move large photometric datasets outside a database for redshift estimation, and utilizes the computational capabilities of DB hardware. The code is able to perform both maximum likelihood and Bayesian estimation, and can handle inputs of variable photometric filter sets and corresponding broad-band magnitudes. It is possible to take into account the full covariance matrix between filters, and filter zero points can be empirically calibrated using measurements with given redshifts. The list of spectral templates and the prior can be specified flexibly, and the expensive synthetic magnitude computations are done via lazy evaluation, coupled with a caching of results. Parallel execution is fully supported. For large upcoming photometric surveys such as the LSST, the ability t...

  9. Photometric Redshifts for the Dark Energy Survey and VISTA and Implications for Large Scale Structure

    CERN Document Server

    Banerji, Manda; Lahav, Ofer; Lin, Huan

    2007-01-01

    We conduct a detailed analysis of the photometric redshift requirements for the proposed Dark Energy Survey (DES) using two sets of mock galaxy simulations and an artificial neural network code - ANNz. In particular, we examine how optical photometry in the DES $grizY$ bands can be complemented with near infra-red photometry from the planned VISTA Hemisphere Survey (VHS) in the $JHK_s$ bands in order to improve the photometric redshift estimate by a factor of two at $z>1$. We draw attention to the effects of galaxy formation scenarios such as reddening on the photo-z estimate and using our neural network code, calculate $A_v$ for these reddened galaxies. We also look at the impact of using different training sets when calculating photometric redshifts. In particular, we find that using the ongoing DEEP2 and VVDS-Deep spectroscopic surveys to calibrate photometric redshifts for DES, will prove effective. However we need to be aware of uncertainties in the photometric redshift bias that arise when using differe...

  10. Photometric Redshifts for High Resolution Radio Galaxies in the SuperCLASS Field

    Science.gov (United States)

    Manning, Sinclaire; Casey, Caitlin; Battye, Richard; Hales, Christopher A.; Chapman, Scott; Smail, Ian; SuperCLASS Team

    2017-01-01

    SuperCLASS (the Super-Cluster Assisted Shear Survey) is a deep, wide-area (~2 square degrees) extragalactic field with high resolution (0.1”) radio continuum coverage from e-MERLIN (Multi-Element Radio Linked Interferometer Network.) The combination of sensitivity and spatial resolution make e-MERLIN an ideal tool to trace spatially resolved star-formation in heavily obscured, dusty star-forming galaxies (DSFGs). Plus, thanks to the tight relationship between radio continuum and far-IR observations we have an observationally inexpensive and accurate method of mapping star formation density in distant galaxies. We present a photometric redshift catalog for DSFGs located in the SuperCLASS field. Multiwavelength photometric data was obtained with Subaru SuprimeCam (B,V,r,i,z) and photometric redshifts were generated using the public photometric redshift code, EAZY. With these redshifts we aim to conduct the first large sample morphological analysis of z~1-3 obscured galaxies. We plan to address two important questions: 1) Are the majority of obscured SFR>50 Msolar/yr galaxies driven by major collisions? and 2) do luminous active galactic nuclei (AGN) play a crucial role in the quenching of highly obscured star-formation? These photometric redshifts are crucial in determining the physical origins of our DSFG sample and to also conduct radio weak lensing experiments with the e-MERLIN dataset.

  11. Two Novel Approaches for Photometric Redshift Estimation based on SDSS and 2MASS

    Institute of Scientific and Technical Information of China (English)

    Dan Wang; Yan-Xia Zhang; Chao Liu; Yong-Heng Zhao

    2008-01-01

    We investigate two training-set methods: support vector machines (SVMs) and Kernel Regression (KR) for photometric redshift estimation with the data from the databases of Sloan Digital Sky Survey Data Release 5 and Two Micron All Sky Survey. We probe the performances of SVMs and KR for different input patterns. Our experiments show that with more parameters considered, the accuracy does not always increase, and only when appropriate parameters are chosen, the accuracy can improve. For different approaches, the best input pattern is different. With different parameters as input, the optimal bandwidth is dissimilar for KR. The rms errors of photometric redshifts based on SVM and KR methods are less than 0.03 and 0.02, respectively. Strengths and weaknesses of the two approaches are summarized. Compared to other methods of estimating photometric redshifts, they show their superiorities, especially KR, in terms of accuracy.

  12. 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...

  13. Two novel approaches for photometric redshift estimation based on SDSS and 2MASS databases

    CERN Document Server

    Wang, Dan; Liu, Chao; Zhao, Yong-Heng

    2007-01-01

    We investigate two training-set methods: support vector machines (SVMs) and Kernel Regression (KR) for photometric redshift estimation with the data from the Sloan Digital Sky Survey Data Release 5 and Two Micron All Sky Survey databases. We probe the performances of SVMs and KR for different input patterns. Our experiments show that the more parameters considered, the accuracy doesn't always increase, and only when appropriate parameters chosen, the accuracy can improve. Moreover for different approaches, the best input pattern is different. With different parameters as input, the optimal bandwidth is dissimilar for KR. The rms errors of photometric redshifts based on SVM and KR methods are less than 0.03 and 0.02, respectively. Finally the strengths and weaknesses of the two approaches are summarized. Compared to other methods of estimating photometric redshifts, they show their superiorities, especially KR, in terms of accuracy.

  14. 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.

  15. Simultaneous constraints on cosmology and photometric redshift bias from weak lensing and galaxy clustering

    Science.gov (United States)

    Samuroff, S.; Troxel, M. A.; Bridle, S. L.; Zuntz, J.; MacCrann, N.; Krause, E.; Eifler, T.; Kirk, D.

    2017-02-01

    We investigate the expected cosmological constraints from a combination of cosmic shear and large-scale galaxy clustering using realistic photometric redshift distributions. Introducing a systematic bias in the lensing distributions (of 0.05 in redshift) produces a >2σ bias in the recovered matter power spectrum amplitude and dark energy equation of state for preliminary Stage III surveys. We demonstrate that cosmological error can be largely removed by marginalizing over biases in the assumed weak-lensing redshift distributions. Furthermore, the cosmological constraining power is retained despite removing much of the information on the lensing redshift biases. This finding relies upon high-quality redshift estimates for the clustering sample, but does not require spectroscopy. All galaxies in this analysis can thus be assumed to come from a single photometric survey. We show that this internal constraint on redshift biases arises from complementary degeneracy directions between cosmic shear and the combination of galaxy clustering and shear-density cross-correlations. Finally we examine a case where the assumed redshift distributions differ from the truth by more than a simple uniform bias. We find that the effectiveness of this self-calibration method will depend on the survey details and the nature of the uncertainties on the estimated redshift distributions.

  16. Galaxy and Mass Assembly (GAMA): Colour and luminosity dependent clustering from calibrated photometric redshifts

    CERN Document Server

    Christodoulou, L; Loveday, J; Norberg, P; Baldry, I K; Hurley, P D; Driver, S P; Bamford, S P; Hopkins, A M; Liske, J; Peacock, J A; Bland-Hawthorn, J; Brough, S; Cameron, E; Conselice, C J; Croom, S M; Frenk, C S; Gunawardhana, M; Jones, D H; Kelvin, L S; Kuijken, K; Nichol, R C; Parkinson, H; Pimbblet, K A; Popescu, C C; Prescott, M; Robotham, A S G; Sharp, R G; Sutherland, W J; Taylor, E N; Thomas, D; Tuffs, R J; van Kampen, E; Wijesinghe, D

    2012-01-01

    We measure the two-point angular correlation function of a sample of 4,289,223 galaxies with r < 19.4 mag from the Sloan Digital Sky Survey as a function of photometric redshift, absolute magnitude and colour down to M_r - 5log h = -14 mag. Photometric redshifts are estimated from ugriz model magnitudes and two Petrosian radii using the artificial neural network package ANNz, taking advantage of the Galaxy and Mass Assembly (GAMA) spectroscopic sample as our training set. The photometric redshifts are then used to determine absolute magnitudes and colours. For all our samples, we estimate the underlying redshift and absolute magnitude distributions using Monte-Carlo resampling. These redshift distributions are used in Limber's equation to obtain spatial correlation function parameters from power law fits to the angular correlation function. We confirm an increase in clustering strength for sub-L* red galaxies compared with ~L* red galaxies at small scales in all redshift bins, whereas for the blue populati...

  17. Photometric Redshifts and Systematic Variations in the Spectral Energy Distributions of Luminous Red Galaxies from SDSS DR7

    Science.gov (United States)

    Greisel, N.; Seitz, S.; Drory, N.; Bender, R.; Saglia, R. P.; Snigula, J.

    2013-05-01

    We describe the construction of a template set of spectral energy distributions (SEDs) for the estimation of photometric redshifts of luminous red galaxies (LRGs) with a Bayesian template fitting method. By examining the color properties of several publicly available SED sets within a redshift range of 0 code (PhotoZ) are nearly unbiased, with a scatter of σΔz = 0.027 (including outliers), a fraction of catastrophic outliers (|z phot - z spec|/(1 + z spec) > 0.15) of η = 0.12%, and a normalized median absolute rest frame deviation (NMAD) of σNMAD = 1.48 × MAD = 0.017 for non-outliers. We show that templates that optimally describe the brightest galaxies (-24.5 <= MR <= -22.7) indeed vary from z = 0.1 to z = 0.5, consistent with aging of the stellar population. Furthermore, we find that templates that optimally describe galaxies at z < 0.1 strongly differ as a function of the absolute magnitude of the galaxies, indicating an increase in star formation activity for less luminous galaxies. Our findings based on the photometry of the SDSS LRGs and our SED template fitting are supported by comparison to the average SDSS LRG spectra in different luminosity and redshift bins.

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

    Science.gov (United States)

    Roseboom, I. G.; Ivison, R. J.; Greve, T. R.; Amblard, A.; Arumugam, V.; Auld, R.; Aussel, H.; Bethermin, M.; Blain, A.; Block, J.; Boselli, A.; Brisbin, D.; Buat, V.; Burgarella, D.; Castro-Rodriquez, N.; Cava, A.; Chanial, P.; Chapin, E.; Chapman, S.; Clements, D. L.; Conley, A.; Conversi, L.; Dowell, C. D.; Dunlop, J. S.; Dwek, E.

    2012-01-01

    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 micron by the SPIRE instrument on Herschel. From a sample of 63 previously identified mm sources with reliable radio identifications in the Great Observatories Origins Deep Survey North 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 color evolution with redshift, finding that the colors of mm sources are adequately described by a modified blackbody with constant optical depth Tau = (Nu/nu(sub 0))(exp Beta), where Beta = +1.8 and nu(sub 0) = c/100 micron. We find a tight correlation between dust temperature and IR luminosity. Using a single model of the dust temperature and IR luminosity relation, we derive photometric redshift estimates for the 46 SPIRE-detected mm sources. Testing against the 22 sources with known spectroscopic or good quality optical/near-IR photometric redshifts, we find submm/mm photometric redshifts offer a redshift accuracy of (absolute value of Delta sub (z))/(1 + z) = 0.16 (absolute value of Delta sub (z)) = 0.51). Including constraints from the radio-far-IR correlation, the accuracy is improved to (absolute value of Delta sub (z))/(1 + z) = 0.14 (((absolute value of Delta sub (z))) = 0.45). We estimate the redshift distribution of mm-selected sources finding a significant excess at Z > 3 when compared to approx 8S0 micron selected samples.

  19. The Impact of JWST Broadband Filter Choice on Photometric Redshift Estimation

    DEFF Research Database (Denmark)

    Bisigello, L.; Caputi, K. I.; Colina, L.;

    2016-01-01

    The determination of galaxy redshifts in the James Webb Space Telescope's (JWST) 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 μm and Mid Infrared Instrument (MIRI) at λ 5.0 μm. In this work we analyze ...

  20. 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...

  1. 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.

  2. 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...

  3. A Joint Analysis for Cosmology and Photometric Redshift Calculation Using Cross Correlations

    CERN Document Server

    McLeod, Michael; Abdalla, Filipe B

    2016-01-01

    We present a method of calibrating the properties of photometric redshift bins as part of a larger Markov Chain Monte Carlo (MCMC) analysis for the inference of cosmological parameters. The redshift bins are characterised by their mean and variance, which are varied as free parameters and marginalised over when obtaining the cosmological parameters. We demonstrate that the likelihood function for cross-correlations in an angular power spectrum framework tightly constrains the properties of bins such that they may be well determined, reducing their influence on cosmological parameters and avoiding the bias from poorly estimated redshift distributions. We demonstrate that even with only three photometric and three spectroscopic bins, we can recover accurate estimates of the mean redshift of a bin to within $\\Delta\\mu \\approx 3-4 \\times10^{-3}$ and the width of the bin to $\\Delta\\sigma \\approx 1\\times10^{-3}$ for galaxies near $z = 1$. This indicates that we may be able to bring down the photometric redshift err...

  4. Weighing the Giants - II. Improved calibration of photometry from stellar colours and accurate photometric redshifts

    Science.gov (United States)

    Kelly, Patrick L.; von der Linden, Anja; Applegate, Douglas E.; Allen, Mark T.; Allen, Steven W.; Burchat, Patricia R.; Burke, David L.; Ebeling, Harald; Capak, Peter; Czoske, Oliver; Donovan, David; Mantz, Adam; Morris, R. Glenn

    2014-03-01

    We present improved methods for using stars found in astronomical exposures to calibrate both star and galaxy colours as well as to adjust the instrument flat-field. By developing a spectroscopic model for the Sloan Digital Sky Survey (SDSS) stellar locus in colour-colour space, synthesizing an expected stellar locus, and simultaneously solving for all unknown zero-points when fitting to the instrumental locus, we increase the calibration accuracy of stellar locus matching. We also use a new combined technique to estimate improved flat-field models for the Subaru SuprimeCam camera, forming `star flats' based on the magnitudes of stars observed in multiple positions or through comparison with available measurements in the SDSS catalogue. These techniques yield galaxy magnitudes with reliable colour calibration (≲0.01-0.02 mag accuracy) that enable us to estimate photometric redshift probability distributions without spectroscopic training samples. We test the accuracy of our photometric redshifts using spectroscopic redshifts zs for ˜5000 galaxies in 27cluster fields with at least five bands of photometry, as well as galaxies in the Cosmic Evolution Survey (COSMOS) field, finding σ((zp - zs)/(1 + zs)) ≈ 0.03 for the most probable redshift zp. We show that the full posterior probability distributions for the redshifts of galaxies with five-band photometry exhibit good agreement with redshifts estimated from thirty-band photometry in the COSMOS field. The growth of shear with increasing distance behind each galaxy cluster shows the expected redshift-distance relation for a flat Λ cold dark matter (Λ-CDM) cosmology. Photometric redshifts and calibrated colours are used in subsequent papers to measure the masses of 51 galaxy clusters from their weak gravitational shear and determine improved cosmological constraints. We make our PYTHON code for stellar locus matching publicly available at http://big-macs-calibrate.googlecode.com; the code requires only input

  5. METAPHOR: a machine-learning-based method for the probability density estimation of photometric redshifts

    Science.gov (United States)

    Cavuoti, S.; Amaro, V.; Brescia, M.; Vellucci, C.; Tortora, C.; Longo, G.

    2017-02-01

    A variety of fundamental astrophysical science topics require the determination of very accurate photometric redshifts (photo-z). A wide plethora of methods have been developed, based either on template models fitting or on empirical explorations of the photometric parameter space. Machine-learning-based techniques are not explicitly dependent on the physical priors and able to produce accurate photo-z estimations within the photometric ranges derived from the spectroscopic training set. These estimates, however, are not easy to characterize in terms of a photo-z probability density function (PDF), due to the fact that the analytical relation mapping the photometric parameters on to the redshift space is virtually unknown. We present METAPHOR (Machine-learning Estimation Tool for Accurate PHOtometric Redshifts), a method designed to provide a reliable PDF of the error distribution for empirical techniques. The method is implemented as a modular workflow, whose internal engine for photo-z estimation makes use of the MLPQNA neural network (Multi Layer Perceptron with Quasi Newton learning rule), with the possibility to easily replace the specific machine-learning model chosen to predict photo-z. We present a summary of results on SDSS-DR9 galaxy data, used also to perform a direct comparison with PDFs obtained by the LE PHARE spectral energy distribution template fitting. We show that METAPHOR is capable to estimate the precision and reliability of photometric redshifts obtained with three different self-adaptive techniques, i.e. MLPQNA, Random Forest and the standard K-Nearest Neighbors models.

  6. 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...

  7. Weighing the Giants II: Improved Calibration of Photometry from Stellar Colors and Accurate Photometric Redshifts

    CERN Document Server

    Kelly, Patrick L; Applegate, Douglas E; Allen, Mark T; Allen, Steven W; Burchat, Patricia R; Burke, David L; Ebeling, Harald; Capak, Peter; Czoske, Oliver; Donovan, David; Mantz, Adam; Morris, R Glenn

    2012-01-01

    We present improved methods for using stars found in astronomical exposures to calibrate both star and galaxy colors as well as to adjust the instrument flat field. By developing a spectroscopic model for the SDSS stellar locus in color-color space, synthesizing an expected stellar locus, and simultaneously solving for all unknown zeropoints when fitting to the instrumental locus, we increase the calibration accuracy of stellar locus matching. We also use a new combined technique to estimate improved flat-field models for the Subaru SuprimeCam camera, forming `star flats' based on the magnitudes of stars observed in multiple positions or through comparison with available SDSS magnitudes. These techniques yield galaxy magnitudes with reliable color calibration (< 0.01 - 0.02 mag accuracy) that enable us to estimate photometric redshift probability distributions without spectroscopic training samples. We test the accuracy of our photometric redshifts using spectroscopic redshifts z_s for ~5000 galaxies in 27...

  8. 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 ...

  9. 2MASS Photometric Redshift catalog: a comprehensive three-dimensional census of the whole sky

    CERN Document Server

    Bilicki, Maciej; Peacock, John A; Cluver, Michelle E; Steward, Louise

    2014-01-01

    Key cosmological applications require the three-dimensional 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 2MRS and IRAS PSCz -- have median redshifts of only z=0.03 and sample the very local Universe. There exist all-sky galaxy catalogs reaching much deeper -- SuperCOSMOS in the optical, 2MASS in the near-IR and WISE in the mid-IR -- but these lack complete redshift information. At present, the only rapid way towards larger 3D catalogs covering the whole sky is through photometric redshift techniques. In this paper we present the 2MASS Photometric Redshift catalog (2MPZ) containing 1 million galaxies, constructed by cross-matching 2MASS XSC, WISE and SuperCOSMOS all-sky samples and employing the artificial neural network approach (the ANNz algorithm), trained on such redshift surveys as SDSS, 6dFGS and 2dFGRS. T...

  10. Incorporating Photometric Redshift Probability Density Information into Real-Space Clustering Measurements

    CERN Document Server

    Myers, Adam D; Ball, Nicholas M

    2009-01-01

    The use of photometric redshifts in cosmology is increasing. Often, however these photo-zs are treated like spectroscopic observations, in that the peak of the photometric redshift, rather than the full probability density function (PDF), is used. This overlooks useful information inherent in the full PDF. We introduce a new real-space estimator for one of the most used cosmological statistics, the 2-point correlation function, that weights by the PDF of individual photometric objects in a manner that is optimal when Poisson statistics dominate. As our estimator does not bin based on the PDF peak it substantially enhances the clustering signal by usefully incorporating information from all photometric objects that overlap the redshift bin of interest. As a real-world application, we measure QSO clustering in the Sloan Digital Sky Survey (SDSS) and find that our estimator improves the clustering signal by a factor equivalent to increasing the survey size by a factor of 2 to 3. Our technique uses spectroscopic ...

  11. 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.

  12. The Next Generation Virgo Cluster Survey. XV. The photometric redshift estimation for background sources

    CERN Document Server

    Raichoor, A; Erben, T; Hildebrandt, H; Huertas-Company, M; Ilbert, O; Licitra, R; Ball, N M; Boissier, S; Boselli, A; Chen, Y -T; Côté, P; Cuillandre, J -C; Duc, P A; Durrell, P R; Ferrarese, L; Guhathakurta, P; Gwyn, S D J; Kavelaars, J J; Lançon, A; Liu, C; MacArthur, L A; Muller, M; Muñoz, R P; Peng, E W; Puzia, T H; Sawicki, M; Toloba, E; Van Waerbeke, L; Woods, D; Zhang, H

    2014-01-01

    The Next Generation Virgo Cluster Survey is an optical imaging survey covering 104 deg^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 which extends to iAB = 12.5 mag. When using the u*griz-bands, our photometric redshifts for 15.5 \\le i \\lesssim 23 mag or zphot \\lesssim 1 galaxies have a bias |\\Delta z| < 0.02, less than 5% outliers, and a scatter \\sigma_{outl.rej.} and an individual error on zphot that increase 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 t...

  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. GPZ: non-stationary sparse Gaussian processes for heteroscedastic uncertainty estimation in photometric redshifts

    Science.gov (United States)

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

    2016-10-01

    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 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 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, commonly known in statistics as heteroscedastic noise. However, existing approaches are susceptible to outliers and do not take into account variance induced by non-uniform data density and in most cases require manual tuning of many parameters. In this paper, we present a Bayesian machine learning approach that jointly optimizes the model with respect to both the predictive mean and variance we refer to as Gaussian processes for photometric redshifts (GPZ). The predictive variance of the model takes into account both the variance due to data density and photometric noise. Using the Sloan Digital Sky Survey (SDSS) DR12 data, we show that our approach substantially outperforms other machine learning methods for photo-z estimation and their associated variance, such as TPZ and ANNZ2. We provide a MATLAB and PYTHON implementations that are available to download at https://github.com/OxfordML/GPz.

  16. 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.

  17. A Comparison of Six Photometric Redshift Methods Applied to 1.5 Million Luminous Red Galaxies

    CERN Document Server

    Abdalla, Filipe B; Lahav, Ofer; Rashkov, Valery

    2008-01-01

    We present an updated version of MegaZ-LRG (Collister et al.,(2007)) with photometric redshifts derived with the neural network method, ANNz as well as five other publicly available photo-z codes (HyperZ, SDSS, Le PHARE, BPZ and ZEBRA) for ~1.5 million Luminous Red Galaxies (LRGs) in SDSS DR6. This allows us to identify how reliable codes are relative to each other if used as described in their public release. We compare and contrast the relative merits of each code using ~13000 spectroscopic redshifts from the 2SLAQ sample. We find that the performance of each code depends on the figure of merit used to assess it. As expected, the availability of a complete training set means that the training method performs best in the intermediate redshift bins where there are plenty of training objects. Codes such as Le PHARE, which use new observed templates perform best in the lower redshift bins. All codes produce reasonable photometric redshifts, the 1-sigma scatters ranging from 0.057 to 0.097 if averaged over the e...

  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. z-ph-REM: A photometric redshift code for the REM telescope

    CERN Document Server

    Fernández-Soto, A

    2003-01-01

    The REM telescope is being deployed these very days at the La Silla Observatory in Chile, and will be fully operational by the beginning of 2004. It is a very fast-slewing robotized telescope, endowed with optical and near-infrared capabilities, designed with the primary objective of performing rapid follow-up of GRB events. One of the key issues will be the prompt recognition of potentially interesting bursts (those happening at high redshift or peculiarly reddened). Here I present a sketch of z-ph-REM, the photometric redshift code designed for this mission.

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

    Energy Technology Data Exchange (ETDEWEB)

    Singal, J.; Shmakova, M.; Gerke, B.; /KIPAC, Menlo Park /SLAC /Stanford U.; Griffith, R.L.; /Caltech, JPL; Lotz, J.; /NOAO, Tucson

    2011-05-20

    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.

  1. Photo-z with CuBANz: An improved photometric redshift estimator using Clustering aided Back propagation Neural network

    Science.gov (United States)

    Samui, Saumyadip; Samui Pal, Shanoli

    2017-02-01

    We present an improved photometric redshift estimator code, CuBANz, that is publicly available at 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 CuBANz, 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 photometric redshifts using the particular networks that were trained using those cluster members. For galaxies that do not match with any training cluster, the photometric redshifts are obtained from a separate network that uses entire training set. This clustering method enables us to determine the redshifts more accurately. SDSS Stripe 82 catalog has been used here for the demonstration of the code. For the clustered sources with redshift range zspec 1 / 2) in the training/testing phase is as low as 0.03 compared to the existing ANNz code that provides residual error on the same test data set of 0.05. Further, we provide a much better estimate of the uncertainty of the derived photometric redshift.

  2. 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...

  3. Estimating Photometric Redshifts with Artificial Neural Networks and Multi-Parameters

    Institute of Scientific and Technical Information of China (English)

    Li-Li Li; Yan-Xia Zhang; Yong-Heng Zhao; Da-Wei Yang

    2007-01-01

    We calculate photometric redshifts from the Sloan Digital Sky Survey Data Release 2 (SDSS DR2) Galaxy Sample using artificial neural networks(ANNs).Different input sets based on various parameters(e.g.magnitude,color index,flux information)are explored.Mainly,parameters from broadband photometry are utilized and their performances in redshift prediction are compared.While any parameter may be easily incorporated in the input,our results indicate that using the dereddened magnitudes often produces more accurate photometric redshifts than using the Petrosian magnitudes or model magnitudes as input.but the model magnitudes are superior to the Petrosian magnitudes.Also,better performance results when more effective parameters are used in the training set.The method is tested on a sample of 79 346 galaxies from the SDSS DR2.When using 19 parameters based on the dereddened magnitudes,the rms error in redshift estimation is σz=0.020184.The ANN is highly competitive tool compared to the traditional template-fitting methods when a 1arge and representative training set is available.

  4. Cosmology with photometric weak lensing surveys: Constraints with redshift tomography of convergence peaks and moments

    Science.gov (United States)

    Petri, Andrea; May, Morgan; Haiman, Zoltán

    2016-09-01

    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 (Ωm,w ,σ8) for a 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 σ confidence interval in (Ωm,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 (Ωm,w ) by factors of 3 and 4, respectively. When we add cosmic microwave background parameter priors from Planck to our analysis, tomography improves power spectrum constraints by a factor of 3. Adding moments yields an improvement by an additional factor of 2, and adding both moments and peaks improves by almost a factor of 3 over power spectrum tomography alone. We evaluate the effect of uncorrected systematic photometric redshift errors on the parameter constraints. We find that different statistics lead to different bias directions in parameter space, suggesting the possibility of eliminating this bias via self-calibration.

  5. A reliable cluster detection technique using photometric redshifts: introducing the 2TecX algorithm

    CERN Document Server

    van Breukelen, Caroline

    2009-01-01

    We present a new cluster detection algorithm designed for finding high-redshift clusters using optical/infrared imaging data. The algorithm has two main characteristics. First, it utilises each galaxy's full redshift probability function, instead of an estimate of the photometric redshift based on the peak of the probability function and an associated Gaussian error. Second, it identifies cluster candidates through cross-checking the results of two substantially different selection techniques (the name 2TecX representing the cross-check of the two techniques). These are adaptations of the Voronoi Tesselations and Friends-Of-Friends methods. Monte-Carlo simulations of mock catalogues show that cross-checking the cluster candidates found by the two techniques significantly reduces the detection of spurious sources. Furthermore, we examine the selection effects and relative strengths and weaknesses of either method. The simulations also allow us to fine-tune the algorithm's parameters, and define completeness an...

  6. The Impact of JWST Broadband Filter Choice on Photometric Redshift Estimation

    Science.gov (United States)

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

    2016-12-01

    The determination of galaxy redshifts in the James Webb Space Telescope’s (JWST) 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 μm and Mid Infrared Instrument (MIRI) at λ \\gt 5.0 μ {{m}}. In this work we analyze the impact of choosing different combinations of NIRCam and MIRI broadband filters (F070W to F770W), as well as having ancillary data at λ \\lt 0.6 μ {{m}}, on the derived photometric redshifts (z phot) of a total of 5921 real and simulated galaxies, with known input redshifts z = 0-10. We found that observations at λ \\lt 0.6 μ {{m}} are necessary to control the contamination of high-z samples by low-z interlopers. Adding MIRI (F560W and F770W) photometry to the NIRCam data mitigates the absence of ancillary observations at λ \\lt 0.6 μ {{m}} and improves the redshift estimation. At z = 7-10, accurate z phot can be obtained with the NIRCam broadbands alone when {{S}}/{{N}}≥slant 10, but the z phot quality significantly degrades at {{S}}/{{N}}≤slant 5. Adding MIRI photometry with 1 mag brighter depth than the NIRCam depth allows for a redshift recovery of 83%-99%, depending on spectral energy distribution 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] \\lt 28 mag if these sources are at least mildly evolved or have spectra with emission lines boosting the mid-infrared fluxes.

  7. 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...

  8. Photometric redshifts as a tool for studying the Coma cluster galaxy populations

    Science.gov (United States)

    Adami, C.; Ilbert, O.; Pelló, R.; Cuillandre, J. C.; Durret, F.; Mazure, A.; Picat, J. P.; Ulmer, M. P.

    2008-12-01

    Aims: We apply photometric redshift techniques to an investigation of the Coma cluster galaxy luminosity function (GLF) at faint magnitudes, in particular in the u* band where basically no studies are presently available at these magnitudes. Methods: Cluster members were selected based on probability distribution function from photometric redshift calculations applied to deep u^*, B, V, R, I images covering a region of almost 1 deg2 (completeness limit R ~ 24). In the area covered only by the u* image, the GLF was also derived after a statistical background subtraction. Results: Global and local GLFs in the B, V, R, and I bands obtained with photometric redshift selection are consistent with our previous results based on a statistical background subtraction. The GLF in the u* band shows an increase in the faint end slope towards the outer regions of the cluster. The analysis of the multicolor type spatial distribution reveals that late type galaxies are distributed in clumps in the cluster outskirts, where X-ray substructures are also detected and where the GLF in the u* band is steeper. Conclusions: We can reproduce the GLFs computed with classical statistical subtraction methods by applying a photometric redshift technique. The u* GLF slope is steeper in the cluster outskirts, varying from α ~ -1 in the cluster center to α ~ -2 in the cluster periphery. The concentrations of faint late type galaxies in the cluster outskirts could explain these very steep slopes, assuming a short burst of star formation in these galaxies when entering the cluster. Based on observations obtained with MegaPrime/MegaCam, a joint project of CFHT and CEA/DAPNIA, at the Canada-France-Hawaii Telescope (CFHT) which is operated by the National Research Council (NRC) of Canada, the Institut National des Sciences de l'Univers of the Centre National de la Recherche Scientifique (CNRS) of France, and the University of Hawaii. This work is also partly based on data products produced at

  9. 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...

  10. Sub-Megaparsec Individual Photometric Redshift Estimation from Cosmic Web Constraints

    CERN Document Server

    Aragon-Calvo, Miguel A; Jones, Bernard J T; Mobasher, Bahram

    2014-01-01

    We present a method, PhotoWeb, for estimating photometric redshifts of individual galaxies, and their equivalent distance, with megaparsec and even sub-megaparsec accuracy using the Cosmic Web as a constraint over photo-z estimates. PhotoWeb redshift errors for individual galaxies are of the order of delta_z = 0.0007, compared to errors of delta_z = 0.02 for current photo-z techniques. The mean redshift error is of the order of 0.00005-0.0004 compared to mean errors in the range delta_z =z 0.001-0.01 for the best available photo-z estimates in the literature. Current photo-z techniques based on the spectral energy distribution of galaxies and projected clustering 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 of the volume of the Universe, yet they...

  11. CFHTLenS: Improving the quality of photometric redshifts with precision photometry

    CERN Document Server

    Hildebrandt, H; Kuijken, K; van Waerbeke, L; Heymans, C; Coupon, J; Benjamin, J; Bonnett, C; Fu, L; Hoekstra, H; Kitching, T D; Mellier, Y; Miller, L; Velander, M; Hudson, M J; Rowe, B T P; Schrabback, T; Semboloni, E; Benitez, N

    2011-01-01

    Here we present the results of various approaches to measure accurate colours and photometric redshifts (photo-z's) from wide-field imaging data. We use data from the Canada-France-Hawaii-Telescope Legacy Survey (CFHTLS) which have been re- processed by the CFHT Lensing Survey (CFHTLenS) team in order to carry out a number of weak gravitational lensing studies. An emphasis is put on the correction of systematic effects in the photo-z's arising from the different Point Spread Functions (PSF) in the five optical bands. Different ways of correcting these effects are discussed and the resulting photo-z accuracies are quantified by comparing the photo-z's to large spectroscopic redshift (spec-z) data sets. Careful homogenisation of the PSF between bands leads to increased overall accuracy of photo-z's. The gain is particularly pronounced at fainter magnitudes where galaxies are smaller and flux measurements are affected more by PSF-effects. We also study possible re- calibrations of the photometric zeropoints (ZPs...

  12. Galaxies in the Hubble Ultra Deep Field: I. Detection, Multiband Photometry, Photometric Redshifts, and Morphology

    CERN Document Server

    Coe, D; Sánchez, S F; Jee, M; Bouwens, R; Ford, H; Coe, Dan; Benitez, Narciso; Sanchez, Sebastian F.; Jee, Myungkook; Bouwens, Rychard; Ford, Holland

    2006-01-01

    We present aperture-matched PSF-corrected BVi'z'JH photometry and Bayesian photometric redshifts (BPZ) for objects detected in the Hubble Ultra Deep Field (UDF), 8,042 of which are detected at the 10-sigma level (e.g., i'<29.01 or z'<28.43). Most of our objects are defined identically to those in the public STScI catalogs, enabling straightforward object-by-object comparison. We have combined detections from i', z', J+H, and B+V+i'+z' images into a single comprehensive segmentation map. Using a new program called SExSeg we are able to force this segmentation map into SExtractor for photometric analysis. The resulting photometry is corrected for the wider NIC3 PSFs using our ColorPro software. We also correct for the ACS z'-band PSF halo. The NIC3 magnitudes are found to be too faint relative to the ACS fluxes. Based on BPZ SED fits to objects of know spectroscopic redshift, we derived corrections of -0.30 +/- 0.03 mag in J and -0.18 +/- 0.04 mag in H. The offsets appear to be supported by a recent recal...

  13. A Photometrically Detected Forming Cluster of Galaxies at Redshift 1.6 in the GOODS Field

    CERN Document Server

    Castellano, M; Trevese, D; Grazian, A; Pentericci, L; Fiore, F; Fontana, A; Giallongo, E; Santini, P; Cristiani, S; Nonino, M; Vanzella, E

    2007-01-01

    We report the discovery of a localized overdensity at z~1.6 in the GOODS-South Field, presumably a poor cluster in the process of formation. The three-dimensional galaxy density has been estimated on the basis of well calibrated photometric redshifts from the multiband photometric GOODS-MUSIC catalog using the (2+1)D technique. The density peak is embedded in the larger scale overdensity of galaxies known to exist at z=1.61 in the area. The properties of the member galaxies are compared to those of the surrounding field and we found that the two populations are significantly different supporting the reality of the structure. The reddest galaxies, once evolved according to their best fit models, have colors consistent with the red sequence of lower redshift clusters. The estimated M_200 total mass of the cluster is in the range 1.3 x 10^14 - 5.7x 10^14 Msun, depending on the assumed bias factor b. An upper limit for the 2-10 keV X-ray luminosity, based on the 1Ms Chandra observations, is L_X=0.5 x 10^43 erg s^...

  14. 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...

  15. 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...

  16. Photometric Redshifts and Morphologies of Galaxies in the NICMOS Parallel Fields

    CERN Document Server

    Corbin, M R; O'Neill, E; Thompson, R I; Rieke, M J; Schneider, G

    1999-01-01

    We present positions, magnitudes, sizes and morphological classifications for 111 galaxies discovered in the Hubble Space Telescope NICMOS Camera 1 and Camera 2 parallel fields. We combine the magnitudes measured in the JHK-analog filters with those from deep ground-based images in V and/or R to measure photometric redshifts for 71 objects using Bruzual-Charlot population synthesis models. We find that these objects fall in the range z ~ 0.0 - 2.7, with a mean redshift of 0.8 and a mean luminosity of 1.6 L*. The NICMOS images reveal many of the objects to be ordered spirals and ellipticals similar to those in the local universe. However, we find a higher fraction (~ 14%) of morphologically peculiar and/or interacting galaxies than is observed among local galaxies (~ 3% - 4%). This is consistent with the results from other deep HST images including the Hubble Deep Field and Hubble Medium Deep Survey Field that the fraction of peculiar and interacting galaxies increases with redshift. As the NICMOS images of th...

  17. 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...

  18. Using the 2-MASS photometric redshift survey to optimize LIGO follow-up observations

    Science.gov (United States)

    Antolini, Elisa; Heyl, Jeremy S.

    2016-10-01

    The initial discovery of Laser Interferometer Gravitational-Wave Observatory (LIGO) on 2015 September 14 was the inspiral merger and ring-down of the black hole binary at a distance of about 500 Mpc or a redshift of about 0.1. The search for electromagnetic counterparts for the inspiral of binary black holes is impeded by coarse initial source localizations and a lack of a compelling model for the counterpart; therefore, rapid electromagnetic follow-up is required to understand the astrophysical context of these sources. Because astrophysical sources of gravitational radiation are likely to reside in galaxies, it would make sense to search first in regions where the LIGO-Virgo probability is large and where the density of galaxies is large as well. Under the assumption that the probability of a gravitational-wave event from a given region of space is proportional to the density of galaxies within the probed volume, one can calculate an improved localization of the position of the source simply by multiplying the LIGO-Virgo skymap by the density of galaxies in the range of redshifts. We propose using the 2-MASS photometric redshift galaxy catalogue for this purpose and demonstrate that using it can dramatically reduce the search region for electromagnetic counterparts.

  19. 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...

  20. 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...

  1. VizieR Online Data Catalog: COSMOS photometric redshift catalog (Ilbert+, 2009)

    Science.gov (United States)

    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.; Fevre, O. L.; 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.

    2017-03-01

    Compared with the previous optical/NIR catalog (Capak et al., 2007ApJS..172...99C, Cat. II/284), the new photometry implements 14 new medium/narrowband data from the Subaru Telescope, deep ground-based NIR data (J and K bands), and Spitzer-IRAC data. The spectroscopic sample used to calibrate/test the photo-z is 10 times larger at i+ABsample is supplemented with faint IR selected sources and a deep, faint spectroscopic sample at z>1.5. Hereafter, we detail the photometric and spectroscopic data used to measure the photo-z. Fluxes are measured in 30 bands from data taken on the Subaru (4200-9000Åg), CFHT (3900-21500Å), UKIRT (12500Å), Spitzer (3.6-8um), and GALEX (1500.2300Å) telescopes. We refer to P. Capak et al. (2008, in preparation) for a complete description of the observations, data reduction, and the photometry catalog. Photometric catalogue from P. Capak Photo-z catalogue from O. Ilbert PIs of the photometric data: D.B. Sanders, N. Scoville, Y. Tanigushi Data reducers: H. Aussel, P. Capak, H. McCracken, M. Salvato, S. Sasaki,D. Thompson, O. Ilbert, J. Kartaltepe, E. Le Floc'h, D. Looper, D.B. Sanders, N. Scoville Spectroscopic redshifts for validation from the zCOSMOS team (PI S. Lilly), from J. Kartaltepe and from P. Capak Identification of the Xray sources in the optical catalogue M. Brusa, G. Hasinger and the COSMOS/XMM team. (1 data file).

  2. CANDELS/GOODS-S, CDFS, and ECDFS: photometric redshifts for normal and X-ray-detected galaxies

    Energy Technology Data Exchange (ETDEWEB)

    Hsu, Li-Ting; Salvato, Mara; Nandra, Kirpal; Brusa, Marcella; Bender, Ralf; Buchner, Johannes; Brightman, Murray; Georgakakis, Antonis [Max-Planck-Institut für extraterrestrische Physik, Giessenbachstrasse, D-85748 Garching (Germany); Donley, Jennifer L. [Los Alamos National Laboratory, Los Alamos, NM (United States); Kocevski, Dale D. [Department of Physics and Astronomy, University of Kentucky, Lexington, KY 40506 (United States); Guo, Yicheng; Barro, Guillermo; Faber, Sandra M. [UCO/Lick Observatory, Department of Astronomy and Astrophysics, University of California, Santa Cruz, CA (United States); Hathi, Nimish P. [Aix Marseille Université, CNRS, LAM (Laboratoire d' Astrophysique de Marseille) UMR 7326, F-13388 Marseille (France); Rangel, Cyprian [Astrophysics Group, Imperial College London, Blackett Laboratory, Prince Consort Road, London SW7 2AZ (United Kingdom); Willner, S. P.; Ashby, Matthew L. N. [Harvard-Smithsonian Center for Astrophysics, Cambridge, MA (United States); Budavári, Tamás; Szalay, Alexander S. [Department of Physics and Astronomy, The Johns Hopkins University, Baltimore, MD (United States); Dahlen, Tomas [Space Telescope Science Institute, Baltimore, MD (United States); and others

    2014-11-20

    We present photometric redshifts and associated probability distributions for all detected sources in the Extended Chandra Deep Field South (ECDFS). This 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 4 Ms CDFS and 250 ks ECDFS surveys, finding reliable counterparts for 1207 out of 1259 sources (∼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 active galactic nuclei/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 5.2%, respectively. The results within the CANDELS coverage area are even better, as demonstrated both by spectroscopic comparison and by galaxy-pair statistics. Intermediate-band photometry, even if shallow, is valuable when combined with deep broadband photometry. For best accuracy, templates must include emission lines.

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

    NARCIS (Netherlands)

    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.

    2015-01-01

    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 O

  4. 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...

  5. 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.

  6. Photometric Redshifts in the Hawaii-Hubble Deep Field-North (H-HDF-N)

    CERN Document Server

    Yang, G; Luo, B; Brandt, W N; Alexander, D M; Bauer, F E; Cui, W; Kong, X; Lehmer, B D; Wang, J -X; Wu, X -B; Yuan, F; Yuan, Y -F; Zhou, H Y

    2014-01-01

    We derive photometric redshifts (\\zp) for sources in the entire ($\\sim0.4$ deg$^2$) Hawaii-Hubble Deep Field-North (\\hdfn) field with the EAzY code, based on point spread function-matched photometry of 15 broad bands from the ultraviolet (\\bandu~band) to mid-infrared (IRAC 4.5 $\\mu$m). Our catalog consists of a total of 131,678 sources. We evaluate the \\zp~quality by comparing \\zp~with spectroscopic redshifts (\\zs) when available, and find a value of normalized median absolute deviation \\sigm$=$0.029 and an outlier fraction of 5.5\\% (outliers are defined as sources having $\\rm |\\zp - \\zs|/(1+\\zs) > 0.15$) for non-X-ray sources. More specifically, we obtain \\sigm$=0.024$ with 2.7\\% outliers for sources brighter than $R=23$~mag, \\sigm$=0.035$ with 7.4\\% outliers for sources fainter than $R=23$~mag, \\sigm$=$0.026 with 3.9\\% outliers for sources having $z1$. Our \\zp\\ quality shows an overall improvement over an earlier \\zp\\ work that focused only on the central \\hdfn\\ area. We also classify each object as star or...

  7. Deep CFHT Y-band Imaging of VVDS-F22 Field. I. Data Products and Photometric Redshifts

    Science.gov (United States)

    Liu, Dezi; Yang, Jinyi; Yuan, Shuo; Wu, Xue-Bing; Fan, Zuhui; Shan, Huanyuan; Yan, Haojing; Zheng, Xianzhong

    2017-02-01

    We present our deep Y-band imaging data of a 2 square degree field within the F22 region of the VIMOS VLT Deep Survey. The observations were conducted using the WIRCam instrument mounted at the Canada–France–Hawaii Telescope (CFHT). The total on-sky time was 9 hr, distributed uniformly over 18 tiles. The scientific goals of the project are to select faint quasar candidates at redshift z> 2.2 and constrain the photometric redshifts for quasars and galaxies. In this paper, we present the observation and the image reduction, as well as the photometric redshifts that we derived by combining our Y-band data with the CFHTLenS {u}* g\\prime r\\prime i\\prime z\\prime optical data and UKIDSS DXS JHK near-infrared data. With the J-band image as a reference, a total of ∼80,000 galaxies are detected in the final mosaic down to a Y-band 5σ point-source limiting depth of 22.86 mag. Compared with the ∼3500 spectroscopic redshifts, our photometric redshifts for galaxies with zedu.cn/astro/data/DYI.html.

  8. BL Lacertae Objects Beyond Redshift 1.3 - UV-to-NIR Photometry and Photometric Redshift for Fermi/LAT Blazars

    Science.gov (United States)

    Rau, A.; Schady, P.; Greiner, J.; Salvato, M.; Ajello, M.; Bottacini, E.; Gehrels, N.; Afonso, P. M. J.; Elliott, J.; Filgas, R.; Kann, D. A.; Klose, S.; Kruehler, T.; Nardini, M.; Guelbenzu, A. Nicuesa; OlivaresE, F.; Rossi, A.; Sudilovsky. V.; Updike, A. C.; Hartmann, D. H.

    2011-01-01

    Context. Observations of the gamma-ray sky with Fermi led to significant advances towards understanding blazars, the most extreme class of Active Galactic Nuclei. A large fraction of the population detected by Fermi is formed by BL Lacertae (BL Lac) objects, whose sample has always suffered from a severe redshift incompleteness due to the quasi-featureless optical spectra. Aims. Our goal is to provide a significant increase of the number of confirmed high-redshift BL Lac objects contained in the 2 LAC Fermi/LAT catalog. Methods. For 103 Fermi/LAT blazars, photometric redshifts using spectral energy distribution fitting have been obtained. The photometry includes 13 broad-band filters from the far ultraviolet to the near-IR observed with Swift/UVOT and the multi-channel imager GROND at the MPG/ESO 2.2m telescope. Data have been taken quasi-simultaneously and the remaining source-intrinsic variability has been corrected for. Results. We release the UV-to-near-IR 13-band photometry for all 103 sources and provide redshift constraints for 75 sources without previously known redshift. Out of those, eight have reliable photometric redshifts at z > or approx. 1.3, while for the other 67 sources we provide upper limits. Six of the former eight are BL Lac objects, which quadruples the sample of confirmed high-redshift BL Lac. This includes three sources with redshifts higher than the previous record for BL Lac, including CRATES J0402-2615, with the best-fit solution at z approx. = 1.9.

  9. 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...

  10. Photometric Redshifts in the Hawaii-Hubble Deep Field-North

    Science.gov (United States)

    Yang, Guang; Xue, Yongquan

    2015-08-01

    We derive photometric redshifts (\\zp) for sources in the entire (˜0.4 deg^2) Hawaii-Hubble Deep Field-North (H-HDF-N) field with the EAzY code, based on point spread function-matched photometry of 15 broad bands from the ultraviolet to mid-infrared (IRAC 4.5um). Our catalog consists of a total of 131,678 sources. We evaluate the \\zp~quality by comparing \\zp~with spectroscopic redshifts (\\zs) when available, and find a value of normalized median absolute deviation \\sigm=0.029 and an outlier fraction of 5.5\\% (outliers are defined as sources having |\\zp - \\zs|/(1+\\zs)>0.15) for non-X-ray sources. More specifically, we obtain \\sigm=0.024 with 2.7\\% outliers for sources brighter than R=23mag, \\sigm=0.035 with 7.4\\% outliers for sources fainter than R=23mag, \\sigm=0.026 with 3.9\\% outliers for sources having zoutliers for sources having z>1. Our \\zp\\ quality shows an overall improvement over an earlier \\zp\\ work that focused only on the central H-HDF-N area. We also classify each object as star or galaxy through template spectral energy distribution fitting and complementary morphological parametrization, resulting in 4959 stars and 126,719 galaxies. Furthermore, we match our catalog with the 2Ms Chandra Deep Field-North main X-ray catalog. For the 462 matched non-stellar X-ray sources (281 having \\zs), we improve their \\zp~quality by adding three additional AGN templates, achieving \\sigm=0.035 and an outlier fraction of 12.5\\%. We make our catalog publicly available presenting both photometry and \\zp, and provide guidance on how to make use of our catalog. (This work has been published as Yang, Xue, et al. 2014, ApJS, 215, 27; December 2014.)

  11. Photometric Redshifts in the Hawaii-Hubble Deep Field-North (H-HDF-N)

    Science.gov (United States)

    Yang, G.; Xue, Y. Q.; Luo, B.; Brandt, W. N.; Alexander, D. M.; Bauer, F. E.; Cui, W.; Kong, X.; Lehmer, B. D.; Wang, J.-X.; Wu, X.-B.; Yuan, F.; Yuan, Y.-F.; Zhou, H. Y.

    2014-12-01

    We derive photometric redshifts (z phot) for sources in the entire (~0.4 deg2) Hawaii-Hubble Deep Field-North (H-HDF-N) field with the EAzY code, based on point-spread-function-matched photometry of 15 broad bands from the ultraviolet (U band) to mid-infrared (IRAC 4.5 μm). Our catalog consists of a total of 131,678 sources. We evaluate the z phot quality by comparing z phot with spectroscopic redshifts (z spec) when available, and find a value of normalized median absolute deviation σNMAD = 0.029 and an outlier fraction of 5.5% (outliers are defined as sources having |zphot - zspec |/(1 + zspec ) > 0.15) for non-X-ray sources. More specifically, we obtain σNMAD = 0.024 with 2.7% outliers for sources brighter than R = 23 mag, σNMAD = 0.035 with 7.4% outliers for sources fainter than R = 23 mag, σNMAD = 0.026 with 3.9% outliers for sources having z outliers for sources having z > 1. Our z phot quality shows an overall improvement over an earlier z phot work that focused only on the central H-HDF-N area. We also classify each object as a star or galaxy through template spectral energy distribution fitting and complementary morphological parameterization, resulting in 4959 stars and 126,719 galaxies. Furthermore, we match our catalog with the 2 Ms Chandra Deep Field-North main X-ray catalog. For the 462 matched non-stellar X-ray sources (281 having z spec), we improve their z phot quality by adding three additional active galactic nucleus templates, achieving σNMAD = 0.035 and an outlier fraction of 12.5%. We make our catalog publicly available presenting both photometry and z phot, and provide guidance on how to make use of our catalog.

  12. The SDSS-IV Extended Baryon Oscillation Spectroscopic Survey: The Clustering of Luminous Red Galaxies Using Photometric Redshifts

    Science.gov (United States)

    Prakash, Abhishek; SDSS-IV/eBOSS

    2017-01-01

    SDSS-IV/eBOSS survey 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 image both wider areas and deeper volumes than would be possible with spectroscopy, allowing one to probe both larger scales and larger volumes. The ability to make precise clustering measurements with photometric data has been well demonstrated by Padmanabhan et al. (2007).

  13. ANNz2: Photometric Redshift and Probability Distribution Function Estimation using Machine Learning

    Science.gov (United States)

    Sadeh, I.; Abdalla, F. B.; Lahav, O.

    2016-10-01

    We present ANNz2, a new implementation of the public software for photometric redshift (photo-z) estimation of Collister & Lahav, which now includes generation of full probability distribution functions (PDFs). ANNz2 utilizes multiple machine learning methods, such as artificial neural networks and boosted decision/regression trees. The objective of the algorithm is to optimize the performance of the photo-z estimation, to properly derive the associated uncertainties, and to produce both single-value solutions and PDFs. In addition, estimators are made available, which mitigate possible problems of non-representative or incomplete spectroscopic training samples. ANNz2 has already been used as part of the first weak lensing analysis of the Dark Energy Survey, and is included in the experiment's first public data release. Here we illustrate the functionality of the code using data from the tenth data release of the Sloan Digital Sky Survey and the Baryon Oscillation Spectroscopic Survey. The code is available for download at http://github.com/IftachSadeh/ANNZ.

  14. 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...

  15. Comparing Dynamical and Photometric Mass Estimates of Low- and High-Redshift Galaxies: Random and Systematic Uncertainties

    CERN Document Server

    Van der Wel, A; Wuyts, S; Van Dokkum, P G; Huang, J; Rix, H W; Illingworth, G D; Wel, Arjen van der; Franx, Marijn; Wuyts, Stijn; Dokkum, Pieter G. van; Huang, Jiasheng; Rix, Hans-Walter; Illingworth, Garth D.

    2006-01-01

    We determine the importance of redshift-dependent systematic effects in the determination of stellar masses from broad band spectral energy distributions (SEDs), using high quality kinematic and photometric data of early-type galaxies at z~1 and z~0. We find that photometric masses of z~1 galaxies can be systematically different, by up to a factor of 2, from photometric masses of z~0 galaxies with the same dynamical mass. The magnitude of this bias depends on the choice of stellar population synthesis model and the rest-frame wavelength range used in the fits. The best result, i.e., without significant bias, is obtained when rest-frame optical SEDs are fitted with models from Bruzual&Charlot (2003). When the SEDs are extended to the rest-frame near-IR, a bias is introduced: photometric masses of the z~1 galaxies increase by a factor of 2 relative to the photometric masses of the z~0 galaxies. When we use the Maraston (2005) models, the photometric masses of the z~1 galaxies are low relative to the photome...

  16. 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.

  17. Finding Galaxy Groups In Photometric Redshift Space: the Probability Friends-of-Friends (pFoF) Algorithm

    CERN Document Server

    Li, I-hui

    2008-01-01

    We present a structure finding algorithm designed to identify galaxy groups in photometric redshift data sets: the probability friends-of-friends (pFoF) algorithm. This algorithm is derived by combining the friends-of-friends algorithm in the transverse direction and the photometric redshift probability densities in the radial dimension. The innovative characteristic of our group-finding algorithm is the improvement of redshift estimation via the constraints given by the transversely connected galaxies in a group, based on the assumption that all galaxies in a group have the same redshift. Tests using the Virgo Consortium Millennium Simulation mock catalogs allow us to show that the recovery rate of the pFoF algorithm is larger than 80% for mock groups of at least $2\\times10^{13}M_{\\sun}$, while the false detection rate is about 10% for pFoF groups containing at least $\\sim8$ net members. Applying the algorithm to the CNOC2 group catalogs gives results which are consistent with the mock catalog tests. From al...

  18. Improving Photometric Redshifts using GALEX Observations for the SDSS Stripe 82 and the Next Generation of SZ Cluster Surveys

    CERN Document Server

    Niemack, Michael D; Verde, Licia; Menanteau, Felipe; Panter, Ben; Spergel, David

    2008-01-01

    Four large-area Sunyaev-Zeldovich (SZ) experiments -- APEX-SZ, SPT, ACT, and Planck -- promise to detect clusters of galaxies through the distortion of Cosmic Microwave Background photons by hot (> 10^6 K) cluster gas (the SZ effect) over thousands of square degrees. A large observational follow-up effort to obtain redshifts for these SZ-detected clusters is under way. Given the large area covered by these surveys, most of the redshifts will be obtained via the photometric redshift (photo-z) technique. Here we demonstrate, in an application using ~3000 SDSS stripe 82 galaxies with r<20, how the addition of GALEX photometry (FUV, NUV) greatly improves the photometric redshifts of galaxies obtained with optical griz or ugriz photometry. In the case where large spectroscopic training sets are available, empirical neural-network-based techniques (e.g., ANNz) can yield a photo-z scatter of $\\sigma_z = 0.018 (1+z)$. If large spectroscopic training sets are not available, the addition of GALEX data makes possible...

  19. Photometric Redshifts and Systematic Variations in the SEDs of Luminous Red Galaxies from the SDSS DR7

    CERN Document Server

    Greisel, Natascha; Drory, Niv; Bender, Ralf; Saglia, Roberto; Snigula, Jan

    2013-01-01

    We describe the construction of a template set of spectral energy distributions (SEDs) for the estimation of photometric redshifts of luminous red galaxies (LRGs) with a Bayesian template fitting method. By examining the color properties of several publicly available SED sets within a redshift range of 00.15) of 0.12%. We show that templates that optimally describe the brightest galaxies (-24.5redshift bins.

  20. 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

  1. 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...

  2. Clustering Analyses of 300,000 Photometrically Classified Quasars--I. Luminosity and Redshift Evolution in Quasar Bias

    CERN Document Server

    Myers, A D; Nichol, R C; Richards, G T; Schneider, D P; Bahcall, N A; Myers, Adam D.; Brunner, Robert J.; Nichol, Robert C.; Richards, Gordon T.; Schneider, Donald P.; Bahcall, Neta A.

    2006-01-01

    Using ~300,000 photometrically classified quasars, by far the largest quasar sample ever used for such analyses, we study the redshift and luminosity evolution of quasar clustering on scales of ~50 kpc/h to ~20 Mpc/h from redshifts of z~0.75 to z~2.28. We parameterize our clustering amplitudes using realistic dark matter models, and find that a LCDM power spectrum provides a superb fit to our data with a redshift-averaged quasar bias of b_Q = 2.41+/-0.08 ($P_{99.6% using our data set alone, increasing to >99.9999% if stellar contamination is not explicitly parameterized. We measure the quasar classification efficiency across our full sample as a = 95.6 +/- ^{4.4}_{1.9}%, a star-quasar separation comparable with the star-galaxy separation in many photometric studies of galaxy clustering. We derive the mean mass of the dark matter halos hosting quasars as MDMH=(5.2+/-0.6)x10^{12} M_solar/h. At z~1.9 we find a $1.5\\sigma$ deviation from luminosity-independent quasar clustering; this suggests that increasing our ...

  3. 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...

  4. 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~...

  5. 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...

  6. 3D-HST WFC3-selected Photometric Catalogs in the Five CANDELS/3D-HST Fields: Photometry, Photometric Redshifts and Stellar Masses

    CERN Document Server

    Skelton, Rosalind E; Momcheva, Ivelina G; Brammer, Gabriel B; van Dokkum, Pieter G; Labbe, Ivo; Franx, Marijn; van der Wel, Arjen; Bezanson, Rachel; Da Cunha, Elisabete; Fumagalli, Mattia; Schreiber, Natascha Foerster; Kriek, Mariska; Leja, Joel; Lundgren, Britt F; Magee, Daniel; Marchesini, Danilo; Maseda, Michael V; Nelson, Erica J; Oesch, Pascal; Pacifici, Camilla; Patel, Shannon G; Price, Sedona; Rix, Hans-Walter; Tal, Tomer; Wake, David A; Wuyts, Stijn

    2014-01-01

    The 3D-HST and CANDELS programs have obtained WFC3 and ACS spectroscopy and imaging over five fields, comprising a total area of ~900 sq. arcmin: AEGIS, COSMOS, GOODS-North, GOODS-South, and the UKIDSS UDS field. All these fields have a wealth of publicly available imaging datasets in addition to the 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 0.3um -8um. Objects were selected in the WFC3 near-IR bands, and their SEDs were determined by carefully taking the effects of the point spread function into account. A total of 147 distinct imaging datasets 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, determin...

  7. 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...

  8. 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...

  9. 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...

  10. Exploring photometric redshifts as an optimization problem: an ensemble MCMC and simulated annealing-driven template-fitting approach

    Science.gov (United States)

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

    2016-10-01

    Using a 4D grid of ˜2 million model parameters (Δz = 0.005) adapted from Cosmological Origins Survey 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 simplistic gradient-descent optimization schemes. We combine ensemble Markov Chain Monte Carlo sampling with simulated annealing to robustly and efficiently explore these surfaces in approximately constant time. Using a mock catalogue of 384 662 objects, we show our approach samples ˜40 times more efficiently compared to a `brute-force' counterpart while maintaining similar levels of accuracy. Our results represent first steps towards designing template-fitting photo-z approaches limited mainly by memory constraints rather than computation time.

  11. A photometric survey for Lyalpha-HeII dual emitters: Searching for Population III stars in high-redshift galaxies

    CERN Document Server

    Nagao, Tohru; Maiolino, Roberto; Grady, Celestine; Kashikawa, Nobunari; Ly, Chun; Malkan, Matthew; Motohara, Kentaro; Murayama, Takashi; Schaerer, Daniel; Shioya, Yasuhiro; Taniguchi, Yoshiaki

    2008-01-01

    We present a new photometric search for high-z galaxies hosting Population III (PopIII) stars based on deep intermediate-band imaging observations obtained in the Subaru Deep Field (SDF), by using Suprime-Cam on the Subaru Telescope. By combining our new data with the existing broad-band and narrow-band data, we searched for galaxies which emit strongly both in Ly_alpha and in HeII 1640 (``dual emitters'') that are promising candidates for PopIII-hosting galaxies, at 3.93 2 Msun/yr was found by our photometric search in 4.03 x 10^5 Mpc^3 in the SDF. This result disfavors low feedback models for PopIII star clusters, and implies an upper-limit of the PopIII SFR density of SFRD_PopIII < 5 x 10^-6 Msun/yr/Mpc^3. This new selection method to search for PopIII-hosting galaxies should be useful in future narrow-band surveys to achieve the first observational detection of PopIII-hosting galaxies at high redshifts.

  12. 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...

  13. 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...

  14. Photometric properties of intermediate redshift Type Ia Supernovae observed by SDSS-II Supernova Survey

    CERN Document Server

    Takanashi, Naohiro; Yasuda, Naoki; Kuncarayakti, Hanindyo; Konishi, Kohki; Schneider, Donald P; Cinabro, David; Marriner, John

    2016-01-01

    We have analyzed multi-band light curves of 328 intermediate redshift (0.05 2.5) don't have a broad light curve width and the SNe Ia which appeared in blue host galaxies (u - r < 2.0) have a variety of light curve widths. The Kolmogorov-Smirnov test shows that the colour distribution of SNe Ia appeared in red / blue host galaxies is different (significance level of 99.9%). We also investigate the extinction law of host galaxy dust. As a result, we find the value of Rv derived from SNe Ia with medium light curve width is consistent with the standard Galactic value. On the other hand, the value of Rv derived from SNe Ia that appeared in red host galaxies becomes significantly smaller. These results indicate that there may be two types of SNe Ia with different intrinsic colours, and they are obscured by host galaxy dust with two different properties.

  15. 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...

  16. Using the 2-MASS Photometric Redshift Survey to optimize LIGO Follow-Up Observations

    CERN Document Server

    Antolini, Elisa

    2016-01-01

    The initial discovery of LIGO on 14 September 2015 was the in-spiral merger and ring-down of the black hole binary at a distance of about 500~Mpc or a redshift of about 0.1. The search for electromagnetic counterparts for the in-spiral of binary black holes is impeded by poor initial source localizations and a lack of a compelling model for the counterpart; therefore, rapid electromagnetic follow-up is required to understand the astrophysical context of these sources. Because astrophysical sources of gravitational radiation are likely to reside in galaxies, it would make sense to search first in regions where the LIGO-Virgo probability is large and where the density of galaxies is large as well. Under the Bayesian prior assumption that the probability of a gravitational-wave event from a given region of space is proportional to the density of galaxies within the probed volume, one can calculate an improved localization of the position of the source simply by multiplying the LIGO-Virgo skymap by the density of...

  17. 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.

  18. A new (2+1)D cluster finding algorithm based on photometric redshifts: large scale structure in the Chandra Deep Field South

    CERN Document Server

    Trevese, D; Fontana, A; Giallongo, E; Trevese, Dario; Castellano, Marco; Fontana, Adriano; Giallongo, Emanuele

    2006-01-01

    Aims: We study galaxy clustering and explore the dependence of galaxy properties on the the environment up to a redshift z~1, on the basis of a deep multi-band survey in the Chandra Deep Field South. Methods: We have developed a new method which combines galaxy angular positions and photometric redshifts to estimate the local galaxy number-density. This allows both the detection of overdensities in the galaxy distribution and the study of the properties of the galaxy population as a function of the environmental density. Results: We detect two moderate overdensities at z~0.7 and z~1 previously identified spectroscopically. We find that the fraction of red galaxies within each structure increases with volume density, extending to z~1 previous results. We measure ``red sequence'' slopes consistent with the values found in X-ray selected clusters, supporting the notion that the mass-metallicity relation hold constant up to z~1. Conclusions: Our method based on photometric redshifts allows to extend structure det...

  19. 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...

  20. 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...

  1. 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...

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

    Science.gov (United States)

    Granett, B. R.

    2017-01-01

    We introduce an empirical galaxy photometric redshift algorithm based upon the Voronoi tessellation density estimator in the space of redshift and photometric parameters. Our aim is to use sparse survey datasets to estimate the full shape of the redshift distribution that is defined by the degeneracies in galaxy photometric properties and redshift. We describe the algorithm implementation and provide a proof of concept using the first public data release from the VIMOS Public Extragalactic Redshift Survey (VIPERS PDR-1). We validate the method by comparing against the standard empirical redshift distribution code Trees for Photo-Z (TPZ) on both mock and real data. We find that the Voronoi tessellation algorithm accurately recovers the full shape of the redshift distribution quantified by its second moment and inferred redshift confidence intervals. The analysis allows us to properly account for galaxies in the tails of the distributions that would otherwise be classified as catastrophic outliers. The source code is publicly available at http://bitbucket.org/bengranett/tailz.

  3. C3R2 - Complete Calibration of the Color-Redshift Relation: Keck spectroscopy to train photometric redshifts for Euclid and WFIRST

    Science.gov (United States)

    Stern, Daniel; C3R2 Team

    2017-01-01

    A primary objective of both WFIRST and Euclid is to provide a 3D map of the distribution of matter across a significant fraction of the universe from the weak lensing shear field, but to do so requires robust distances to billions of galaxies. I will report on a multi-semester program, expected to total approximately 40 nights with Keck over the next two years. This program, supporting both the NASA PCOS and COR science goals, will obtain the necessary galaxy spectroscopy to calibrate the color-redshift relation for the Euclid mission, and make significant progress towards the WFIRST requirements. The program, called C3R2 or Complete Calibration of the Color-Redshift Relation, already encompasses 10 allocated nights of NASA Keck Key Strategic Mission Support (PI D. Stern), 12 allocated nights from Caltech (PI J. Cohen), 3 allocated nights from the University of Hawaii (PI D. Sanders), and 1.5 allocated nights from UC-Riverside (PI B. Mobasher). We are also pursuing opportunities at additional 8- to 10-meter class telescopes, including Magellan, VLT and GCT. I will present the motivation for this program, the plans, and current results.

  4. QSOs in the ALHAMBRA survey. I. Photometric redshift accuracy through a 23 optical-NIR filter photometry

    CERN Document Server

    Matute, 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; Delgado, R M González; Martínez, V J; Molino, A; Prada, F; Quintana, J M

    2012-01-01

    We characterize the ability of the ALHAMBRA survey to assign accurate photo-z's to BLAGN and QSOs based on their ALHAMBRA very-low-resolution optical-NIR spectroscopy. A sample of 170 spectroscopically identified BLAGN and QSOs have been used together with a library of templates (including SEDs from AGN, normal, starburst galaxies and stars) in order to fit the 23 photometric data points provided by ALHAMBRA in the optical and NIR (20 medium-band optical filters plus the standard JHKs). We find that the ALHAMBRA photometry is able to provide an accurate photo-z and spectral classification for ~88% of the spectroscopic sources over 2.5 deg^2 in different areas of the survey, all of them brighter than m678=23.5 (equivalent to r(SLOAN)~24.0). The derived photo-z accuracy is better than 1% and comparable to the most recent results in other cosmological fields. The fraction of outliers (~12%) is mainly caused by the larger photometric errors for the faintest sources and the intrinsic variability of the BLAGN/QSO p...

  5. Photometric properties of intermediate-redshift Type Ia supernovae observed by the Sloan Digital Sky Survey-II Supernova Survey

    Science.gov (United States)

    Takanashi, N.; Doi, M.; Yasuda, N.; Kuncarayakti, H.; Konishi, K.; Schneider, D. P.; Cinabro, D.; Marriner, J.

    2017-02-01

    We have analysed multiband light curves of 328 intermediate-redshift (0.05 ≤ z method, which can simply parametrize light-curve shapes and peak brightness without dust extinction models. We found that most of the SNe Ia that appeared in red host galaxies (u - r > 2.5) do not have a broad light-curve width and the SNe Ia that appeared in blue host galaxies (u - r extinction law of host galaxy dust. As a result, we find that the value of Rv derived from SNe Ia with medium light-curve widths is consistent with the standard Galactic value, whereas the value of Rv derived from SNe Ia that appear in red host galaxies becomes significantly smaller. These results indicate that there may be two types of SNe Ia with different intrinsic colours, and that they are obscured by host galaxy dust with two different properties.

  6. The Photometric Classification Server for Pan-STARRS1

    Science.gov (United States)

    Saglia, R. P.; Tonry, J. L.; 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.

    2012-02-01

    The Pan-STARRS1 survey is obtaining multi-epoch imaging in five bands (g P1 r P1 i P1 z P1 y P1) 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|z phot - z spec|/(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.

  7. 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})...

  8. Photometrics Laboratory

    Data.gov (United States)

    Federal Laboratory Consortium — Purpose:The Photometrics Laboratory provides the capability to measure, analyze and characterize radiometric and photometric properties of light sources and filters,...

  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. The Multiwavelength Survey by Yale-Chile (MUSYC): Deep Medium-Band optical imaging and high quality 32-band photometric redshifts in the ECDF-S

    CERN Document Server

    Cardamone, Carolin N; Urry, C Megan; Taniguchi, Yoshi; Gawiser, Eric; Brammer, Gabriel; Taylor, Edward; Damen, Maaike; Treister, Ezequiel; Cobb, Bethany E; Bond, Nicholas; Schawinski, Kevin; Lira, Paulina; Murayama, Takashi; Saito, Tomoki; Sumikawa, Kentaro; 10.1088/0067-0049/189/2/270

    2010-01-01

    We present deep optical 18-medium-band photometry from the Subaru telescope over the ~30' x 30' Extended Chandra Deep Field-South (ECDF-S), 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 1 sigma scatter in \\Delta z/(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 red...

  11. Measuring Galaxy Environments with Deep Redshift Surveys

    CERN Document Server

    Cooper, M C; Madgwick, D S; Gerke, B F; Yan, R; Davis, M; Cooper, Michael C.; Newman, Jeffrey A.; Madgwick, Darren S.; Gerke, Brian F.; Yan, Renbin; Davis, Marc

    2005-01-01

    We study the applicability of several galaxy environment measures (n^th-nearest-neighbor distance, counts in an aperture, and Voronoi volume) within deep redshift surveys. Mock galaxy catalogs are employed to mimic representative photometric and spectroscopic surveys at high redshift (z ~ 1). We investigate the effects of survey edges, redshift precision, redshift-space distortions, and target selection upon each environment measure. We find that even optimistic photometric redshift errors (\\sigma_z = 0.02) smear out the line-of-sight galaxy distribution irretrievably on small scales; this significantly limits the application of photometric redshift surveys to environment studies. Edges and holes in a survey field dramatically affect the estimation of environment, with the impact of edge effects depending upon the adopted environment measure. These edge effects considerably limit the usefulness of smaller survey fields (e.g. the GOODS fields) for studies of galaxy environment. In even the poorest groups and c...

  12. Bayesian photometric redshifts with empirical training sets

    CERN Document Server

    Wolf, Christian

    2009-01-01

    We combine in a single framework the two complementary benefits of chi^2-template fits and empirical training sets used e.g. in neural nets: chi^2 is more reliable when its probability density functions (PDFs) are inspected for multiple peaks, while empirical training is more accurate when calibration and priors of query data and training set match. We present a chi^2-empirical method that derives PDFs from empirical models as a subclass of kernel regression methods, and apply it to the SDSS DR5 sample of >75,000 QSOs, which is full of ambiguities. Objects with single-peak PDFs show 2.5, these figures are 2x better. Outliers result purely from the discrete nature and limited size of the model, and rms errors are dominated by the instrinsic variety of object colours. PDFs classed as ambiguous provide accurate probabilities for alternative solutions and thus weights for using both solutions and avoiding needless outliers. E.g., the PDFs predict 78.0% of the stronger peaks to be correct, which is true for 77.9% ...

  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. 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...

  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. 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.)

  17. 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 ...

  18. Cosmic Catastrophes

    Science.gov (United States)

    Wheeler, J. Craig

    2014-08-01

    Preface; 1. Setting the stage: star formation and hydrogen burning in single stars; 2. Stellar death: the inexorable grip of gravity; 3. Dancing with stars: binary stellar evolution; 4. Accretion disks: flat stars; 5. White Dwarfs: quantum dots; 6. Supernovae: stellar catastrophes; 7. Supernova 1987A: lessons and enigmas; 8. Neutron stars: atoms with attitude; 9. Black holes in theory: into the abyss; 10. Black holes in fact: exploring the reality; 11. Gamma-ray bursts, black holes and the universe: long, long ago and far, far away; 12. Supernovae and the universe; 13. Worm holes and time machines: tunnels in space and time; 14. Beyond: the frontiers; Index.

  19. BLAST: the Redshift Survey

    CERN Document Server

    Eales, Stephen; Devlin, Mark J; Dye, Simon; Halpern, Mark; Hughes, David H; Marsden, Gaelen; Mauskopf, Philip; Moncelsi, Lorenzo; Netterfield, Calvin B; Pascale, Enzo; Patanchon, Guillaume; Raymond, Gwenifer; Rex, Marie; Scott, Douglas; Semisch, Christopher; Siana, Brian; Truch, Matthew D P; Viero, Marco P

    2009-01-01

    The Balloon-borne Large Aperture Submillimeter Telescope (BLAST) has recently surveyed ~=8.7 deg^2 centered on GOODS-South at 250, 350 and 500 microns. In Dye et al. (2009) we presented the catalogue of sources detected at $\\rm 5\\sigma$ in at least one band in this field and the probable counterparts to these sources in other wavebands. In this paper, we present the results of a redshift survey in which we succeeded in measuring redshifts for 83 of these counterparts. We have used the spectroscopic redshifts to carry out a test of the ability of photometric redshift methods to estimate the redshifts of dusty galaxies. We have also investigated the cases where there are two possible counterparts to the BLAST source, finding that in at least half of these there is evidence that the two galaxies are physically associated, either because they are interacting or because they are in the same large-scale structure. Finally, we have made the first direct measurements of the luminosity function in the three BLAST band...

  20. Volcanic Catastrophes

    Science.gov (United States)

    Eichelberger, J. C.

    2003-12-01

    The big news from 20th century geophysics may not be plate tectonics but rather the surprise return of catastrophism, following its apparent 19th century defeat to uniformitarianism. Divine miracles and plagues had yielded to the logic of integrating observations of everyday change over time. Yet the brilliant interpretation of the Cretaceous-Tertiary Boundary iridium anomaly introduced an empirically based catastrophism. Undoubtedly, decades of contemplating our own nuclear self-destruction played a role in this. Concepts of nuclear winter, volcanic winter, and meteor impact winter are closely allied. And once the veil of threat of all-out nuclear exchange began to lift, we could begin to imagine slower routes to destruction as "global change". As a way to end our world, fire is a good one. Three-dimensional magma chambers do not have as severe a magnitude limitation as essentially two-dimensional faults. Thus, while we have experienced earthquakes that are as big as they get, we have not experienced volcanic eruptions nearly as great as those preserved in the geologic record. The range extends to events almost three orders of magnitude greater than any eruptions of the 20th century. Such a calamity now would at the very least bring society to a temporary halt globally, and cause death and destruction on a continental scale. At maximum, there is the possibility of hindering photosynthesis and threatening life more generally. It has even been speculated that the relative genetic homogeneity of humankind derives from an evolutionary "bottleneck" from near-extinction in a volcanic cataclysm. This is somewhat more palatable to contemplate than a return to a form of Original Sin, in which we arrived at homogeneity by a sort of "ethnic cleansing". Lacking a written record of truly great eruptions, our sense of human impact must necessarily be aided by archeological and anthropological investigations. For example, there is much to be learned about the influence of

  1. 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...

  2. 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...

  3. Stacking for machine learning redshifts applied to SDSS galaxies

    OpenAIRE

    Zitlau, Roman; Hoyle, Ben; 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...

  4. 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 $K_s\\times15$.

  5. 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

    Science.gov (United States)

    Straatman, Caroline M. S.; Spitler, Lee R.; Quadri, Ryan F.; Labbé, 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.

    2016-10-01

    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 arcmin2 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, 5σ, total), and >80% complete to K s MIPS and Herschel/PACS data. We derive rest-frame U - V and V - J colors, and illustrate how these correlate with specific SFR and dust emission to z = 3.5. We confirm the existence of quiescent galaxies at z ˜ 3, demonstrating their SFRs are suppressed by > ×15. This paper contains data gathered with the 6.5 meter Magellan Telescopes located at Las Campanas observatory, Chile

  6. The-wiZZ: Clustering redshift estimation for everyone

    CERN Document Server

    Morrison, Christopher B; Schmidt, Samuel J; Baldry, Ivan K; Bilicki, Maciej; Choi, Ami; Erben, Thomas; Schneider, Peter

    2016-01-01

    We present The-wiZZ, an open source and user-friendly software for estimating the redshift distributions of photometric galaxies with unknown redshifts by spatially cross-correlating them against a reference sample with known redshifts. The main benefit of The-wiZZ is in separating the angular pair finding and correlation estimation from the computation of the output clustering redshifts allowing anyone to create a clustering redshift for their sample without the intervention of an "expert". It allows the end user of a given survey to select any sub-sample of photometric galaxies with unknown redshifts, match this sample's catalog indices into a value-added data file, and produce a clustering redshift estimation for this sample in a fraction of the time it would take to run all the angular correlations needed to produce a clustering redshift. We show results with this software using photometric data from the Kilo-Degree Survey (KiDS) and spectroscopic redshifts from the Galaxy and Mass Assembly (GAMA) survey ...

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

    Science.gov (United States)

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

    2017-04-01

    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 choosing a suboptimal redshift histogram bin width 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 6σ 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 generalized 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 surveys to obtain unbiased cosmological parameter constraints using a minimum number of spectroscopic calibration data. For a DES-like galaxy clustering forecast, we obtain unbiased results with respect to errors caused by suboptimal histogram bin width selection, using only 5k representative spectroscopic calibration objects per tomographic redshift bin.

  8. 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...

  9. The Ongoing Catastrophe

    DEFF Research Database (Denmark)

    Kublitz, Anja

    for the girl talk is centred on catastrophes or Nakbas, as they are referred to in Arabic. Not only al-Nakba of 1948 when the Palestinians were displaced from their homeland, but also the many recurring wars and the individual catastrophes that involve dead family members, rapes, loss of children and abusive...

  10. 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...

  11. 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.

  12. 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.

  13. The ALHAMBRA photometric system

    CERN Document Server

    Villegas, T Aparicio; Cabrera-Cano, J; Moles, M; Benitez, N; Perea, J; del Olmo, A; Fernandez-Soto, A; Cristobal-Hornillos, D; Husillos, C; Aguerri, J A L; Broadhurst, T; Castander, F J; Cepa, J; Cervino, M; Delgado, R M Gonzalez; Infante, L; Marquez, I; Masegosa, J; Martinez, V J; Prada, F; Quintana, J M; Sanchez, S F

    2010-01-01

    This paper presents the characterization of the optical range of the ALHAMBRA photometric system, a 20 contiguous, equal-width, medium-band CCD system with wavelength coverage from 3500A to 9700A. The photometric description of the system is done by presenting the full response curve as a product of the filters, CCD and atmospheric transmission curves, and using some first and second order moments of this response function. We also introduce the set of standard stars that defines the system, formed by 31 classic spectrophotometric standard stars which have been used in the calibration of other known photometric systems, and 288 stars, flux calibrated homogeneously, from the Next Generation Spectral Library (NGSL). Based on the NGSL, we determine the transformation equations between Sloan Digital Sky Survey (SDSS) ugriz photometry and the ALHAMBRA photometric system, in order to establish some relations between both systems. Finally we develop and discuss a strategy to calculate the photometric zero points of ...

  14. Constraining Source Redshift Distributions with Gravitational Lensing

    CERN Document Server

    Wittman, D

    2012-01-01

    We introduce a new method for constraining the redshift distribution of a set of galaxies, using weak gravitational lensing shear. Instead of using observed shears and redshifts to constrain cosmological parameters, we ask how well the shears around clusters can constrain the redshifts, assuming fixed cosmological parameters. This provides a check on photometric redshifts, independent of source spectral energy distribution properties and therefore free of confounding factors such as misidentification of spectral breaks. We find that ~40 massive ($\\sigma_v=1200$ km/s) cluster lenses are sufficient to determine the fraction of sources in each of six coarse redshift bins to ~11%, given weak (20%) priors on the masses of the highest-redshift lenses, tight (5%) priors on the masses of the lowest-redshift lenses, and only modest (20-50%) priors on calibration and evolution effects. Additional massive lenses drive down uncertainties as $N_{lens}^0.5$, but the improvement slows as one is forced to use lenses further ...

  15. 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...

  16. 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...

  17. [The abdominal catastrophe].

    Science.gov (United States)

    Seiler, Christian A

    2011-08-01

    Patients with an abdominal catastrophe are in urgent need of early, interdisciplinary medical help. The treatment plan should be based on medical priorities and clear leadership. First priority should be given to achieve optimal oxygenation of blood and stabilization of circulation during all treatment-phases. The sicker the patient, the less invasive the (surgical) treatment should to be, which means "damage control only". This short article describes 7 important, pragmatic rules that will help to increase the survival of a patient with an abdominal catastrophe. Preexisting morbidity and risk factors must be included in the overall risk-evaluation for every therapeutic intervention. The challenge in patients with an abdominal catastrophe is to carefully balance the therapeutic stress and the existing resistance of the individual patient. The best way to avoid abdominal disaster, however, is its prevention.

  18. The Ongoing Catastrophe

    DEFF Research Database (Denmark)

    Kublitz, Anja

    2015-01-01

    were expelled from their homeland. However, according to my interlocutors, al-Nakba never stopped, but continues in the present. To understand this phenomenon, I suggest that it is conducive to think of al-Nakba as a reverse national myth, a figure of un-becoming, which is replicated in the present. I...... argue that, unlike the spectacular catastrophes in Palestine and later in Lebanon, life in the Danish camps is characterized by minor mundane catastrophes that are each so small that they barely register or elicit a moral response, but nevertheless erode the lives of my interlocutors....

  19. 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 than...

  20. 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

  1. 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...

  2. 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.

  3. [Catastrophic antiphospholipid syndrome].

    Science.gov (United States)

    Wisłowska, Małgorzata

    2015-01-01

    Catastrophic antiphospholipid syndrome is the most dangerous form of the antiphospholipid syndrome, which is characterized by rapid onset of thrombosis in small vessels of many organs and intravascular coagulation, thrombocytopenia and hemolytic anemia. The syndrome develops over a short period of time with acute multi-organ failure, including kidney, respiratory, cardiovascular, central nervous system and adrenal glands, often associated with disseminated thrombotic microangiopathy. The catastrophic antiphospholipid syndrome involves three or more systems, organs and/or tissues, the development of symptoms must occur within less than one week, it is necessary to confirm the histopathological vascular occlusion in at least one organ or tissue, and laboratory confirmation of the presence of antiphospholipid antibodies in the serum on two occasions over an interval of 12 weeks. This syndrome is characterized by a high mortality despite the use of optimal treatment. Early diagnosis and aggressive treatment of patients with catastrophic antiphospholipid syndrome is essential to save the life of these patients. In the last 10 years, the mortality in this disease decreased from 50% to 30% with simultaneous treatment with anticoagulants, corticosteroids, plasmapheresis and immunoglobulins.

  4. 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

  5. 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

  6. 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.

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

    Science.gov (United States)

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

    2016-10-01

    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 (˜40 deg2), which combines a slitless spectroscopic survey limited at Hα flux ≥5 × 10-17 erg cm-2 s-1 and a photometric survey limited in H band (H ≤ 26). 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 from 1 to 10 h-1Mpc, over the redshift range 0.9 < z < 1.8. We compare this density field with the one computed in a mock catalogue with the same depth as the Euclid Deep survey (H = 26) but without redshift measurement errors. We find that our method successfully separates high- from low-density environments (the last from the first quintile of the density distribution), with higher efficiency at low redshift and large cells: the fraction of low-density regions mistaken by high-density peaks is <1 per cent for all scales and redshifts explored, but for scales of 1 h-1Mpc for which is a few per cent. These results show that we can efficiently study environment in photometric samples if spectroscopic information is available for a smaller sample of objects that sparsely samples the same volume. We demonstrate that these studies are possible in the Euclid Deep survey, i.e. in a redshift range in which environmental effects are different from those observed in the local Universe, hence providing new constraints for galaxy evolution models.

  8. Identifying high-redshift GRBs with RATIR

    CERN Document Server

    Littlejohns, O M; Cucchiara, A; Watson, A M; Kutyrev, A S; Lee, W H; Richer, M G; Klein, C R; Fox, O D; Prochaska, J X; Bloom, J S; Troja, E; Ramirez-Ruiz, E; de Diego, J A; Georgiev, L; González, J; Román-Zúñiga, C G; Gehrels, N; Moseley, H

    2013-01-01

    We present a template fitting algorithm for determining photometric redshifts, $z_{\\rm phot}$, 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 spectrum, 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 RATIR photometry of GRB 130606A, finding $z_{\\rm phot} = 6.01_{-0.08}^{+0.16}$ for a model with negligible host dust extinction, consistent with spectroscopic measurements of the redshift of this GRB. Using simulated RATIR photometry, we find our algorithm provides precise measures of $z_{\\rm phot}$ in the ranges $4 4$. Further testing highlights the required caution in cases of highly dust extincted host galaxies. These tests also show that our algorithm minimizes false negatives thus allowing us to rapidly identify all potential high-redshift eve...

  9. 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.

  10. Measuring and Modelling the Redshift Evolution of Clustering the Hubble Deep Field North

    CERN Document Server

    Arnouts, S; Moscardini, L; Matarrese, S; Lucchin, F; Fontana, A; Giallongo, E; Arnouts, Stephane; Cristiani, Stefano; Moscardini, Lauro; Matarrese, Sabino; Lucchin, Francesco; Fontana, Adriano; Giallongo, Emanuele

    1999-01-01

    (abridged) The evolution of galaxy clustering from z=0 to z=4.5 is analyzed using the angular correlation function and the photometric redshift distribution of galaxies brighter than I_{AB}\\le 28.5 in the HDF North. The reliability of the photometric redshift estimates is discussed on the basis of the available spectroscopic redshifts, comparing different codes and investigating the effects of photometric errors. The redshift bins in which the clustering properties are measured are then optimized to take into account the uncertainties of the photometric redshifts. The results show that the comoving correlation length has a small decrease in the range 0redshift galaxies are biased tracers of the dark matter with an effective bias b strongly i...

  11. 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.

  12. 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...

  13. 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...

  14. Bayesian Single-Epoch Photometric Classification of Supernovae

    CERN Document Server

    Poznanski, D; Gal-Yam, A; Poznanski, Dovi; Maoz, Dan; Gal-Yam, Avishay

    2006-01-01

    (abridged) Ongoing supernova (SN) surveys find hundreds of candidates, that require confirmation for their use. Traditional classification based on followup spectroscopy of all candidates is virtually impossible for these large samples. We present an automatic Bayesian classifying algorithm for supernovae, the SN-ABC. We rely solely on single-epoch multiband photometry and host-galaxy (photometric) redshift information to sort SN candidates into the two major types, Ia and core-collapse supernovae. We test the SN-ABC performance on published samples of SNe from the SNLS and GOODS projects that have both broad-band photometry and spectroscopic classification (so the true type is known). The SN-ABC correctly classifies up to 97% (85%) of the type Ia (II-P) SNe in SNLS, and similar fractions of the GOODS SNe, depending on photometric redshift quality. We further test our method on large artificial samples to explore possible biases, and find that, in deep surveys, SNe Ia are best classified at redshifts z >~ 0.6...

  15. ALMA REDSHIFTS OF MILLIMETER-SELECTED GALAXIES FROM THE SPT SURVEY: THE REDSHIFT DISTRIBUTION OF DUSTY STAR-FORMING GALAXIES

    Energy Technology Data Exchange (ETDEWEB)

    Weiss, A. [Max-Planck-Institut fuer Radioastronomie, Auf dem Huegel 69, D-53121 Bonn (Germany); De Breuck, C.; Aravena, M.; Biggs, A. D. [European Southern Observatory, Karl-Schwarzschild Strasse, D-85748 Garching bei Muenchen (Germany); Marrone, D. P.; Bothwell, M. [Steward Observatory, University of Arizona, 933 North Cherry Avenue, Tucson, AZ 85721 (United States); Vieira, J. D.; Bock, J. J. [California Institute of Technology, 1200 E. California Blvd., Pasadena, CA 91125 (United States); Aguirre, J. E. [University of Pennsylvania, 209 South 33rd Street, Philadelphia, PA 19104 (United States); Aird, K. A. [University of Chicago, 5640 South Ellis Avenue, Chicago, IL 60637 (United States); Ashby, M. L. N.; Bayliss, M. [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States); Benson, B. A.; Bleem, L. E.; Carlstrom, J. E.; Chang, C. L. [Kavli Institute for Cosmological Physics, University of Chicago, 5640 South Ellis Avenue, Chicago, IL 60637 (United States); Bethermin, M. [Laboratoire AIM-Paris-Saclay, CEA/DSM/Irfu - CNRS - Universite Paris Diderot, CEA-Saclay, Orme des Merisiers, F-91191 Gif-sur-Yvette (France); Bradford, C. M. [Jet Propulsion Laboratory, 4800 Oak Grove Drive, Pasadena, CA 91109 (United States); Brodwin, M. [Department of Physics and Astronomy, University of Missouri, 5110 Rockhill Road, Kansas City, MO 64110 (United States); Chapman, S. C. [Department of Physics and Atmospheric Science, Dalhousie University, Halifax, NS B3H 3J5 Canada (Canada); and others

    2013-04-10

    Using the Atacama Large Millimeter/submillimeter Array, we have conducted a blind redshift survey in the 3 mm atmospheric transmission window for 26 strongly lensed dusty star-forming galaxies (DSFGs) selected with the South Pole Telescope. The sources were selected to have S{sub 1.4{sub mm}} > 20 mJy and a dust-like spectrum and, to remove low-z sources, not have bright radio (S{sub 843{sub MHz}} < 6 mJy) or far-infrared counterparts (S{sub 100{sub {mu}m}} < 1 Jy, S{sub 60{sub {mu}m}} < 200 mJy). We robustly detect 44 line features in our survey, which we identify as redshifted emission lines of {sup 12}CO, {sup 13}CO, C I, H{sub 2}O, and H{sub 2}O{sup +}. We find one or more spectral features in 23 sources yielding a {approx}90% detection rate for this survey; in 12 of these sources we detect multiple lines, while in 11 sources we detect only a single line. For the sources with only one detected line, we break the redshift degeneracy with additional spectroscopic observations if available, or infer the most likely line identification based on photometric data. This yields secure redshifts for {approx}70% of the sample. The three sources with no lines detected are tentatively placed in the redshift desert between 1.7 < z < 2.0. The resulting mean redshift of our sample is z-bar = 3.5. This finding is in contrast to the redshift distribution of radio-identified DSFGs, which have a significantly lower mean redshift of z-bar = 2.3 and for which only 10%-15% of the population is expected to be at z > 3. We discuss the effect of gravitational lensing on the redshift distribution and compare our measured redshift distribution to that of models in the literature.

  16. 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...

  17. Journeying the Redshift Desert

    CERN Document Server

    Renzini, Alvio

    2009-01-01

    The cosmic star formation rate, AGN activity, galaxy growth, mass assembly and morphological differentiation all culminate at redshift $\\sim 2$. Yet, the redshift interval $1.4\\lsim z\\lsim 3$ is harder to explore than the closer and the more distant Universe. In spite of so much action taking place in this spacetime portion of the Universe, it has been dubbed the ``Redshift Desert'', as if very little was happening within its boundaries. The difficulties encountered in properly mapping the galaxy populations inhabiting the Desert are illustrated in this paper, along with some possible remedy.

  18. Observational Constraints on the Catastrophic Disruption Rate of Small Main Belt Asteroids

    CERN Document Server

    Denneau, Larry; Fitzsimmons, Alan; Hsieh, Henry; Kleyna, Jan; Granvik, Mikael; Micheli, Marco; Spahr, T; Vereš, Peter; Wainscoat, Richard; Burgett, W S; Chambers, K C; Draper, P W; Flewelling, H; Huber, M E; Kaiser, N; Morgan, J S; Tonry, J L

    2014-01-01

    We have calculated 90% confidence limits on the steady-state rate of catastrophic disruptions of main belt asteroids in terms of the absolute magnitude at which one catastrophic disruption occurs per year (HCL) as a function of the post-disruption increase in brightness (delta m) and subsequent brightness decay rate (tau). The confidence limits were calculated using the brightest unknown main belt asteroid (V = 18.5) detected with the Pan-STARRS1 (Pan-STARRS1) telescope. We measured the Pan-STARRS1's catastrophic disruption detection efficiency over a 453-day interval using the Pan-STARRS moving object processing system (MOPS) and a simple model for the catastrophic disruption event's photometric behavior in a small aperture centered on the catastrophic disruption event. Our simplistic catastrophic disruption model suggests that delta m = 20 mag and 0.01 mag d-1 99% of main belt catastrophic disruptions in the size range to which this study was sensitive (100 m) are not impact-generated, but are instead due ...

  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. Kernel PCA for type Ia supernovae photometric classification

    CERN Document Server

    Ishida, Emille E O

    2013-01-01

    The problem of photometric identification will be extremely important for large surveys in the next decade. In this work, we propose the use of KPCA combined with k = 1 nearest neighbor algorithm (KPCA+1NN) as a framework for SNe photometric classification. The method does not rely on information about redshift or local enviromental variables, so it is less sensitive to bias than its template fitting counterparts. We applied the method to $\\approx$ 20000 SNe light curve released after the \\textit{Supernova Photometric Classification Challenge} (SNPCC). Results for the photometric sample achieved up to 89% efficiency (eff), 97% purity (pur), 96% successful classification (SC) rates and figure of merit (FoM) of 0.79 (SNR$\\geq$5). If we impose no SNR cuts, we obtain up to 64% eff, 43% pur, 46% SC and FoM of 0.10. We also present the classification results using only pre-maximum epoches, obtaining 80% eff, 73% pur, 84% SC and FoM of 0.32 (SNR$\\geq$5). Comparing the performance of our classifier with MLCS2k2 fit p...

  1. Spherical Redshift Distortions

    OpenAIRE

    1995-01-01

    Peculiar velocities induce apparent line of sight displacements of galaxies in redshift space, distorting the pattern of clustering in the radial versus transverse directions. On large scales, the amplitude of the distortion yields a measure of the dimensionless linear growth rate $\\beta \\approx \\Omega^{0.6}/b$, where $\\Omega$ is the cosmological density and $b$ the linear bias factor. To make the maximum statistical use of the data in a wide angle redshift survey, and for the greatest accura...

  2. 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.

  3. Plasma Redshift Cosmology

    Science.gov (United States)

    Brynjolfsson, Ari

    2011-04-01

    The newly discovered plasma redshift cross section explains a long range of phenomena; including the cosmological redshift, and the intrinsic redshift of Sun, stars, galaxies and quasars. It explains the beautiful black body spectrum of the CMB, and it predicts correctly: a) the observed XRB, b) the magnitude redshift relation for supernovae, and c) the surface- brightness-redshift relation for galaxies. There is no need for Big Bang, Inflation, Dark Energy, Dark Matter, Accelerated Expansion, and Black Holes. The universe is quasi-static and can renew itself forever (for details, see: http://www.plasmaredshift.org). There is no cosmic time dilation. In intergalactic space, the average electron temperature is T = 2.7 million K, and the average electron density is N = 0.0002 per cubic cm. Plasma redshift is derived theoretically from conventional axioms of physics by using more accurate methods than those conventionally used. The main difference is: 1) the proper inclusion of the dielectric constant, 2) more exact calculations of imaginary part of the dielectric constant, and as required 3) a quantum mechanical treatment of the interactions.

  4. Photometric stereo endoscopy

    Science.gov (United States)

    Parot, Vicente; Lim, Daryl; González, Germán; Traverso, Giovanni; Nishioka, Norman S.; Vakoc, Benjamin J.

    2013-01-01

    Abstract. While color video endoscopy has enabled wide-field examination of the gastrointestinal tract, it often misses or incorrectly classifies lesions. Many of these missed lesions exhibit characteristic three-dimensional surface topographies. An endoscopic system that adds topographical measurements to conventional color imagery could therefore increase lesion detection and improve classification accuracy. We introduce photometric stereo endoscopy (PSE), a technique which allows high spatial frequency components of surface topography to be acquired simultaneously with conventional two-dimensional color imagery. We implement this technique in an endoscopic form factor and demonstrate that it can acquire the topography of small features with complex geometries and heterogeneous optical properties. PSE imaging of ex vivo human gastrointestinal tissue shows that surface topography measurements enable differentiation of abnormal shapes from surrounding normal tissue. Together, these results confirm that the topographical measurements can be obtained with relatively simple hardware in an endoscopic form factor, and suggest the potential of PSE to improve lesion detection and classification in gastrointestinal imaging. PMID:23864015

  5. Spectroscopic confirmation of a redshift 1.55 supernova host galaxy from the Subaru Deep Field Supernova Survey

    CERN Document Server

    Frederiksen, Teddy F; Hjorth, Jens; Maoz, Dan; Poznanski, Dovi

    2012-01-01

    The Subaru Deep Field (SDF) Supernova Survey discovered 10 Type Ia supernovae (SNe Ia) in the redshift range $1.5photometric redshifts of the host galaxies. However, photometric redshifts might be biased, and the SN sample could be contaminated by active galactic nuclei (AGNs). Unfortunately, measuring spectroscopic redshifts of galaxies in the "redshift desert" 1.5 < z < 2.0 is hard because any prominent emission lines get shifted out of the optical and into the near infrared. Here we report the first robust redshift measurement and classification of hSDF0705.25, an SDF SN Ia host galaxy. Using the X-shooter spectrograph on the Very Large Telescope, we measure a spectroscopic redshift of 1.5456 +/- 0.0003, consistent with its photometric redshift of 1.552 +/- 0.018. From the strong emission-line spectrum we are able to rule out AGN activity and show that the SN host galaxy is a low-metallicity, star-burst dwarf galaxy, similar to typical SN Ia hosts at lower red...

  6. Is there a redshift cutoff for submillimetre galaxies?

    CERN Document Server

    Raymond, G; Dye, S; Carlberg, R; Sullivan, M

    2008-01-01

    We present new optical and infrared photometry for a statistically complete sample of seven 1.1 mm selected sources with accurate Submillimetre Array coordinates. We determine photometric redshifts for four of the seven sources of 4.47, 4.50, 1.49 and 0.64. Of the other three sources two are undetected at optical wavelengths down to the limits of very deep Subaru and Canada-France-Hawaii Telescope images ($\\sim$27 mag AB, i band) and the photometry of the remaining source is corrupted by a bright nearby galaxy. The sources with the highest redshifts are at higher redshifts than all but one of the $\\sim$200 sources taken from the largest recent 850 $\\mu$m surveys, which may indicate that 1.1 mm surveys are more efficient at finding sources at very high redshifts than 850 $\\mu$m surveys. We investigate the evolution of the number density with redshift of our sample using a banded $V_{e}/V_{a}$ analysis and find no evidence for a redshift cutoff, although the number of sources is very small. We also perform the ...

  7. 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.

  8. 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.

  9. 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.

  10. Catastrophizing and perceived partner responses to pain.

    Science.gov (United States)

    Boothby, Jennifer L; Thorn, Beverly E; Overduin, Lorraine Y; Ward, L Charles

    2004-06-01

    This study examined the relationship between catastrophizing and patient-perceived partner responses to pain behaviors. The Catastrophizing subscale of the Cognitive Coping Strategy Inventory and the West Haven-Yale Multidimensional Pain Inventory were completed by 62 adult chronic pain patients. Consistent with past research, catastrophizing and patient-perceived solicitous partner behaviors were positively correlated with negative pain outcomes. The communal coping theory of catastrophizing suggests that catastrophizing might be undertaken to solicit support and empathy from others. However, catastrophizing was not related to perceived solicitous partner behavior in this study. Rather, catastrophizing was associated with perceived punishing partner responses. Implications are that catastrophizing and perceived solicitous partner behaviors are independently associated with pain and that catastrophizing may not be reinforced by empathy from significant others.

  11. 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...

  12. GRB 070714B - Discovery of the Highest Spectroscopically Confirmed Short Burst Redshift

    CERN Document Server

    Graham, J F; Levan, A J; Nysewander, M; Tanvir, N R; Dahlen, T; Bersier, D; Peér, A

    2008-01-01

    Gemini Nod & Shuffle spectroscopy on the host of the short GRB 070714B shows a single emission line at 7167 angstroms which, based on a grizJHK photometric redshift, we conclude is the 3727 angstrom [O II] line. This places the host at a redshift of z=.923 exceeding the previous record for the highest spectroscopically confirmed short burst redshift of z=.546 held by 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.

  13. 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...

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

    Science.gov (United States)

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

    2016-12-01

    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 (0.2 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 samples. Using the Area Under the Curve (AUC) metric, where perfect classification is given by 1, we find that our best-performing classifier (Extreme Gradient Boosting Decision Tree) has an AUC of 0.98.We show that it is possible to obtain a large photometrically selected type Ia SN sample with an estimated contamination of less than 5%. When applied to data from the first three years of SNLS, we obtain 529 events. We investigate the differences between classifying simulated SNe, and real SN survey data. In particular, we find that applying a thorough set of selection cuts to the SN sample is essential for good classification. This work demonstrates for the first time the feasibility of machine learning classification in a high-z SN survey with application to real SN data.

  15. 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...

  16. THE DEEP2 GALAXY REDSHIFT SURVEY: DESIGN, OBSERVATIONS, DATA REDUCTION, AND REDSHIFTS

    Energy Technology Data Exchange (ETDEWEB)

    Newman, Jeffrey A. [Department of Physics and Astronomy, University of Pittsburgh, Pittsburgh, PA 15260 (United States); Cooper, Michael C. [Center for Galaxy Evolution, Department of Physics and Astronomy, University of California, Irvine, 4129 Frederick Reines Hall, Irvine, CA 92697 (United States); Davis, Marc [Department of Astronomy and Physics, University of California, 601 Campbell Hall, Berkeley, CA 94720 (United States); Faber, S. M.; Guhathakurta, Puragra; Koo, David C.; Phillips, Andrew C.; Conroy, Charlie; Harker, Justin J.; Lai, Kamson [UCO/Lick Observatory, University of California, 1156 High Street, Santa Cruz, CA 95064 (United States); Coil, Alison L. [Department of Physics, University of California, San Diego, La Jolla, CA 92093 (United States); Dutton, Aaron A. [Max Planck Institute for Astronomy, Koenigstuhl 17, D-69117 Heidelberg (Germany); Finkbeiner, Douglas P. [Harvard-Smithsonian Center for Astrophysics, Harvard University, 60 Garden St., Cambridge, MA 02138 (United States); Gerke, Brian F. [Lawrence Berkeley National Laboratory, 1 Cyclotron Rd., MS 90R4000, Berkeley, CA 94720 (United States); Rosario, David J. [Max-Planck-Institut fuer Extraterrestrische Physik, Giessenbachstrasse, D-85748 Garching (Germany); Weiner, Benjamin J.; Willmer, C. N. A. [Steward Observatory, University of Arizona, 933 N. Cherry Ave., Tucson, AZ 85721-0065 (United States); Yan Renbin [Department of Physics and Astronomy, University of Kentucky, 505 Rose Street, Lexington, KY 40506-0055 (United States); Kassin, Susan A. [Astrophysics Science Division, Goddard Space Flight Center, Code 665, Greenbelt, MD 20771 (United States); Konidaris, N. P., E-mail: janewman@pitt.edu, E-mail: djm70@pitt.edu, E-mail: m.cooper@uci.edu, E-mail: mdavis@berkeley.edu, E-mail: faber@ucolick.org, E-mail: koo@ucolick.org, E-mail: raja@ucolick.org, E-mail: phillips@ucolick.org [Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218 (United States); and others

    2013-09-15

    other artifacts that in some cases remain after data reduction. Redshift errors and catastrophic failure rates are assessed through more than 2000 objects with duplicate observations. Sky subtraction is essentially photon-limited even under bright OH sky lines; we describe the strategies that permitted this, based on high image stability, accurate wavelength solutions, and powerful B-spline modeling methods. We also investigate the impact of targets that appear to be single objects in ground-based targeting imaging but prove to be composite in Hubble Space Telescope data; they constitute several percent of targets at z {approx} 1, approaching {approx}5%-10% at z > 1.5. Summary data are given that demonstrate the superiority of DEEP2 over other deep high-precision redshift surveys at z {approx} 1 in terms of redshift accuracy, sample number density, and amount of spectral information. We also provide an overview of the scientific highlights of the DEEP2 survey thus far.

  17. 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, Puragra; Koo, David C.; Phillips, Andrew C.; Conroy, Charlie; Dutton, Aaron A.; Finkbeiner, Douglas P.; Gerke, Brian F.; Rosario, David J.; Weiner, Benjamin J.; Willmer, 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.; Connolly, A. J.; Kaiser, N.; Kirby, Evan N.; Lemaux, Brian C.; Lin, Lihwai; Lotz, Jennifer M.; Luppino, G. A.; Marinoni, C.; Matthews, Daniel J.; Metevier, Anne; Schiavon, Ricardo P.

    2013-09-01

    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 ~ 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 ~ 1 via ~90 nights of observation on the Keck telescope. The survey covers an area of 2.8 deg2 divided into four separate fields observed to a limiting apparent magnitude of R AB = 24.1. Objects with z 0.7 to be targeted ~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 ~ 1.45, where the [O II] 3727 Å doublet lies in the infrared. The DEIMOS 1200 line mm-1 grating used for the survey delivers high spectral resolution (R ~ 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 through more than 2000 objects with duplicate observations. Sky subtraction is

  18. 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

  19. Photometric Selection of a Massive Galaxy Catalog with z ≥ 0.55

    Science.gov (United States)

    Núñez, Carolina; Spergel, David N.; Ho, Shirley

    2017-02-01

    We present the development of a photometrically selected massive galaxy catalog, targeting Luminous Red Galaxies (LRGs) and massive blue galaxies at redshifts of z≥slant 0.55. Massive galaxy candidates are selected using infrared/optical color–color cuts, with optical data from the Sloan Digital Sky Survey (SDSS) and infrared data from “unWISE” forced photometry derived from the Wide-field Infrared Survey Explorer (WISE). The selection method is based on previously developed techniques to select LRGs with z> 0.5, and is optimized using receiver operating characteristic curves. The catalog contains 16,191,145 objects, selected over the full SDSS DR10 footprint. The redshift distribution of the resulting catalog 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. Using DEEP2, the resulting catalog has an average redshift of z = 0.65, with a standard deviation of σ =2.0, and an average restframe of U-B=1.0, with a standard deviation of σ =0.27. Using COSMOS, the resulting catalog has an average redshift of z = 0.60, with a standard deviation of σ =1.8. We estimate 34 % of the catalog to be blue galaxies with z≥slant 0.55. An estimated 9.6 % of selected objects are blue sources with redshift z< 0.55. Stellar contamination is estimated to be 1.8%.

  20. THE CATASTROPHIC RISK REINSURANCE: FOREIGN EXPERIENCE

    Directory of Open Access Journals (Sweden)

    T. Tatarina

    2014-03-01

    Full Text Available The article deals with foreign experience of catastrophic risks reinsurance. The directions to ensure savings and increase capitalization of insurance companies under reinsurance protection. The necessary of catastrophic risk reinsurance in Ukraine has brought.

  1. Guidance for Catastrophic Emergency Situations Involving Asbestos

    Science.gov (United States)

    This document addresses the types of asbestos issues that may arise during catastrophic events and how EPA has addressed such issues. It replaces the Guidelines for Catastrophic Emergency Situations Involving Asbestos which was issued in 1992.

  2. Measuring the Redshift Evolution of Clustering the Hubble Deep Field South

    CERN Document Server

    Arnouts, S; Cristiani, S; Fontana, A; Giallongo, E; Matarrese, S; Moscardini, L; Saracco, P; Vanzella, E

    2002-01-01

    We present an analysis of the evolution of galaxy clustering in the redshift interval 0photometric redshifts are used for all the galaxies brighter than I_AB<27.5. The clustering signal is obtained in different redshift bins using two different approaches: a standard one, which uses the best redshift estimate of each object, and a second one, which takes into account the redshift probability function of each object. This second method makes it possible to improve the information in the redshift intervals where contamination from objects with insecure redshifts is important. With both methods, we find that the clustering strength up to z~3.5 in the HDF-S is consistent with the previous results in the HDF-N. While at redshift lower than z~1 the HDF galaxy population is un/anti-biased (b<1) with respect to the underlying dark matter, at high redshift the bias increases up to b~2-3, depending on the cosmol...

  3. High-Redshift Cosmography

    CERN Document Server

    Vitagliano, Vincenzo; Liberati, Stefano; Viel, Matteo

    2009-01-01

    We constrain the parameters describing the kinematical state of the universe using a cosmographic approach, which is fundamental in that it requires a very minimal set of assumptions (namely to specify a metric) and does not rely on the dynamical equations for gravity. On the data side, we consider the most recent compilations of Supernovae and Gamma Ray Bursts catalogs. This allows to further extend the cosmographic fit up to $z=6.6$, i.e. up to redshift for which one could start to resolve the low $z$ degeneracy among competing cosmological models. In order to reliably control the cosmographic approach at high redshifts, we adopt the expansion in the improved parameter $y=z/(1+z)$ (as proposed in Class. Quant. Grav., 24 (2007) 5985). This series has the great advantage to hold also for $z>1$ and hence it is the appropriate tool for handling data including non-nearby distance indicators. We find that Gamma Ray Bursts, probing higher redshifts than Supernovae, have constraining power and do require (and stati...

  4. 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

  5. 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.

  6. The Carnegie Supernova Project: The Low-Redshift Survey

    CERN Document Server

    Hamuy, M; Morrell, N I; Phillips, M M; Suntzeff, N B; Persson, S E; Roth, M; González, S; Krzeminski, W; Contreras, C S; Freedman, W L; Murphy, D C; Madore, B F; Wyatt, P; Maza, J; Filippenko, A V; Li, W; Pinto, P A; Hamuy, Mario; Folatelli, Gast\\'on; Morrell, Nidia I.; Phillips, Mark M.; Suntzeff, Nicholas B.; Roth, Miguel; Gonzalez, Sergio; Krzeminski, Wojtek; Contreras, Carlos; Freedman, Wendy L.; Madore, Barry F.; Maza, Jos\\'{e}; Filippenko, Alexei V.; Li, Weidong

    2005-01-01

    Supernovae are essential to understanding the chemical evolution of the Universe. Type Ia supernovae also provide the most powerful observational tool currently available for studying the expansion history of the Universe and the nature of dark energy. Our basic knowledge of supernovae comes from the study of their photometric and spectroscopic properties. However, the presently available data sets of optical and near-infrared light curves of supernovae are rather small and/or heterogeneous, and employ photometric systems that are poorly characterized. Similarly, there are relatively few supernovae whose spectral evolution has been well sampled, both in wavelength and phase, with precise spectrophotometric observations. The low-redshift portion of the Carnegie Supernova Project (CSP) seeks to remedy this situation by providing photometry and spectrophotometry of a large sample of supernovae taken on telescope/filter/detector systems that are well understood and well characterized. During a five-year program w...

  7. Systematic effects in large-scale angular power spectra of photometric quasars and implications for constraining primordial nongaussianity

    CERN Document Server

    Pullen, Anthony R

    2013-01-01

    Primordial non-Gaussianity of local type is predicted to lead to enhanced halo clustering on very large scales. Photometric quasars, which can be seen from cosmological redshifts z>2 even in wide-shallow optical surveys, are promising tracers for constraining non-Gaussianity using this effect. However, large-scale systematics can also mimic this signature of non-Gaussianity. In order to assess the contribution of systematic effects, we cross-correlate overdensity maps of photometric quasars from the Sloan Digital Sky Survey (SDSS) Data Release 6 (DR6) in different redshift ranges. We find that the maps are significantly correlated on large scales, even though we expect the angular distributions of quasars at different redshifts to be uncorrelated. This implies that the quasar maps are contaminated with systematic errors. We investigate the use of external templates that provide information on the spatial dependence of potential systematic errors to reduce the level of spurious clustering in the quasar data. W...

  8. 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...

  9. 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...

  10. UV Properties and Evolution of High-redshift Galaxies

    Science.gov (United States)

    Buzzoni, Alberto

    I assess the problem of morphological and photometric evolution of high-redshift galaxies in the ultraviolet wavelength range. My discussion will partly rely on a new set of template galaxy models, in order to infer the expected changes along the Hubble morphological sequence at the different cosmic epochs. The impact of evolution on the faint-end galaxy luminosity function at z~1 and beyond will also be evaluated and briefly discussed. See http://www.merate.mi.astro.it/~eps/home.html for more info and model retrieval.

  11. UV properties and evolution of high-redshift galaxies

    OpenAIRE

    Buzzoni, Alberto

    2002-01-01

    I assess the problem of morphological and photometric evolution of high-redshift galaxies in the ultraviolet wavelength range. My discussion will partly rely on a new set of template galaxy models, in order to infer the expected changes along the Hubble morphological sequence at the different cosmic epochs. The impact of evolution on the faint-end galaxy luminosity function at z~1 and beyond will also be evaluated and briefly discussed. See http://www.merate.mi.astro.it/~eps/home.html for mor...

  12. UV properties and evolution of high-redshift galaxies

    CERN Document Server

    Buzzoni, A

    2002-01-01

    I assess the problem of morphological and photometric evolution of high-redshift galaxies in the ultraviolet wavelength range. My discussion will partly rely on a new set of template galaxy models, in order to infer the expected changes along the Hubble morphological sequence at the different cosmic epochs. The impact of evolution on the faint-end galaxy luminosity function at z~1 and beyond will also be evaluated and briefly discussed. See http://www.merate.mi.astro.it/~eps/home.html for more info and model retrieval.

  13. Optimizing Spectroscopic and Photometric Galaxy Surveys: Same-Sky Benefits for Dark Energy and Modified Gravity

    Energy Technology Data Exchange (ETDEWEB)

    Kirk, Donnacha [University Coll. London; Lahav, Ofer [University Coll. London; Bridle, Sarah [Manchester U.; Jouvel, Stephanie [Barcelona, IEEC; Abdalla, Filipe B. [University Coll. London; Frieman, Joshua A. [Chicago U., KICP

    2015-08-21

    The combination of multiple cosmological probes can produce measurements of cosmological parameters much more stringent than those possible with any individual probe. We examine the combination of two highly correlated probes of late-time structure growth: (i) weak gravitational lensing from a survey with photometric redshifts and (ii) galaxy clustering and redshift space distortions from a survey with spectroscopic redshifts. We choose generic survey designs so that our results are applicable to a range of current and future photometric redshift (e.g. KiDS, DES, HSC, Euclid) and spectroscopic redshift (e.g. DESI, 4MOST, Sumire) surveys. Combining the surveys greatly improves their power to measure both dark energy and modified gravity. An independent, non-overlapping combination sees a dark energy figure of merit more than 4 times larger than that produced by either survey alone. The powerful synergies between the surveys are strongest for modified gravity, where their constraints are orthogonal, producing a non-overlapping joint figure of merit nearly 2 orders of magnitude larger than either alone. Our projected angular power spectrum formalism makes it easy to model the cross-correlation observable when the surveys overlap on the sky, producing a joint data vector and full covariance matrix. We calculate a same-sky improvement factor, from the inclusion of these cross-correlations, relative to non-overlapping surveys. We find nearly a factor of 4 for dark energy and more than a factor of 2 for modified gravity. The exact forecast figures of merit and same-sky benefits can be radically affected by a range of forecasts assumption, which we explore methodically in a sensitivity analysis. We show that that our fiducial assumptions produce robust results which give a good average picture of the science return from combining photometric and spectroscopic surveys.

  14. High redshift galaxies in the ALHAMBRA survey . I. Selection method and number counts based on redshift PDFs

    Science.gov (United States)

    Viironen, K.; Marín-Franch, A.; López-Sanjuan, C.; Varela, J.; Chaves-Montero, J.; Cristóbal-Hornillos, D.; Molino, A.; Fernández-Soto, A.; Vilella-Rojo, G.; 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.; González Delgado, R. M.; Husillos, C.; Infante, L.; Martínez, V. J.; Perea, J.; Prada, F.; Quintana, J. M.

    2015-04-01

    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-α selection. However, the availability of multifilter data now allows the dropout selections to be replaced 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 to the study of the brightest, least 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, reaching both a complete and clean sample with this method is challenging. Hence, a method to derive statistical properties by summing the zPDFs of all the galaxies in the redshift bin of interest is introduced. Results: Using this methodology we derive the galaxy rest frame UV number counts in five redshift bins centred at z = 2.5,3.0,3.5,4.0, and 4.5, being complete up to the limiting magnitude at mUV(AB) = 24, where mUV refers to the first ALHAMBRA filter redwards of the Ly-α line. With the wide field ALHAMBRA data we especially contribute to the study of the brightest ends of these counts, accurately sampling the surface densities down to mUV(AB) = 21-22. Conclusions: We show that using the zPDFs it is easy to select a very clean sample of high redshift galaxies. We also show that it is better to do statistical analysis of the properties of galaxies using a probabilistic approach, which takes into account both the incompleteness and contamination issues in a

  15. Galaxy Redshifts from Discrete Optimization of Correlation Functions

    Science.gov (United States)

    Lee, Benjamin C. G.; Budavári, Tamás; Basu, Amitabh; Rahman, Mubdi

    2016-12-01

    We propose a new method of constraining the redshifts of individual extragalactic sources based on celestial coordinates and their ensemble statistics. Techniques from integer linear programming (ILP) 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 also is readily implementable in off-the-shelf solvers. We adopt Gurobi, a commercial optimization solver, and use Python to build the cost function dynamically. The preliminary results on simulated data show potential for future applications to sky surveys by complementing and enhancing photometric redshift estimators. Our approach is the first application of ILP to astronomical analysis.

  16. Spectroscopic redshifts of galaxies within the Frontier Fields

    CERN Document Server

    Ebeling, H; Barrett, E

    2014-01-01

    We present a catalog of 1848 spectroscopic redshifts measured in the fields of the massive galaxy clusters MACSJ0416.1-2403 ($z=0.397$), MACSJ0717.5+3745 ($z=0.546$), and MACSJ1149.5+2223 ($z=0.544$), i.e., three of the four clusters selected by STScI as the targets of the Frontier Fields (FF) initiative for studies of the distant Universe via gravitational lensing. Compiled in the course of the MACS project (Massive Cluster Survey) that detected the FF clusters, this catalog is provided to the community for three purposes: (1) to allow the identification of cluster members for studies of the galaxy population of these extreme systems, (2) to facilitate the removal of unlensed galaxies and thus reduce shear dilution in weak-lensing analyses, and (3) to improve the calibration of photometric redshifts based on both ground- and spacebased observations of the FF clusters.

  17. 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.

  18. 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......” within the realm of public climate change communication. For that reason, the essay centers on the interplay between news media and entertainment. It argues that blockbuster disaster films represent an inversion of traditional risk and disaster news....

  19. 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

  20. 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.

  1. Photometric Variability in Earthshine Observations

    OpenAIRE

    Langford, Sally V.; Wyithe, J. Stuart B.; 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 th...

  2. 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.

  3. Stellar Populations and Galaxy Morphology at High Redshift

    CERN Document Server

    Bunker, A J; Stern, D; Thompson, R; Moustakas, L; Davis, M; Dey, A; Bunker, Andrew; Spinrad, Hyron; Stern, Daniel; Thompson, Rodger; Moustakas, Leonidas; Davis, Marc; Dey, Arjun

    2000-01-01

    In this article we investigate the morphology and stellar populations of high-redshift galaxies through multi-waveband HST imaging and ground-based spatially-resolved spectroscopy. We study the redshift evolution of galaxy morphology in the Hubble Deep Field, using the deep IDT-NICMOS near-infrared HST imaging coupled with spectroscopic and photometric redshifts. Using the multi-waveband data to compare the appearance of galaxies at the same rest-frame wavelengths reveals that "morphological k-corrections" (the change in appearance when viewing high-z objects at shorter rest-frame wavelengths) are only important in a minority of cases, and that galaxies were intrinsically more peculiar at high redshift. One example of significant morphological k-corrections is spiral galaxies, which often show more pronounced barred structure in the near-infrared than in the optical. Therefore, the apparent decline in the fraction of barred spirals at faint magnitudes in the optical HDF may be due to band-shifting effects at ...

  4. Real or Interloper? The Redshift Likelihoods of Galaxies in the HUDF12

    CERN Document Server

    Pirzkal, Nor; Ryan, Russell; Coe, Dan; Malhotra, Sangeeta; Rhoads, James; Noeske, Kai

    2013-01-01

    In the absence of spectra, fitting template model spectra to observed photometric fluxes, known as Spectral Energy Distribution (SED) fitting, has become the workhorse for identifying high-z galaxies. In this paper, we present an analysis of the most recent and possibly most distant galaxies discovered in the Hubble Ultra Deep Field using a more robust method of redshift estimation based on Markov Chain Monte Carlo fitting (MCMC), rather than relying on the redshift of "best fit" models obtained using common chi^2 minimization techniques. The advantage of MCMC fitting is the ability to accurately estimate the probability density function of the redshift, as well as any other input model parameters, allowing us to derive accurate credible intervals by properly marginalizing over all other input model parameters. We apply our method to 13 recently identified sources and show that, despite claims based on chi^2 minimization, none of these sources can be securely ruled out as low redshift interlopers given the lo...

  5. The VIMOS Public Extragalactic Redshift Survey (VIPERS). Full spectroscopic data and auxiliary information release (PDR-2)

    CERN Document Server

    Scodeggio, M; Garilli, B; Granett, B R; Bolzonella, M; de la Torre, S; Abbas, U; Adami, C; Arnouts, S; Bottini, D; Cappi, A; Coupon, J; Cucciati, O; Davidzon, I; Franzetti, P; Fritz, A; Iovino, A; Krywult, J; Brun, V Le; Févre, O Le; Maccagni, D; Malek, K; Marchetti, A; Marulli, F; Polletta, M; Pollo, A; Tasca, L A M; Tojeiro, R; Vergani, D; Zanichelli, A; Bel, J; Branchini, E; De Lucia, G; Ilbert, O; McCracken, H J; Moutard, T; Peacock, J A; Zamorani, G; Burden, A; Fumana, M; Jullo, E; Marinoni, C; Mellier, Y; Moscardini, L; Percival, W J

    2016-01-01

    We present the full public data release (PDR-2) of the VIMOS Public Extragalactic Redshift Survey (VIPERS), performed at the ESO VLT. We release redshifts, spectra, CFHTLS magnitudes and ancillary information (as masks and weights) for a complete sample of 86,775 galaxies (plus 4,732 other objects, including stars and serendipitous galaxies); we also include their full photometrically-selected parent catalogue. The sample is magnitude limited to i_AB = 2 are shown to have a confidence level of 96% or larger and make up 88% of all measured galaxy redshifts (76,552 out of 86,775), constituting the VIPERS prime catalogue for statistical investigations. For this sample the rms redshift error, estimated using repeated measurements of about 3,000 galaxies, is found to be sigma_z = 0.00054(1+z). All data are available at http://vipers.inaf.it and on the ESO Archive.

  6. 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...

  7. Getting started With Amazon Redshift

    CERN Document Server

    Bauer, Stefan

    2013-01-01

    Getting Started With Amazon Redshift is a step-by-step, practical guide to the world of Redshift. Learn to load, manage, and query data on Redshift.This book is for CIOs, enterprise architects, developers, and anyone else who needs to get familiar with RedShift. The CIO will gain an understanding of what their technical staff is working on; the technical implementation personnel will get an in-depth view of the technology, and what it will take to implement their own solutions.

  8. Catastrophic Evaporation of Rocky Planets

    CERN Document Server

    Perez-Becker, Daniel

    2013-01-01

    Short-period exoplanets can have dayside surface temperatures surpassing 2000 K, hot enough to vaporize rock and drive a thermal wind. Small enough planets evaporate completely. We construct a radiative-hydrodynamic model of atmospheric escape from strongly irradiated, low-mass rocky planets, accounting for dust-gas energy exchange in the wind. Rocky planets with masses 2000 K are found to disintegrate entirely in 0.1 M_Earth/Gyr --- our model yields a present-day planet mass of < 0.02 M_Earth or less than about twice the mass of the Moon. Mass loss rates depend so strongly on planet mass that bodies can reside on close-in orbits for Gyrs with initial masses comparable to or less than that of Mercury, before entering a final short-lived phase of catastrophic mass loss (which KIC 12557548b has entered). Because this catastrophic stage lasts only up to a few percent of the planet's life, we estimate that for every object like KIC 12557548b, there should be 10--100 close-in quiescent progenitors with sub-da...

  9. 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.

  10. 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...

  11. Photometric selection of emission-line galaxies, clustering analysis and a search for the integrated Sachs-Wolfe effect

    Science.gov (United States)

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

    2010-04-01

    We investigate the use of simple colour cuts applied to the Sloan Digital Sky Survey (SDSS) optical imaging to perform photometric selections of emission-line galaxies (ELGs) out to z S11). We thus perform colour cuts using the SDSS g, r and i bands and obtain mean photometric redshifts of and . We further calibrate our high-redshift selection using spectroscopic observations with the AAOmega spectrograph on the 4-m Anglo-Australian Telescope, observing ~50-200 galaxy candidates in four separate fields. With just 1h of integration time and seeing of ~ 1.6arcsec, we successfully determined redshifts for ~65 per cent of the targeted candidates. We compare our spectroscopic redshifts to the photometric redshifts from the COMBO-17 survey and find reasonable agreement between the two. We calculate the angular correlation functions of these samples and find correlation lengths of r0 = 2.78 +/- 0.08, 3.71 +/- 0.11 and 5.50 +/- 0.13h-1Mpc 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 = 0.72 +/- 0.02, b = 0.93 +/- 0.03 and b = 1.43 +/- 0.03. We calculate the two-point redshift-space autocorrelation function at z ~ 0.6 and find a clustering amplitude of so = 6.4 +/- 0.8h-1Mpc. Finally, we use our photometric sample to search for the integrated Sachs-Wolfe signal in the Wilkinson Microwave Anisotropy Probe (WMAP) 5-yr data. We cross-correlate our three redshift samples with the WMAP W, V, Q and K bands and find an overall trend for a positive signal similar to that expected from models. However, the signal in each is relatively weak, with the results in the WMAP W band being wTg(<100arcmin) = 0.25 +/- 0.27, 0.17 +/- 0.20 and 0.17 +/- 0.16μK for the low-, mid- and high-redshift samples, respectively. Combining all three galaxy samples, we find a signal of wTg(<100arcmin) = 0.20 +/- 0.12μK in the WMAP W band, a significance of 1.7σ. However, in

  12. The Highest Redshift Radio Galaxies

    CERN Document Server

    Van Breugel, W

    2000-01-01

    At low redshifts powerful radio sources are uniquely associated with massive galaxies, and are thought to be powered by supermassive black holes. Modern 8m -- 10m telescopes may be used used to find their likely progenitors at very high redshifts to study their formation and evolution.

  13. 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.

  14. 2dFLenS and KiDS: determining source redshift distributions with cross-correlations

    Science.gov (United States)

    Johnson, Andrew; Blake, Chris; Amon, Alexandra; Erben, Thomas; Glazebrook, Karl; Harnois-Deraps, Joachim; Heymans, Catherine; Hildebrandt, Hendrik; Joudaki, Shahab; Klaes, Dominik; Kuijken, Konrad; Lidman, Chris; Marin, Felipe A.; McFarland, John; Morrison, Christopher B.; Parkinson, David; Poole, Gregory B.; Radovich, Mario; Wolf, Christian

    2017-03-01

    We develop a statistical estimator to infer the redshift probability distribution of a photometric sample of galaxies from its angular cross-correlation in redshift bins with an overlapping spectroscopic sample. This estimator is a minimum-variance weighted quadratic function of the data: a quadratic estimator. This extends and modifies the methodology presented by McQuinn & White. The derived source redshift distribution is degenerate with the source galaxy bias, which must be constrained via additional assumptions. We apply this estimator to constrain source galaxy redshift distributions in the Kilo-Degree imaging survey through cross-correlation with the spectroscopic 2-degree Field Lensing Survey, presenting results first as a binned step-wise distribution in the range z inferring the redshift distribution.

  15. Catastrophic Disruption of Comet ISON

    Science.gov (United States)

    Keane, Jacqueline V.; Milam, Stefanie N.; Coulson, Iain M.; Kleyna, Jan T.; Sekanina, Zdenek; Kracht, Rainer; Riesen, Timm-Emmanuel; Meech, Karen J.; Charnley, Steven B.

    2016-01-01

    We report submillimeter 450 and 850 microns dust continuum observations for comet C/2012 S1 (ISON) obtained at heliocentric distances 0.31-0.08 au prior to perihelion on 2013 November 28 (rh?=?0.0125 au). These observations reveal a rapidly varying dust environment in which the dust emission was initially point-like. As ISON approached perihelion, the continuum emission became an elongated dust column spread out over as much as 60? (greater than 10(exp 5) km in the anti-solar direction. Deconvolution of the November 28.04 850 microns image reveals numerous distinct clumps consistent with the catastrophic disruption of comet ISON, producing approximately 5.2?×?10(exp 10) kg of submillimeter-sized dust. Orbital computations suggest that the SCUBA-2 emission peak coincides with the comet's residual nucleus.

  16. 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...

  17. 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...

  18. 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.

  19. Photometric Characteristics of Lunar Terrains

    Science.gov (United States)

    Sato, Hiroyuki; Hapke, Bruce W.; Denevi, Brett W.; Robinson, Mark

    2016-10-01

    The photometric properties of the lunar depend on albedo, surface roughness, porosity, and the internal/external structure of particles. Hapke parameter maps derived using a bidirectional reflectance model [Hapke, 2012] from Lunar Reconnaissance Orbiter Camera (LROC) Wide Angle Camera (WAC) images demonstrated the spatial and spectral variation of the photometric properties of the Moon [Sato et al., 2014]. Using the same methodology, here we present the photometric characteristics of typical lunar terrains, which were not systematically analyzed in the previous study.We selected five representative terrain types: mare, highland, swirls, and two Copernican (fresh) crater ejecta (one mare and one highlands example). As for the datasets, we used ~39 months of WAC repeated observations, and for each image pixel, we computed latitude, longitude, incidence, emission, and phase angles using the WAC GLD100 stereo DTM [Scholten et al., 2012]. To obtain similar phase and incidence angle ranges, all sampling sites are near the equator and in the vicinity of Reiner Gamma. Three free Hapke parameters (single scattering albedo: w, HG2 phase function parameter: c, and angular width of SHOE: hs) were then calculated for the seven bands (321-689 nm). The remaining parameters were fixed by simplifying the model [Sato et al., 2014].The highlands, highland ejecta, and swirl (Reiner Gamma) showed clearly higher w than the mare and mare ejecta. The derived c values were lower (less backscattering) for the swirl and higher (more backscattering) for the highlands (and ejecta) relative to the other sites. Forward scattering materials such as unconsolidated transparent crystalline materials might be relatively enriched in the swirl. In the highlands, anorthositic agglutinates with dense internal scattering could be responsible for the strong backscattering. The mare and mare ejecta showed continuously decreasing c from UV to visible wavelengths. This might be caused by the FeO-rich pyroxene

  20. 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.

  1. Catastrophizing delays the analgesic effect of distraction.

    Science.gov (United States)

    Campbell, Claudia M; Witmer, Kenny; Simango, Mpepera; Carteret, Alene; Loggia, Marco L; Campbell, James N; Haythornthwaite, Jennifer A; Edwards, Robert R

    2010-05-01

    Behavioral analgesic techniques such as distraction reduce pain in both clinical and experimental settings. Individuals differ in the magnitude of distraction-induced analgesia, and additional study is needed to identify the factors that influence the pain relieving effects of distraction. Catastrophizing, a set of negative emotional and cognitive processes, is widely recognized to be associated with increased reports of pain. We sought to evaluate the relationship between catastrophizing and distraction analgesia. Healthy participants completed three sessions in a randomized order. In one session (Pain Alone), pain was induced by topical application of a 10% capsaicin cream and simultaneous administration of a tonic heat stimulus. In another session (Pain+Distraction), identical capsaicin+heat application procedures were followed, but subjects played video games that required a high level of attention. During both sessions, verbal ratings of pain were obtained and participants rated their degree of catastrophizing. During the other session (Distraction Alone) subjects played the video games in the absence of any pain stimulus. Pain was rated significantly lower during the distraction session compared to the "Pain Alone" session. In addition, high catastrophizers rated pain significantly higher regardless of whether the subjects were distracted. Catastrophizing did not influence the overall degree of distraction analgesia; however, early in the session high catastrophizers had little distraction analgesia, though later in the session low and high catastrophizers rated pain similarly. These results suggest that both distraction and catastrophizing have substantial effects on experimental pain in normal subjects and these variables interact as a function of time.

  2. Does catastrophic thinking enhance oesophageal pain sensitivity?

    DEFF Research Database (Denmark)

    Martel, M O; Olesen, A E; Jørgensen, D;

    2016-01-01

    that catastrophic thinking exerts an influence on oesophageal pain sensitivity, but not necessarily on the magnitude of acid-induced oesophageal sensitization. WHAT DOES THIS STUDY ADD?: Catastrophizing is associated with heightened pain sensitivity in the oesophagus. This was substantiated by assessing responses...

  3. 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

  4. 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.

  5. Reddening Behaviors of Galaxies in the SDSS Photometric System

    CERN Document Server

    Kim, Sungsoo S

    2008-01-01

    We analyze the behaviors of reddening vectors in the SDSS photometric system for galaxies of different morphologies, ages, and redshifts. As seen in other photometric systems, the dependence of reddening on the spectral energy distribution (SED) and the nonlinearity of reddening are likewise non-negligible for the SDSS system if extinction is significant (~> 1 mag). These behaviors are most significant for the g filter, which has the largest bandwidth-to-central wavelength ratio among SDSS filters. The SDSS colors involving adjacent filters show greater SED-dependence and nonlinearity. A procedure for calculating the correct amount of extinction from an observed color excess is provided. The relative extinctions between (i.e., the extinction law for) SDSS filters given by Schlegel et al., which were calculated with an older version of filter response functions, would underestimate the amount of extinction in most cases by ~5 to 10 % (maximum ~20 %). We recommend A/A_{5500} values of 1.574, 1.191, 0.876, 0.671...

  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. 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.

  8. 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.

  9. 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...

  10. The Canada-France redshift survey; 5, global properties of the sample

    CERN Document Server

    Crampton, D S; Lilly, S J; Hammer, F; Crampton, David

    1995-01-01

    The photometric and spectroscopic data of the CFRS survey of objects with 17.5 1 The distributions of magnitudes and colors demonstrate that galaxies at these high redshifts have very similar colors to those observed locally. The survey thus represents a major improvement in our knowledge of field galaxies at large look-back times. Only ~1% of the galaxies are as compact as stars (on images with FWHM ~ 0.9") and comparisons of the photometric and spectroscopic data show that only one galaxy was initially incorrectly classified spectroscopically as a star, and only two stars were misclassified as galaxies. It is demonstrated that the redshift distributions in the five fields are statistically consistent with each other, once the reduction in the effective number of independent galaxies due to small-scale clustering in redshift is taken into account. The photometric properties of the spectroscopically-unidentified objects indicate that most are likely to be galaxies rather than stars. At least half of these mu...

  11. 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...

  12. Dust Attenuation in High Redshift Galaxies -- 'Diamonds in the Sky'

    CERN Document Server

    Scoville, Nick; Capak, Peter; Kakazu, Yuko; Li, Gongjie; Steinhardt, Charles

    2014-01-01

    We use observed optical to near infrared spectral energy distributions (SEDs) of 266 galaxies in the COSMOS survey to derive the wavelength dependence of the dust attenuation at high redshift. All of the galaxies have spectroscopic redshifts in the range z = 2 to 6.5. The presence of the CIV absorption feature, indicating that the rest-frame UV-optical SED is dominated by OB stars, is used to select objects for which the intrinsic, unattenuated spectrum has a well-established shape. Comparison of this intrinsic spectrum with the observed broadband photometric SED then permits derivation of the wavelength dependence of the dust attenuation. The derived dust attenuation curve is similar in overall shape to the Calzetti curve for local starburst galaxies. We also see the 2175 \\AA~bump feature which is present in the Milky Way and LMC extinction curves but not seen in the Calzetti curve. The bump feature is commonly attributed to graphite or PAHs. No significant dependence is seen with redshift between sub-sample...

  13. 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...

  14. New High-z Fermi BL Lacs with the Photometric Dropout Technique

    CERN Document Server

    Kaur, A; Ajello, M; Greiner, J; Hartmann, D H; Paliya, V S; Dominguez, A; Bolmer, J; Schady, P

    2016-01-01

    Determining redshifts for BL Lacertae (BL Lac) objects using the traditional spectroscopic method is challenging due to the absence of strong emission lines in their optical spectra. We employ the photometric dropout technique to determine redshifts for this class of blazars using the combined 13 broad-band filters from Swift-UVOT and the multi-channel imager GROND at the MPG 2.2 m telescope at ESO's La Silla Observatory. The wavelength range covered by these 13 filters extends from far ultraviolet to the near-Infrared. We report results on 40 new Fermi detected BL Lacs with the photometric redshifts determinations for 5 sources, with 3FGL J1918.2-4110 being the most distant in our sample at z=2.16. Reliable upper limits are provided for 20 sources in this sample. Using the highest energy photons for these Fermi-LAT sources, we evaluate the consistency with the Gamma-ray horizon due to the extragalactic background light.

  15. New High-z Fermi BL Lacs with the Photometric Dropout Technique

    Science.gov (United States)

    Kaur, A.; Rau, A.; Ajello, M.; Greiner, J.; Hartmann, D. H.; Paliya, V. S.; Domínguez, A.; Bolmer, J.; Schady, P.

    2017-01-01

    Determining redshifts for BL Lacertae (BL Lac) objects using the traditional spectroscopic method is challenging due to the absence of strong emission lines in their optical spectra. We employ the photometric dropout technique to determine redshifts for this class of blazars using the combined 13 broadband filters from Swift-UVOT and the multi-channel imager GROND at the MPG 2.2 m telescope at ESO's La Silla Observatory. The wavelength range covered by these 13 filters extends from far-ultraviolet to the near-infrared. We report results on 40 new Fermi-detected BL Lacs with the photometric redshift determinations for five sources, with 3FGL J1918.2–4110 being the most distant in our sample at z = 2.16. Reliable upper limits are provided for 20 sources in this sample. Using the highest energy photons for these Fermi-LAT sources, we evaluate the consistency with the gamma-ray horizon due to the extragalactic background light.

  16. 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.

  17. Very high redshift radio galaxies

    Energy Technology Data Exchange (ETDEWEB)

    van Breugel, W.J.M., LLNL

    1997-12-01

    High redshift radio galaxies (HzRGs) provide unique targets for the study of the formation and evolution of massive galaxies and galaxy clusters at very high redshifts. We discuss how efficient HzRG samples ae selected, the evidence for strong morphological evolution at near-infracd wavelengths, and for jet-induced star formation in the z = 3 800 HzRG 4C41 17

  18. The Redshift of GRB 970508

    CERN Document Server

    Reichart, D E

    1997-01-01

    GRB 970508 is the second gamma-ray burst (GRB) for which an optical afterglow has been detected. It is the first GRB for which a distance scale has been determined: absorption and emission features in spectra of the optical afterglow place GRB 970508 at a redshift of z >= 0.835 (Metzger et al. 1997a, 1997b). The lack of a Lyman-alpha forest in these spectra further constrains this redshift to be less than approximately 2.3. I show that the spectrum of the optical afterglow of GRB 970508, once corrected for Galactic absorption, is inconsistent with the relativistic blast-wave model unless a second, redshifted source of extinction is introduced. This second source of extinction may be the yet unobserved host galaxy. I determine its redshift to be z = 1.09^{+0.14}_{-0.41}, which is consistent with the observed redshift of z = 0.835. Redshifts greater than z = 1.40 are ruled out at the 3 sigma confidence level.

  19. 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.

  20. Catastrophic antiphospholipid syndrome: task force report summary.

    Science.gov (United States)

    Cervera, R; Rodríguez-Pintó, I

    2014-10-01

    The Task Force on Catastrophic Antiphospholipid Syndrome (CAPS) aimed to assess the current knowledge on pathogenesis, clinical and laboratory features, diagnosis and classification, precipitating factors and treatment of CAPS. This article summarizes the main aspects of its final report.

  1. 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.

  2. 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.

  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. 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.

  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. 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. 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...

  8. Photometric H alpha and [O II] Luminosity Function of SDF and SXDF Galaxies: Implications for Future Baryon Oscillation Surveys

    CERN Document Server

    Sumiyoshi, Masanao; Oshige, Shunsuke; Glazebrook, Karl; Akiyama, Masayuki; Morokuma, Tomoki; Motohara, Kentaro; Shimasaku, Kazuhiro; Hayashi, Masao; Yoshida, Makiko; Kashikawa, Nobunari; Kodama, Tadayuki

    2009-01-01

    Efficient selection of emission line galaxies at z > 1 by photometric information in wide field surveys is one of the keys for future spectroscopic surveys to constrain dark energy using the baryon acoustic oscillation (BAO) signature. Here we estimate the H alpha and [O II] line luminosity functions of galaxies at z = 0.5-1.7 using a novel approach where multi-wavelength imaging data is used to jointly estimate both photometric redshifts and star-formation rates. These photometric estimates of line luminosities at high-redshift use the large data sets of the Subaru Deep Field and Subaru XMM-Newton Deep Field (covering \\sim 1 deg^2) and are calibrated with the spectroscopic data of the local Sloan Digital Sky Survey galaxies. The derived luminosity functions (especially H alpha) are in reasonable agreement with the past estimates based on spectroscopic or narrow-band-filter surveys. This dataset is useful for examining the photometric selection of target galaxies for BAO surveys because of the large cosmologi...

  9. Creating catastrophes in the classroom

    Science.gov (United States)

    Andersson, Thommy

    2013-04-01

    Buildings, infrastructure and human life are being destroyed by wind and landslides. To interest and motivate pupils and to help them understand abstract knowledge, a practical experiment could be useful. These experiments will show why strong winds circulate around tropical cyclones and how fluvial geological processes affect nature and communities. The experiments are easy to set up and the equipment is not expensive. Experiment 1: Exogenic processes of water are often slow processes. This experiment will simulate water processes that can take thousands of years, in less than 40 minutes. This experiment can be presented for and understood by pupils at all levels. Letting the pupils build up the scenery will make them more curious about the course of events. During that time they will see the geomorphological genesis of landforms such as landslides, sandurs, deltas, canyons sedimentations, selective erosions. Placing small houses, bridges etc. we can lead to discussions about natural catastrophes and community planning. Material needed for the experiment is a water bucket, erosion gutter, clay (simulating rock), sand and smaller pebbles (simulating the soil), houses of "Monopoly" size and tubes. By using a table with wheels it is easy to reuse the result for other lessons. Installation of a pump can make the experiment into a closed loop system. This installation can be used for presentations outside the classroom. Experiment 2: The Coriolis Effect explains why the wind (moving objects) deflects when moving. In the northern hemisphere the deflection is clockwise and anti-clockwise in the southern hemisphere. This abstract effect is often hard for upper secondary pupils to understand. This experiment will show the effect and thus make the theory real and visible. Material needed for this experiment is a bucket, pipes, a string. At my school we had cooperation with pupils from the Industrial Technology programme who made a copper pipe construction. During the

  10. 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.

  11. 2dFLenS and KiDS: Determining source redshift distributions with cross-correlations

    CERN Document Server

    Johnson, Andrew; Amon, Alexandra; Erben, Thomas; Glazebrook, Karl; Harnois-Deraps, Joachim; Heymans, Catherine; Hildebrandt, Hendrik; Joudaki, Shahab; Klaes, Dominik; Kuijken, Konrad; Lidman, Chris; Marin, Felipe A; McFarland, John; Morrison, Christopher B; Parkinson, David; Poole, Gregory B; Radovich, Mario; Wolf, Christian

    2016-01-01

    We develop a statistical estimator to infer the redshift probability distribution of a photometric sample of galaxies from its angular cross-correlation in redshift bins with an overlapping spectroscopic sample. This estimator is a minimum variance weighted quadratic function of the data: a quadratic estimator. This extends and modifies the methodology presented by McQuinn & White (2013). The derived source redshift distribution is degenerate with the source galaxy bias, which must be constrained via additional assumptions. We apply this estimator to constrain source galaxy redshift distributions in the Kilo-Degree imaging survey through cross-correlation with the spectroscopic 2-degree Field Lensing Survey, presenting results first as a binned step-wise distribution in the range z < 0.8, and then building a continuous distribution using a Gaussian process model. We demonstrate the robustness of our methodology using mock catalogues constructed from N-body simulations, and comparisons with other techni...

  12. Photometric determinants of perceived transparency.

    Science.gov (United States)

    Singh, Manish; Anderson, Barton L

    2006-03-01

    Photometric constraints for the perception of transparency were investigated using stereoscopic textured displays. A contrast discontinuity divided the textured displays into two lateral halves, with one (reference) half fixed. Observers adjusted the luminance range within the other (test) half in order to perform two tasks: (i) indicate the highest luminance range for which the test side is perceived to be transparent, and (ii) indicate the lowest luminance range for which the test side is seen as being in plain view. Settings were obtained for multiple values of test mean luminance, in order to map out the perceptual locus of transition between transparency and non-transparency. The results revealed a systematic violation of Metelli's magnitude constraint in predicting the percept of transparency. Observer settings were approximated instead by a constraint based on perceived contrast (which matched Michelson contrast for the textures used). The results also revealed large asymmetries between darkening and lightening transparency. When the test was darker than the reference, settings were highly consistent across observers and closely followed the Michelson-contrast prediction. When the test was lighter, however, there was greater variability across observers, with two observers exhibiting shifts toward Metelli's magnitude constraint. Moreover, each observer's setting reliability was significantly worse for lightening transparency than darkening transparency. These results suggest that (polarity-preserving) darkening serves as an additional cue to perceptual transparency.

  13. Photometric Metallicities in Bootes I

    CERN Document Server

    Hughes, J; Dotter, A; Geisler, D

    2014-01-01

    We present new Stromgren and Washington data sets for the Bootes I dwarf galaxy, and combine them with the available SDSS photometry. The goal of this project is to refine a ground-based, practical, accurate method to determine age and metallicity for individual stars in Bootes I that can be selected in an unbiased imaging survey, without having to take spectra. We produce photometric metallicities from Stromgren and Washington photometry, for stellar systems with a range of $-1.0>[Fe/H]>-3.5$. To avoid the decrease in sensitivity of the Stromgren metallicity index on the lower red-giant branch, we replace the Stromgren v-filter with the broader Washington C-filter; we find that $CT_1by$ is the most successful filter combination, for individual stars with $[Fe/H]<-2.0$, to maintain ~0.2 dex $[Fe/H]$-resolution over the whole red-giant branch. We demonstrate that we can break the isochrones' age-metallicity degeneracy with these filters, using stars with log g=2.5-3.0, which have less than a 2% change in th...

  14. Photometrical Observations "SBIRS GEO-2"

    Science.gov (United States)

    Sukhov, P. P.; Epishev, V. P.; Karpenko, G. F.; Sukhov, K. P.; Kudak, V. I.

    Photometrical observations GSS "SBIRS GEO 2" in B,V,R filters were carried near the equinoxes 2014-2015. Used velocity electrophotometer based on the FEU-79 in the pulse-counting mode. Received more than 25 light curves. From the known dimensions are defined; effective reflecting area - Sγλ, the spectral reflectance index - γλ, periods of light variation. Color-indices showed that in the reflected light flux from the GSS prevails "red" component. In the light curves are periodically dips and specular flash. This shows that GSS orbit is not in a static position specified triaxial orientation as in dynamic motion. Assumed following dynamics of the satellite "SBIRS GEO 2" in orbit. Helical scanning the Earth's surface visible infrared sensors satellite occurs with a period P1 = 15.66 sec. and swinging of the GSS about the direction of the motion vector of the satellite in an orbit with P2 = 62.64 sec., from the northern to the southern pole. Thus, during the period of swinging GSS going on 2 scan the visible part of the northern and southern hemispheres. In some dates observations dynamics work satellite in orbit changed.

  15. 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...

  16. Redshift Measurement and Spectral Classification for eBOSS Galaxies with the redmonster Software

    Science.gov (United States)

    Hutchinson, Timothy A.; Bolton, Adam S.; Dawson, Kyle S.; Allende Prieto, Carlos; 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; Tojeiro, Rita; Vivek, M.; Ben Zhu, Guangtun

    2016-12-01

    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 ≲ z ≲ 1.0). The 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 {{Δ }}{χ }r2 threshold for declaring statistical confidence. Statistical errors on redshift measurement due to photon shot noise are assessed, and we find typical values of a few tens of km s-1. An investigation of redshift differences in repeat observations scaled by error estimates yields a distribution with a Gaussian mean and standard deviation of μ ˜ 0.01 and σ ˜ 0.65, respectively, suggesting the reported statistical redshift uncertainties are over-estimated by ˜54%. We assess the effects of object magnitude, signal-to-noise ratio, fiber number, and fiber head location on the pipeline’s redshift success rate. Finally, we describe directions of ongoing development.

  17. 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...

  18. Modeling the angular correlation function and its full covariance in Photometric Galaxy Surveys

    CERN Document Server

    Crocce, Martin; Gaztañaga, Enrique

    2010-01-01

    Near future cosmology will see the advent of wide area photometric galaxy surveys, like the Dark Energy Survey (DES), that extent to high redshifts (z ~ 1 - 2) but with poor radial distance resolution. In such cases splitting the data into redshift bins and using the angular correlation function $w(\\theta)$, or the $C_{\\ell}$ power spectrum, will become the standard approach to extract cosmological information or to study the nature of dark energy through the Baryon Acoustic Oscillations (BAO) probe. In this work we present a detailed model for $w(\\theta)$ at large scales as a function of redshift and bin width, including all relevant effects, namely nonlinear gravitational clustering, bias, redshift space distortions and photo-z uncertainties. We also present a model for the full covariance matrix characterizing the angular correlation measurements, that takes into account the same effects as for $w(\\theta)$ and also the possibility of a shot-noise component and partial sky coverage. Provided with a large vo...

  19. Recovering galaxy stellar population properties from broad-band spectral energy distribution fitting II. The case with unknown redshift

    CERN Document Server

    Pforr, Janine; Tonini, Chiara

    2013-01-01

    (Abridged) In a recent work we explored the dependence of galaxy stellar population properties derived from broad-band spectral energy distribution fitting on the fitting parameters, e.g. SFHs, age grid, metallicity, IMF, dust reddening, reddening law, filter setup and wavelength coverage. In this paper we consider also redshift as a free parameter in the fit and study whether one can obtain reasonable estimates of photometric redshifts and stellar population properties at once. We use mock star-forming as well as passive galaxies placed at various redshifts (0.5 to 3) as test particles. Mock star-forming galaxies are extracted from a semi-analytical galaxy formation model. We show that for high-z star-forming galaxies photometric redshifts, stellar masses and reddening can be determined simultaneously when using a broad wavelength coverage and a wide template setup in the fit. Masses are similarly well recovered (median ~ 0.2 dex) as at fixed redshift. For old galaxies with little recent star formation masse...

  20. Evolutionary Catastrophes and the Goldilocks Problem

    CERN Document Server

    Cirkovic, Milan M

    2007-01-01

    One of the mainstays of the controversial "rare Earth" hypothesis is the "Goldilocks problem" regarding various parameters describing a habitable planet, partially involving the role of mass extinctions and other catastrophic processes in biological evolution. Usually, this is construed as support for the uniqueness of the Earth's biosphere and intelligent human life. Here I argue that this is a misconstrual and that, on the contrary, observation-selection effects, when applied to catastrophic processes, make it very difficult for us to discern whether the terrestrial biosphere and evolutionary processes which created it are exceptional in the Milky Way or not. In particular, an anthropic overconfidence bias related to the temporal asymmetry of evolutionary processes appears when we try to straightforwardly estimate catastrophic risks from the past records on Earth. This agnosticism, in turn, supports the validity and significance of practical astrobiological and SETI research.

  1. Catastrophic expenditure on medicines in Brazil

    Science.gov (United States)

    Luiza, Vera Lucia; Tavares, Noemia Urruth Leão; Oliveira, Maria Auxiliadora; Arrais, Paulo Sergio Dourado; Ramos, Luiz Roberto; Pizzol, Tatiane da Silva Dal; Mengue, Sotero Serrate; Farias, Mareni Rocha; Bertoldi, Andréa Dâmaso

    2016-01-01

    ABSTRACT OBJECTIVE To describe the magnitude of the expenditure on medicines in Brazil according to region, household size and composition in terms of residents in a situation of dependency. METHODS Population-based data from the national household survey were used, with probabilistic sample, applied between September 2013 and February 2014 in urban households. The expenditure on medicines was the main outcome of interest. The prevalence and confidence intervals (95%CI) of the outcomes were stratified according to socioeconomic classification and calculated according to the region, the number of residents dependent on income, the presence of children under five years and residents in a situation of dependency by age. RESULTS In about one of every 17 households (5.3%) catastrophic health expenditure was reported and, in 3.2%, the medicines were reported as one of the items responsible for this situation. The presence of three or more residents (3.6%) and resident in a situation of dependency (3.6%) were the ones that most reported expenditure on medicines. Southeast was the region with the lowest prevalence of expenditure on medicines. The prevalence of households with catastrophic health expenditure and on medicines in relation to the total of households showed a regressive tendency for economic classes. CONCLUSIONS Catastrophic health expenditure was present in 5.3%, and catastrophic expenditure on medicines in 3.2% of the households. Multi-person households, presence of residents in a situation of economic dependency and belonging to the class D or E had the highest proportion of catastrophic expenditure on medicines. Although the problem is important, permeated by aspects of iniquity, Brazilian policies seem to be protecting families from catastrophic expenditure on health and on medicine. PMID:27982383

  2. The redshift-distance relation.

    Science.gov (United States)

    Segal, I E

    1993-06-01

    Key predictions of the Hubble law are inconsistent with direct observations on equitable complete samples of extragalactic sources in the optical, infrared, and x-ray wave bands-e.g., the predicted dispersion in apparent magnitude is persistently greatly in excess of its observed value, precluding an explanation via hypothetical perturbations or irregularities. In contrast, the predictions of the Lundmark (homogeneous quadratic) law are consistent with the observations. The Lundmark law moreover predicts the deviations between Hubble law predictions and observation with statistical consistency, while the Hubble law provides no explanation for the close fit of the Lundmark law. The flux-redshift law F [symbol, see text] (1 + z)/z appears consistent with observations on equitable complete samples in the entire observed redshift range, when due account is taken of flux limits by an optimal statistical method. Under the theoretical assumption that space is a fixed sphere, as in the Einstein universe, this law implies the redshift-distance relation z = tan2(r/2R), where R is the radius of the spherical space. This relation coincides with the prediction of chronometric cosmology, which estimates R as 160 +/- 40 Mpc (1 parsec = 3.09 x 10(16) m) from the proper motion to redshift relation of superluminal sources. Tangential aspects, including statistical methodology, fundamental physical theory, bright cluster galaxy samples, and proposed luminosity evolution, are briefly considered.

  3. Obscured AGN at High Redshift

    Science.gov (United States)

    Stern, Daniel

    2008-01-01

    This viewgraph presentation reviews the obscured sources of Active Galactic Nuclei (AGN) in the universe at high redshift. The cosmic X-ray background, unified models of AGN and clues to galaxy formation/evolution is the motivation for this study.

  4. On a new global catastrophic ICT model

    DEFF Research Database (Denmark)

    Riaz, M. Tahir; Bhalerao, Dipashree M.; Madsen, Ole Brun

    2011-01-01

    of the world's population suffers from affordable ICT solutions and the presence of sufficient ICT infrastructure. The main goal of this paper is to create a framework to define catastrophic areas from an ICT point of view. QOS features like packet loss rate, delay, throughput and delivery ratio for 50 nodes...... coverage before and after calamities. This definition of catastrophic area from ICT point of view has no one tried before. Network parameters behavioural graphs are also important. This paper presents only behavioural part....

  5. 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...

  6. A New Determination of the High Redshift Type Ia Supernova Rateswith the Hubble Space Telescope Advanced Camera for Surveys

    Energy Technology Data Exchange (ETDEWEB)

    Kuznetsova, N.; Barbary, K.; Connolly, B.; Kim, A.G.; Pain, R.; Roe, N.A.; Aldering, G.; Amanullah, R.; Dawson, K.; Doi, M.; Fadeyev, V.; Fruchter, A.S.; Gibbons, R.; Goldhaber, G.; Goober, A.; Gude, A.; Knop,R.A.; Kowalski, M.; Lidman, C.; Morokuma, T.; Meyers, J.; Perlmutter, S.; Rubin, D.; Schlegel, D.J.; Spadafora, A.L.; Stanishev, V.; Strovink, M.; Suzuki, N.; Wang, L.; Yasuda, N.

    2007-10-01

    We present a new measurement of the volumetric rate of Type Ia supernova up to a redshift of 1.7, using the Hubble Space Telescope (HST) GOODS data combined with an additional HST dataset covering the North GOODS field collected in 2004. We employ a novel technique that does not require spectroscopic data for identifying Type Ia supernovae (although spectroscopic measurements of redshifts are used for over half the sample); instead we employ a Bayesian approach using only photometric data to calculate the probability that an object is a Type Ia supernova. This Bayesian technique can easily be modified to incorporate improved priors on supernova properties, and it is well-suited for future high-statistics supernovae searches in which spectroscopic follow up of all candidates will be impractical. Here, the method is validated on both ground- and space-based supernova data having some spectroscopic follow up. We combine our volumetric rate measurements with low redshift supernova data, and fit to a number of possible models for the evolution of the Type Ia supernova rate as a function of redshift. The data do not distinguish between a flat rate at redshift > 0.5 and a previously proposed model, in which the Type Ia rate peaks at redshift {approx} 1 due to a significant delay from star-formation to the supernova explosion. Except for the highest redshifts, where the signal to noise ratio is generally too low to apply this technique, this approach yields smaller or comparable uncertainties than previous work.

  7. New quasar surveys with WIRO: Searching for high redshift (z~6) quasar candidates

    Science.gov (United States)

    Haze Nunez, Evan; Bassett, Neil; Deam, Sophie; Dixon, Don; Griffith, Emily; Harvey, William Bradford; Lee, Daniel; Lyke, Bradley; Parziale, Ryan; Witherspoon, Catherine; Myers, Adam D.; Findlay, Joseph; Kobulnicky, Henry A.; Dale, Daniel A.

    2017-01-01

    High redshift quasars (z~6) are of great interest to fundamental astronomy due to the information they hold about the early universe. With their low number density in the sky, however, they are elusive objects. Reported here is our search for these high redshift quasars using the Wyoming Infrared Observatory (WIRO) 2.3m telescope. We search for potential candidates that have been detected by surveys such as WISE, which have been mostly redshifted out of the optical. The main emission feature of these quasars (the Lyman-Alpha line at ~1216 Angstroms rest-frame) would be redshifted to the z-band or beyond. This means that the quasars should have very low levels of i-band flux. These objects are known as i-dropouts. By imaging the quasars in the i-band and running photometric analysis on our fields, candidates can be identified or rejected by whether or not they appear in our fields. We also provide an analysis of the colors of our candidate high-redshift quasars.This work is supported by the National Science Foundation under REU grant AST1560461

  8. Spectroscopic Confirmation of Two Lyman Break Galaxies at Redshift Beyond 7

    Science.gov (United States)

    Vanzella, E.; Pentericci, L.; Fontana, A.; Grazian, A.; Castellano, M.; Boutsia, K.; Cristiani, S.; Dickinson, M.; Gallozzi, S.; Giallongo, E.; Giavalisco, M.; Maiolino, R.; Moorwood, A.; Paris, D.; Santini, P.

    2011-04-01

    We report the spectroscopic confirmation of two Lyman break galaxies at redshift >7. The galaxies were observed as part of an ultra-deep spectroscopic campaign with FORS2 at the ESO/VLT for the confirmation of z ~= 7 "z-band dropout" candidates selected from our VLT/Hawk-I imaging survey. Both galaxies show a prominent emission line at 9735 Å and 9858 Å, respectively: the lines have fluxes of ~(1.6-1.2) × 10-17 erg s-1 cm-2 and exhibit a sharp decline on the blue side and a tail on the red side. The asymmetry is quantitatively comparable to the observed asymmetry in z ~ 6 Lyα lines, where absorption by neutral hydrogen in the intergalactic medium (IGM) truncates the blue side of the emission-line profile. We carefully evaluate the possibility that the galaxies are instead at lower redshift and we are observing either [O II], [O III], or Hα emission: however from the spectroscopic and the photometric data we conclude that there are no other plausible identifications, except for Lyα at redshift >7, implying that these are two of the most robust redshift determination for galaxies in the reionization epoch. Based on their redshifts and broadband photometry, we derive limits on the star formation rate and on the ultraviolet spectral slopes of the two galaxies. We argue that these two galaxies alone are unlikely to have ionized the IGM in their surroundings.

  9. 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...

  10. The superluminous supernova PS1-11ap: bridging the gap between low and high redshift

    Science.gov (United States)

    McCrum, M.; Smartt, S. J.; Kotak, R.; Rest, A.; Jerkstrand, A.; Inserra, C.; Rodney, S. A.; Chen, T.-W.; Howell, D. A.; Huber, M. E.; Pastorello, A.; Tonry, J. L.; Bresolin, F.; Kudritzki, R.-P.; Chornock, R.; Berger, E.; Smith, K.; Botticella, M. T.; Foley, R. J.; Fraser, M.; Milisavljevic, D.; Nicholl, M.; Riess, A. G.; Stubbs, C. W.; Valenti, S.; Wood-Vasey, W. M.; Wright, D.; Young, D. R.; Drout, M.; Czekala, I.; Burgett, W. S.; Chambers, K. C.; Draper, P.; Flewelling, H.; Hodapp, K. W.; Kaiser, N.; Magnier, E. A.; Metcalfe, N.; Price, P. A.; Sweeney, W.; Wainscoat, R. J.

    2014-01-01

    We present optical photometric and spectroscopic coverage of the superluminous supernova (SLSN) PS1-11ap, discovered with the Pan-STARRS1 Medium Deep Survey at z = 0.524. This intrinsically blue transient rose slowly to reach a peak magnitude of Mu = -21.4 mag and bolometric luminosity of 8 × 1043 erg s-1 before settling on to a relatively shallow gradient of decline. The observed decline is significantly slower than those of the SLSNe-Ic which have been the focus of much recent attention. Spectroscopic similarities with the lower redshift SN2007bi and a decline rate similar to 56Co decay time-scale initially indicated that this transient could be a candidate for a pair instability supernova (PISN) explosion. Overall the transient appears quite similar to SN2007bi and the lower redshift object PTF12dam. The extensive data set, from 30 d before peak to 230 d after, allows a detailed and quantitative comparison with published models of PISN explosions. We find that the PS1-11ap data do not match these model explosion parameters well, supporting the recent claim that these SNe are not pair instability explosions. We show that PS1-11ap has many features in common with the faster declining SLSNe-Ic, and the light-curve evolution can also be quantitatively explained by the magnetar spin-down model. At a redshift of z = 0.524, the observer-frame optical coverage provides comprehensive rest-frame UV data and allows us to compare it with the SLSNe recently found at high redshifts between z = 2 and 4. While these high-z explosions are still plausible PISN candidates, they match the photometric evolution of PS1-11ap and hence could be counterparts to this lower redshift transient.

  11. Photometric Variability of the Be Star Population

    CERN Document Server

    Labadie-Bartz, Jonathan; McSwain, M Virginia; Bjorkman, J E; Bjorkman, K S; Lund, Michael B; Rodriguez, Joseph E; Stassun, Keivan G; Stevens, Daniel J; Gaudi, B Scott; James, David J; Kuhn, Rudolf B; Siverd, Robert J; Beatty, Thomas G

    2016-01-01

    Be stars have generally been characterized by the emission lines in their spectra, and especially the time variability of those spectroscopic features. They are known to also exhibit photometric variability at multiple timescales, but have not been broadly compared and analyzed by that behavior. We have taken advantage of the advent of wide-field, long-baseline, and high-cadence photometric surveys that search for transiting exoplanets to perform a comprehensive analysis of brightness variations among a large number of known Be stars. The photometric data comes from the KELT transit survey, with a typical cadence of 30 minutes, baseline of up to ten years, photometric precision of about 1%, and coverage of about 60% of the sky. We analyze KELT light curves of 610 known Be stars in both the Northern and Southern hemispheres in an effort to study their variability. Consistent with other studies of Be star variability, we find most of the stars to be photometrically variable. We derive lower limits on the fracti...

  12. The Pain Catastrophizing Scale: Development and Validation.

    Science.gov (United States)

    Sullivan, Michael J. L.; And Others

    1995-01-01

    A series of 4 studies involving 547 college students and community adults report the development of the Pain Catastrophizing Scale, its validity with clinical and nonclinical samples, and its correlation with measures of related constructs. The scale provides information about heightened responses to aversive procedures or events. (SLD)

  13. Mindfulness, Acceptance and Catastrophizing in Chronic Pain

    NARCIS (Netherlands)

    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 exami

  14. Catastrophizing and Causal Beliefs in Whiplash

    NARCIS (Netherlands)

    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 disor

  15. Extension of catastrophe theory to Dulac unfoldings

    NARCIS (Netherlands)

    Broer, HW; Naudot, [No Value; Roussarie, R; Dumortier, F; Broer, H; Mawhin, J; Vanderbauwhede, A; Lunel, SV

    2005-01-01

    We consider a perturbation of a Hamiltonian planar vector field. The bifurcation set of limit cycles is studied. If the vector field is defined in an annulus, limit cycles are in one to one correspondence to the zeros of a polynomial. Catastrophe theory is relevant for the study of the ensuing bifur

  16. Thoracic aortic catastrophes : towards the endovascular solution

    NARCIS (Netherlands)

    Jonker, F.H.W.

    2010-01-01

    Descending thoracic aortic catastrophes include a variety of acute pathologies of the descending thoracic aorta, which are all associated with high morbidity and mortality rates, requiring immediate intervention. For this thesis, we explored the management and outcomes of several thoracic aortic cat

  17. 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.

  18. 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.

  19. Sonneberg Sky Patrol Archive - Photometric Analysis

    CERN Document Server

    Spasovic, Milan; Lange, Christian; Jovanovic, Dragan; Schrimpf, Andreas

    2016-01-01

    The Sonneberg Sky Patrol archive so far has not yet been analyzed systematically. In this paper we present first steps towards an automated photometric analysis aiming at the search for variable stars and transient phenomena like novae. Early works on the sky patrol plates showed that photometric accuracy can be enhanced with fitting algorithms. The procedure used was a manually supported click-and-fit-routine, not suitable for automatic analysis of vast amount of photographic plates. We will present our progress on deconvolution of overlapping sources on the plates and compare photometric analysis using different methods. Our goal is to get light curves of sufficient quality from sky patrol plates, which can be classified with machine learning algorithms. The development of an automated scheme for finding transient events is in progress and the first results are very promising.

  20. Modifying Gravity at Low Redshift

    CERN Document Server

    Brax, Philippe; Davis, Anne-Christine; Shaw, Douglas

    2010-01-01

    We consider the growth of cosmological perturbations in modified gravity models where a scalar field mediates a non-universal Yukawa force between different matter species. The growth of the density contrast is altered for scales below the Compton wave-length of the scalar field. As the universe expands, the Compton wave-length varies in time in such a way that scales which where outside the range of the scalar field force may feel it at a lower redshift. In this case, both the exponent $\\gamma$ measuring the growth of Cold Dark Matter perturbations and the shift function representing the ratio of the two Newtonian potentials $\\psi$ and $\\phi$ may differ from their values in General Relativity at low redshift.

  1. Searches for High Redshift Clusters

    CERN Document Server

    Dickinson, M

    1996-01-01

    High redshift galaxy clusters have traditionally been a fruitful place to study galaxy evolution. I review various search strategies for finding clusters at z > 1. Most efforts to date have concentrated on the environments of distant AGN. I illustrate these with data on the cluster around 3C 324 (z=1.2) and other, more distant systems, and discuss possibilities for future surveys with large telescopes.

  2. Cosmology with Photometrically-Classified Type Ia Supernovae from the SDSS-II Supernova Survey

    CERN Document Server

    Campbell, Heather; Nichol, Robert C; Sako, Masao; Smith, Mathew; Lampeitl, Hubert; Olmstead, Matthew D; Bassett, Bruce; Biswas, Rahul; Brown, Peter; Cinabro, David; Dawson, Kyle S; Dilday, Ben; Foley, Ryan J; Frieman, Joshua A; Garnavich, Peter; Hlozek, Renee; Jha, Saurabh W; Kuhlmann, Steve; Kunz, Martin; Marriner, John; Miquel, Ramon; Richmond, Michael; Riess, Adam; Schneider, Donald P; Sollerman, Jesper; Taylor, Matt; Zhao, Gong-Bo

    2012-01-01

    We present the cosmological analysis of 752 photometrically-classified Type Ia Supernovae (SNe Ia) obtained from the full Sloan Digital Sky Survey II (SDSS-II) Supernova (SN) Survey, supplemented with host-galaxy spectroscopy from the SDSS-III Baryon Oscillation Spectroscopic Survey (BOSS). Our photometric-classification method is based on the SN typing technique of Sako et al. (2011), aided by host galaxy redshifts (0.05photometric sample alone gives omega_m=0.24+0.07-0.05 (statistical errors only). If we relax the constraint on flatness, then our sample provides competitive joint stati...

  3. El Universo a alto redshift

    Science.gov (United States)

    Alonso, M. V.

    The Universe we see today is the result of structures and galaxies that have been evolving since earlier times. Looking the evolution of the galaxy population at z ˜ 1 has emphasized the important role played by high redshift data. This is the case of the morphology - density relationship, where the morphological type of galaxies in distant clusters has given us a clear vision of evolutionary processes, partly led by environmental effects. I review part of the data available at high redshifts that are fundamental today to check the validity of galaxy formation models in reproducing local and basic galaxy properties. Briefly, I will comment about high redshift studies, a still little explored portion of the Universe, and the current strategies that allow us the study. In this sense, the epoch of reionization is essential for understanding the formation of structures because it is the phase where the first protogalaxies were formed, creating stars and enriching the intergalactic medium. Because of the great distances involved in these studies, gamma-ray bursts, quasars and Lyman-α galaxies are the best tools to study these earlier times. FULL TEXT IN SPANISH

  4. Old Galaxies at High Redshift

    CERN Document Server

    Dunlop, J

    1997-01-01

    The most passive galaxies at high redshift are unlikely to be identified by either narrow-band emission-line searches, or by Lyman limit searches (both techniques which have been highlighted at this meeting) simply because such selection methods rely on the presence of a strong ultraviolet component. Selection on the basis of extreme radio power has also proved to yield optically active objects with the majority of high-redshift objects studied to date displaying complex elongated optical/UV morphologies, relatively blue optical-ultraviolet continuum colours, and strong emission lines. These features, coupled with the failure to detect any spectral signatures of old stars at $z > 1$, has led to the suggestion that these galaxies are being observed close to or even during a general epoch of formation. However, we have recently demonstrated that radio selection at significantly fainter (mJy) flux densities can be used to identify apparently passively evolving elliptical galaxies at high redshift. Deep Keck spec...

  5. Photometric Calibrations for the SIRTF Infrared Spectrograph

    CERN Document Server

    Morris, P W; Herter, T L; Armus, L; Houck, J; Sloan, G

    2002-01-01

    The SIRTF InfraRed Spectrograph (IRS) is faced with many of the same calibration challenges that were experienced in the ISO SWS calibration program, owing to similar wavelength coverage and overlapping spectral resolutions of the two instruments. Although the IRS is up to ~300 times more sensitive and without moving parts, imposing unique calibration challenges on their own, an overlap in photometric sensitivities of the high-resolution modules with the SWS grating sections allows lessons, resources, and certain techniques from the SWS calibration programs to be exploited. We explain where these apply in an overview of the IRS photometric calibration planning.

  6. Personality and temperament correlates of pain catastrophizing in young adolescents

    NARCIS (Netherlands)

    P.E.H.M. Muris (Peter); C.M.G. Meesters (Cor); M.F.C.M. Van Den Hout (Mari F. C. M.); S. Wessels (Sylvia); I.H.A. Franken (Ingmar); E.G.C. Rassin (Eric)

    2007-01-01

    textabstractPain catastrophizing is generally viewed as an important cognitive factor underlying chronic pain. The present study examined personality and temperament correlates of pain catastrophizing in a sample of young adolescents (N = 132). Participants completed the Pain Catastrophizing Scale f

  7. 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...

  8. 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.

  9. The evolution of the luminosity functions in the FORS Deep Field from low to high redshift: I. The blue bands

    CERN Document Server

    Gabasch, A; Seitz, S; Hopp, U; Saglia, Roberto P; Feulner, G; Snigula, J; Drory, N; Appenzeller, I; Heidt, J; Mehlert, D; Noll, S; Böhm, A; Jäger, K; Ziegler, B L; Fricke, K J

    2004-01-01

    We use the very deep and homogeneous I-band selected dataset of the FORS Deep Field (FDF) to trace the evolution of the luminosity function over the redshift range 0.5 < z < 5.0. We show that the FDF I-band selection down to I(AB)=26.8 misses of the order of 10 % of the galaxies that would be detected in a K-band selected survey with magnitude limit K(AB)=26.3 (like FIRES). Photometric redshifts for 5558 galaxies are estimated based on the photometry in 9 filters (U, B, Gunn g, R, I, SDSS z, J, K and a special filter centered at 834 nm). A comparison with 362 spectroscopic redshifts shows that the achieved accuracy of the photometric redshifts is (Delta z / (z_spec+1)) < 0.03 with only ~ 1 % outliers. This allows us to derive luminosity functions with a reliability similar to spectroscopic surveys. In addition, the luminosity functions can be traced to objects of lower luminosity which generally are not accessible to spectroscopy. We investigate the evolution of the luminosity functions evaluated in ...

  10. 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...

  11. System for clinical photometric stereo endoscopy

    Science.gov (United States)

    Durr, Nicholas J.; González, Germán.; Lim, Daryl; Traverso, Giovanni; Nishioka, Norman S.; Vakoc, Benjamin J.; Parot, Vicente

    2014-02-01

    Photometric stereo endoscopy is a technique that captures information about the high-spatial-frequency topography of the field of view simultaneously with a conventional color image. Here we describe a system that will enable photometric stereo endoscopy to be clinically evaluated in the large intestine of human patients. The clinical photometric stereo endoscopy system consists of a commercial gastroscope, a commercial video processor, an image capturing and processing unit, custom synchronization electronics, white light LEDs, a set of four fibers with diffusing tips, and an alignment cap. The custom pieces that come into contact with the patient are composed of biocompatible materials that can be sterilized before use. The components can then be assembled in the endoscopy suite before use. The resulting endoscope has the same outer diameter as a conventional colonoscope (14 mm), plugs into a commercial video processor, captures topography and color images at 15 Hz, and displays the conventional color image to the gastroenterologist in real-time. We show that this system can capture a color and topographical video in a tubular colon phantom, demonstrating robustness to complex geometries and motion. The reported system is suitable for in vivo evaluation of photometric stereo endoscopy in the human large intestine.

  12. The Red Sequence of High-Redshift Clusters: a Comparison with Cosmological Galaxy Formation Models

    OpenAIRE

    Menci, N.; Rosati, P.; Gobat, R.; Strazzullo, V.; Rettura, A.; S. Mei; Demarco, R.

    2008-01-01

    We compare the results from a semi-analytic model of galaxy formation with spectro-photometric observations of distant galaxy clusters observed in the range 0.8< z< 1.3. We investigate the properties of their red sequence (RS) galaxies and compare them with those of the field at the same redshift. In our model we find that i) a well-defined, narrow RS is obtained already by z= 1.2; this is found to be more populated than the field RS, analogously to what observed and predicted at z=0; ii) the...

  13. Diagrama color-magnitud en grupos de galaxias a "redshifts" intermedios

    Science.gov (United States)

    Nilo Castellón, J. L.; Alonso, M. V.; Cuevas, H.; García Lambas, D.; Ramirez, A.

    This is a report with the first results of the photometric analysis of two low luminosity X-ray clusters: RXJ1117.4+0743 and RXJ1252.0+2920, selected from the 160 Square Degree ROSAT Cluster Survey (Vikhlinin et al. 1998). This work is part of an ongoing project to study the cluster properties and the galaxy population of poor clusters in the redshift range of 0.1 < z < 0.5. Preliminary results show that, while RXJ1117.4+0743 is probably in the assembly period, the cluster RXJ1252.0+2920 would be in a more advanced evolutionary stage. FULL TEXT IN SPANISH

  14. 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...

  15. 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.

  16. Galaxy And Mass Assembly (GAMA): curation and reanalysis of 16.6k redshifts in the G10/COSMOS region

    Science.gov (United States)

    Davies, L. J. M.; Driver, S. P.; Robotham, A. S. G.; Baldry, I. K.; Lange, R.; Liske, J.; Meyer, M.; Popping, A.; Wilkins, S. M.; Wright, A. H.

    2015-02-01

    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 deg2 field. 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 use all available redshift information (AUTOZ, zCOSMOS-bright 10k, PRIMUS, VVDS, SDSS and photometric redshifts) to calculate robust best-fitting redshifts for all galaxies and visually inspect all 1D and 2D spectra to obtain 16 583 robust redshifts in the full COSMOS region. We then define the G10 region to be the central ˜1 deg2 of COSMOS, which has relatively high spectroscopic completeness, and encompasses the CHILES VLA region. We define a combined r sources with reliable high-precision VLT-VIMOS spectra. All tables, spectra and imaging are available at http://ict.icrar.org/cutout/G10.

  17. 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

  18. Prediction of Catastrophes: an experimental model

    CERN Document Server

    Peters, Randall D; Pomeau, Yves

    2012-01-01

    Catastrophes of all kinds can be roughly defined as short duration-large amplitude events following and followed by long periods of "ripening". Major earthquakes surely belong to the class of 'catastrophic' events. Because of the space-time scales involved, an experimental approach is often difficult, not to say impossible, however desirable it could be. Described in this article is a "laboratory" setup that yields data of a type that is amenable to theoretical methods of prediction. Observations are made of a critical slowing down in the noisy signal of a solder wire creeping under constant stress. This effect is shown to be a fair signal of the forthcoming catastrophe in both of two dynamical models. The first is an "abstract" model in which a time dependent quantity drifts slowly but makes quick jumps from time to time. The second is a realistic physical model for the collective motion of dislocations (the Ananthakrishna set of equations for creep). Hope thus exists that similar changes in the response to ...

  19. Performance studies – the theory of catastrophes?

    Directory of Open Access Journals (Sweden)

    Konrad Wojnowski

    2014-01-01

    Full Text Available The author of Performatyka – teoria katastrof? [“Performance studies – the theory of catastrophes?”], which is a cross-sectional investigation into performance studies, tracks the trains of thought about catastrophes in different theories of performativity, ranging from J. L. Austin’s to Jon McKenzie’s ideas. Of particular interest is how particular theoreticians integrate the term ‘catastrophe’ into their conceptual frameworks and how they evaluate it. By criticizing the approach taken by Judith Butler, who postulates “melancholic performance studies”, which brings to mind Adorno’s idea that is explicated in Minima Moralia (traurige Wissenschaft, the author tries to show how we can productively use Austin’s theses that are presented in the first chapters of his famous How to Do Things with Words. In the author’s opinion, Austin allows us to approach communicational catastrophes from a different perspective, which is often forgotten, i.e. of the functioning of contextual systems. It is shown that the tension between felicity and infelicity may be at the core of the popularity of performativity which is understood as a tool for researching contemporary cultural phenomena.

  20. 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...

  1. The Supernova Legacy Survey 3-year sample: Type Ia Supernovae photometric distances and cosmological constraints

    CERN Document Server

    Guy, J; Conley, A; Regnault, N; Astier, P; Balland, C; Basa, S; Carlberg, R G; Fouchez, D; Hardin, D; Hook, I M; Howell, D A; Pain, R; Palanque-Delabrouille, N; Perrett, K M; Pritchet, C J; Rich, J; Ruhlmann-Kleider, V; Balam, D; Baumont, S; Ellis, R S; Fabbro, S; Fakhouri, H K; Fourmanoit, N; Gonzalez-Gaitan, S; Graham, M L; Hsiao, E; Kronborg, T; Lidman, C; Mourao, A M; Perlmutter, S; Ripoche, P; Suzuki, N; Walker, E S

    2010-01-01

    We present photometric properties and distance measurements of 252 high redshift Type Ia supernovae (0.15 < z < 1.1) discovered during the first three years of the Supernova Legacy Survey (SNLS). These events were detected and their multi-colour light curves measured using the MegaPrime/MegaCam instrument at the Canada-France-Hawaii Telescope (CFHT), by repeatedly imaging four one-square degree fields in four bands. Follow-up spectroscopy was performed at the VLT, Gemini and Keck telescopes to confirm the nature of the supernovae and to measure their redshifts. Systematic uncertainties arising from light curve modeling are studied, making use of two techniques to derive the peak magnitude, shape and colour of the supernovae, and taking advantage of a precise calibration of the SNLS fields. A flat LambdaCDM cosmological fit to 231 SNLS high redshift Type Ia supernovae alone gives Omega_M = 0.211 +/- 0.034(stat) +/- 0.069(sys). The dominant systematic uncertainty comes from uncertainties in the photometri...

  2. 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...

  3. Catastrophe theory and its application status in mechanical engineering

    Directory of Open Access Journals (Sweden)

    Jinge LIU

    Full Text Available Catastrophe theory is a kind of mathematical method which aims to apply and interpret the discontinuous phenomenon. Since its emergence, it has been widely used to explain a variety of emergent phenomena in the fields of natural science, social science, management science and some other science and technology fields. Firstly, this paper introduces the theory of catastrophe in several aspects, such as its generation, radical principle, basic characteristics and development. Secondly, it summarizes the main applications of catastrophe theory in the field of mechanical engineering, focusing on the research progress of catastrophe theory in revealing catastrophe of rotor vibration state, analyzing friction and wear failure, predicting metal fracture, and so on. Finally, it advises that later development of catastrophe theory should pay more attention to the combination of itself with other traditional nonlinear theories and methods. This paper provides a beneficial reference to guide the application of catastrophe theory in mechanical engineering and related fields for later research.

  4. Fire phenomena and nonlinearity (II). Catastrophic fire dynamics

    Energy Technology Data Exchange (ETDEWEB)

    Xie, Z. [University of Science and Technology, Hefei (China). State Key Laboratory of Fire Science

    2000-09-01

    As one of the most important non-linear mechanisms to cause fire or exacerbate fire disaster, there is a great deal of catastrophe behaviours existing in fire processes. The main tasks of the study of catastrophic fire dynamics are: 1) analysis of the catastrophe mechanisms of discontinuity behaviours in fire systems; 2) investigation of the controlling methods of discontinuity behaviours of fire system; 3) qualitative analysis of the dynamical characteristics of fire systems; and 4) catastrophe classifying of discontinuity phenomena in fire system. The other disciplines, such as physics, chemistry, biology, geoscience, astronomy, or even social sciences (for instance, political, economics, strategics and management science), may also take the similar method to establish the corresponding branch discipline of catastrophe science and catastrophe classification method. It is pointed out that an ignition behaviour of the uniform temperature thermal explosion system under the control of radiation has cusp catastrophe mechanism. 10 refs., 3 figs.

  5. The Southern Sky Redshift Survey

    Science.gov (United States)

    da Costa, L. Nicolaci; Willmer, C. N. A.; Pellegrini, P. S.; Chaves, O. L.; Rité, C.; Maia, M. A. G.; Geller, M. J.; Latham, D. W.; Kurtz, M. J.; Huchra, J. P.; Ramella, M.; Fairall, A. P.; Smith, C.; Lípari, S.

    1998-07-01

    We report redshifts, magnitudes, and morphological classifications for 5369 galaxies with m_B Complejo Astronomico El Leoncito, operated under agreement between the Consejo Nacional de Investigaciones Científicas de la República Argentina and the National Universities of La Plata, Córdoba, and San Juan; the European Southern Observatory, La Silla, Chile, partially under the bilateral ESO-Observatório Nacional agreement; Fred Lawrence Whipple Observatory; Laboratório Nacional de Astrofísica, Brazil; and the South African Astronomical Observatory.

  6. Redshift Properties of MASIV Sources

    Science.gov (United States)

    2010-06-01

    prerequisite. For optical identification we used mainly the Sloan Digital Sky Survey ( SDSS DR 5 Adelman-McCarthy et aJ. 2007) and GSC 2.3 (Lasker et...aJ. 2008). 165 sources werc identified from the SDSS DR5, which is complcte down to r=22.5 (Aef! rv6230A) with astrometric accuracy about (1.𔃻...than the SDSS . The new redshift were obtained using the 2.56 m Nordic Optical Telescope ·(NOT) which is locatcd at La Palma and the 5 m Palomar Hale

  7. High Redshift Gamma Ray Bursts

    Science.gov (United States)

    Gehrels, Neil

    2012-01-01

    The Swift Observatory has been detecting 100 gamma-ray bursts per year for 7 years and has greatly stimulated the field with new findings. Observations are made of the X-ray and optical afterglow from 1 minute after the burst, continuing for days. GRBs are providing a new tool to study the high redshift universe. Swift has detected several events at z>5 and one at z=9.4 giving information on metallicity, star formation rate and reionization. The talk will present the latest results.

  8. 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.

  9. 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.

  10. Redshift uncertainties and baryonic acoustic oscillations

    CERN Document Server

    Chaves-Montero, Jonás; Hernández-Monteagudo, Carlos

    2016-01-01

    In the upcoming era of high-precision galaxy surveys, it becomes necessary to understand the impact of uncertain redshift estimators on cosmological observables. In this paper we present a detailed exploration of the galaxy clustering and baryonic acoustic oscillation (BAO) signal under the presence of redshift errors. We provide analytic expressions for how the monopole and the quadrupole of the redshift-space power spectrum (together with their covariances) are affected. Additionally, we discuss the modifications in the shape, signal to noise, and cosmological constraining power of the BAO signature. We show how and why the BAO contrast is $\\mathit{enhanced}$ with small redshift uncertainties, and explore in detail how the cosmological information is modulated by the interplay of redshift-space distortions, redshift errors, and the number density of the sample. We validate our results by comparing them with measurements from a ensemble of $N$-body simulations with $8100h^{-3}\\text{Gpc}^3$ aggregated volume....

  11. Cosmological Parameters from Redshift-Space Correlations

    CERN Document Server

    Matsubara, T; Matsubara, Takahiko; Szalay, Alexander S.

    2002-01-01

    We estimate how clustering in large-scale redshift surveys can constrain various cosmological parameters. Depth and sky coverage of modern redshift surveys are greater than ever, opening new possibilities for statistical analysis. We have constructed a novel maximum likelihood technique applicable to deep redshift surveys of wide sky coverage by taking into account the effects of both curvature and linear velocity distortions. The Fisher information matrix is evaluated numerically to show the bounds derived from a given redshift sample. We find that intermediate-redshift galaxies, such as the Luminous Red Galaxies (LRGs) in the Sloan Digital Sky Survey, can constrain cosmological parameters, including the cosmological constant, unexpectedly well. The importance of the dense as well as deep sampling in designing redshift surveys is emphasized.

  12. The Advanced Camera for Surveys General Catalog: A High Redshift Galaxy Morphology Catalog

    Science.gov (United States)

    Griffith, Roger; Newman, J.; Cooper, M.; Stern, D.; Moustakas, L.; Davis, M.

    2009-05-01

    We use publicly available data obtained with the Advanced Camera for Surveys (ACS) instrument on the Hubble Space Telescope to construct the ACS General Catalog (ACS-GC). The ACS-GC includes over 370,000 astronomical sources (stars + galaxies) derived from the AEGIS, COSMOS, GEMS, and GOODS surveys. We include publicly available redshifts from the DEEP2, COMBO-17, TKRS, PEARS and zCOSMOS surveys to supply redshifts for a considerable fraction ( 52%) of the imaging sample. GALAPAGOS was used to construct photometric (SExtractor) and morphological (GALFIT) catalogs. The morphological analysis assumes a single Sersic model for each object to derive quantitative structural parameters. Galaxy Zoo will measure visual morphologies for 200,000 of these galaxies. The ACS-GC includes color images, GALFIT residual images, a galaxy atlas, and a photometry + morphology + redshift catalog. We use these data to investigate the size-redshift relationship for both early and late-type galaxies out to z 1. The entire data set will be made publicly available through the NASA Extragalactic Database (NED) and LEVEL5.

  13. 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.

  14. The Space Density of High-Redshift QSOs in the GOODS Survey

    CERN Document Server

    Cristiani, S; Bauer, F; Brandt, W N; Chatzichristou, E T; Fontanot, F; Grazian, A; Koekemoer, A M; Lucas, R A; Monaco, P; Nonino, M; Padovani, P; Stern, D; Tozzi, P; Treister, E; Urry, C M; Vanzella, E

    2004-01-01

    We present a sample of 17 high-redshift (3.5photometric redshifts we estimate that the final sample will contain between two and four QSOs with 4redshift, moderate-luminosity (M_{145}=~-23) QSOs is observed with respect to predictions based on a) the extrapolation of the z~2.7 luminosity function (LF), according to a pure luminosity evolution calibrated by the results of the Sloan Digital Sky Survey; and b) a constant universal efficiency in the formation of super-massive black holes (SMBHs) in dark-matter halos. Evidence is gathered in favor of a density evolution of the LF at high redshift and of a suppress...

  15. 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...

  16. The New Physics of Cosmic Redshift

    CERN Document Server

    Hebel, Wolfgang

    2011-01-01

    Light rays received on earth from distant stars show redshift, being attributed conventionally to the well-known Doppler-effect of wave dynamics. The present study concludes that cosmic redshift rather is an effect of the quantum mechanical propagation of photons as explained by Nobel Laureate Richard FEYNMAN in his book on QED {2}. This alternative physics of cosmic redshift is fundamentally different from the conventional velocity argument and can therefore do without the controversial big bang idea.

  17. Catastrophizing and symptoms of sleep disturbances in children.

    Science.gov (United States)

    Gregory, Alice M; Noone, Deirdre M; Eley, Thalia C; Harvey, Allison G

    2010-03-01

    Catastrophizing about sleeplessness is a cognitive process associated with sleep disturbance in adults. This study aimed to (1) examine whether children catastrophize about the consequences of not sleeping; (2) define the topics that children catastrophize about; (3) assess whether there is a link between catastrophizing and sleep disturbance in children; and (4) examine whether an association between catastrophizing and sleep in children is mediated by anxiety and depression symptoms. Children completed the sleep self-report and a catastrophizing interview. Testing took place in two inner-city schools in London, UK and participants comprised 123 children aged between 8 and 10 years (49% male). Thirty-four (28%) participants reported concerns in response to the catastrophizing questionnaire. The main topics being catastrophized were concerns about sleep, physiological issues and one's own emotions. Catastrophes predicted sleep disturbance after controlling for age and sex (beta = 0.35, P anxiety and depression symptoms (beta = 0.15, P = 0.106). Symptoms of anxiety (Sobel test = 3.30, P sleep. A proportion of children catastrophized about the consequences of sleeplessness and this was associated with sleep disturbance, an association which was mediated through anxiety and depression symptoms.

  18. COSMOLOGY WITH PHOTOMETRICALLY CLASSIFIED TYPE Ia SUPERNOVAE FROM THE SDSS-II SUPERNOVA SURVEY

    Energy Technology Data Exchange (ETDEWEB)

    Campbell, Heather; D' Andrea, Chris B; Nichol, Robert C.; Smith, Mathew; Lampeitl, Hubert [Institute of Cosmology and Gravitation, University of Portsmouth, Portsmouth, PO1 3FX (United Kingdom); Sako, Masao [Department of Physics and Astronomy, University of Pennsylvania, 209 South 33rd Street, Philadelphia, PA 19104 (United States); Olmstead, Matthew D.; Brown, Peter; Dawson, Kyle S. [Department of Physics and Astronomy, University of Utah, 115 South 1400 East 201, Salt Lake City, UT 84112 (United States); Bassett, Bruce [Mathematics Department, University of Cape Town, Rondebosch, Cape Town (South Africa); Biswas, Rahul; Kuhlmann, Steve [Argonne National Laboratory, 9700 South Cass Avenue, Lemont, IL 60439 (United States); Cinabro, David [Department of Physics and Astronomy, Wayne State University, Detroit, MI 48126 (United States); Dilday, Ben [Las Cumbres Observatory Global Telescope Network, 6740 Cortona Dr., Suite 102, Goleta, CA 93117 (United States); Foley, Ryan J. [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States); Frieman, Joshua A. [Department of Astronomy and Astrophysics, The University of Chicago, 5640 South Ellis Avenue, Chicago, IL 60637 (United States); Garnavich, Peter [Department of Physics, University of Notre Dame, Notre Dame, IN 46556 (United States); Hlozek, Renee [Department of Astrophysical Sciences, Princeton University, Princeton, NJ 08544 (United States); Jha, Saurabh W. [Department of Physics and Astronomy, Rutgers University, 136 Frelinghuysen Road, Piscataway, NJ 08854 (United States); Kunz, Martin, E-mail: Heather.Campbell@port.ac.uk [African Institute for Mathematical Sciences, Muizenberg, 7945, Cape Town (South Africa); and others

    2013-02-15

    We present the cosmological analysis of 752 photometrically classified Type Ia Supernovae (SNe Ia) obtained from the full Sloan Digital Sky Survey II (SDSS-II) Supernova (SN) Survey, supplemented with host-galaxy spectroscopy from the SDSS-III Baryon Oscillation Spectroscopic Survey. Our photometric-classification method is based on the SN classification technique of Sako et al., aided by host-galaxy redshifts (0.05 < z < 0.55). SuperNova ANAlysis simulations of our methodology estimate that we have an SN Ia classification efficiency of 70.8%, with only 3.9% contamination from core-collapse (non-Ia) SNe. We demonstrate that this level of contamination has no effect on our cosmological constraints. We quantify and correct for our selection effects (e.g., Malmquist bias) using simulations. When fitting to a flat {Lambda}CDM cosmological model, we find that our photometric sample alone gives {Omega} {sub m} = 0.24{sup +0.07} {sub -0.05} (statistical errors only). If we relax the constraint on flatness, then our sample provides competitive joint statistical constraints on {Omega} {sub m} and {Omega}{sub {Lambda}}, comparable to those derived from the spectroscopically confirmed Three-year Supernova Legacy Survey (SNLS3). Using only our data, the statistics-only result favors an accelerating universe at 99.96% confidence. Assuming a constant wCDM cosmological model, and combining with H {sub 0}, cosmic microwave background, and luminous red galaxy data, we obtain w = -0.96{sup +0.10} {sub -0.10}, {Omega} {sub m} = 0.29{sup +0.02} {sub -0.02}, and {Omega} {sub k} = 0.00{sup +0.03} {sub -0.02} (statistical errors only), which is competitive with similar spectroscopically confirmed SNe Ia analyses. Overall this comparison is reassuring, considering the lower redshift leverage of the SDSS-II SN sample (z < 0.55) and the lack of spectroscopic confirmation used herein. These results demonstrate the potential of photometrically classified SN Ia samples in improving

  19. 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.

  20. Asteroid taxonomic signatures from photometric phase curves

    CERN Document Server

    Oszkiewicz, D A; Wasserman, L H; Muinonen, K; Penttilä, A; Pieniluoma, T; Trilling, D E; Thomas, C A

    2012-01-01

    We explore the correlation between an asteroid's taxonomy and photometric phase curve using the H, G12 photometric phase function, with the shape of the phase function described by the single parameter G12. We explore the usability of G12 in taxonomic classification for individual objects, asteroid families, and dynamical groups. We conclude that the mean values of G12 for the considered taxonomic complexes are statistically different, and also discuss the overall shape of the G12 distribution for each taxonomic complex. Based on the values of G12 for about half a million asteroids, we compute the probabilities of C, S, and X complex membership for each asteroid. For an individual asteroid, these probabilities are rather evenly distributed over all of the complexes, thus preventing meaningful classification. We then present and discuss the G12 distributions for asteroid families, and predict the taxonomic complex preponderance for asteroid families given the distribution of G12 in each family. For certain ast...

  1. A Photometric Search for Extrasolar Planets

    Science.gov (United States)

    Howell, S. B.; Everett, M.; Davis, D. R.; Weidenschilling, S. J.; McGruder, C. H., III; Gelderman, R.

    2000-10-01

    We describe a new program for the photometric detection of extrasolar planets using the 1.3 m telescope on Kitt Peak, which will be operated by a consortium of universities headed by Western Kentucky Univ. and including South Carolina State Univ., Planetary Science Institute, Boston Univ., and UC-Berkeley (SSL). This approach will complement the existing, highly successful, spectroscopic searches. The theory of photometric transit detection has been discussed by a number of authors (e.g. Borucki & Summers 1984; Howell & Merline 1995; Howell et al. 1996) and shown to be well within the capabilities of both photomultiplier and CCD observations. The first photometric transit detection was recently accomplished for the spectroscopically discovered planet orbiting HD209458 (Henry et al. 2000). The detection of extrasolar planet transits requires high photometric precision rather than accuracy. The necessary photometric precision to detect Jupiter-, Neptune-, and Earth-sized planets in orbit around F-M dwarfs is 1%, 0.1% and 0.00001%, respectively. The required precision to observe transits by Jupiter-sized extrasolar planets is easily obtained with modern CCD detectors and the differential ensemble photometric techniques pioneered by Howell et al. (1988). The use of such a technique for ultra-high precision photometry has been described in numerous papers (Charbonneau et al. 2000, Howell 2000, plus many others). Everett and Howell recently used the Kitt Peak NOAO 0.9 m telescope with the wide-field MOSAIC camera to search for extrasolar planet transits. During this run, they achieved a photometric precision of 0.024% for this dataset. With the 1.3 m telescope, we expect to reach a photometric precision of ~ 0.01% (10-4 mag). Our consortium has recently begun to refurbish and automate the 1.3 m telescope, which will be known as the Remote-Controlled Telescope (RCT). The primary instrument will be a CCD camera with a SITe 2048 x 2048 CCD having pixel well depths of 363

  2. Measurement of photometric characteristics of daylighting systems

    Energy Technology Data Exchange (ETDEWEB)

    Aydinli, S.; Kaase, H. [Technical Univ., Berlin (Germany); Kischkoweit-Lopin, M. [Institut fuer Licht- und Bautechnik an der FH Koln, Cologne (Germany); Scartezzini, J. L.; Michel, L. [Ecole Poytechnuque Federale de Lausanne (Switzerland); Wienold, J.; Apian-Bennewitz, P. [Frauenhofer Institute for Solar Energy Systems, Freiburg (Germany)

    1998-09-01

    The photometric properties of daylighting systems determine the quality of the daylighting in the interior of a building, as well as the possible energy savings by the daylight responsive artificial lighting control systems. Photometric characteristics of daylighting systems and the principles of their measurements in laboratory facilities are described. Characteristics that depend on light incidence and observation of radiation can be measured using integrating sphere photometers or goniophotometers. Luminous transmittance measurements are usually carried out using integrating sphere photometers (cheaper and less time -consuming than measurements with a goniometer). Although the principles involved in the measurement are well understood, results frequently show certain deviations. The various errors that might be responsible for these deviations, whether attributable to the method, or the instrument, or the sample, are also discussed. 10 refs., 8 figs.

  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. Bladder Pneumatosis From a Catastrophic Vascular Event

    Directory of Open Access Journals (Sweden)

    Ian J. Cooke

    2016-09-01

    Full Text Available Air within the bladder wall, or bladder pneumatosis, is a very rare finding typically resulting from an infectious etiology, as in emphysematous cystitis (EC. However, there have been reports of bladder pneumatosis occurring without clear infectious origins. We present a case of a female patient found to have concurrent bladder and ileal pneumatosis secondary to a catastrophic vascular event. Prompt recognition of non-infectious etiologies of bladder pneumatosis is essential as this distinction may dramatically alter clinical decision-making.

  5. Catastrophic volcanic collapse: relation to hydrothermal processes.

    Science.gov (United States)

    López, D L; Williams, S N

    1993-06-18

    Catastrophic volcanic collapse, without precursory magmatic activity, is characteristic of many volcanic disasters. The extent and locations of hydrothermal discharges at Nevado del Ruiz volcano, Colombia, suggest that at many volcanoes collapse may result from the interactions between hydrothermal fluids and the volcanic edifice. Rock dissolution and hydrothermal mineral alteration, combined with physical triggers such as earth-quakes, can produce volcanic collapse. Hot spring water compositions, residence times, and flow paths through faults were used to model potential collapse at Ruiz. Caldera dimensions, deposits, and alteration mineral volumes are consistent with parameters observed at other volcanoes.

  6. Photometric defocus observations of transiting extrasolar planets

    CERN Document Server

    Hinse, Tobias C; Yoon, Jo-Na; Lee, Chung-Uk; Kim, Yong-Gi; Kim, Chun-Hwey

    2015-01-01

    We have carried out photometric follow-up observations of bright transiting extrasolar planets using the CbNUOJ 0.6m telescope. We have tested the possibility of obtaining high photometric precision by applying the telescope defocus technique allowing the use of several hundred seconds in exposure time for a single measurement. We demonstrate that this technique is capable of obtaining a root-mean-square scatter of order sub-millimagnitude over several hours for a V $\\sim$ 10 host star typical for transiting planets detected from ground-based survey facilities. We compare our results with transit observations with the telescope operated in in-focus mode. High photometric precision is obtained due to the collection of a larger amount of photons resulting in a higher signal compared to other random and systematic noise sources. Accurate telescope tracking is likely to further contribute to lowering systematic noise by probing the same pixels on the CCD. Furthermore, a longer exposure time helps reducing the eff...

  7. A Blind Test of Hapke's Photometric Model

    Science.gov (United States)

    Helfenstein, P.; Shepard, M. K.

    2003-01-01

    Hapke's bidirectional reflectance equation is a versatile analytical tool for predicting (i.e. forward modeling) the photometric behavior of a particulate surface from the observed optical and structural properties of its constituents. Remote sensing applications of Hapke s model, however, generally seek to predict the optical and structural properties of particulate soil constituents from the observed photometric behavior of a planetary surface (i.e. inverse-modeling). Our confidence in the latter approach can be established only if we ruthlessly test and optimize it. Here, we summarize preliminary results from a blind-test of the Hapke model using laboratory measurements obtained with the Bloomsburg University Goniometer (B.U.G.). The first author selected eleven well-characterized powder samples and measured the spectrophotometric behavior of each. A subset of twenty undisclosed examples of the photometric measurement sets were sent to the second author who fit the data using the Hapke model and attempted to interpret their optical and mechanical properties from photometry alone.

  8. Measurements of the Rate of Type Ia Supernovae at Redshift z < ~0.3 from the SDSS-II Supernova Survey

    CERN Document Server

    Dilday, Benjamin; Bassett, Bruce; Becker, Andrew; Bender, Ralf; Castander, Francisco; Cinabro, David; Filippenko, Alexei V; Frieman, Joshua A; Galbany, Lluis; Garnavich, Peter M; Goobar, Ariel; Hopp, Ulrich; Ihara, Yutaka; Jha, Saurabh W; Kessler, Richard; Lampeitl, Hubert; Marriner, John; Miquel, Ramon; Molla, Mercedes; Nichol, Robert C; Nordin, Jakob; Riess, Adam G; Sako, Masao; Schneider, Donald P; Sollerman, Jesper; Wheeler, J Craig; Ostman, Linda; Bizyaev, Dmitry; Brewington, Howard; Malanushenko, Elena; Malanushenko, Viktor; Oravetz, Dan; Pan, Kaike; Simmons, Audrey; Snedden, Stephanie

    2010-01-01

    We present a measurement of the volumetric Type Ia supernova (SN Ia) rate based on data from the Sloan Digital Sky Survey II (SDSS-II) Supernova Survey. The adopted sample of supernovae (SNe) includes 516 SNe Ia at redshift z \\lesssim 0.3, of which 270 (52%) are spectroscopically identified as SNe Ia. The remaining 246 SNe Ia were identified through their light curves; 113 of these objects have spectroscopic redshifts from spectra of their host galaxy, and 133 have photometric redshifts estimated from the SN light curves. Based on consideration of 87 spectroscopically confirmed non-Ia SNe discovered by the SDSS-II SN Survey, we estimate that 2.04+1.61-0.95 % of the photometric SNe Ia may be misidentified. The sample of SNe Ia used in this measurement represents an order of magnitude increase in the statistics for SN Ia rate measurements in the redshift range covered by the SDSS-II Supernova Survey. If we assume a SN Ia rate that is constant at low redshift (z < 0.15), then the SN observations can be used t...

  9. Changing universe model of redshift

    CERN Document Server

    Hodge, J C

    2004-01-01

    The changing universe model (CUM) describes galaxy parameter relationships (SESAPS '03, session EB 2). The CUM must be successfully applied to cosmological scale observations to be considered a cosmological model. A major component of current cosmological models is the Hubble constant $H_\\mathrm{o}$. An equation is derived using the CUM model relating redshift $z$ and the distance $D$ to galaxies and is applied to a sample of 32 spiral galaxies with $D$ calculated using Cepheid variable stars. The equation predicts a galaxy may have $z<0$ in special circumstances. Three elliptical galaxies with peculiar characteristics are discovered to be CUM Sinks. The Sinks give a physical explanation of the ``Virgocentric infall'' and ``Great Attractor'' observations without a large, unobserved mass. At low cosmological distances, the equation reduces to $z \\approx \\exp(KD) -1 \\approx KD$, where $K$ is a constant, positive value. The equation predicts $z$ from galaxies over 23 Gpc distant approaches a constant value on...

  10. Lost Baryons at Low Redshift

    CERN Document Server

    Mathur, Smita; Williams, Rik J

    2007-01-01

    We review our attempts to discover lost baryons at low redshift with ``X-ray forest'' of absorption lines from the warm-hot intergalactic medium. We discuss the best evidence to date along the Mrk 421 sightline. We then discuss the missing baryons in the Local Group and the significance of the z=0 absorption systems in X-ray spectra. We argue that the debate over the Galactic vs. extragalactic origin of the z=0 systems is premature as these systems likely contain both components. Observations with next generation X-ray missions such as Constellation-X and XEUS will be crucial to map out the warm-hot intergalactic medium.

  11. Element abundances at high redshift

    Energy Technology Data Exchange (ETDEWEB)

    Meyer, D.M.; Welty, D.E.; York, D.G. (Northwestern Univ., Evanston, IL (USA); Chicago Univ., IL (USA))

    1989-08-01

    Abundances of Si(+), S(+), Cr(+), Mn(+), Fe( ), and Zn(+) are considered for two absorption-line systems in the spectrum of the QSO PKS 0528 - 250. Zinc and sulfur are underabundant, relative to H, by a factor of 10 compared to their solar and Galactic interstellar abundances. The silicon-, chromium-, iron-, and nickel-to-hydrogen ratios are less than the solar values and comparable to the local interstellar ratios. A straightforward interpretation is that nucleosynthesis in these high-redshift systems has led to only about one-tenth as much heavy production as in the gas clouds around the sun, and that the amount of the observed underabundances attributable to grain depletion is small. The dust-to-gas ratio in these clouds is less than 8 percent of the Galactic value. 25 refs.

  12. Element abundances at high redshift

    Science.gov (United States)

    Meyer, David M.; Welty, D. E.; York, D. G.

    1989-01-01

    Abundances of Si(+), S(+), Cr(+), Mn(+), Fe(_), and Zn(+) are considered for two absorption-line systems in the spectrum of the QSO PKS 0528 - 250. Zinc and sulfur are underabundant, relative to H, by a factor of 10 compared to their solar and Galactic interstellar abundances. The silicon-, chromium-, iron-, and nickel-to-hydrogen ratios are less than the solar values and comparable to the local interstellar ratios. A straightforward interpretation is that nucleosynthesis in these high-redshift systems has led to only about one-tenth as much heavy production as in the gas clouds around the sun, and that the amount of the observed underabundances attributable to grain depletion is small. The dust-to-gas ratio in these clouds is less than 8 percent of the Galactic value.

  13. Multiple Sclerosis and Catastrophic Health Expenditure in Iran

    Science.gov (United States)

    Juyani, Yaser; Hamedi, Dorsa; Hosseini Jebeli, Seyede Sedighe; Qasham, Maryam

    2016-01-01

    Background: There are many disabling medical conditions which can result in catastrophic health expenditure. Multiple Sclerosis is one of the most costly medical conditions through the world which encounter families to the catastrophic health expenditures. This study aims to investigate on what extent Multiple sclerosis patients face catastrophic costs. Method: This study was carried out in Ahvaz, Iran (2014). The study population included households that at least one of their members suffers from MS. To analyze data, Logit regression model was employed by using the default software STATA12. Results: 3.37% of families were encountered with catastrophic costs. Important variables including brand of drug, housing, income and health insurance were significantly correlated with catastrophic expenditure. Conclusions: This study suggests that although a small proportion of MS patients met the catastrophic health expenditure, mechanisms that pool risk and cost (e.g. health insurance) are required to protect them and improve financial and access equity in health care.

  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. Gamma-ray bursts at high redshift

    NARCIS (Netherlands)

    R.A.M.J. Wijers

    1999-01-01

    Gamma-ray bursts are much brighter than supernovae, and could therefore possibly probe the Universe to high redshift. The presently established GRB redshifts range from 0.83 to 5, and quite possibly even beyond that. Since most proposed mechanisms for GRB link them closely to deaths of massive stars

  16. High Redshift Lyman-α Hunt

    DEFF Research Database (Denmark)

    Kochiashvili, Ia

    constitute the backbone of thisthesis, I investigated the nature of almost 100 emission-line galaxies selected with thenarrow-band selection method. These candidates can be: galaxies with Hα emissionlines at redshift z ∼ 0.6, [Oiii]/Hβ emission-line galaxies at redshift z ∼ 1.15 and [Oii]emitters at z ∼ 1...

  17. Structure and substructure analysis of DAFT/FADA galaxy clusters in the [0.4–0.9] redshift range

    Energy Technology Data Exchange (ETDEWEB)

    Guennou, L.; et al.

    2014-01-17

    Context. The DAFT/FADA survey is based on the study of ~90 rich(masses found in the literature >2 x 10^14 M_⊙)and moderately distant clusters (redshifts 0.4 < z < 0.9), all withHST imaging data available. This survey has two main objectives: to constrain dark energy(DE) using weak lensing tomography on galaxy clusters and to build a database (deepmulti-band imaging allowing photometric redshift estimates, spectroscopic data, X-raydata) of rich distant clusters to study their properties.

  18. Personality and temperament correlates of pain catastrophizing in young adolescents

    OpenAIRE

    Muris, Peter; Meesters, Cor; van den Hout, Mari F. C. M.; Wessels, Sylvia; Franken, Ingmar; Rassin, Eric

    2007-01-01

    textabstractPain catastrophizing is generally viewed as an important cognitive factor underlying chronic pain. The present study examined personality and temperament correlates of pain catastrophizing in a sample of young adolescents (N = 132). Participants completed the Pain Catastrophizing Scale for Children, as well as scales for measuring sensitivity of the behavioral inhibition and behavioral activation systems (BIS-BAS), and various reactive and regulative temperament traits. Results de...

  19. 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.

  20. 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.

  1. Inside money, procyclical leverage, and banking catastrophes.

    Directory of Open Access Journals (Sweden)

    Charles D Brummitt

    Full Text Available 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.

  2. 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.

  3. 5. Nonmalignant diseases after the Chernobyl catastrophe.

    Science.gov (United States)

    Yablokov, Alexey V

    2009-11-01

    This section describes the spectrum and the scale of the nonmalignant diseases that have been found among exposed populations. Adverse effects as a result of Chernobyl irradiation have been found in every group that has been studied. Brain damage has been found in individuals directly exposed--liquidators and those living in the contaminated territories, as well as in their offspring. Premature cataracts; tooth and mouth abnormalities; and blood, lymphatic, heart, lung, gastrointestinal, urologic, bone, and skin diseases afflict and impair people, young and old alike. Endocrine dysfunction, particularly thyroid disease, is far more common than might be expected, with some 1,000 cases of thyroid dysfunction for every case of thyroid cancer, a marked increase after the catastrophe. There are genetic damage and birth defects especially in children of liquidators and in children born in areas with high levels of radioisotope contamination. Immunological abnormalities and increases in viral, bacterial, and parasitic diseases are rife among individuals in the heavily contaminated areas. For more than 20 years, overall morbidity has remained high in those exposed to the irradiation released by Chernobyl. One cannot give credence to the explanation that these numbers are due solely to socioeconomic factors. The negative health consequences of the catastrophe are amply documented in this chapter and concern millions of people.

  4. The kinematic component of the cosmological redshift

    CERN Document Server

    Chodorowski, Michał

    2009-01-01

    It is widely believed that the cosmological redshift is not a Doppler shift. However, Bunn & Hogg have recently pointed out that to settle properly this problem, one has to transport parallelly the velocity four-vector of a distant galaxy to the observer's position. Performing such a transport along the null geodesic of photons arriving from the galaxy, they found that the cosmological redshift is purely kinematic. Here we argue that one should rather transport the velocity four-vector along the geodesic connecting the points of intersection of the world-lines of the galaxy and the observer with the hypersurface of constant COSMIC TIME. We find that the resulting relation between the transported velocity and the redshift of arriving photons is NOT given by a relativistic Doppler formula. Instead, for small redshifts it coincides with the well known non-relativistic decomposition of the redshift into a Doppler (kinematic) component and a gravitational component. We perform such a decomposition for arbitrar...

  5. Real-time cosmography with redshift derivatives

    CERN Document Server

    Martins, C J A P; Calabrese, E; Ramos, M P L P

    2016-01-01

    The drift in the redshift of objects passively following the cosmological expansion has long been recognized as a key model-independent probe of cosmology. Here, we study the cosmological relevance of measurements of time or redshift derivatives of this drift, arguing that the combination of first and second redshift derivatives is a powerful test of the $\\Lambda$CDM cosmological model. In particular, the latter can be obtained numerically from a set of measurements of the drift at different redshifts. We show that, in the low-redshift limit, a measurement of the derivative of the drift can provide a constraint on the jerk parameter, which is $j=1$ for flat $\\Lambda$CDM, while generically $j\

  6. Origin of redshift asymmetries: How LambdaCDM explains anomalous redshift

    CERN Document Server

    Niemi, Sami-Matias

    2008-01-01

    Several authors have found a statistically significant excess of galaxies with higher redshifts relative to the group centre, so called discordant redshifts, in particular in groups where the brightest galaxy, identified in apparent magnitudes, is a spiral. Our aim is to explain the observed redshift excess. We use a semi-analytical galaxy catalogue constructed from the Millennium Simulation to study redshift asymmetries in spiral-dominated groups in the Lambda cold dark matter (LambdaCDM) cosmology. We show that discordant redshifts in small galaxy groups arise when these groups are gravitationally unbound and the dominant galaxy of the group is misidentified. The redshift excess is especially significant when the apparently brightest galaxy can be identified as a spiral, in full agreement with observations. On the other hand, the groups that are gravitationally bound do not show a significant redshift asymmetry. When the dominant members of groups in mock catalogues are identified by using the absolute B-ba...

  7. A Photometrically Selected Galaxy Cluster Catalog from the SDSS DR4

    Science.gov (United States)

    Koester, B. P.; McKay, T. A.; Evrard, A. E.; Becker, M.; Bleem, L.; Annis, J.; Wechsler, R. H.; Sheldon, E. S.; Johnston, D.; Scranton, R.; Miller, C. J.; Nichol, R. C.

    2005-12-01

    We present an overview of a new BCG/red-sequence galaxy cluster catalog drawn from the Data Release 4 sample of Sloan Digital Sky Survey imaging. Galaxy clusters are selected by calculating the likelihood that each observed galaxy is a brightest cluster galaxy based on its color and magnitude, along with the degree to which galaxies cluster around it in color, magnitude, and space. This method provides a list of cluster locations together with estimates of their total galaxy content and accurate photometric redshifts (σ z X-ray clusters, optically-selected clusters, and massive halos in mock galaxy catalogs with a low false-positive rate. Further details of the cluster finding algorithm and its performance, together with a description of the properties of the derived catalog will be presented.

  8. The VIMOS Public Extragalactic Redshift Survey (VIPERS). Never mind the gaps: comparing techniques to restore homogeneous sky coverage

    CERN Document Server

    Cucciati, O; Branchini, E; Marulli, F; Iovino, A; Moscardini, L; Bel, J; Cappi, A; Peacock, J A; de la Torre, S; Bolzonella, M; Guzzo, L; Polletta, M; Fritz, A; Adami, C; Bottini, D; Coupon, J; Davidzon, I; Franzetti, P; Fumana, M; Garilli, B; Krywult, J; Malek, K; Paioro, L; Pollo, A; Scodeggio, M; Tasca, L A M; Vergani, D; Zanichelli, A; Di Porto, C; Zamorani, G

    2014-01-01

    [Abridged] Non-uniform sampling and gaps in sky coverage are common in galaxy redshift surveys but these effects can degrade galaxy counts-in-cells and density estimates. We carry out a comparison of methods that aim to fill the gaps to correct for the systematic effects. Our study is motivated by the analysis of the VIMOS Extragalactic Redshift Survey (VIPERS), a flux-limited survey (i<22.5) based on one-pass observations with VIMOS, with gaps covering 25% of the surveyed area and a mean sampling rate of 35%. Our findings are applicable to other surveys with similar observing strategies. We compare 1) two algorithms based on photometric redshift, that assign redshifts to galaxies based on the spectroscopic redshifts of the nearest neighbours, 2) two Bayesian methods, the Wiener filter and the Poisson-Lognormal filter. Using galaxy mock catalogues we quantify the accuracy of the counts-in-cells measurements on scales of R=5 and 8 Mpc/h after applying each of these methods. We also study how they perform to...

  9. Scalar potential model of redshift and discrete redshift

    CERN Document Server

    Hodge, J C

    2006-01-01

    On the galactic scale the universe is inhomogeneous and redshift $z$ is occasionally less than zero. A scalar potential model (SPM) that links the galaxy scale $z$ to the cosmological scale $z$ of the Hubble Law is postulated. Several differences among galaxy types suggest that spiral galaxies are Sources and that early type, lenticular, and irregular galaxies are Sinks of a scalar potential field. The morphology-radius and the intragalactic medium cluster observations support the movement of matter from Source galaxies to Sink galaxies. A cell structure of galaxy groups and clusters is proposed to resolve a paradox concerning the scalar potential like the Olber's paradox concerning light. For the sample galaxies, the ratio of the luminosity of Source galaxies to the luminosity of Sink galaxies approaches $2.7 \\pm 0.1$. An equation is derived from sample data, which is anisotropic and inhomogeneous, relating $z$ of and the distance $D$ to galaxies. The calculated $z$ has a correlation coefficient of 0.88 with...

  10. 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

  11. MagAl: A new tool to analyse galaxies photometric data

    Science.gov (United States)

    Schoenell, W.; Benítez, N.; Cid Fernandes, R.

    2014-10-01

    On galaxy spectra, one can find mainly two features: emission lines, which tell us about the ionised gas content, and the continuum plus absorption lines, which tell us about the stellar content. They thus allow us to derive gas-phase abundances, the main radiation sources, chemical enrichment and star formation histories. Braad-band photometry, on the other hand, is much more limited and hinders our ability to recover a galaxy's physical properties to such a degree of detail. However, with the recent development of redshift surveys using the technology of ultra-narrow filters (≍ 100 Å), such as ALHAMBRA, J-PAS and DES, it will be invaluable to be able to retrieve information on physical properties of galaxies from photometric data. Motivated by this data avalanche (which goes up to the petabyte scale), we decided to build our own SED-fitting code: Magnitudes Analyser (MagAl), which has three modules. 1) A template library generation module: generates empirical and theoretical template libraries. 2) Bayesian fitting module: calculates probability distribution functions (PDFs) for given observed and library template data. This is similar to the method to measure photometric redshifts by Benitez (2000). 3) A result-analyser module: streamlines data analysis from the large output PDFs files. A fourth module to manage 3D data is being developed and a few preliminary tests are also shown. To investigate the reliability of results obtained by MagAl, we have created a mock galaxy sample for the ALHAMBRA survey filter system (http://alhambrasurvey.com) and tried to recover their physical properties. We show that for our sample of simulated galaxies we can measure stellar ages, metallicities and extinctions with a precision of less than 0.3 dex. Also, we apply the code to the ALHAMBRA survey catalog and show that we can measure stellar masses with an accuracy of 0.2 dex when comparing to previous results like COSMOS masses measured by Bundy et al. (2006).

  12. Characterization and Modeling of Contamination for Lyman Break Galaxy Samples at High Redshift

    Science.gov (United States)

    Vulcani, Benedetta; Trenti, Michele; Calvi, Valentina; Bouwens, Rychard; Oesch, Pascal; Stiavelli, Massimo; Franx, Marijn

    2017-02-01

    The selection of high-redshift sources from broadband photometry using the Lyman-break galaxy (LBG) technique is a well established methodology, but the characterization of its contamination for the faintest sources is still incomplete. We use the optical and near-IR data from four (ultra)deep Hubble Space Telescope legacy fields to investigate the contamination fraction of LBG samples at z∼ 5{--}8 selected using a color–color method. Our approach is based on characterizing the number count distribution of interloper sources, that is, galaxies with colors similar to those of LBGs, but showing detection at wavelengths shorter than the spectral break. Without sufficient sensitivity at bluer wavelengths, a subset of interlopers may not be properly classified, and contaminate the LBG selection. The surface density of interlopers in the sky gets steeper with increasing redshift of LBG selections. Since the intrinsic number of dropouts decreases significantly with increasing redshift, this implies increasing contamination from misclassified interlopers with increasing redshift, primarily by intermediate redshift sources with unremarkable properties (intermediate ages, lack of ongoing star formation and low/moderate dust content). Using Monte-Carlo simulations, we estimate that the CANDELS deep data have contamination induced by photometric scatter increasing from ∼ 2 % at z∼ 5 to ∼ 6 % at z∼ 8 for a typical dropout color ≥slant 1 mag, with contamination naturally decreasing for a more stringent dropout selection. Contaminants are expected to be located preferentially near the detection limit of surveys, ranging from 0.1 to 0.4 contaminants per arcmin2 at {J}125 = 30, depending on the field considered. This analysis suggests that the impact of contamination in future studies of z> 10 galaxies needs to be carefully considered.

  13. Understanding the dark matter-light connection at high redshifts

    Science.gov (United States)

    Lee, Kyoung-Soo

    Deep, wide-field surveys have enhanced our understanding of galaxy formation and its close connection to the large-scale structures of dark matter in the universe. At high redshifts ( z > 2), in particular, where it is not possible to observe dark matter structures in other methods such as gravitational lensing or galaxy rotation curves, study of galaxy clustering provides a unique view into the formation of galaxies in large look-back times. In this thesis, I present a clustering study of star-forming galaxies at high redshifts ( z ~ 3- 5), observed and selected from two of the deepest multi-wavelength photometric data to date. First, I show that the UV luminosity (or star formation rate) of these galaxies scales closely with the degree of spatial clustering at all cosmic epochs probed from these surveys. In conjunction with the current, well- established theoretical framework of cold dark matter cosmology, this implies that star formation rate is primarily determined by the total mass of the virialized dark matter structures, or dark matter halos. In addition, I show that the measures of galaxy correlation function exhibits a strong upturn on small scales, which cannot be explained with the clustering of halos hosting these galaxies alone. This strongly suggests that multiple galaxies can share a single massive dark matter halo. A simple scaling law between the number of galaxy occupants and halo mass is sufficient to successfully reproduce the observed shape of the correlation function. However, there is uncertainty in drawing physical parameters of the halo-galaxy association which depends on the assumed form of the scaling law, or the halo occupation distribution (HOD). Physical interpretations are further exacerbated by the unknown degree of "fairness" that color-selected galaxies represent. I present an alternative approach which requires precise measurements of both the luminosity function and correlation function (of various luminosity thresholds). By

  14. IONIZED NITROGEN AT HIGH REDSHIFT

    Energy Technology Data Exchange (ETDEWEB)

    Decarli, R.; Walter, F. [Max-Planck Institut fuer Astronomie, Koenigstuhl 17, D-69117 Heidelberg (Germany); Neri, R.; Cox, P. [IRAM, 300 rue de la piscine, F-38406 Saint-Martin d' Heres (France); Bertoldi, F. [Argelander Institute for Astronomy, University of Bonn, Auf dem Huegel 71, D-53121 Bonn (Germany); Carilli, C. [NRAO, Pete V. Domenici Array Science Center, P.O. Box O, Socorro, NM 87801 (United States); Kneib, J. P. [Laboratoire d' Astrophysique de Marseille, Observatoire d' Astronomie Marseille-Provence, BP 8, F-13376 Marseille (France); Lestrade, J. F. [Observatoire de Paris, CNRS, 61 Av. de l' Observatoire, F-75014 Paris (France); Maiolino, R. [INAF-Osservatorio Astronomico di Roma, via di Frascati 33, I-00040 Monte Porzio Catone (Italy); Omont, A. [Institut d' Astrophysique de Paris, UPMC and CNRS, 98bis Bld. Arago, F-75014 Paris (France); Richard, J. [CRAL, Observatoire de Lyon, Universite Lyon 1, 9 Avenue Ch. Andre, F-69561 Saint Genis Laval Cedex (France); Riechers, D. [Astronomy Department, Caltech, 1200 East California Boulevard, Pasadena, CA 91125 (United States); Thanjavur, K. [Canada-France-Hawaii Telescope Corporation, HI 96743 (United States); Weiss, A., E-mail: decarli@mpia.de [Max-Planck-Institut fuer Radioastronomie, Auf dem Huegel 69, D-53121 Bonn (Germany)

    2012-06-10

    We present secure [N II]{sub 205{mu}m} detections in two millimeter-bright, strongly lensed objects at high redshift, APM 08279+5255 (z = 3.911) and MM 18423+5938 (z = 3.930), using the IRAM Plateau de Bure Interferometer. Due to its ionization energy [N II]{sub 205{mu}m} is a good tracer of the ionized gas phase in the interstellar medium. The measured fluxes are S([N II]{sub 205{mu}m}) = (4.8 {+-} 0.8) Jy km s{sup -1} and (7.4 {+-} 0.5) Jy km s{sup -1}, respectively, yielding line luminosities of L([N II]{sub 205{mu}m}) = (1.8 {+-} 0.3) Multiplication-Sign 10{sup 9} {mu}{sup -1} L{sub Sun} for APM 08279+5255 and L([N II]{sub 205{mu}m}) = (2.8 {+-} 0.2) Multiplication-Sign 10{sup 9} {mu}{sup -1} L{sub Sun} for MM 18423+5938. Our high-resolution map of the [N II]{sub 205{mu}m} and 1 mm continuum emission in MM 18423+5938 clearly resolves an Einstein ring in this source and reveals a velocity gradient in the dynamics of the ionized gas. A comparison of these maps with high-resolution EVLA CO observations enables us to perform the first spatially resolved study of the dust continuum-to-molecular gas surface brightness ({Sigma}{sub FIR}{proportional_to}{Sigma}{sup N}{sub CO}, which can be interpreted as the star formation law) in a high-redshift object. We find a steep relation (N = 1.4 {+-} 0.2), consistent with a starbursting environment. We measure a [N II]{sub 205{mu}m}/FIR luminosity ratio in APM 08279+5255 and MM 18423+5938 of 9.0 Multiplication-Sign 10{sup -6} and 5.8 Multiplication-Sign 10{sup -6}, respectively. This is in agreement with the decrease of the [N II]{sub 205{mu}m}/FIR ratio at high FIR luminosities observed in local galaxies.

  15. Quest for COSMOS submillimeter galaxy counterparts using CARMA and VLA: Identifying three high-redshift starburst galaxies

    CERN Document Server

    Smolcic, V; Aravena, M; Ilbert, O; Yun, M S; Sheth, K; Salvato, M; McCracken, H J; Diener, C; Aretxaga, I; Riechers, D A; Finoguenov, A; Bertoldi, F; Capak, P; Hughes, D; Karim, A; Schinnerer, E; Scoville, N Z; Wilson, G

    2012-01-01

    We report on interferometric observations at 1.3 mm at 2"-3" resolution using the Combined Array for Research in Millimeter-wave Astronomy (CARMA). We identify multi-wavelength counterparts of three submillimeter galaxies (SMGs; F(1mm)>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 that further 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-red...

  16. The Luminosity Function of Low-Redshift Abell Galaxy Clusters

    CERN Document Server

    Barkhouse, Wayne A; López-Cruz, Omar

    2007-01-01

    We present the results from a survey of 57 low-redshift Abell galaxy clusters to study the radial dependence of the luminosity function (LF). The dynamical radius of each cluster, r200, was estimated from the photometric measurement of cluster richness, Bgc. The shape of the LFs are found to correlate with radius such that the faint-end slope, alpha, is generally steeper on the cluster outskirts. The sum of two Schechter functions provides a more adequate fit to the composite LFs than a single Schechter function. LFs based on the selection of red and blue galaxies are bimodal in appearance. The red LFs are generally flat for -22 -18. The blue LFs contain a larger contribution from faint galaxies than the red LFs. The blue LFs have a rising faint-end component (alpha ~ -1.7) for M_Rc > -21, with a weaker dependence on radius than the red LFs. The dispersion of M* was determined to be 0.31 mag, which is comparable to the median measurement uncertainty of 0.38 mag. This suggests that the bright-end of the LF is...

  17. The fate of high-redshift massive compact galaxies

    CERN Document Server

    de la Rosa, Ignacio G; Ferreras, Ignacio; Almeida, Jorge Sánchez; Vecchia, Claudio Dalla; Martínez-Valpuesta, Inma; Stringer, Martin

    2016-01-01

    Massive high-redshift quiescent compact galaxies (nicknamed red nuggets) have been traditionally connected to present-day elliptical galaxies, often overlooking the relationships that they may have with other galaxy types. We use large bulge-disk decomposition catalogues based on the Sloan Digital Sky Survey (SDSS) to check the hypothesis that red nuggets have survived as compact cores embedded inside the haloes or disks of present-day massive galaxies. In this study, we designate a "compact core" as the bulge component that satisfies a prescribed compactness criterion. Photometric and dynamic mass-size and mass-density relations are used to show that, in the inner regions of galaxies at z ~ 0.1, there are "abundant" compact cores matching the peculiar properties of the red nuggets, an abundance comparable to that of red nuggets at z ~ 1.5. Furthermore, the morphology distribution of the present-day galaxies hosting compact cores is used to demonstrate that, in addition to the standard channel connecting red ...

  18. Thermodynamics Insights for the Redshift Drift

    Science.gov (United States)

    Zhang, Ming-Jian; Liu, Wen-Biao

    2015-01-01

    The secular redshift drift is a potential measurement to directly probe the cosmic expansion. Previous study on the redshift drift mainly focused on the model-dependent simulation. Apparently, the physical insights on the redshift drift are very necessary. So in this paper, it is investigated using thermodynamics on the apparent, Hubble and event horizons. Thermodynamics could analytically present the model-independent upper bounds of redshift drift. For specific assumption on the cosmological parameters, we find that the thermodynamics bounds are nearly one order of magnitude larger than the expectation in standard ΛCDM model. We then examine ten observed redshift drift from Green Bank Telescope at redshift 0.09 < z < 0.69, and find that these observational results are inconsistent with the thermodynamics. The size of the errorbars on these measurements is about three orders of magnitude larger than the effect of thermodynamical bounds for the redshift drift. Obviously, we have not yet hit any instrumental systematics at the shift level of 1m s-1 yr-1.

  19. Giving cosmic redshift drift a whirl

    Science.gov (United States)

    Kim, Alex G.; Linder, Eric V.; Edelstein, Jerry; Erskine, David

    2015-03-01

    Redshift drift provides a direct kinematic measurement of cosmic acceleration but it occurs with a characteristic time scale of a Hubble time. Thus redshift observations with a challenging precision of 10-9 require a 10 year time span to obtain a signal-to-noise of 1. We discuss theoretical and experimental approaches to address this challenge, potentially requiring less observer time and having greater immunity to common systematics. On the theoretical side we explore allowing the universe, rather than the observer, to provide long time spans; speculative methods include radial baryon acoustic oscillations, cosmic pulsars, and strongly lensed quasars. On the experimental side, we explore beating down the redshift precision using differential interferometric techniques, including externally dispersed interferometers and spatial heterodyne spectroscopy. Low-redshift emission line galaxies are identified as having high cosmology leverage and systematics control, with an 8 h exposure on a 10-m telescope (1000 h of exposure on a 40-m telescope) potentially capable of measuring the redshift of a galaxy to a precision of 10-8 (few ×10-10). Low-redshift redshift drift also has very strong complementarity with cosmic microwave background measurements, with the combination achieving a dark energy figure of merit of nearly 300 (1400) for 5% (1%) precision on drift.

  20. Difficult cases in photometric studies of asteroids

    Science.gov (United States)

    Marciniak, Anna; Pilcher, Frederick; Oszkiewicz, Dagmara; Bartczak, Przemysław; Santana-Ros, Toni; Kamiński, Krzysztof; Urakawa, Seitaro; Ogłoza, Waldemar; Fauvaud, Stéphane; Kankiewicz, Paweł; Kudak, Viktor; Żejmo, Michał; Nishiyama, Kota; Okumura, Shin-ichiro; Nimura, Tokuhiro; Hirsch, Roman; Konstanciak, Izabella; Tychoniec, Łukasz; Figas, Michał

    2016-06-01

    We present a photometric campaign targeted at asteroids that display both long periods of rotation and small amplitudes of brightness variations. Our aim is to debias available sample of spin and shape modelled asteroids and to correct previous wrong period determinations. Our newest findings are corrected period determinations for asteroids (279) Thule (P=23.896h ± 0.005 h), (673) Edda (P=22.340h ± 0.004 h), and (737) Arequipa (P=7.0259h ± 0.0003 h). Supporting lightcurves are presented in this paper.

  1. Hyperspectral photometric stereo for a single capture.

    Science.gov (United States)

    Ozawa, Keisuke; Sato, Imari; Yamaguchi, Masahiro

    2017-03-01

    We present a single-capture photometric stereo method using a hyperspectral camera. A spectrally and spatially designed illumination enables a point-wise estimation of reflectance spectra and surface normals from a single hyperspectral image. The illumination works as a reflectance probe in wide spectral regions where reflectance spectra are measured, and the full spectra are estimated by interpolation. It also works as the resource for shadings in other spectral regions. The accuracy of estimation is evaluated in a simulation. Also, we prepare an experimental setup and demonstrate a surface reconstruction against a real scene.

  2. Photometric Solutions of Some Contact ASAS Binaries

    CERN Document Server

    Gezer, I

    2015-01-01

    We present the first light curve solution of 6 contact binary systems which are chosen from the ASAS catalog. The photometric elements and the estimated absolute parameters of all systems are obtained with the light curve analyses. We calculated the values of degree of contact for the systems. The location of the targets on the Hertzsprung-Russell diagram and the mass-radius plane is compared to the other well-known contact binaries and the evolutionary status of the systems are also discussed.

  3. Photometric solutions of some contact ASAS binaries

    Science.gov (United States)

    Gezer, İ.; Bozkurt, Z.

    2016-04-01

    We present the first light curve solution of 6 contact binary systems which are chosen from the ASAS catalog. The photometric elements and the estimated absolute parameters of all systems are obtained with the light curve analyses. We calculated the values of degree of contact for the systems. The location of the targets on the Hertzsprung-Russell diagram and the mass-radius plane is compared to the other well-known contact binaries and the evolutionary status of the systems are also discussed.

  4. Photometric monitoring of Luminous Blue Variables

    CERN Document Server

    Buemi, Carla; Leto, Paolo; Schilliro', Francesco; Trigilio, Corrado; Umana, Grazia; Bernabei, Stefano; Cutispoto, Giuseppe; Messina, Sergio

    2010-01-01

    We present some preliminary results from our program of intensive near-infrared photometric monitoring of a sample of confirmed and candidate Luminous Blue Variables (LBVs) conducted from 2008 to 2010. Clear long-term variability has been observed for Wray 17-96 and V481 Sct, with overall brightness variation greater than 1 mag in the J band. Other sources, such as LBV 1806-20 showed detectable variability with amplitudes of few tenths of a magnitude with time-scale of about 60 days.

  5. Photometric monitoring of Luminous Blue Variables

    Science.gov (United States)

    Buemi, Carla; Distefano, Elisa; Leto, Paolo; Schillirò, Francesco; Trigilio, Corrado; Umana, Grazia; Bernabei, Stefano; Cutispoto, Giuseppe; Messina, Sergio

    2011-01-01

    We present some preliminary results from our program of intensive near-infrared photometric monitoring of a sample of confirmed and candidate Luminous Blue Variables (LBVs) conducted from 2008 to 2010. Clear long-term variability has been observed for Wray 17-96 and V481 Sct, with overall brightness variation greater than 1 mag in the J band. Other sources, such as LBV 1806-20 showed detectable variability with amplitudes of few tenths of a magnitude with a time-scale of about 60 days.

  6. Simple, Fast and Accurate Photometric Estimation of Specific Star Formation Rate

    CERN Document Server

    Stensbo-Smidt, Kristoffer; Igel, Christian; Zirm, Andrew; Pedersen, Kim Steenstrup

    2015-01-01

    Large-scale surveys make huge amounts of photometric data available. Because of the sheer amount of objects, spectral data cannot be obtained for all of them. Therefore it is important to devise techniques for reliably estimating physical properties of objects from photometric information alone. These estimates are needed to automatically identify interesting objects worth a follow-up investigation as well as to produce the required data for a statistical analysis of the space covered by a survey. We argue that machine learning techniques are suitable to compute these estimates accurately and efficiently. This study considers the task of estimating the specific star formation rate (sSFR) of galaxies. It is shown that a nearest neighbours algorithm can produce better sSFR estimates than traditional SED fitting. We show that we can obtain accurate estimates of the sSFR even at high redshifts using only broad-band photometry based on the u, g, r, i and z filters from Sloan Digital Sky Survey (SDSS). We addtional...

  7. Photometric and Spectroscopic analysis of lensed re-ionising sources at the frontier of the Universe

    Science.gov (United States)

    Laporte, N.; Ellis, R.; Roberts-Borsani, G.; Infante, L.; Zheng, W.; Bauer, F. E.; Bina, D.; Chilingarian, I.; Kim, S.; Pelló, R.; Pérez-Fournon, I.; Richard, J.; Troncoso-Iribarren, P.; Streblyanska, A.

    2016-12-01

    Our team is performing an automatic search for very distant sources using HST, VLT, Magellan, Gemini, Spitzer and ALMA dataset around Frontier Fields aiming to study the nature and properties of sources during the epoch of reionization. In this paper, we report on our photometric sample selection, the photometric properties of our z>6 candidates and the evolution of galaxy number densities during the first billion years from a statistical point of view. Thanks to the huge depth of HST FF data, we identified several z>7 candidates selected in previous HST surveys as mid-z interlopers that could bias our conclusions on the evolution of the first galaxies. We also briefly discuss several interesting objects that will benefit from the arrival of the JWST. The spectroscopic follow-up has just started, and our team is observing a sample of z>7 sources with ground-based spectrographs in order to confirm the redshift of these objects and add robust constraints on their physical properties.

  8. Photometric selection of Type Ia supernovae in the Supernova Legacy Survey

    CERN Document Server

    Bazin, G; Palanque-Delabrouille, N; Rich, J; Aubourg, E; Astier, P; Balland, C; Basa, S; Carlberg, R G; Conley, A; Fouchez, D; Guy, J; Hardin, D; Hook, I M; Howell, D A; Pain, R; Perrett, K; Pritchet, C J; Regnault, N; Sullivan, M; Fourmanoit, N; Gonzalez-Gaitan, S; Lidman, C; Perlmutter, S; Ripoche, P; Walker, E S

    2011-01-01

    We present a sample of 485 photometrically identified Type Ia supernova candidates mined from the first three years of data of the CFHT SuperNova Legacy Survey (SNLS). The images were submitted to a deferred processing independent of the SNLS real-time detection pipeline. Light curves of all transient events were reconstructed in the g_M, r_M, i_M and z_M filters and submitted to automated sequential cuts in order to identify possible supernovae. Pure noise and long-term variable events were rejected by light curve shape criteria. Type Ia supernova identification relied on event characteristics fitted to their light curves assuming the events to be normal SNe Ia. The light curve fitter SALT2 was used for this purpose, assigning host galaxy photometric redshifts to the tested events. The selected sample of 485 candidates is one magnitude deeper than that allowed by the SNLS spectroscopic identification. The contamination by supernovae of other types is estimated to be 4%. Testing Hubble diagram residuals with ...

  9. Supercal: Cross-Calibration of Multiple Photometric Systems to Improve Cosmological Measurements with Type Ia Supernovae

    CERN Document Server

    Scolnic, D; Riess, A G; Rest, A; Schlafly, E; Foley, R J; Finkbeiner, D; Tang, C; Burgett, W S; Chambers, K C; Draper, P W; Hodapp, K W; Huber, M E; Kaiser, N; Kudritzki, R P; Magnier, E A; Metcalfe, N; Stubbs, C W

    2015-01-01

    Current cosmological analyses which use Type Ia supernova (SN Ia) observations combine SN samples to expand the redshift range beyond that of a single sample and increase the overall sample size. The inhomogeneous photometric calibration between different SN samples is one of the largest systematic uncertainties of the cosmological parameter estimation. To place these different samples on a single system, analyses currently use observations of a small sample of very bright flux standards on the $HST$ system. We propose a complementary method, called `Supercal', in which we use measurements of secondary standards in each system, compare these to measurements of the same stars in the Pan-STARRS1 (PS1) system, and determine offsets for each system relative to PS1, placing all SN observations on a single, consistent photometric system. PS1 has observed $3\\pi$ of the sky and has a relative calibration of better than 5 mmag (for $\\sim15

  10. 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...

  11. Simple scaling of catastrophic landslide dynamics.

    Science.gov (United States)

    Ekström, Göran; Stark, Colin P

    2013-03-22

    Catastrophic landslides involve the acceleration and deceleration of millions of tons of rock and debris in response to the forces of gravity and dissipation. Their unpredictability and frequent location in remote areas have made observations of their dynamics rare. Through real-time detection and inverse modeling of teleseismic data, we show that landslide dynamics are primarily determined by the length scale of the source mass. When combined with geometric constraints from satellite imagery, the seismically determined landslide force histories yield estimates of landslide duration, momenta, potential energy loss, mass, and runout trajectory. Measurements of these dynamical properties for 29 teleseismogenic landslides are consistent with a simple acceleration model in which height drop and rupture depth scale with the length of the failing slope.

  12. Neurosurgical management for complicated catastrophic antiphospholipid syndrome.

    Science.gov (United States)

    Drazin, Doniel; Westley Phillips, H; Shirzadi, Ali; Drazin, Noam; Schievink, Wouter

    2014-04-01

    Antiphospholipid syndrome (APS) is an autoimmune condition involving arterial and venous thrombosis. An unusual APS variant, catastrophic antiphospholipid syndrome (CAPS), includes rapid multi-organ failure from widespread small vessel thrombosis. Central nervous system complications arise in one-third of CAPS patients. In rare cases, CAPS co-manifests with cerebellar hemorrhage presenting a neurosurgical emergency. We present a 65-year-old woman with CAPS-related cerebellar hematoma, co-morbid idiopathic thrombocytopenic purpura, deep vein thrombosis and altered mental status, with treatment complicated by thrombocytopenia. The patient suddenly deteriorated, secondary to a cerebellar subdural hematoma, and underwent decompression and excision of the hematoma. After recovery in the intensive care unit, she developed a new spontaneous epidural hematoma requiring additional surgery. Management of these patients is hematologically complex and often requires a multi-disciplinary team of physicians. This patient provides an important learning point for clinicians - consider CAPS when hemorrhage and thrombosis are present.

  13. The OPTX Project. I. The Flux and Redshift Catalogs for the CLANS, CLASXS, and CDF-N Fields

    Science.gov (United States)

    Trouille, L.; Barger, A. J.; Cowie, L. L.; Yang, Y.; Mushotzky, R. F.

    2008-11-01

    We present the redshift catalogs for the X-ray sources detected in the Chandra Deep Field-North (CDF-N), the Chandra Large Area Synoptic X-ray Survey (CLASXS), and the Chandra Lockman Area North Survey (CLANS). The catalogs for the CDF-N and CLASXS fields include redshifts from previous work, while the redshifts for the CLANS field are all new. For fluxes above 10-14 ergs cm-2 s-1 (2-8 keV) we have redshifts for 76% of the sources. We extend the redshift information for the full sample using photometric redshifts. The goal of the OPTX Project is to use these three surveys, which are among the most spectroscopically complete surveys to date, to analyze the effect of spectral type on the shape and evolution of the X-ray luminosity functions and to compare the optical spectral types with the X-ray spectral properties. We also present the CLANS X-ray catalog. The nine ACIS-I fields cover a solid angle of ~0.6 deg2 and reach fluxes of 7 × 10-16 ergs cm-2 s-1 (0.5-2 keV) and 3.5 × 10-15 ergs cm-2 s-1 (2-8 keV). We find a total of 761 X-ray point sources. In addition, we present the optical and infrared photometric catalog for the CLANS X-ray sources, as well as updated optical and infrared photometric catalogs for the X-ray sources in the CLASXS and CDF-N fields. The CLANS and CLASXS surveys bridge the gap between the ultradeep pencil-beam surveys, such as the CDFs, and the shallower, very large-area surveys. As a result, they probe the X-ray sources that contribute the bulk of the 2-8 keV X-ray background and cover the flux range of the observed break in the log N-log S distribution. We construct differential number counts for each individual field and for the full sample. Some of the data presented herein were obtained at the W. M. Keck Observatory, which is operated as a scientific partnership among the California Institute of Technology, the University of California, and the National Aeronautics and Space Administration. The observatory was made possible by the

  14. 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

  15. Redshift drift in a pressure gradient cosmology

    CERN Document Server

    Balcerzak, Adam

    2012-01-01

    We derive the redshift drift formula for the inhomogeneous pressure spherically symmetric Stephani universes which are complementary to inhomogeneous density Lema\\^itre-Tolman-Bondi (LTB) models. We show that there is a clear difference between the redshift drift predictions for these two models. The Stephani models have positive drift values at small redshift and behave qualitatively as the $\\Lambda$CDM models while the drift for LTB models is always negative. This prediction can be tested in future space experiments such as E-ELT, TMT, GMT or CODEX.

  16. Lensing convergence in galaxy redshift surveys

    CERN Document Server

    Cardona, Wilmar; Kunz, Martin; Montanari, Francesco

    2016-01-01

    In this letter we demonstrate the importance of including the lensing contribution in galaxy clustering analyses with large galaxy redshift surveys. It is well known that radial cross-correlations between different redshift bins of galaxy surveys are dominated by lensing. But we show here that also neglecting lensing in the auto-correlations within one bin severely biases cosmological parameter estimation with redshift surveys. It leads to significant shifts for several cosmological parameters, most notably the scalar amplitude, the scalar spectral index and in particular the neutrino mass scale. Especially the latter parameter is one of the main targets of future galaxy surveys.

  17. Photometric study of the eclipsing binary ET Psc

    Science.gov (United States)

    Özalp, G. Z.; Özkardeş, B.

    2016-03-01

    We present the photometric solution of the eclipsing binary ET Psc (GSC 00608-00490). The ASAS V-band photometric data of the system was modelled using the Wilson-Devinney method. The result shows that the eclipsing pair could be classified as A-subtype of W UMa-type binary system. The absolute dimensions of the system were also estimated based on the photometric solution.

  18. Molecular Gas at High Redshift

    CERN Document Server

    Solomon, P M

    2005-01-01

    The Early Universe Molecular Emission Line Galaxies (EMGs) are a population of galaxies with only 36 examples that hold great promise for the study of galaxy formation and evolution at high redshift. The classification, luminosity of molecular line emission, molecular mass, far-infrared (FIR) luminosity, star formation efficiency, morphology, and dynamical mass of the currently known sample are presented and discussed. The star formation rates derived from the FIR luminosity range from about 300 to 5000 M(sun)per year and the molecular mass from 4 x 10^9 to 1 x 10^{11} M(sun). At the lower end, these star formation rates, gas masses, and diameters are similar to those of local ultraluminous infrared galaxies, and represent starbursts in centrally concentrated disks, sometimes, but not always, associated with active galactic nuclei. The evidence for large (> 5 kpc) molecular disks is limited. Morphology and several high angular resolution images suggest that some EMGs are mergers with a massive molecular inter...

  19. The New Redshift Interpretation Affirmed

    CERN Document Server

    Gentry, R V

    1998-01-01

    In late 1997 I reported (Mod. Phys. Lett. A 12 (1997) 2919; astro-ph/9806280) the discovery of A New Redshift Interpretation (NRI) of the Hubble relation and the 2.7K CBR, which showed for the first time that it was possible to explain these phenomena within the framework of a universe governed by Einstein's static-spacetime general relativity (GR) instead of the Friedmann-Lemaitre expanding-spacetime paradigm. More recently Carlip and Scranton (astro-ph/9808021; C&S) claim to find flaws in this discovery, while also claiming the standard cosmology is error free. Their analysis assumes the NRI represents a static cosmological model of the universe. This is wrong. My MPLA report clearly states the NRI encompasses an expanding universe wherein galaxies are undergoing Doppler recession due to vacuum density repulsion. C&S's confusion on this crucial point leads to serious errors in their analysis. Next, in claiming the standard cosmology is error free, C&S fail to respond to the contradictory evidenc...

  20. Sacrificing information for the greater good: how to select photometric bands for optimal accuracy

    Science.gov (United States)

    Stensbo-Smidt, Kristoffer; Gieseke, Fabian; Igel, Christian; Zirm, Andrew; Steenstrup Pedersen, Kim

    2017-01-01

    Large-scale surveys make huge amounts of photometric data available. Because of the sheer amount of objects, spectral data cannot be obtained for all of them. Therefore, it is important to devise techniques for reliably estimating physical properties of objects from photometric information alone. These estimates are needed to automatically identify interesting objects worth a follow-up investigation as well as to produce the required data for a statistical analysis of the space covered by a survey. We argue that machine learning techniques are suitable to compute these estimates accurately and efficiently. This study promotes a feature selection algorithm, which selects the most informative magnitudes and colours for a given task of estimating physical quantities from photometric data alone. Using k-nearest neighbours regression, a well-known non-parametric machine learning method, we show that using the found features significantly increases the accuracy of the estimations compared to using standard features and standard methods. We illustrate the usefulness of the approach by estimating specific star formation rates (sSFRs) and redshifts (photo-z's) using only the broad-band photometry from the Sloan Digital Sky Survey (SDSS). For estimating sSFRs, we demonstrate that our method produces better estimates than traditional spectral energy distribution fitting. For estimating photo-z's, we show that our method produces more accurate photo-z's than the method employed by SDSS. The study highlights the general importance of performing proper model selection to improve the results of machine learning systems and how feature selection can provide insights into the predictive relevance of particular input features.

  1. Cell death by mitotic catastrophe: a molecular definition

    NARCIS (Netherlands)

    Castedo, M.; Perfettini, J.-L.; Roumier, T.; Andreau, K.; Medema, R.H.; Kroemer, G.

    2004-01-01

    The current literature is devoid of a clearcut definition of mitotic catastrophe, a type of cell death that occurs during mitosis. Here, we propose that mitotic catastrophe results from a combination of deficient cell-cycle checkpoints (in particular the DNA structure checkpoints and the spindle ass

  2. Catastrophe, gender and urban experience 1648-1920

    DEFF Research Database (Denmark)

    Employing a broad definition of catastrophe, this book examines how urban communities conceived, adapted to and were transformed by catastrophes. Competing views of gender figure in the telling and retelling of these trag- edies, which are mediated by myth and memory. This is a nuanced account...

  3. Purchase of Catastrophe Insurance by Dutch Dairy and Arable Farmers

    NARCIS (Netherlands)

    Ogurtsov, V.; Asseldonk, van M.A.P.M.; Huirne, R.B.M.

    2009-01-01

    This article analyzed the impact of risk perception, risk attitude, and other farmer personal and farm characteristics on the actual purchase of catastrophe insurance by Dutch dairy and arable farmers. The specific catastrophe insurance types considered were hail–fire–storm insurance for buildings,

  4. 'Performative narrativity': Palestinian identity and the performance of catastrophe

    NARCIS (Netherlands)

    Saloul, I.

    2008-01-01

    The day Israel annually celebrates as its "Day of Independence" Palestinians commemorate as their day of catastrophe (al-nakba). To most Palestinians, the catastrophic loss of Palestine in 1948 represents the climactic formative event of their lives. In the aftermath of this loss, the Palestinian so

  5. Catastrophic healthcare expenditure - drivers and protection: the Portuguese case.

    Science.gov (United States)

    Kronenberg, Christoph; Barros, Pedro Pita

    2014-03-01

    The objective of this paper is to assess the extent of catastrophic healthcare expenditure, which can lead to impoverishment, even in a country with a National Health Service, such as Portugal. The level of catastrophic healthcare expenditure will be identified before the determinants of these catastrophic payments are analyzed. Afterwards, the effects of existing exemptions to copayments in health care use will be tested and the relationship between catastrophe and impoverishment will be discussed. Catastrophe is calculated from the Portuguese Household Budget Surveys of 2000 and 2005, and then analyzed using logistic regression models. The results show that catastrophe due to healthcare out-of-pocket payments are a sizeable issue in Portugal. Exemptions from out-of-pocket expenses for medical care should be created to prevent vulnerable groups from facing catastrophic healthcare spending. These vulnerable groups include children, people with disabilities and individuals suffering from chronic conditions. Disability proxies offer straightforward policy options for an exemption for the elderly with recognized disabilities. An exemption of retired people with disabilities is therefore recommended to policymakers as it targets a vulnerable group with high risk of facing catastrophic healthcare expenditure.

  6. Psychological resilience predicts decreases in pain catastrophizing through positive emotions.

    Science.gov (United States)

    Ong, Anthony D; Zautra, Alex J; Reid, M Carrington

    2010-09-01

    The study used a daily process design to examine the role of psychological resilience and positive emotions in the day-to-day experience of pain catastrophizing. A sample of 95 men and women with chronic pain completed initial assessments of neuroticism, psychological resilience, and demographic data, and then completed short diaries regarding pain intensity, pain catastrophizing, and positive and negative emotions every day for 14 consecutive days. Multilevel modeling analyses indicated that independent of level of neuroticism, negative emotions, pain intensity, income, and age, high-resilient individuals reported greater positive emotions and exhibited lower day-to-day pain catastrophizing compared with low-resilient individuals. Mediation analyses revealed that psychologically resilient individuals rebound from daily pain catastrophizing through experiences of positive emotion. Implications for research on psychological resilience, pain catastrophizing, and positive emotions are discussed.

  7. Grey forewarning and prediction for mine water inflowing catastrophe periods

    Institute of Scientific and Technical Information of China (English)

    MA Qi-hua; CAO Jian-jun

    2007-01-01

    Based on the theory of grey system, established GM (1, 1) grey catastrophe predict model for the first time in order to forecast the catastrophe periods of mine water inflowing (not the volume of water inflowing). After establishing the grey predict system of the catastrophe regularity of 10 month-average volume of water inflowing, the grey forewarning for mine water inflowing catastrophe periods was established which was used to analyze water disaster in -400 meter level of Wennan Colliery. Based on residual analysis,it shows that the result of grey predict system is almost close to the actual value. And the scene actual result also shows the reliability of prediction. Both the theoretical analysis and the scene actual result indicate feasibility and reliability of the method of grey catastrophe predict system.

  8. Asteroid models from the Lowell Photometric Database

    CERN Document Server

    Durech, J; Oszkiewicz, D; Vanco, R

    2016-01-01

    We use the lightcurve inversion method to derive new shape models and spin states of asteroids from the sparse-in-time photometry compiled in the Lowell Photometric Database. To speed up the time-consuming process of scanning the period parameter space through the use of convex shape models, we use the distributed computing project Asteroids@home, running on the Berkeley Open Infrastructure for Network Computing (BOINC) platform. This way, the period-search interval is divided into hundreds of smaller intervals. These intervals are scanned separately by different volunteers and then joined together. We also use an alternative, faster, approach when searching the best-fit period by using a model of triaxial ellipsoid. By this, we can independently confirm periods found with convex models and also find rotation periods for some of those asteroids for which the convex-model approach gives too many solutions. From the analysis of Lowell photometric data of the first 100,000 numbered asteroids, we derived 328 new ...

  9. GRB 130606A within a sub-DLA at redshift 5.91

    CERN Document Server

    Castro-Tirado, A J; Ellison, S L; Jelínek, M; Martín-Carrillo, A; Bromm, V; Gorosabel, J; Bremer, M; Winters, J M; Hanlon, L; Meegan, S; Topinka, M; Pandey, S B; Guziy, S; Jeong, S; Sonbas, E; Pozanenko, A S; Cunniffe, R; Fernández-Muñoz, R; Ferrero, P; Gehrels, N; Hudec, R; Kubánek, P; Lara-Gil, O; Muñoz-Martínez, V F; Pérez-Ramírez, D; Štrobl, J; Álvarez-Iglesias, C; Inasaridze, R; Rumyantsev, V; Volnova, A; Hellmich, S; Mottola, S; Cerón, J M Castro; Cepa, J; Göğüş, E; Güver, T; Taş, Ö Önal; Park, I H; Sabau-Graziati, L; Tejero, A

    2013-01-01

    Events such as GRB130606A at z=5.91, offer an exciting new window into pre-galactic metal enrichment in these very high redshift host galaxies. We study the environment and host galaxy of GRB 130606A, a high-z event, in the context of a high redshift population of GRBs. We have obtained multiwavelength observations from radio to gamma-ray, concentrating particularly on the X-ray evolution as well as the optical photometric and spectroscopic data analysis. With an initial Lorentz bulk factor in the range \\Gamma_0 ~ 65-220, the X-ray afterglow evolution can be explained by a time-dependent photoionization of the local circumburst medium, within a compact and dense environment. The host galaxy is a sub-DLA (log N (HI) = 19.85+/-0.15), with a metallicity content in the range from ~1/7 to ~1/60 of solar. Highly ionized species (N V and Si IV) are also detected. This is the second highest redshift burst with a measured GRB-DLA metallicity and only the third GRB absorber with sub-DLA HI column density. GRB ' lightho...

  10. Spectroscopic confirmation of two Lyman break galaxies at redshift beyond 7

    CERN Document Server

    Vanzella, E; Fontana, A; Grazian, A; Castellano, M; Boutsia, K; Cristiani, S; Dickinson, M; Gallozzi, S; Giallongo, E; Giavalisco, M; Maiolino, R; Moorwood, A; Paris, D; Santini, P

    2010-01-01

    We report the spectroscopic confirmation of two Lyman break galaxies at redshift > 7. The galaxies were observed as part of an utra-deep spectroscopic campaign with FORS2 at the ESO/VLT for the confirmation of z~7 "z--band dropout'' candidates selected from our VLT/Hawk-I imaging survey. Both galaxies show a prominent emission line at 9735A and 9858A respectively: the lines have fluxes around ~ 1-1.2 x 10^(-17) erg/s/cm2 and exhibit a sharp decline on the blue side and a tail on the red side. The asymmetry is quantitatively comparable to the observed asymmetry in z~6 Lya lines, where absorption by neutral hydrogen in the IGM truncates the blue side of the emission line profile. We carefully evaluate the possibility that the galaxies are instead at lower redshift and we are observing either [OII], [OIII] or Ha emission: however from the spectroscopic and the photometric data we conclude that there are no other plausible identifications, except for Lya at redshift > 7, making these the first robust Lyman break ...

  11. Subluminous Type Ia Supernovae at High Redshift from the Supernova Legacy Survey

    CERN Document Server

    Gonzalez-Gaitan, S; Sullivan, M; Conley, A; Howell, D A; Carlberg, R G; Astier, P; Balam, D; Balland, C; Basa, S; Fouchez, D; Guy, J; Hardin, D; Hook, I M; Pain, R; Pritchet, C J; Regnault, N; Rich, J

    2010-01-01

    The rate evolution of subluminous Type Ia Supernovae is presented using data from the Supernova Legacy Survey. This sub-sample represents the faint and rapidly-declining light-curves of the observed supernova Ia (SN Ia) population here defined by low stretch values (s<0.8). Up to redshift z=0.6, we find 18 photometrically-identified subluminous SNe Ia, of which six have spectroscopic redshift (and three are spectroscopically-confirmed SNe Ia). The evolution of the subluminous volumetric rate is constant or slightly decreasing with redshift, in contrast to the increasing SN Ia rate found for the normal stretch population, although a rising behaviour is not conclusively ruled out. The subluminous sample is mainly found in early-type galaxies with little or no star formation, so that the rate evolution is consistent with a galactic mass dependent behavior: $r(z)=A\\times M_g$, with $A=(1.1\\pm0.3)\\times10^{-14}$ SNe per year and solar mass.

  12. Bulgeless Galaxies at Intermediate Redshift: Sample Selection, Colour Properties, and the Existence of Powerful AGN

    CERN Document Server

    Bizzocchi, Luca; Leonardo, Elvira; Grossi, Marco; Griffith, Roger L; Afonso, José; Fernandes, Cristina; Retrê, João; Anton, Sonia; Bell, Eric F; Brinchmann, Jarle; Henriques, Bruno; Lobo, Catarina; Messias, Hugo

    2014-01-01

    We present a catalogue of bulgeless galaxies, which includes 19225 objects selected in four of the deepest, largest multi-wavelength datasets available -- COSMOS, AEGIS, GEMS and GOODS -- at intermediate redshift ($0.4 \\leq z \\leq 1.0$). The morphological classification was provided by the Advanced Camera for Surveys General Catalogue (ACS-GC), which used publicly available data obtained with the ACS instrument on the Hubble Space Telescope. Rest-frame photometric quantities were derived using kcorrect. We analyse the properties of the sample and the evolution of pure-disc systems with redshift. Very massive [$\\log (M_\\star/M_{\\odot}) > 10.5$] bulgeless galaxies contribute to ~30% of the total galaxy population number density at $z \\geq 0.7$, but their number density drops substantially with decreasing redshift. We show that only a negligible fraction of pure discs appear to be quiescent systems, and red sequence bulgeless galaxies show indications of dust-obscured star formation. X-ray catalogues were used t...

  13. The Quest for Dusty Star-forming Galaxies at High Redshift z>4

    CERN Document Server

    Mancuso, C; Shi, J; Gonzalez-Nuevo, J; Aversa, R; Danese, L

    2016-01-01

    We exploit the continuity equation approach and the `main sequence' star-formation timescales to show that the observed high abundance of galaxies with stellar masses > a few 10^10 M_sun at redshift z>4 implies the existence of a galaxy population featuring large star formation rates (SFRs) > 10^2 M_sun/yr in heavily dust-obscured conditions. These galaxies constitute the high-redshift counterparts of the dusty star-forming population already surveyed for z30 M_sun/yr cannot be estimated relying on the UV luminosity function alone, even when standard corrections for dust extinction based on the UV slope are applied. We compute the number counts and redshift distributions (including galaxy-scale gravitational lensing) of this galaxy population, and show that current data from AzTEC-LABOCA, SCUBA-2 and ALMA-SPT surveys are already digging into it. We substantiate how an observational strategy based on a color preselection in the far-IR or (sub-)mm band with Herschel and SCUBA-2, supplemented by photometric data...

  14. Combining spectroscopic and photometric surveys using angular cross-correlations III: Galaxy bias and stochastisity

    CERN Document Server

    Eriksen, Martin

    2015-01-01

    In the first paper of this series, we studied the effect of baryon acoustic oscillations (BAO), redshift space distortions (RSD) and weak lensing (WL) on measurements of angular cross-correlations in narrow redshift bins. Paper-II presented a multitracer forecast as Figures of Merit (FoM), combining a photometric and spectroscopic stage-IV survey. The uncertainties from galaxy bias, the way light traces mass, is an important ingredient in the forecast. Fixing the bias would increase our FoM equivalent to 3.3 times larger area for the combined constraints. This paper focus on how the modelling of bias affect these results. In the combined forecast, lensing both help and benefit from the improved bias measurements in overlapping surveys after marginalizing over the cosmological parameters. Adding a second lens population in counts-shear does not have a large impact on bias error, but removing all counts-shear information increases the bias error in a significant way. We also discuss the relative impact of WL, m...

  15. Clustering of Sloan Digital Sky Survey III Photometric Luminous Galaxies: The Measurement, Systematics and Cosmological Implications

    CERN Document Server

    Ho, Shirley; Seo, Hee-Jong; de Putter, Roland; Ross, Ashley J; White, Martin; Padmanabhan, Nikhil; Saito, Shun; Schlegel, David J; Schlafly, Eddie; Seljak, Uros; Hernandez-Monteagudo, Carlos; Sanchez, Ariel G; Percival, Will J; Blanton, Michael; Skibba, Ramin; Schneider, Don; Reid, Beth; Mena, Olga; Viel, Matteo; Eisenstein, Daniel J; Prada, Francisco; Weaver, Benjamin; Bahcall, Neta; Bizyaev, Dimitry; Brewinton, Howard; Brinkman, Jon; da Costa, Luiz Nicolaci; Gott, John R; Malanushenko, Elena; Malanushenko, Viktor; Nichol, Bob; Oravetz, Daniel; Pan, Kaike; Palanque-Delabrouille, Nathalie; Ross, Nicholas P; Simmons, Audrey; de Simoni, Fernando; Snedden, Stephanie; Yeche, Christophe

    2012-01-01

    The Sloan Digital Sky Survey (SDSS) surveyed 14,555 square degrees, and delivered over a trillion pixels of imaging data. We present a study of galaxy clustering using 900,000 luminous galaxies with photometric redshifts, spanning between $z=0.45$ and $z=0.65$, constructed from the SDSS using methods described in Ross et al. (2011). This data-set spans 11,000 square degrees and probes a volume of $3h^{-3} \\rm{Gpc}^3$, making it the largest volume ever used for galaxy clustering measurements. We present a novel treatment of the observational systematics and its applications to the clustering signals from the data set. In this paper, we measure the angular clustering using an optimal quadratic estimator at 4 redshift slices with an accuracy of ~15% with bin size of delta_l = 10 on scales of the Baryon Acoustic Oscillations (BAO) (at l~40-400). We derive cosmological constraints using the full-shape of the power-spectra. For a flat Lambda CDM model, when combined with Cosmic Microwave Background Wilkinson Microw...

  16. The ALHAMBRA Project: A large area multi medium-band optical and NIR photometric survey

    CERN Document Server

    Moles, M; López-Aguerri, J A; Alfaro, E J; Broadhurst, T; Cabrera-Caño, J; Castander, F J; Cepa, J; Cerviño, M; Cristóbal-Hornillos, D; Fernández-Soto, A; Delgado, R M González; Infante, L; Márquez, I; Martínez, V J; Masegosa, J; del Olmo, A; Perea, J; Prada, F; Quintana, J M; Sánchez, S F

    2008-01-01

    (ABRIDGED) We describe the first results of the ALHAMBRA survey which provides cosmic tomography of the evolution of the contents of the Universe over most of Cosmic history. Our approach employs 20 contiguous, equal-width, medium-band filters covering from 3500 to 9700 A, plus the JHKs bands, to observe an area of 4 sqdeg on the sky. The optical photometric system has been designed to maximize the number of objects with accurate classification by SED and redshift, and to be sensitive to relatively faint emission lines. The observations are being carried out with the Calar Alto 3.5m telescope using the cameras LAICA and O-2000. The first data confirm that we are reaching the expected magnitude limits of AB<~25 mag in the optical filters from the blue to 8300 A, and from AB=24.7 to 23.4 for the redder ones. The limit in the NIR is (Vega) K_s~20, H~21, J~22. We expect to obtain accurate redshift values, Delta z/(1+z) <~ 0.03 for about 5x10^5 galaxies with I<~25 (60% complete), and z_med=0.74. This accu...

  17. Manipulation of pain catastrophizing: An experimental study of healthy participants

    Directory of Open Access Journals (Sweden)

    Joel E Bialosky

    2008-11-01

    Full Text Available Joel E Bialosky1*, Adam T Hirsh2,3, Michael E Robinson2,3, Steven Z George1,3*1Department of Physical Therapy; 2Department of Clinical and Health Psychology; 3Center for Pain Research and Behavioral Health, University of Florida, Gainesville, Florida, USAAbstract: Pain catastrophizing is associated with the pain experience; however, causation has not been established. Studies which specifically manipulate catastrophizing are necessary to establish causation. The present study enrolled 100 healthy individuals. Participants were randomly assigned to repeat a positive, neutral, or one of three catastrophizing statements during a cold pressor task (CPT. Outcome measures of pain tolerance and pain intensity were recorded. No change was noted in catastrophizing immediately following the CPT (F(1,84 = 0.10, p = 0.75, partial η2 < 0.01 independent of group assignment (F(4,84 = 0.78, p = 0.54, partial η2 = 0.04. Pain tolerance (F(4 = 0.67, p = 0.62, partial η2 = 0.03 and pain intensity (F(4 = 0.73, p = 0.58, partial η2 = 0.03 did not differ by group. This study suggests catastrophizing may be difficult to manipulate through experimental pain procedures and repetition of specific catastrophizing statements was not sufficient to change levels of catastrophizing. Additionally, pain tolerance and pain intensity did not differ by group assignment. This study has implications for future studies attempting to experimentally manipulate pain catastrophizing.Keywords: pain, catastrophizing, experimental, cold pressor task, pain catastrophizing scale

  18. Decoding quasars: gravitationally redshifted spectral lines !

    CERN Document Server

    Kantharia, Nimisha G

    2016-01-01

    Further investigation of data on quasars, especially in the ultraviolet band, yields an amazingly coherent narrative which we present in this paper. Quasars are characterised by strong continuum emission and redshifted emission and absorption lines which includes the famous Lyman $\\alpha$ forest. We present irrefutable evidence in support of (1) the entire line spectrum arising in matter located inside the quasar system, (2) the range of redshifts shown by the lines being due to the variable contribution of the gravitational redshift in the observed line velocity, (3) existence of rotating black holes and of matter inside its ergosphere, (4) quasars located within cosmological redshifts $\\sim 3$, (5) $\\gamma$ ray bursts being explosive events in a quasar. These results are significant and a game-changer when we realise that the absorbing gas has been postulated to exist along the line-of-sight to the quasar and observations have accordingly been interpreted. In light of these definitive results which uniquely...

  19. Giving Cosmic Redshift Drift a Whirl

    CERN Document Server

    Kim, Alex G; Edelstein, Jerry; Erskine, David

    2014-01-01

    Redshift drift provides a direct kinematic measurement of cosmic acceleration but it occurs with a characteristic time scale of a Hubble time. Thus redshift observations with a challenging precision of $10^{-9}$ require a 10 year time span to obtain a signal-to-noise of 1. We discuss theoretical and experimental approaches to address this challenge, potentially requiring less observer time and having greater immunity to common systematics. On the theoretical side we explore allowing the universe, rather than the observer, to provide long time spans; speculative methods include radial baryon acoustic oscillations, cosmic pulsars, and strongly lensed quasars. On the experimental side, we explore beating down the redshift precision using differential interferometric techniques, including externally dispersed interferometers and spatial heterodyne spectroscopy. Low-redshift emission line galaxies are identified as having high cosmology leverage and systematics control, with an 8 hour exposure on a 10-meter telesc...

  20. Gravitational redshifts from large-scale structure

    CERN Document Server

    Croft, Rupert A C

    2013-01-01

    The recent measurement of the gravitational redshifts of galaxies in galaxy clusters by Wojtak et al. has opened a new observational window on dark matter and modified gravity. By stacking clusters this determination effectively used the line of sight distortion of the cross-correlation function of massive galaxies and lower mass galaxies to estimate the gravitational redshift profile of clusters out to 4 Mpc/h. Here we use a halo model of clustering to predict the distortion due to gravitational redshifts of the cross-correlation function on scales from 1 - 100 Mpc/h. We compare our predictions to simulations and use the simulations to make mock catalogues relevant to current and future galaxy redshift surveys. Without formulating an optimal estimator, we find that the full BOSS survey should be able to detect gravitational redshifts from large-scale structure at the ~4 sigma level. Upcoming redshift surveys will greatly increase the number of galaxies useable in such studies and the BigBOSS and Euclid exper...

  1. Assessment of Systematic Chromatic Errors that Impact Sub-1% Photometric Precision in Large-area Sky Surveys

    Science.gov (United States)

    Li, T. S.; DePoy, D. L.; Marshall, J. L.; Tucker, D.; Kessler, R.; Annis, J.; Bernstein, G. M.; Boada, S.; Burke, D. L.; Finley, D. A.; James, D. J.; Kent, S.; Lin, H.; Marriner, J.; Mondrik, N.; Nagasawa, D.; Rykoff, E. S.; Scolnic, D.; Walker, A. R.; Wester, W.; Abbott, T. M. C.; Allam, S.; Benoit-Lévy, A.; Bertin, E.; Brooks, D.; Capozzi, D.; Carnero Rosell, A.; Carrasco Kind, M.; Carretero, J.; Crocce, M.; Cunha, C. E.; D'Andrea, C. B.; da Costa, L. N.; Desai, S.; Diehl, H. T.; Doel, P.; Flaugher, B.; Fosalba, P.; Frieman, J.; Gaztanaga, E.; Goldstein, D. A.; Gruen, D.; Gruendl, R. A.; Gutierrez, G.; Honscheid, K.; Kuehn, K.; Kuropatkin, N.; Maia, M. A. G.; Melchior, P.; Miller, C. J.; Miquel, R.; Mohr, J. J.; Neilsen, E.; Nichol, R. C.; Nord, B.; Ogando, R.; Plazas, A. A.; Romer, A. K.; Roodman, A.; Sako, M.; Sanchez, E.; Scarpine, V.; Schubnell, M.; Sevilla-Noarbe, I.; Smith, R. C.; Soares-Santos, M.; Sobreira, F.; Suchyta, E.; Tarle, G.; Thomas, D.; Vikram, V.; DES Collaboration

    2016-06-01

    Meeting the science goals for many current and future ground-based optical large-area sky surveys requires that the calibrated broadband photometry is both stable in time and uniform over the sky to 1% precision or better. Past and current surveys have achieved photometric precision of 1%-2% by calibrating the survey’s stellar photometry with repeated measurements of a large number of stars observed in multiple epochs. The calibration techniques employed by these surveys only consider the relative frame-by-frame photometric zeropoint offset and the focal plane position-dependent illumination corrections, which are independent of the source color. However, variations in the wavelength dependence of the atmospheric transmission and the instrumental throughput induce source color-dependent systematic errors. These systematic errors must also be considered to achieve the most precise photometric measurements. In this paper, we examine such systematic chromatic errors (SCEs) using photometry from the Dark Energy Survey (DES) as an example. We first define a natural magnitude system for DES and calculate the systematic errors on stellar magnitudes when the atmospheric transmission and instrumental throughput deviate from the natural system. We conclude that the SCEs caused by the change of airmass in each exposure, the change of the precipitable water vapor and aerosol in the atmosphere over time, and the non-uniformity of instrumental throughput over the focal plane can be up to 2% in some bandpasses. We then compare the calculated SCEs with the observed DES data. For the test sample data, we correct these errors using measurements of the atmospheric transmission and instrumental throughput from auxiliary calibration systems. The residual after correction is less than 0.3%. Moreover, we calculate such SCEs for Type Ia supernovae and elliptical galaxies and find that the chromatic errors for non-stellar objects are redshift-dependent and can be larger than those for

  2. Assessment of Systematic Chromatic Errors that Impact Sub-1% Photometric Precision in Large-Area Sky Surveys

    Energy Technology Data Exchange (ETDEWEB)

    Li, T. S. [et al.

    2016-05-27

    Meeting the science goals for many current and future ground-based optical large-area sky surveys requires that the calibrated broadband photometry is stable in time and uniform over the sky to 1% precision or better. Past surveys have achieved photometric precision of 1-2% by calibrating the survey's stellar photometry with repeated measurements of a large number of stars observed in multiple epochs. The calibration techniques employed by these surveys only consider the relative frame-by-frame photometric zeropoint offset and the focal plane position-dependent illumination corrections, which are independent of the source color. However, variations in the wavelength dependence of the atmospheric transmission and the instrumental throughput induce source color-dependent systematic errors. These systematic errors must also be considered to achieve the most precise photometric measurements. In this paper, we examine such systematic chromatic errors using photometry from the Dark Energy Survey (DES) as an example. We define a natural magnitude system for DES and calculate the systematic errors on stellar magnitudes, when the atmospheric transmission and instrumental throughput deviate from the natural system. We conclude that the systematic chromatic errors caused by the change of airmass in each exposure, the change of the precipitable water vapor and aerosol in the atmosphere over time, and the non-uniformity of instrumental throughput over the focal plane, can be up to 2% in some bandpasses. We compare the calculated systematic chromatic errors with the observed DES data. For the test sample data, we correct these errors using measurements of the atmospheric transmission and instrumental throughput. The residual after correction is less than 0.3%. We also find that the errors for non-stellar objects are redshift-dependent and can be larger than those for stars at certain redshifts.

  3. Asteroid models from the Lowell photometric database

    Science.gov (United States)

    Ďurech, J.; Hanuš, J.; Oszkiewicz, D.; Vančo, R.

    2016-03-01

    Context. Information about shapes and spin states of individual asteroids is important for the study of the whole asteroid population. For asteroids from the main belt, most of the shape models available now have been reconstructed from disk-integrated photometry by the lightcurve inversion method. Aims: We want to significantly enlarge the current sample (~350) of available asteroid models. Methods: We use the lightcurve inversion method to derive new shape models and spin states of asteroids from the sparse-in-time photometry compiled in the Lowell Photometric Database. To speed up the time-consuming process of scanning the period parameter space through the use of convex shape models, we use the distributed computing project Asteroids@home, running on the Berkeley Open Infrastructure for Network Computing (BOINC) platform. This way, the period-search interval is divided into hundreds of smaller intervals. These intervals are scanned separately by different volunteers and then joined together. We also use an alternative, faster, approach when searching the best-fit period by using a model of triaxial ellipsoid. By this, we can independently confirm periods found with convex models and also find rotation periods for some of those asteroids for which the convex-model approach gives too many solutions. Results: From the analysis of Lowell photometric data of the first 100 000 numbered asteroids, we derived 328 new models. This almost doubles the number of available models. We tested the reliability of our results by comparing models that were derived from purely Lowell data with those based on dense lightcurves, and we found that the rate of false-positive solutions is very low. We also present updated plots of the distribution of spin obliquities and pole ecliptic longitudes that confirm previous findings about a non-uniform distribution of spin axes. However, the models reconstructed from noisy sparse data are heavily biased towards more elongated bodies with high

  4. The Redshift Evolution of the High-Mass End of the Red Sequence Luminosity Function from the SDSS-III/BOSS CMASS Sample

    CERN Document Server

    Montero-Dorta, Antonio D; Brownstein, Joel R; Swanson, Molly; Dawson, Kyle; Prada, Francisco; Eisenstein, Daniel; Maraston, Claudia; Thomas, Daniel; Comparat, Johan; Chuang, Chia-Hsun; McBride, Cameron K; Favole, Ginevra; Guo, Hong; Rodriguez, Sergio; Schneider, Donald P

    2014-01-01

    We present the redshift evolution of the high-mass end of the ^{0.55}i-band Red Sequence Luminosity Function (RS LF) within the redshift range 0.52photometric errors and accounting for selection effects. This procedure requires modeling the covariance matrix for the i-band magnitude, g-r color and r-i color using Stripe 82 multi-epoch data. The error-deconvolved intrinsic RS distribution is consistent with a single point in the color-color plane, which implies that the great majority of the observed scatter is due to photometric errors. We estimate that RS completeness is ~0.80-0.85 at z\\geq0.52 in the CMASS sample, dropping drastically below that redshift. Approximately 37% of all objects in the CMASS sample belong intrinsically to the blue cloud. Within the redshift and absolu...

  5. Mass Calibration of Galaxy Clusters at Redshift 0.1-1.0 using Weak Lensing in the Sloan Digital Sky Survey Stripe 82 Co-add

    CERN Document Server

    Wiesner, Matthew P; Soares-Santos, Marcelle

    2015-01-01

    We present mass-richness relations found in the Sloan Digital Sky Survey Stripe 82 co-add. These relations were found using stacked weak lensing shear observed in a large sample of galaxy clusters. These mass-richness relations are presented for four redshift bins, $0.1 < z \\leq 0.4$, $0.4 < z \\leq 0.7$, $0.7 < z \\leq 1.0$ and $0.1 < z \\leq 1.0$. We describe the sample of galaxy clusters and explain how these clusters were found using a Voronoi Tessellation cluster finder. We fit an NFW profile to the stacked weak lensing shear signal in redshift and richness bins in order to measure virial mass $(M_{200})$. We describe several effects that can bias weak lensing measurements, including photometric redshift bias, the effect of the central BCG, halo miscentering, photometric redshift uncertainty and foreground galaxy contamination. We present mass-richness relations using richness measure $N_{VT}$ with each of these effects considered separately as well as considered altogether. We present values fo...

  6. Supernovae in the Subaru Deep Field: the rate and delay-time distribution of type Ia supernovae out to redshift 2

    CERN Document Server

    Graur, Or; Maoz, Dan; Yasuda, Naoki; Totani, Tomonori; Fukugita, Masataka; Filippenko, Alexei V; Foley, Ryan J; Silverman, Jeffrey M; Gal-Yam, Avishay; Horesh, Assaf; Jannuzi, Buell T

    2011-01-01

    The type Ia supernova (SN Ia) rate, when compared to the cosmic star formation history (SFH), can be used to derive the delay-time distribution (DTD) of SNe Ia, which can distinguish among progenitor models. We present the results of a SN survey to ~27 mag in the Subaru Deep Field (SDF). Over a period of 3 years, we have observed the SDF on 4 independent epochs with Suprime-Cam on the Subaru 8.2-m telescope, with 2 nights of exposure per epoch, in the R, i', and z' bands. We have discovered 150 SNe out to redshift z~2. Using 11 photometric bands from the observer-frame far-ultraviolet to the near-infrared, we derive photometric redshifts for the SN host galaxies (for 24 we also have spectroscopic redshifts). This information is combined with the SN photometry to determine the type and redshift distribution of the SN sample. Our final sample includes 26 SNe Ia in the range 1.0

  7. Herschel-ATLAS: Dust temperature and redshift distribution of SPIRE and PACS detected sources using submillimetre colours

    OpenAIRE

    Amblard, A.; Blain, A.; Bock, J.; Frayer, D; Vieira, J.

    2010-01-01

    We present colour–colour diagrams of detected sources in the Herschel-ATLAS science demonstration field from 100 to 500 μm using both PACS and SPIRE. We fit isothermal modified black bodies to the spectral energy distribution (SED) to extract the dust temperature of sources with counterparts in Galaxy And Mass Assembly (GAMA) or SDSS surveys with either a spectroscopic or a photometric redshift. For a subsample of 330 sources detected in at least three FIR bands with a significance greater th...

  8. SHARDS: AN OPTICAL SPECTRO-PHOTOMETRIC SURVEY OF DISTANT GALAXIES

    Energy Technology Data Exchange (ETDEWEB)

    Perez-Gonzalez, Pablo G.; Cava, Antonio; Barro, Guillermo; Villar, Victor; Cardiel, Nicolas; Espino, Nestor; Gallego, Jesus [Departamento de Astrofisica, Facultad de CC. Fisicas, Universidad Complutense de Madrid, E-28040 Madrid (Spain); Ferreras, Ignacio [Mullard Space Science Laboratory, University College London, Holmbury St Mary, Dorking, Surrey RH5 6NT (United Kingdom); Rodriguez-Espinosa, Jose Miguel; Balcells, Marc; Cepa, Jordi [Instituto de Astrofisica de Canarias, E-38200 La Laguna, Tenerife (Spain); Alonso-Herrero, Almudena [Instituto de Fisica de Cantabria, CSIC-Universidad de Cantabria, E-39005 Santander (Spain); Cenarro, Javier [Centro de Estudios de Fisica del Cosmos de Aragon, Plaza San Juan 1, Planta 2, E-44001 Teruel (Spain); Charlot, Stephane [Institut d' Astrophysique de Paris, CNRS, Universite Pierre and Marie Curie, UMR 7095, 98bis bd Arago, F-75014 Paris (France); Cimatti, Andrea [Dipartimento di Astronomia, Universita degli Studi di Bologna, I-40127 Bologna (Italy); Conselice, Christopher J. [School of Physics and Astronomy, University of Nottingham, Nottingham NG7 2RD (United Kingdom); Daddi, Emmanuele; Elbaz, David [CEA, Laboratoire AIM, Irfu/SAp, F-91191 Gif-sur-Yvette (France); Donley, Jennifer [Los Alamos National Laboratory, Los Alamos, NM (United States); Gobat, R. [Laboratoire AIM-Paris-Saclay, CEA/DSM-CNRS-Universite Paris Diderot, Irfu/Service d' Astrophysique, CEA Saclay, Orme des Merisiers, F-91191 Gif-sur-Yvette (France); and others

    2013-01-01

    We present the Survey for High-z Absorption Red and Dead Sources (SHARDS), an ESO/GTC Large Program carried out using the OSIRIS instrument on the 10.4 m Gran Telescopio Canarias (GTC). SHARDS is an ultra-deep optical spectro-photometric survey of the GOODS-N field covering 130 arcmin{sup 2} at wavelengths between 500 and 950 nm with 24 contiguous medium-band filters (providing a spectral resolution R {approx} 50). The data reach an AB magnitude of 26.5 (at least at a 3{sigma} level) with sub-arcsec seeing in all bands. SHARDS' main goal is to obtain accurate physical properties of intermediate- and high-z galaxies using well-sampled optical spectral energy distributions (SEDs) with sufficient spectral resolution to measure absorption and emission features, whose analysis will provide reliable stellar population and active galactic nucleus (AGN) parameters. Among the different populations of high-z galaxies, SHARDS' principal targets are massive quiescent galaxies at z > 1, whose existence is one of the major challenges facing current hierarchical models of galaxy formation. In this paper, we outline the observational strategy and include a detailed discussion of the special reduction and calibration procedures which should be applied to the GTC/OSIRIS data. An assessment of the SHARDS data quality is also performed. We present science demonstration results on the detection and study of emission-line galaxies (star-forming objects and AGNs) at z = 0-5. We also analyze the SEDs for a sample of 27 quiescent massive galaxies with spectroscopic redshifts in the range 1.0 < z {approx}< 1.4. We discuss the improvements introduced by the SHARDS data set in the analysis of their star formation history and stellar properties. We discuss the systematics arising from the use of different stellar population libraries, typical in this kind of study. Averaging the results from the different libraries, we find that the UV-to-MIR SEDs of the massive quiescent galaxies at

  9. Empirical Bayes Credibility Models for Economic Catastrophic Losses by Regions

    Directory of Open Access Journals (Sweden)

    Jindrová Pavla

    2017-01-01

    Full Text Available Catastrophic events affect various regions of the world with increasing frequency and intensity. The number of catastrophic events and the amount of economic losses is varying in different world regions. Part of these losses is covered by insurance. Catastrophe events in last years are associated with increases in premiums for some lines of business. The article focus on estimating the amount of net premiums that would be needed to cover the total or insured catastrophic losses in different world regions using Bühlmann and Bühlmann-Straub empirical credibility models based on data from Sigma Swiss Re 2010-2016. The empirical credibility models have been developed to estimate insurance premiums for short term insurance contracts using two ingredients: past data from the risk itself and collateral data from other sources considered to be relevant. In this article we deal with application of these models based on the real data about number of catastrophic events and about the total economic and insured catastrophe losses in seven regions of the world in time period 2009-2015. Estimated credible premiums by world regions provide information how much money in the monitored regions will be need to cover total and insured catastrophic losses in next year.

  10. The relation between catastrophizing and the communication of pain experience.

    Science.gov (United States)

    Sullivan, M J L; Martel, M O; Tripp, D; Savard, A; Crombez, G

    2006-06-01

    The Communal Coping Model of pain catastrophizing proposes that pain catastrophizers enact pain behaviors in order to solicit support or empathy from their social environment. By this account, pain catastrophizers might be expected to engage in behavior aimed at maximizing the probability that their pain will be perceived by others in their social environment. To test this prediction, 40 undergraduates were videotaped during a cold pressor procedure. A separate sample of 20 (10 men, 10 women) undergraduates were asked to view the video sequences and infer the pain ratings of the cold pressor participants. Correlational analyses revealed that higher levels of pain catastrophizing of the cold pressor participants were associated with observer inferences of more intense pain, r=.39, ppain catastrophizing and observer inferences of pain intensity was mediated by the cold pressor participants' pain behavior. Although pain catastrophizing was associated with observers' inferences of more intense pain, cold pressor participants' level of pain catastrophizing was not associated with observers' accuracy in inferring self-reported pain. Implications of the findings for theory and clinical practice are addressed.

  11. Planck 2013 results. VIII. HFI photometric calibration and mapmaking

    DEFF Research Database (Denmark)

    Planck Collaboration,; Ade, P. A. R.; Aghanim, N.;

    2013-01-01

    This paper describes the processing applied to the HFI cleaned time-ordered data to produce photometrically calibrated maps. HFI observes the sky over a broad range of frequencies, from 100 to 857 GHz. To get the best accuracy on the calibration on such a large range, two different photometric ca...

  12. Spectral clustering for optical confirmation and redshift estimation of X-ray selected galaxy cluster candidates in the SDSS Stripe 82

    Science.gov (United States)

    Mahmoud, E.; Takey, A.; Shoukry, A.

    2016-07-01

    We develop a galaxy cluster finding algorithm based on spectral clustering technique to identify optical counterparts and estimate optical redshifts for X-ray selected cluster candidates. As an application, we run our algorithm on a sample of X-ray cluster candidates selected from the third XMM-Newton serendipitous source catalog (3XMM-DR5) that are located in the Stripe 82 of the Sloan Digital Sky Survey (SDSS). Our method works on galaxies described in the color-magnitude feature space. We begin by examining 45 galaxy clusters with published spectroscopic redshifts in the range of 0.1-0.8 with a median of 0.36. As a result, we are able to identify their optical counterparts and estimate their photometric redshifts, which have a typical accuracy of 0.025 and agree with the published ones. Then, we investigate another 40 X-ray cluster candidates (from the same cluster survey) with no redshift information in the literature and found that 12 candidates are considered as galaxy clusters in the redshift range from 0.29 to 0.76 with a median of 0.57. These systems are newly discovered clusters in X-rays and optical data. Among them 7 clusters have spectroscopic redshifts for at least one member galaxy.

  13. The VIMOS Ultra Deep Survey First Data Release: spectra and spectroscopic redshifts of 698 objects up to z~6 in CANDELS

    CERN Document Server

    Tasca, L A M; Ribeiro, B; Thomas, R; Moreau, C; Cassata, P; Garilli, B; Brun, V Le; Lemaux, B C; Maccagni, D; Pentericci, L; Schaerer, D; Vanzella, E; Zamorani, G; Zucca, E; Amorin, R; Bardelli, S; Cassara, L P; Castellano, M; Cimatti, A; Cucciati, O; Durkalec, A; Fontana, A; Giavalisco, M; Grazian, A; Hathi, N P; Ilbert, O; Paltani, S; Pforr, J; Scodeggio, M; Sommariva, V; Talia, M; Tresse, L; Vergani, D; Capak, P; Charlot, S; Contini, T; de la Torre, S; Dunlop, J; Fotopoulou, S; Guaita, L; Koekemoer, A; Lopez-Sanjuan, C; Mellier, Y; Salvato, M; Scoville, N; Taniguchi, Y; Wang, P W

    2016-01-01

    This paper describes the first data release (DR1) of the VIMOS Ultra Deep Survey (VUDS). The DR1 includes all low-resolution spectroscopic data obtained in 276.9 arcmin2 of the CANDELS-COSMOS and CANDELS-ECFDS survey areas, including accurate spectroscopic redshifts z_spec and individual spectra obtained with VIMOS on the ESO-VLT. A total of 698 objects have a measured redshift, with 677 galaxies, two type-I AGN and a small number of 19 contaminating stars. The targets of the spectroscopic survey are selected primarily on the basis of their photometric redshifts to ensure a broad population coverage. About 500 galaxies have z_spec>2, 48 with z_spec>4, and the highest reliable redshifts reach beyond z_spec=6. This dataset approximately doubles the number of galaxies with spectroscopic redshifts at z>3 in these fields. We discuss the general properties of the sample in terms of the spectroscopic redshift distribution, the distribution of Lyman-alpha equivalent widths, and physical properties including stellar m...

  14. Comparing High-redshift Galaxy Dropouts in GOODS-S from SelfCal and MultiDrizzle Maps

    Science.gov (United States)

    Cooper, Jennifer; Cooray, Asantha R.; Nayyeri, Hooshang

    2017-01-01

    A subset of the multi-wavelength CANDELS survey is utilized to compare results of high-redshift photometric dropout galaxies from two different image processing techniques in the GOODS-S region. The maps used are the publicly available CANDELS mosaics and SelfCal, which is a self-calibration method that removes anisotropy offsets that are introduced from combining frames taken at different times. The identified dropout sources for redshifts 4 and larger from each dataset are compared to Lyman-break galaxy catalogs. Preliminary results indicate a low match rate for sources between the SelfCal maps and published catalogs, which could be attributed to differing map depth and processing techniques.

  15. Photometrical research geostationary satellite "SBIRS GEO-2"

    Science.gov (United States)

    Sukhov, P. P.; Epishev, V. P; Sukhov, K. P; Kudak, V. I.

    The multicolor photometrical observations GSS "Sbirs Geo-2" were carried in B,V,R filters out during the autumn equinox 2014 and spring 2015 y. Periodic appearance of many light curves and dips of mirror reflections suggests that the GSS was not in orbit in a static position, predetermined three-axis orientation and in dynamic motion. On the basis of computer modeling suggests the following dynamics GSS "Sbirs Geo-2" in orbit. Helically scanning the visible Earth's surface infrared satellite sensors come with period P1 = 15.66 sec. and the rocking of the GSS about the direction of the motion vector of the satellite in orbit with P2 = 62.64 sec., most likely with the purpose to survey the greatest possible portion of the earth's surface.

  16. Photometric Supernova Classification With Machine Learning

    CERN Document Server

    Lochner, Michelle; Peiris, Hiranya V; Lahav, Ofer; Winter, Max K

    2016-01-01

    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 Telescope (LSST), given that spectroscopic confirmation of type for all supernovae discovered with these surveys 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 fitting 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. We test the pipeline on simulated multi-ba...

  17. Catastrophic Cracking Courtesy of Quiescent Cavitation

    CERN Document Server

    Daily, D Jesse; Thomson, Scott L; Truscott, Tadd T

    2012-01-01

    A popular party trick is to fill a glass bottle with water and hit the top of the bottle with an open hand, causing the bottom of the bottle to break open. We investigate the source of the catastrophic cracking through the use of high-speed video and an accelerometer attached to the bottom of a glass bottle. Upon closer inspection, it is obvious that the acceleration caused by hitting the top of the bottle is followed by the formation of bubbles near the bottom. The nearly instantaneous acceleration creates an area of low pressure on the bottom of the bottle where cavitation bubbles form. Moments later, the cavitation bubbles collapse at roughly 10 times the speed of formation, causing the bottle to break. The accelerometer data shows that the bottle is broken after the bubbles collapse and that the magnitude of the bubble collapse is greater than the initial impact. The fluid dynamics video highlights that this trick will not work if the bottle is empty nor if it is filled with a carbonated fluid because the...

  18. Avoiding Environmental Catastrophes: Varieties of Principled Precaution

    Directory of Open Access Journals (Sweden)

    Alan R. Johnson

    2012-09-01

    Full Text Available The precautionary principle is often proposed as a guide to action in environmental management or risk assessment, and has been incorporated in various legal and regulatory contexts. For many, it reflects the common sense notion of being safe rather than sorry, but it has attracted numerous critics. At times, proponents and critics talk at cross purposes, due to the multiplicity of ways the precautionary principle has been formulated. The approach taken here is to examine four general varieties of precaution, relating each to arguments made in various contexts by others. First, I examine the parallel between the precautionary principle and an argument referred to as Pascal's wager. Critics are right to dismiss versions of the precautionary principle that follow the logic of Pascal's wager, because that argument requires assumption of an infinite catastrophe, which is seldom the case in environmental decisions. Second, I explore precaution viewed as an instance of the phenomenon of ambiguity aversion as described by Daniel Ellsberg. Third, I evaluate precautionary perspectives on our duties to future generations, drawing inspiration from the views of Gifford Pinchot. Fourth, I consider the precautionary principle as an instance of Aldo Leopold's notion of intelligent tinkering. Although controversy persists, I find that a legitimate theoretical foundation exists to implement Ellsbergian, Pinchotian and Leopoldean varieties of precaution in environmental decision making. Additionally, I remark on the role of adaptive management and maintaining resilience in ecological and social systems as an approach to implementing the precautionary principle.

  19. The Potential for Space Intervention in Global Catastrophes

    Science.gov (United States)

    Hempsell, M.

    There is a growing understanding of the risks facing mankind of global catastrophe, which is defined as an event that kills a quarter the world population and risks destruction of organised society. Such catastrophes can be triggered by either naturally occurring, or arthropogenic, initiating events. And history shows that catastrophes with a natural origin do occur, with a mean separation time of around 1000 years. Anthropogenic initiated events are a recent possibility resulting from an expansion of technology capabilities, economic activity and population and, while they clearly significantly increase the total risk level above the natural background, it is more difficult to determine quantitatively by how much. Some initiating events and be directly tackled by an appropriate space capability. For example intercepting Near Earth Object before collision, or using Solar Power Satellites to eliminating carbon dioxide production in the power generation process to which many attribute global warming. Obviously prevention is the preferred option and so, not surprisingly, these particular uses of space as a means of preventing global catastrophe have received considerable attention. However space capability has a much wider potential for intervention in global catastrophes, even in those where the initiating event itself cannot be prevented. Previous work highlighting the risks through consideration of historic catastrophes has identified that global catastrophes have a complex structure with the initiating event triggering chains of vectors, which in turn trigger death causing agents. The work also highlighted that the vectors and agents during a catastrophe are similar regardless of the initiating event. This opens the possibility that space systems capable of addressing generic vectors and agents on a global scale can help deal with any global catastrophe regardless of its cause. The paper lists known (and credible) components to global catastrophes and highlight

  20. Risk Measure and Premium Distribution on Catastrophe Reinsurance

    Institute of Scientific and Technical Information of China (English)

    XUN LI; WANG DE-HUI

    2012-01-01

    In this paper,we propose a new risk measure which is based on the Orlicz premium principle to characterize catastrophe risk premium.The intention is to develop a formulation strategy for Catastrophe Fund.The logarithm equivalent form of reinsurance premium is regarded as the retention of reinsurer,and the differential earnings between the reinsurance premium and the reinsurer's retention is accumulated as a part of Catastrophe Fund.We demonstrate that the aforementioned risk measure has some good properties,which are further confirmed by numerical simulations in R environment.