We describe the creation, content, and validation of the Dark Energy Survey (DES) internal year-one cosmology data set, Y1A1 GOLD, in support of upcoming cosmological analyses. The Y1A1 GOLD data set ...is assembled from multiple epochs of DES imaging and consists of calibrated photometric zero-points, object catalogs, and ancillary data products-e.g., maps of survey depth and observing conditions, star-galaxy classification, and photometric redshift estimates-that are necessary for accurate cosmological analyses. The Y1A1 GOLD wide-area object catalog consists of million objects detected in co-added images covering in the DES grizY filters. The 10 limiting magnitude for galaxies is , , , , and . Photometric calibration of Y1A1 GOLD was performed by combining nightly zero-point solutions with stellar locus regression, and the absolute calibration accuracy is better than 2% over the survey area. DES Y1A1 GOLD is the largest photometric data set at the achieved depth to date, enabling precise measurements of cosmic acceleration at z 1.
ABSTRACT
We describe the derivation and validation of redshift distribution estimates and their uncertainties for the populations of galaxies used as weak-lensing sources in the Dark Energy Survey ...(DES) Year 1 cosmological analyses. The Bayesian Photometric Redshift (bpz) code is used to assign galaxies to four redshift bins between z ≈ 0.2 and ≈1.3, and to produce initial estimates of the lensing-weighted redshift distributions $n^i_{\rm PZ}(z)\propto \mathrm{d}n^i/\mathrm{d}z$ for members of bin i. Accurate determination of cosmological parameters depends critically on knowledge of ni, but is insensitive to bin assignments or redshift errors for individual galaxies. The cosmological analyses allow for shifts $n^i(z)=n^i_{\rm PZ}(z-\Delta z^i)$ to correct the mean redshift of ni(z) for biases in $n^i_{\rm PZ}$. The Δzi are constrained by comparison of independently estimated 30-band photometric redshifts of galaxies in the Cosmic Evolution Survey (COSMOS) field to bpz estimates made from the DES griz fluxes, for a sample matched in fluxes, pre-seeing size, and lensing weight to the DES weak-lensing sources. In companion papers, the Δzi of the three lowest redshift bins are further constrained by the angular clustering of the source galaxies around red galaxies with secure photometric redshifts at 0.15 < z < 0.9. This paper details the bpz and COSMOS procedures, and demonstrates that the cosmological inference is insensitive to details of the ni(z) beyond the choice of Δzi. The clustering and COSMOS validation methods produce consistent estimates of Δzi in the bins where both can be applied, with combined uncertainties of $\sigma_{\Delta z^i}=0.015, 0.013, 0.011,$ and 0.022 in the four bins. Repeating the photo-z procedure instead using the Directional Neighbourhood Fitting algorithm, or using the ni(z) estimated from the matched sample in COSMOS, yields no discernible difference in cosmological inferences.
Abstract
We construct the largest curved-sky galaxy weak lensing mass map to date from the DES first-year (DES Y1) data. The map, about 10 times larger than the previous work, is constructed over a ...contiguous ≈1500 deg2, covering a comoving volume of ≈10 Gpc3. The effects of masking, sampling, and noise are tested using simulations. We generate weak lensing maps from two DES Y1 shear catalogues, MetaCalibration and Im3shape, with sources at redshift 0.2 < z < 1.3, and in each of four bins in this range. In the highest signal-to-noise map, the ratio between the mean signal to noise in the E-mode map and the B-mode map is ∼1.5 (∼2) when smoothed with a Gaussian filter of σG = 30 (80) arcmin. The second and third moments of the convergence κ in the maps are in agreement with simulations. We also find no significant correlation of κ with maps of potential systematic contaminants. Finally, we demonstrate two applications of the mass maps: (1) cross-correlation
with different foreground tracers of mass and (2) exploration of the largest peaks and voids in the maps.
This volume is the first focused effort to compile state-of-the-art research and address future directions of UGC. It explains how to collect, index, and analyze UGC to uncover social trends and user ...habits. The book describes how to mine various media, including social annotation, music information retrieval, and networks, and discusses the mining and searching of different types of UGC, such as Wikis and blogs. It also presents many applications of UGC, including the use of UGC to answer questions and summarize information.
We present Magellan/M2FS, Very Large Telescope/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 + or - 0.5 km s super(-1) and a velocity dispersion of 3.3 + or - 0.7 km s super(-1). The mass-to-light ratio of Ret II within its half-light radius is 470 + or - 210 M sub(middot in circle)L sub(middot in circle), demonstrating that it is a strongly dark matter-dominated system. Despite its spatial proximity to the Magellanic Clouds, the radial velocity of Ret II differs from that of the LMC and SMC by 199 and 83 km s super(-1), respectively, suggesting that it is not gravitationally bound to the Magellanic system. The likely member stars of Ret II span 1.3 dex in metallicity, with a dispersion of 0.28 + or - 0.09 dex, and we identify several extremely metal-poor stars with Fe/H < -3. In combination with its luminosity, size, and ellipticity, these results confirm that Ret II is an ultra-faint dwarf galaxy. With a mean metallicity of Fe/H = -2.65 + or - 0.07, Ret II matches Segue 1 as the most metal-poor galaxy known. Although Ret II is the third-closest dwarf galaxy to the Milky Way, the line-of-sight integral of the dark matter density squared is log sub(10) (J) = 18.8 0.6 GeV cm = + or - 2 -5 within 0degrees.2, indicating that the predicted gamma-ray flux from dark matter annihilation in Ret II is lower than that of several other dwarf galaxies.
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 deg2 area from the Dark Energy Survey (DES) science verification 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. We demonstrate that candidate superclusters and voids along the line of sight can be identified, exploiting the tight scatter of the cluster photometric redshifts. We cross-correlate the mass map with a foreground magnitude-limited galaxy sample from the same data. Our measurement gives results consistent with mock catalogs from N-body simulations that include the primary sources of statistical uncertainties in the galaxy, lensing, and photo-z catalogs. The statistical significance of the cross-correlation is at the 6.8σ level with 20 arcminute smoothing. We find that the contribution of systematics to the lensing mass maps is generally within measurement uncertainties. In this study, we analyze less than 3% of the final area that will be mapped by the DES; the tools and analysis techniques developed in this paper can be applied to forthcoming larger data sets from the survey.
This study describes the frequency of occurrence of work-related injuries and musculoskeletal disorders (MSDs) among factory workers in Shenzhen, China, and examines the determinants of injuries and ...MSDs.
A cross-sectional survey was conducted with 3479 frontline workers in 60 factories during 2008–2009. We calculated the annual incidence rates of work-related injuries and the prevalence rates of MSD (based on the Nordic Standard Form) for the factory workers. Logistic regression analysis was applied to explore the associations between potential risk factors and occupational injury and MSD.
Among all participating workers, 8.3% reported acute traumatic injuries in the previous 12 months. The event-based incidence rate was 119.6 per 1000 person-years. About half of the frontline workers reported suffering from MSDs during the previous 12 months. The injury risk was reduced for female workers (Odds ratio, OR: 0.48; 95% confidence interval, CI: 0.36–0.66) and those with higher educational levels, but increased in workers with over 55 work hours/week (OR: 1.64; 95% CI: 1.21–2.22), high mental stress at work (OR: 3.50; 95% CI: 1.70–7.19) and previous injury history (OR: 3.94; 95% CI: 2.78–5.58). The MSD risk was increased among female workers (OR: 1.58; 95% CI: 1.34–1.87), and those with over 55 work hours/week (OR: 1.56; 95% CI: 1.28–1.90), high mental stress at work (OR: 3.16; 95% CI: 2.04–4.89) and a past injury history (OR: 3.04; 95% CI: 2.14–4.32).
High proportions of frontline workers were affected by work injuries and MSDs in these factories in China. Long work hours, high mental stress at work and previous injury history were important risk factors for work-related injury and MSD.
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