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 ∼ 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 and list the current caveats and issues that should be understood before using these photometric redshifts in statistical analyses of the SDSS galaxies.

Abstract. We present the results of a CCD imaging survey for gravitational lensing in a sample of 38 X-ray-selected clusters of galaxies. Our sample consists of the most X-ray luminous

The cluster correlation function and its richness dependence are determined from 1108 clusters of galaxies -the largest sample of clusters studied so far -found in 379 deg 2 of Sloan Digital Sky Survey early data. The results are compared with previous samples of optically and X-ray selected clusters. The richness-dependent correlation function increases monotonically from an average correlation scale of ∼ 12 h −1 Mpc for poor clusters to ∼25 h −1 Mpc for the richer, more massive clusters with a mean separation of ∼90 h −1 Mpc. X-ray selected clusters suggest slightly stronger correlations than optically selected clusters (∼ 2-σ). The results are compared with large-scale cosmological simulations. The observed richness-dependent cluster correlation function is well represented by the standard flat LCDM model (Ω m ≃0.3, h ≃0.7), and is inconsistent with the considerably weaker correlations predicted by Ω m = 1 models. An analytic relation for the correlation scale versus cluster mean separation, r 0 − d, that best describes the observations and the LCDM prediction is r 0 ≃ 2.6 √ d (for d ≃ 20 -90 h −1 Mpc). Data from the complete Sloan Digital Sky Survey, when available, will greatly enhance the accuracy of the results and allow a more precise determination of cosmological parameters.

We present angular diameter distance measurements obtained by locating the baryon acoustic oscillations (BAO) scale in the distribution of galaxies selected from the first year of Dark Energy Survey data. We consider a sample of over 1.3 million galaxies distributed over a footprint of 1336 deg2 with 0.6 < $z$photo < 1 and a typical redshift uncertainty of 0.03(1 + $z$). This sample was selected, as fully described in a companion paper, using a colour/magnitude selection that optimizes trade-offs between number density and redshift uncertainty. We investigate the BAO signal in the projected clustering using three conventions, the angular separation, the comoving transverse separation, and spherical harmonics. Further, we compare results obtained from template-based and machine-learning photometric redshift determinations. We use 1800 simulations that approximate our sample in order to produce covariance matrices and allow us to validate our distance scale measurement methodology. We measure the angular diameter distance, DA, at the effective redshift of our sample divided by the true physical scale of the BAO feature, rd. We obtain close to a 4 per cent distance measurement of DA($z$eff = 0.81)/rd = 10.75 ± 0.43. These results are consistent with the flat Λ cold dark matter concordance cosmological model supported by numerous other recent experimental results.

Small temperature anisotropies in the Cosmic Microwave Background can be sourced by density perturbations via the late-time integrated Sachs-Wolfe effect. Large voids and superclusters are excellent environments to make a localized measurement of this tiny imprint. In some cases excess signals have been reported. We probed these claims with an independent data set, using the first year data of the Dark Energy Survey in a different footprint, and using a different super-structure finding strategy. We identified 52 large voids and 102 superclusters at redshifts 0.2 < z < 0.65. We used the Jubilee simulation to a priori evaluate the optimal ISW measurement configuration for our compensated top-hat filtering technique, and then performed a stacking measurement of the CMB temperature field based on the DES data. For optimal configurations, we detected a cumulative cold imprint of voids with ∆T f ≈ −5.0 ± 3.7 µK and a hot imprint of superclusters ∆T f ≈ 5.1 ± 3.2 µK ; this is ∼ 1.2σ higher than the expected |∆T f | ≈ 0.6 µK imprint of such super-structures in ΛCDM. If we instead use an a posteriori selected filter size (R/R v = 0.6), we can find a temperature decrement as large as ∆T f ≈ −9.8 ± 4.7 µK for voids, which is ∼ 2σ above ΛCDM expectations and is comparable to previous measurements made using SDSS super-structure data.