Characterization of DECam focal plane detectors

DECam is a 520 Mpix, 3 square-deg FOV imager being built for the Blanco 4m Telescope at CTIO. This facility instrument will be used for the 'Dark Energy Survey' of the southern galactic cap. DECam has chosen 250 ?m thick CCDs, developed at LBNL, with good QE in the near IR for the focal plane. In this work we present the characterization of these detectors done by the DES team, and compare it to the DECam technical requirements. The results demonstrate that the detectors satisfy the needs for instrument

The Dark Energy Survey Camera (DECam)

The Dark Energy Survey (DES) is a next generation optical survey aimed at understanding the expansion rate of the Universe using four complementary methods: weak gravitational lensing, galaxy cluster counts, baryon acoustic oscillations, and Type Ia supernovae. To perform the survey, the DES Collaboration is building the Dark Energy Camera (DECam), a 3 square degree, 570 Megapixel CCD camera that will be mounted at the prime focus of the Blanco 4-meter telescope at the Cerro Tololo Inter-American Observatory. CCD production has finished, yielding roughly twice the required 62 2k x 4k detectors. The construction of DECam is nearly finished. Integration and commissioning on a 'telescope simulator' of the major hardware and software components, except for the optics, recently concluded at Fermilab. Final assembly of the optical corrector has started at University College, London. Some components have already been received at CTIO. 'First-light' will be sometime in 2012. This oral presentation concentrates on the technical challenges involved in building DECam (and how we overcame them), and the present status of the instrument

Dark energy survey year 1 results: Constraining baryonic physics in the Universe

International audienceMeasurements of large-scale structure are interpreted using theoretical predictions for the matter distribution, including potential impacts of baryonic physics. We constrain the feedback strength of baryons jointly with cosmology using weak lensing and galaxy clustering observables (3 × 2pt) of Dark Energy Survey (DES) Year 1 data in combination with external information from baryon acoustic oscillations (BAO) and Planck cosmic microwave background polarization. Our baryon modelling is informed by a set of hydrodynamical simulations that span a variety of baryon scenarios; we span this space via a Principal Component (PC) analysis of the summary statistics extracted from these simulations. We show that at the level of DES Y1 constraining power, one PC is sufficient to describe the variation of baryonic effects in the observables, and the first PC amplitude (Q_1) generally reflects the strength of baryon feedback. With the upper limit of Q_1 prior being bound by the Illustris feedback scenarios, we reach |$\sim 20{{\ \rm per\ cent}}$| improvement in the constraint of |$S_8=\sigma _8(\Omega _{\rm m}/0.3)^{0.5}=0.788^{+0.018}_{-0.021}$| compared to the original DES 3 × 2pt analysis. This gain is driven by the inclusion of small-scale cosmic shear information down to 2.5 arcmin, which was excluded in previous DES analyses that did not model baryonic physics. We obtain |$S_8=0.781^{+0.014}_{-0.015}$| for the combined DES Y1+Planck EE+BAO analysis with a non-informative Q_1 prior. In terms of the baryon constraints, we measure |$Q_1=1.14^{+2.20}_{-2.80}$| for DES Y1 only and |$Q_1=1.42^{+1.63}_{-1.48}$| for DESY1+Planck EE+BAO, allowing us to exclude one of the most extreme AGN feedback hydrodynamical scenario at more than 2σ