G. M. Bernstein - University of Michigan

G. M. Bernstein
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Name
G. M. Bernstein
Affiliation
University of Michigan
City
Ann Arbor
Country
United States

Pubs By Year

Pub Categories

 
Cosmology and Nongalactic Astrophysics (32)
 
Instrumentation and Methods for Astrophysics (14)
 
Astrophysics of Galaxies (13)
 
High Energy Astrophysical Phenomena (3)
 
Computer Science - Graphics (2)
 
Earth and Planetary Astrophysics (2)
 
High Energy Physics - Phenomenology (1)
 
High Energy Physics - Experiment (1)
 
Statistics - Machine Learning (1)
 
Computer Science - Programming Languages (1)
 
Computer Science - Computer Vision and Pattern Recognition (1)
 
Solar and Stellar Astrophysics (1)
 
Computer Science - Learning (1)

Publications Authored By G. M. Bernstein

We characterize the ability of the Dark Energy Camera (DECam) to perform relative astrometry across its 500~Mpix, 3 deg^2 science field of view, and across 4 years of operation. This is done using internal comparisons of ~4x10^7 measurements of high-S/N stellar images obtained in repeat visits to fields of moderate stellar density, with the telescope dithered to move the sources around the array. An empirical astrometric model includes terms for: optical distortions; stray electric fields in the CCD detectors; chromatic terms in the instrumental and atmospheric optics; shifts in CCD relative positions of up to ~10 um when the DECam temperature cycles; and low-order distortions to each exposure from changes in atmospheric refraction and telescope alignment. Read More

We report the observation and physical characterization of the possible dwarf planet \UZ\ ("DeeDee"), a dynamically detached trans-Neptunian object discovered at 92 AU. This object is currently the second-most distant known trans-Neptunian object with reported orbital elements, surpassed in distance only by the dwarf planet Eris. The object was discovered with an $r$-band magnitude of 23. Read More

In this paper the effect of weak lensing magnification on galaxy number counts is studied by cross-correlating the positions of two galaxy samples, separated by redshift, using data from the Dark Energy Survey Science Verification dataset. The analysis is carried out for two photometrically-selected galaxy samples, with mean photometric redshifts in the $0.2 < z < 0. Read More

We search for excess gamma-ray emission coincident with the positions of confirmed and candidate Milky Way satellite galaxies using 6 years of data from the Fermi Large Area Telescope (LAT). Our sample of 45 stellar systems includes 28 kinematically confirmed dark-matter-dominated dwarf spheroidal galaxies (dSphs) and 17 recently discovered systems that have photometric characteristics consistent with the population of known dSphs. For each of these targets, the relative predicted gamma-ray flux due to dark matter annihilation is taken from kinematic analysis if available, and estimated from a distance-based scaling relation otherwise, assuming that the stellar systems are dark-matter-dominated dSphs. Read More

We use weak-lensing shear measurements to determine the mean mass of optically selected galaxy clusters in Dark Energy Survey Science Verification data. In a blinded analysis, we split the sample of more than 8,000 redMaPPer clusters into 15 subsets, spanning ranges in the richness parameter $5 \leq \lambda \leq 180$ and redshift $0.2 \leq z \leq 0. Read More

We derive a free-form mass distribution for the unrelaxed cluster A370 (z=0.375), using the latest Hubble Frontier Fields images and GLASS spectroscopy. Starting from a reliable set of 10 multiply lensed systems we produce a free-form lens model that identifies ~ 80 multiple-images. Read More

Galaxies and their dark matter halos populate a complicated filamentary network around large, nearly empty regions known as cosmic voids. Cosmic voids are usually identified in spectroscopic galaxy surveys, where 3D information about the large-scale structure of the Universe is available. Although an increasing amount of photometric data is being produced, its potential for void studies is limited since photometric redshifts induce line-of-sight position errors of $\sim50$ Mpc/$h$ or more that can render many voids undetectable. Read More

It is well known that the probability distribution function (PDF) of galaxy density contrast is approximately lognormal; whether the PDF of mass fluctuations derived from weak lensing convergence (kappa_WL) is lognormal is less well established. We derive PDFs of the galaxy and projected matter density distributions via the Counts in Cells (CiC) method. We use maps of galaxies and weak lensing convergence produced from the Dark Energy Survey (DES) Science Verification data over 139 deg^2. Read More

We present cosmological constraints from the Dark Energy Survey (DES) using a combined analysis of angular clustering of red galaxies and their cross-correlation with weak gravitational lensing of background galaxies. We use a 139 square degree contiguous patch of DES data from the Science Verification (SV) period of observations. Using large scale measurements, we constrain the matter density of the Universe as Omega_m = 0. Read More

Many graphics and vision problems can be expressed as non-linear least squares optimizations of objective functions over visual data, such as images and meshes. The mathematical descriptions of these functions are extremely concise, but their implementation in real code is tedious, especially when optimized for real-time performance on modern GPUs in interactive applications. In this work, we propose a new language, Opt (available under http://optlang. Read More

We address the problem of estimating the parameters of a time-homogeneous Markov chain given only noisy, aggregate data. This arises when a population of individuals behave independently according to a Markov chain, but individual sample paths cannot be observed due to limitations of the observation process or the need to protect privacy. Instead, only population-level counts of the number of individuals in each state at each time step are available. Read More

We present galaxy-galaxy lensing results from 139 square degrees of Dark Energy Survey (DES) Science Verification (SV) data. Our lens sample consists of red galaxies, known as redMaGiC, which are specifically selected to have a low photometric redshift error and outlier rate. The lensing measurement has a total signal-to-noise of 29 over scales $0. Read More

We detect the kinematic Sunyaev-Zel'dovich (kSZ) effect with a statistical significance of $4.2 \sigma$ by combining a cluster catalogue derived from the first year data of the Dark Energy Survey (DES) with CMB temperature maps from the South Pole Telescope Sunyaev-Zel'dovich (SPT-SZ) Survey. This measurement is performed with a differential statistic that isolates the pairwise kSZ signal, providing the first detection of the large-scale, pairwise motion of clusters using redshifts derived from photometric data. Read More

We measure the correlation of galaxy lensing and cosmic microwave background lensing with a set of galaxies expected to trace the matter density field. The measurements are performed using pre-survey Dark Energy Survey (DES) Science Verification optical imaging data and millimeter-wave data from the 2500 square degree South Pole Telescope Sunyaev-Zel'dovich (SPT-SZ) survey. The two lensing-galaxy correlations are jointly fit to extract constraints on cosmological parameters, constraints on the redshift distribution of the lens galaxies, and constraints on the absolute shear calibration of DES galaxy lensing measurements. Read More

We describe updates to the \redmapper{} algorithm, a photometric red-sequence cluster finder specifically designed for large photometric surveys. The updated algorithm is applied to $150\,\mathrm{deg}^2$ of Science Verification (SV) data from the Dark Energy Survey (DES), and to the Sloan Digital Sky Survey (SDSS) DR8 photometric data set. The DES SV catalog is locally volume limited, and contains 786 clusters with richness $\lambda>20$ (roughly equivalent to $M_{\rm{500c}}\gtrsim10^{14}\,h_{70}^{-1}\,M_{\odot}$) and $0. Read More

2016Jan
Authors: Dark Energy Survey Collaboration, T. Abbott, F. B. Abdalla, J. Aleksic, S. Allam, A. Amara, D. Bacon, E. Balbinot, M. Banerji, K. Bechtol, A. Benoit-Levy, G. M. Bernstein, E. Bertin, J. Blazek, C. Bonnett, S. Bridle, D. Brooks, R. J. Brunner, E. Buckley-Geer, D. L. Burke, G. B. Caminha, D. Capozzi, J. Carlsen, A. Carnero-Rosell, M. Carollo, M. Carrasco-Kind, J. Carretero, F. J. Castander, L. Clerkin, T. Collett, C. Conselice, M. Crocce, C. E. Cunha, C. B. D'Andrea, L. N. da Costa, T. M. Davis, S. Desai, H. T. Diehl, J. P. Dietrich, S. Dodelson, P. Doel, A. Drlica-Wagner, J. Estrada, J. Etherington, A. E. Evrard, J. Fabbri, D. A. Finley, B. Flaugher, R. J. Foley, P. Rosalba, J. Frieman, J. Garcia-Bellido, E. Gaztanaga, D. W. Gerdes, T. Giannantonio, D. A. Goldstein, D. Gruen, R. A. Gruendl, P. Guarnieri, G. Gutierrez, W. Hartley, K. Honscheid, B. Jain, D. J. James, T. Jeltema, S. Jouvel, R. Kessler, A. King, D. Kirk, R. Kron, K. Kuehn, N. Kuropatkin, O. Lahav, T. S. Li, M. Lima, H. Lin, M. A. G. Maia, M. Makler, M. Manera, C. Maraston, J. L. Marshall, P. Martini, R. G. McMahon, P. Melchior, A. Merson, C. J. Miller, R. Miquel, J. J. Mohr, X. Morice-Atkinson, K. Naidoo, E. Neilsen, R. C. Nichol, B. Nord, R. Ogando, F. Ostrovski, A. Palmese, A. Papadopoulos, H. Peiris, J. Peoples, W. J. Percival, A. A. Plazas, S. L. Reed, A. Refregier, A. K. Romer, A. Roodman, A. Ross, E. Rozo, E. S. Rykoff, I. Sadeh, M. Sako, C. Sanchez, E. Sanchez, B. Santiago, V. Scarpine, M. Schubnell, I. Sevilla-Noarbe, E. Sheldon, M. Smith, R. C. Smith, M. Soares-Santos, F. Sobreira, M. Soumagnac, E. Suchyta, M. Sullivan, M. Swanson, G. Tarle, J. Thaler, D. Thomas, R. C. Thomas, D. Tucker, J. D. Vieira, V. Vikram, A. R. Walker, R. H. Wechsler, J. Weller, W. Wester, L. Whiteway, H. Wilcox, B. Yanny, Y. Zhang, J. Zuntz

This overview article describes the legacy prospect and discovery potential of the Dark Energy Survey (DES) beyond cosmological studies, illustrating it with examples from the DES early data. DES is using a wide-field camera (DECam) on the 4m Blanco Telescope in Chile to image 5000 sq deg of the sky in five filters (grizY). By its completion the survey is expected to have generated a catalogue of 300 million galaxies with photometric redshifts and 100 million stars. Read More

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. Read More

We measure the cross-correlation between weak lensing of galaxy images and of the cosmic microwave background (CMB). The effects of gravitational lensing on different sources will be correlated if the lensing is caused by the same mass fluctuations. We use galaxy shape measurements from 139 deg$^{2}$ of the Dark Energy Survey (DES) Science Verification data and overlapping CMB lensing from the South Pole Telescope (SPT) and Planck. Read More

2015Sep
Affiliations: 1The DES Collaboration, 2The DES Collaboration, 3The DES Collaboration, 4The DES Collaboration, 5The DES Collaboration, 6The DES Collaboration, 7The DES Collaboration, 8The DES Collaboration, 9The DES Collaboration, 10The DES Collaboration, 11The DES Collaboration, 12The DES Collaboration, 13The DES Collaboration, 14The DES Collaboration, 15The DES Collaboration, 16The DES Collaboration, 17The DES Collaboration, 18The DES Collaboration, 19The DES Collaboration, 20The DES Collaboration, 21The DES Collaboration, 22The DES Collaboration, 23The DES Collaboration, 24The DES Collaboration, 25The DES Collaboration, 26The DES Collaboration, 27The DES Collaboration, 28The DES Collaboration, 29The DES Collaboration, 30The DES Collaboration, 31The DES Collaboration, 32The DES Collaboration, 33The DES Collaboration, 34The DES Collaboration, 35The DES Collaboration, 36The DES Collaboration, 37The DES Collaboration, 38The DES Collaboration, 39The DES Collaboration, 40The DES Collaboration, 41The DES Collaboration, 42The DES Collaboration, 43The DES Collaboration, 44The DES Collaboration, 45The DES Collaboration, 46The DES Collaboration, 47The DES Collaboration, 48The DES Collaboration, 49The DES Collaboration, 50The DES Collaboration, 51The DES Collaboration, 52The DES Collaboration

We report the discovery of a stellar stream in the Dark Energy Survey (DES) Year 1 (Y1A1) data. The discovery was made through simple color-magnitude filters and visual inspection of the Y1A1 data. We refer to this new object as the Phoenix stream, after its resident constellation. Read More

We demonstrate highly accurate recovery of weak gravitational lensing shear using an implementation of the Bayesian Fourier Domain (BFD) method proposed by Bernstein & Armstrong (2014, BA14), extended to correct for selection biases. The BFD formalism is rigorously correct for Nyquist-sampled, background-limited, uncrowded image of background galaxies. BFD does not assign shapes to galaxies, instead compressing the pixel data D into a vector of moments M, such that we have an analytic expression for the probability P(M|g) of obtaining the observations with gravitational lensing distortion g along the line of sight. Read More

We report the discovery of eight new ultra-faint dwarf galaxy candidates in the second year of optical imaging data from the Dark Energy Survey (DES). Six of these candidates are detected at high confidence, while two lower-confidence candidates are identified in regions of non-uniform survey coverage. The new stellar systems are found by three independent automated search techniques and are identified as overdensities of stars, consistent with the isochrone and luminosity function of an old and metal-poor simple stellar population. Read More

We measure the weak lensing shear around galaxy troughs, i.e. the radial alignment of background galaxies relative to underdensities in projections of the foreground galaxy field over a wide range of redshift in Science Verification data from the Dark Energy Survey. Read More

We introduce redMaGiC, an automated algorithm for selecting Luminous Red Galaxies (LRGs). The algorithm was specifically developed to minimize photometric redshift uncertainties in photometric large-scale structure studies. redMaGiC achieves this by self-training the color-cuts necessary to produce a luminosity-thresholded LRG sample of constant comoving density. Read More

We measure the cross-correlation between the galaxy density in the Dark Energy Survey (DES) Science Verification data and the lensing of the cosmic microwave background (CMB) as reconstructed with the Planck satellite and the South Pole Telescope (SPT). When using the DES main galaxy sample over the full redshift range $0.2 < z < 1. Read More

2015Jul
Authors: The Dark Energy Survey Collaboration, T. Abbott, F. B. Abdalla, S. Allam, A. Amara, J. Annis, R. Armstrong, D. Bacon, M. Banerji, A. H. Bauer, E. Baxter, M. R. Becker, A. Benoit-Lévy, R. A. Bernstein, G. M. Bernstein, E. Bertin, J. Blazek, C. Bonnett, S. L. Bridle, D. Brooks, C. Bruderer, E. Buckley-Geer, D. L. Burke, M. T. Busha, D. Capozzi, A. Carnero Rosell, M. Carrasco Kind, J. Carretero, F. J. Castander, C. Chang, J. Clampitt, M. Crocce, C. E. Cunha, C. B. D'Andrea, L. N. da Costa, R. Das, D. L. DePoy, S. Desai, H. T. Diehl, J. P. Dietrich, S. Dodelson, P. Doel, A. Drlica-Wagner, G. Efstathiou, T. F. Eifler, B. Erickson, J. Estrada, A. E. Evrard, A. Fausti Neto, E. Fernandez, D. A. Finley, B. Flaugher, P. Fosalba, O. Friedrich, J. Frieman, C. Gangkofner, J. Garcia-Bellido, E. Gaztanaga, D. W. Gerdes, D. Gruen, R. A. Gruendl, G. Gutierrez, W. Hartley, M. Hirsch, K. Honscheid, E. M. Huff, B. Jain, D. J. James, M. Jarvis, T. Kacprzak, S. Kent, D. Kirk, E. Krause, A. Kravtsov, K. Kuehn, N. Kuropatkin, J. Kwan, O. Lahav, B. Leistedt, T. S. Li, M. Lima, H. Lin, N. MacCrann, M. March, J. L. Marshall, P. Martini, R. G. McMahon, P. Melchior, C. J. Miller, R. Miquel, J. J. Mohr, E. Neilsen, R. C. Nichol, A. Nicola, B. Nord, R. Ogando, A. Palmese, H. V. Peiris, A. A. Plazas, A. Refregier, N. Roe, A. K. Romer, A. Roodman, B. Rowe, E. S. Rykoff, C. Sabiu, I. Sadeh, M. Sako, S. Samuroff, C. Sánchez, E. Sanchez, H. Seo, I. Sevilla-Noarbe, E. Sheldon, R. C. Smith, M. Soares-Santos, F. Sobreira, E. Suchyta, M. E. C. Swanson, G. Tarle, J. Thaler, D. Thomas, M. A. Troxel, V. Vikram, A. R. Walker, R. H. Wechsler, J. Weller, Y. Zhang, J. Zuntz

We present the first constraints on cosmology from the Dark Energy Survey (DES), using weak lensing measurements from the preliminary Science Verification (SV) data. We use 139 square degrees of SV data, which is less than 3\% of the full DES survey area. Using cosmic shear 2-point measurements over three redshift bins we find $\sigma_8 (\Omega_{\rm m}/0. Read More

We present measurements of weak gravitational lensing cosmic shear two-point statistics using Dark Energy Survey Science Verification data. We demonstrate that our results are robust to the choice of shear measurement pipeline, either ngmix or im3shape, and robust to the choice of two-point statistic, including both real and Fourier-space statistics. Our results pass a suite of null tests including tests for B-mode contamination and direct tests for any dependence of the two-point functions on a set of 16 observing conditions and galaxy properties, such as seeing, airmass, galaxy color, galaxy magnitude, etc. Read More

We present weak lensing shear catalogues for 139 square degrees of data taken during the Science Verification (SV) time for the new Dark Energy Camera (DECam) being used for the Dark Energy Survey (DES). We describe our object selection, point spread function estimation and shear measurement procedures using two independent shear pipelines, IM3SHAPE and NGMIX, which produce catalogues of 2.12 million and 3. Read More

2015Jul

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. Read More

Spatially-varying depth and characteristics of observing conditions, such as seeing, airmass, or sky background, are major sources of systematic uncertainties in modern galaxy survey analyses, in particular in deep multi-epoch surveys. We present a framework to extract and project these sources of systematics onto the sky, and apply it to the Dark Energy Survey (DES) to map the observing conditions of the Science Verification (SV) data. The resulting distributions and maps of sources of systematics are used in several analyses of DES SV to perform detailed null tests with the data, and also to incorporate systematics in survey simulations. Read More

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. Read More

We describe the difference imaging pipeline (DiffImg) used to detect transients in deep images from the Dark Energy Survey Supernova program (DES-SN) in its first observing season from Aug 2013 through Feb 2014. DES-SN is a search for transients in which ten 3-deg^2 fields are repeatedly observed in the g,r,i,z passbands with a cadence of about 1 week. The observing strategy has been optimized to measure high-quality light curves and redshifts for thousands of Type Ia supernova (SN Ia) with the goal of measuring dark energy parameters. Read More

We cross-match galaxy cluster candidates selected via their Sunyaev-Zel'dovich effect (SZE) signatures in 129.1 deg$^2$ of the South Pole Telescope 2500d SPT-SZ survey with optically identified clusters selected from the Dark Energy Survey (DES) science verification data. We identify 25 clusters between $0. Read More

Designing programming environments for physical simulation is challenging because simulations rely on diverse algorithms and geometric domains. These challenges are compounded when we try to run efficiently on heterogeneous parallel architectures. We present Ebb, a domain-specific language (DSL) for simulation, that runs efficiently on both CPUs and GPUs. Read More

2015Apr
Affiliations: 1The DES Collaboration, 2The DES Collaboration, 3The DES Collaboration, 4The DES Collaboration, 5The DES Collaboration, 6The DES Collaboration, 7The DES Collaboration, 8The DES Collaboration, 9The DES Collaboration, 10The DES Collaboration, 11The DES Collaboration, 12The DES Collaboration, 13The DES Collaboration, 14The DES Collaboration, 15The DES Collaboration, 16The DES Collaboration, 17The DES Collaboration, 18The DES Collaboration, 19The DES Collaboration, 20The DES Collaboration, 21The DES Collaboration, 22The DES Collaboration, 23The DES Collaboration, 24The DES Collaboration, 25The DES Collaboration, 26The DES Collaboration, 27The DES Collaboration, 28The DES Collaboration, 29The DES Collaboration, 30The DES Collaboration, 31The DES Collaboration, 32The DES Collaboration, 33The DES Collaboration, 34The DES Collaboration, 35The DES Collaboration, 36The DES Collaboration, 37The DES Collaboration, 38The DES Collaboration, 39The DES Collaboration, 40The DES Collaboration, 41The DES Collaboration, 42The DES Collaboration, 43The DES Collaboration, 44The DES Collaboration, 45The DES Collaboration, 46The DES Collaboration, 47The DES Collaboration, 48The DES Collaboration, 49The DES Collaboration, 50The DES Collaboration, 51The DES Collaboration, 52The DES Collaboration, 53The DES Collaboration, 54The DES Collaboration, 55The DES Collaboration, 56The DES Collaboration, 57The DES Collaboration, 58The DES Collaboration, 59The DES Collaboration, 60The DES Collaboration, 61The DES Collaboration, 62The DES Collaboration, 63The DES Collaboration, 64The DES Collaboration, 65The DES Collaboration, 66The DES Collaboration, 67The DES Collaboration, 68The DES Collaboration, 69The DES Collaboration, 70The DES Collaboration, 71The DES Collaboration, 72The DES Collaboration

We present Magellan/M2FS, VLT/GIRAFFE, and Gemini South/GMOS spectroscopy of the newly discovered Milky Way satellite Reticulum II. Based on the spectra of 25 Ret II member stars selected from Dark Energy Survey imaging, we measure a mean heliocentric velocity of 62.8 +/- 0. Read More

Weak gravitational lensing allows one to reconstruct the spatial distribution of the projected mass density across the sky. These "mass maps" provide a powerful tool for studying cosmology as they probe both luminous and dark matter. In this paper, we present a weak lensing mass map reconstructed from shear measurements in a 139 sq. Read More

2015Apr

The Dark Energy Camera is a new imager with a 2.2-degree diameter field of view mounted at the prime focus of the Victor M. Blanco 4-meter telescope on Cerro Tololo near La Serena, Chile. Read More

We report the discovery of eight new Milky Way companions in ~1,800 deg^2 of optical imaging data collected during the first year of the Dark Energy Survey (DES). Each system is identified as a statistically significant over-density of individual stars consistent with the expected isochrone and luminosity function of an old and metal-poor stellar population. The objects span a wide range of absolute magnitudes (M_V from -2. Read More

2015Mar
Authors: The Fermi-LAT Collaboration, The DES Collaboration, :, A. Drlica-Wagner, A. Albert, K. Bechtol, M. Wood, L. Strigari, M. Sanchez-Conde, L. Baldini, R. Essig, J. Cohen-Tanugi, B. Anderson, R. Bellazzini, E. D. Bloom, R. Caputo, C. Cecchi, E. Charles, J. Chiang, A. de Angelis, S. Funk, P. Fusco, F. Gargano, N. Giglietto, F. Giordano, S. Guiriec, M. Gustafsson, M. Kuss, F. Loparco, P. Lubrano, N. Mirabal, T. Mizuno, A. Morselli, T. Ohsugi, E. Orlando, M. Persic, S. Raino, N. Sehgal, F. Spada, D. J. Suson, G. Zaharijas, S. Zimmer, T. Abbott, S. Allam, E. Balbinot, A. H. Bauer, A. Benoit-Levy, R. A. Bernstein, G. M. Bernstein, E. Bertin, D. Brooks, E. Buckley-Geer, D. L. Burke, A. Carnero Rosell, F. J. Castander, R. Covarrubias, C. B. D'Andrea, L. N. da Costa, D. L. DePoy, S. Desai, H. T. Diehl, C. E Cunha, T. F. Eifler, J. Estrada, A. E. Evrard, A. Fausti Neto, E. Fernandez, D. A. Finley, B. Flaugher, J. Frieman, E. Gaztanaga, D. Gerdes, D. Gruen, R. A. Gruendl, G. Gutierrez, K. Honscheid, B. Jain, D. James, T. Jeltema, S. Kent, R. Kron, K. Kuehn, N. Kuropatkin, O. Lahav, T. S. Li, E. Luque, M. A. G. Maia, M. Makler, M. March, J. Marshall, P. Martini, K. W. Merritt, C. Miller, R. Miquel, J. Mohr, E. Neilsen, B. Nord, R. Ogando, J. Peoples, D. Petravick, A. Pieres, A. A. Plazas, A. Queiroz, A. K. Romer, A. Roodman, E. S. Rykoff, M. Sako, E. Sanchez, B. Santiago, V. Scarpine, M. Schubnell, I. Sevilla, R. C. Smith, M. Soares-Santos, F. Sobreira, E. Suchyta, M. E. C. Swanson, G. Tarle, J. Thaler, D. Thomas, D. Tucker, A. Walker, R. H. Wechsler, W. Wester, P. Williams, B. Yanny, J. Zuntz

Due to their proximity, high dark-matter content, and apparent absence of non-thermal processes, Milky Way dwarf spheroidal satellite galaxies (dSphs) are excellent targets for the indirect detection of dark matter. Recently, eight new dSph candidates were discovered using the first year of data from the Dark Energy Survey (DES). We searched for gamma-ray emission coincident with the positions of these new objects in six years of Fermi Large Area Telescope data. Read More

Interaction of charges in CCDs with the already accumulated charge distribution causes both a flux dependence of the point-spread function (an increase of observed size with flux, also known as the brighter/fatter effect) and pixel-to-pixel correlations of the Poissonian noise in flat fields. We describe these effects in the Dark Energy Camera (DECam) with charge dependent shifts of effective pixel borders, i.e. Read More

GALSIM is a collaborative, open-source project aimed at providing an image simulation tool of enduring benefit to the astronomical community. It provides a software library for generating images of astronomical objects such as stars and galaxies in a variety of ways, efficiently handling image transformations and operations such as convolution and rendering at high precision. We describe the GALSIM software and its capabilities, including necessary theoretical background. Read More

We present the combination of optical data from the Science Verification phase of the Dark Energy Survey (DES) with near infrared data from the ESO VISTA Hemisphere Survey (VHS). The deep optical detections from DES are used to extract fluxes and associated errors from the shallower VHS data. Joint 7-band ($grizYJK$) photometric catalogues are produced in a single 3 sq-deg DECam field centred at 02h26m$-$04d36m where the availability of ancillary multi-wavelength photometry and spectroscopy allows us to test the data quality. Read More

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. Read More

We measure the weak-lensing masses and galaxy distributions of four massive galaxy clusters observed during the Science Verification phase of the Dark Energy Survey. This pathfinder study is meant to 1) validate the DECam imager for the task of measuring weak-lensing shapes, and 2) utilize DECam's large field of view to map out the clusters and their environments over 90 arcmin. We conduct a series of rigorous tests on astrometry, photometry, image quality, PSF modeling, and shear measurement accuracy to single out flaws in the data and also to identify the optimal data processing steps and parameters. Read More

Photo-generated charge in thick, back-illuminated, fully-depleted CCDs is transported by electric fields from the silicon substrate to the collecting well at the front gate of the CCDs. However, electric fields transverse to the surface of the CCD -with diverse origins such as doping gradients, guard rings around the imaging area of the sensor, and physical stresses on the silicon lattice- displace this charge, effectively modifying the pixel area and producing noticeable signals in astrometric and photometric measurements. We use data from the science verification period of the Dark Energy Survey (DES) to characterize these effects in the Dark Energy Camera (DECam) CCDs. Read More

We implement an algorithm for detecting and removing artifacts from astronomical images by means of outlier rejection during stacking. Our method is capable of addressing both small, highly significant artifacts such as cosmic rays and, by applying a filtering technique to generate single frame masks, larger area but lower surface brightness features such as secondary (ghost) images of bright stars. In contrast to the common method of building a median stack, the clipped or outlier-filtered mean stacked point-spread function (PSF) is a linear combination of the single frame PSFs as long as the latter are moderately homogeneous, a property of great importance for weak lensing shape measurement or model fitting photometry. Read More