Bulletin of the American Physical Society
APS April Meeting 2015
Volume 60, Number 4
Saturday–Tuesday, April 11–14, 2015; Baltimore, Maryland
Session Y2: Cosmology III: Dark Energy Survey |
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Sponsoring Units: DAP Chair: Bhuvnesh Jain, University of Pennsylvania Room: Holiday 1 |
Tuesday, April 14, 2015 1:30PM - 1:42PM |
Y2.00001: The Dark Energy Survey and Operations H. Thomas Diehl The Dark Energy Survey (DES) is a currently running optical survey aimed at understanding the accelerating expansion of the universe using four complementary methods: weak gravitational lensing, galaxy cluster counts, baryon acoustic oscillations, and Type Ia supernovae. To perform the 5000 sq-degree wide field and 30 sq-degree supernova surveys, the DES Collaboration built the Dark Energy Camera (DECam), a 3 square degree, 570 Megapixel CCD camera that was installed at the prime focus of the Blanco 4-meter telescope at the Cerro Tololo Inter-American Observatory. In Feb. 2015 DES completed its second 105-night season. We'll start up again in August. This presentation will describe DES, the survey strategy and goals, the efficiency of survey operations, and the quality and calibration of the data recorded through Year 2. [Preview Abstract] |
Tuesday, April 14, 2015 1:42PM - 1:54PM |
Y2.00002: Galaxy Clustering in the Dark Energy Survey Science Verification Data Ashley Ross, Martin Crocce I present the results of a study of galaxy clustering in a flux-limited sample ($i_{AB} < 22.5$) selected from the photometric Science Verification (SV) data of the Dark Energy Survey (DES), conducted by the DES large scale structure working group. The SV data provides science-quality images for more than 250 deg$^2$ at the nominal DES depth ($i_{AB} ? 24$). I will present the clustering analysis of this data, performed over five tomographic bins, with photometric redshifts, z, in the range 0.2 < z < 1.2. I will describe our work to identify and ameliorate systematics in the data set, which has allowed us to robustly measure the clustering amplitude of the galaxies in each tomographic bin. We test the relationship between the clustering of the galaxies and analytic predictions of the clustering of the dark matter, known as the bias relationship and determine the regime where it is described by a linear model I will present these results and compare them against a similar sample from the (previously) state-of-the-art CFHTLS, with which we find very good agreement. These results pave the way for exciting cosmological measurements to be made with future (larger) DES data sets and by combining the results with other probes such as CMB lensing and galaxy-galaxy lensing. [Preview Abstract] |
Tuesday, April 14, 2015 1:54PM - 2:06PM |
Y2.00003: CMB Lensing Tomography with the Dark Energy Survey Science Verification galaxies Ross Cawthon, Tommaso Giannantonio, Pablo Fosalba, Franz Elsner, Boris Leistedt, Aurelien Benoit-Levy, Donnacha Kirk, Martin Crocce, Scott Dodelson, Gil Holder, Yuuki Omori We present a detection of the cross-correlation between galaxies in the Dark Energy Survey (DES) Science Verification data and the lensing of the CMB as reconstructed by the Planck satellite and the South Pole Telescope (SPT). When considering the DES main galaxy sample, the significance of the detection is at the level of $> 5$ and $> 2\sigma$ for SPT and Planck respectively. Given the high significance recovered for the SPT correlation, we perform for the first time a tomographic analysis of the redshift evolution of the CMB lensing signal, by dividing the DES galaxies in five photometric redshift bins. We find that the signal evolves in redshift as expected in the fiducial cosmology, recovering significant ($> 2 \sigma$) detections in most bins. We further extend our analysis to a smaller Luminous Red Galaxy sample to test the correlation in the high-mass range, also finding a positive $\sim 3 \sigma$ signal in agreement with the fiducial model. We perform an extended test of the possible systematics that could affect our result, finding no evidence for them. We finally demonstrate how these measurements can be used to constrain the growth of structure across cosmic time. [Preview Abstract] |
Tuesday, April 14, 2015 2:06PM - 2:18PM |
Y2.00004: Measuring Scatter in the Cluster Richness-Mass Relation for the Dark Energy Survey Devon Hollowood, Tesla Jeltema, Eli Rykoff, Eduardo Rozo Measuring the number density of galaxy clusters as a function of density and redshift places strong constraints on the dark energy equation of state. This measurement can be cheaply and cleanly accomplished using galaxy cluster richness as a mass proxy. In order to understand the intrinsic scatter in the richness-mass relationship, I have developed a pipeline to determine comparatively low-scatter x-ray mass proxies for galaxy clusters which appear in both archival Chandra data and in the Dark Energy Survey catalogue. These data can then be used to constrain the cluster richness-mass relation, which in turn is expected to improve the Dark Energy Survey figure-of-merit by a factor of two. [Preview Abstract] |
Tuesday, April 14, 2015 2:18PM - 2:30PM |
Y2.00005: The Dark Energy Survey Science Verification Shear Catalog Michael Jarvis, Erin Sheldon, Joe Zuntz, Sarah Bridle, Tomasz Kacprzak We present results of the weak lensing analysis of the Dark Energy Survey (DES) science verification data. The science verification (SV) data use the same telescope and camera as the full DES is using, but the data were taken during commissioning time the year prior to the start of the DES. We have undergone a large battery of null tests to look for systematic errors in the shear values. The catalogs pass all tests at the levels required for doing weak lensing science with the SV data. We will show here the results of some of the more interesting tests. We will mention briefly some plans for improvements to the pipeline to help meet the more stringent demands of the full 5-year DES survey. [Preview Abstract] |
Tuesday, April 14, 2015 2:30PM - 2:42PM |
Y2.00006: Galaxy-Galaxy Lensing in Dark Energy Survey Science Verification Data Juliana Kwan, Bhuvnesh Jain, Joseph Clampitt, Carles Sanchez, Niall Maccrann We present galaxy-galaxy lensing results from 150 square degrees of Dark Energy Survey science verification data. Our lens sample consists of red galaxies which are specifically selected to have a low photometric redshift outlier rate. The lenses cover a wide redshift range 0.2 $<$ z $<$ 0.8, which divided into three bins yields a S/N $>$ 20 lensing measurement for each bin. The result is checked by performing a number of null tests, including various checks on the shear catalog and photometric redshifts. Covariances from jackknife subsamples of the data are validated with a suite of 100 mock surveys. We fit an HOD model that constrains the lens sample's central halo mass, mass-luminosity scatter, and satellite population. [Preview Abstract] |
Tuesday, April 14, 2015 2:42PM - 2:54PM |
Y2.00007: Combining Galaxy-Galaxy Lensing and Galaxy Clustering: A Practical Approach Youngsoo Park, Elisabeth Krause, Scott Dodelson, Bhuvnesh Jain Combining galaxy-galaxy lensing and galaxy clustering is a promising method for inferring the growth rate of large scale structure, a quantity that will shed light on the mechanism driving the acceleration of the Universe. The Dark Energy Survey (DES) is a prime candidate for such an analysis, with its measurements of both the distribution of galaxies on the sky and the tangential shears of background galaxies induced by these foreground lenses. By constructing an end-to-end analysis that combines large-scale galaxy clustering and small-scale galaxy-galaxy lensing, we forecast the potential of a combined probes analysis on DES datasets. In particular, we develop a practical approach to a DES combined probes analysis by jointly modeling the assumptions and systematics affecting the data vectors, employing a shared halo model, HOD parametrization, photometric redshift errors, and shear measurement errors. We also study the effect of external priors on different subsets of these parameters. We conclude that data from the first year of DES will provide powerful constraints on the evolution of structure growth in the universe, constraining the growth function to better than 5\%. [Preview Abstract] |
Tuesday, April 14, 2015 2:54PM - 3:06PM |
Y2.00008: Cosmic Shear Measurements with the Dark Energy Survey Science Verification Data Matthew Becker, Michael Troxel, Tim Eifler, Niall MacCrann We present the first cosmic shear measurements with the Dark Energy Survey Science Verification data, approximately 160 square degrees of four band, multiepoch imaging. We use two independent shear measurement pipelines developed for this data to perform a large suite null tests of the comsic shear signal, test for the presence of B-modes and search for instrumental contamination in the shear measurements. Combined with a suite of 126 ray traced weak lensing simulations, we are able to calibrate the covariance matrix of the cosmic shear measurements for the final likelihood analysis. [Preview Abstract] |
Tuesday, April 14, 2015 3:06PM - 3:18PM |
Y2.00009: Wide-Field Lensing Mass Maps from DES Science Verification Data Chihway Chang, Vinu Vikram, Bhuvnesh Jain, David Bacon 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 the 139 deg$^2$ SPT-E field from the Dark Energy Survey (DES) Science Verification (SV) data. We compare the distribution of mass with that of the foreground distribution of galaxies and clusters. The overdensities in the reconstructed map correlate well with the distribution of optically detected clusters. Cross-correlating the mass map with the foreground galaxies from the same DES SV data gives results consistent with mock catalogs that include the primary sources of statistical errors in the galaxy, lensing and photo-z catalogs. The statistical significance of the cross-correlation is at the 6.8$\sigma$ level with 20 arcminute smoothing. We test and validate our results with mock catalogs from N-body simulations. The tools and analysis techniques developed in this paper can be applied to forthcoming larger datasets from DES. [Preview Abstract] |
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