| Home | [11–20] << 21 22 23 24 25 26 27 28 29 30 >> [31–40] |
|
ANTARES Collaboration(Adrian-Martinez, S. et al), Aguilar, J. A., Bigongiari, C., Dornic, D., Emanuele, U., Gomez-Gonzalez, J. P., et al. (2012). The positioning system of the ANTARES Neutrino Telescope. J. Instrum., 7, T08002–20pp.
Abstract: The ANTARES neutrino telescope, located 40km off the coast of Toulon in the Mediterranean Sea at a mooring depth of about 2475m, consists of twelve detection lines equipped typically with 25 storeys. Every storey carries three optical modules that detect Cherenkov light induced by charged secondary particles (typically muons) coming from neutrino interactions. As these lines are flexible structures fixed to the sea bed and held taut by a buoy, sea currents cause the lines to move and the storeys to rotate. The knowledge of the position of the optical modules with a precision better than 10cm is essential for a good reconstruction of particle tracks. In this paper the ANTARES positioning system is described. It consists of an acoustic positioning system, for distance triangulation, and a compass-tiltmeter system, for the measurement of the orientation and inclination of the storeys. Necessary corrections are discussed and the results of the detector alignment procedure are described.
Keywords: Timing detectors; Detector modelling and simulations II (electric fields, charge transport, multiplication and induction, pulse formation, electron emission, etc); Detector alignment and calibration methods (lasers, sources, particle-beams); Detector control systems (detector and experiment monitoring and slow-control systems, architecture, hardware, algorithms, databases)
|
|
Norena, J., Verde, L., Barenboim, G., & Bosch, C. (2012). Prospects for constraining the shape of non-Gaussianity with the scale-dependent bias. J. Cosmol. Astropart. Phys., 08(8), 019–16pp.
Abstract: We consider whether the non-Gaussian scale-dependent halo bias can be used not only to constrain the local form of non-Gaussianity but also to distinguish among different shapes. In particular, we ask whether it can constrain the behavior of the primordial three-point function in the squeezed limit where one of the momenta is much smaller than the other two. This is potentially interesting since the observation of a three-point function with a squeezed limit that does not go like the local nor equilateral templates would be a signal of non-trivial dynamics during inflation. To this end we use the quasi-single field inflation model of Chen & Wang [1, 2] as a representative two-parameter model, where one parameter governs the amplitude of non-Gaussianity and the other the shape. We also perform a model-independent analysis by parametrizing the scale-dependent bias as a power-law on large scales, where the power is to be constrained from observations. We find that proposed large-scale structure surveys (with characteristics similar to the dark energy task force stage IV surveys) have the potential to distinguish among the squeezed limit behavior of different bispectrum shapes for a wide range of fiducial model parameters. Thus the halo bias can help discriminate between different models of inflation.
|
|
Das, S., de Putter, R., Linder, E. V., & Nakajima, R. (2012). Weak lensing cosmology beyond Lambda CDM. J. Cosmol. Astropart. Phys., 11(11), 23pp.
Abstract: Weak gravitational lensing is one of the key probes of the cosmological model, dark energy, and dark matter, providing insight into both the cosmic expansion history and large scale structure growth history. Taking into account a broad spectrum of physics affecting growth – dynamical dark energy, extended gravity, neutrino masses, and spatial curvature – we analyze the cosmological constraints. Similarly we consider the effects of a range of systematic uncertainties, in shear measurement, photometric redshifts, intrinsic alignments, and the nonlinear power spectrum, on cosmological parameter extraction. We also investigate, and provide fitting formulas tor, the influence of survey parameters such as redshift depth, galaxy number densities, and sky area on the cosmological constraints in the beyond-ACDM parameter space. Finally, we examine the robustness of results for different fiducial cosmologies.
|
|
de Putter, R., Mena, O., Giusarma, E., Ho, S., Cuesta, A., Seo, H. J., et al. (2012). New Neutrino Mass Bounds from SDSS-III Data Release 8 Photometric Luminous Galaxies. Astrophys. J., 761(1), 12–12pp.
Abstract: We present neutrino mass bounds using 900,000 luminous galaxies with photometric redshifts measured from Sloan Digital Sky Survey III Data Release 8. The galaxies have photometric redshifts between z = 0.45 and z = 0.65 and cover 10,000 deg(2), thus probing a volume of 3 h(-3) Gpc(3) and enabling tight constraints to be derived on the amount of dark matter in the form of massive neutrinos. A new bound on the sum of neutrino masses Sigma m nu < 0.27 eV, at the 95% confidence level (CL), is obtained after combining our sample of galaxies, which we call “CMASS,” with Wilkinson Microwave Anisotropy Probe (WMAP) seven-year cosmic microwave background data and the most recent measurement of the Hubble parameter from the Hubble Space Telescope (HST). This constraint is obtained with a conservative multipole range of 30 < l < 200 in order to minimize nonlinearities, and a free bias parameter in each of the four redshift bins. We study the impact of assuming this linear galaxy bias model using mock catalogs and find that this model causes a small (similar to 1 sigma-1.5 sigma) bias in Omega(DM)h(2). For this reason, we also quote neutrino bounds based on a conservative galaxy bias model containing additional, shot-noise-like free parameters. In this conservative case, the bounds are significantly weakened, e. g., Sigma m(nu) < 0.38 eV (95% CL) for WMAP+HST+CMASS (l(max) = 200). We also study the dependence of the neutrino bound on the multipole range (l(max) = 150 versus l(max) = 200) and on which combination of data sets is included as a prior. The addition of supernova and/or baryon acoustic oscillation data does not significantly improve the neutrino mass bound once the HST prior is included. A companion paper describes the construction of the angular power spectra in detail and derives constraints on a general cosmological model, including the dark energy equation of state w and the spatial curvature Omega(K), while a second companion paper presents a measurement of the scale of baryon acoustic oscillations from the same data set. All three works are based on the catalog by Ross et al.
|
|
Ho, S. et al, de Putter, R., & Mena, O. (2012). Clustering of Sloan Digital Sky Survey III Photometric Luminous Galaxies: The Measurement, Systematics and Cosmological Implications. Astrophys. J., 761(1), 14–24pp.
Abstract: The Sloan Digital Sky Survey (SDSS) surveyed 14,555 deg(2), and delivered over a trillion pixels of imaging data. We present a study of galaxy clustering using 900,000 luminous galaxies with photometric redshifts, spanning between z = 0.45 and z = 0.65, constructed from the SDSS using methods described in Ross et al. This data set spans 11,000 deg(2) and probes a volume of 3 h(-3) Gpc(3), making it the largest volume ever used for galaxy clustering measurements. We describe in detail the construction of the survey window function and various systematics affecting our measurement. With such a large volume, high-precision cosmological constraints can be obtained given careful control and understanding of the observational systematics. We present a novel treatment of the observational systematics and its applications to the clustering signals from the data set. In this paper, we measure the angular clustering using an optimal quadratic estimator at four redshift slices with an accuracy of similar to 15%, with a bin size of delta(l) = 10 on scales of the baryon acoustic oscillations (BAOs; at l similar to 40-400). We also apply corrections to the power spectra due to systematics and derive cosmological constraints using the full shape of the power spectra. For a flat Lambda CDM model, when combined with cosmic microwave background Wilkinson Microwave Anisotropy Probe 7 (WMAP7) and H-0 constraints from using 600 Cepheids observed by Wide Field Camera 3 (WFC3; HST), we find Omega(Lambda) = 0.73 +/- 0.019 and H-0 to be 70.5 +/- 1.6 s(-1) Mpc(-1) km. For an open Lambda CDM model, when combined with WMAP7 + HST, we find Omega(K) = 0.0035 +/- 0.0054, improved over WMAP7+HST alone by 40%. For a wCDM model, when combined with WMAP7+HST+ SN, we find w = -1.071 +/- 0.078, and H-0 to be 71.3 +/- 1.7 s(-1) Mpc(-1) km, which is competitive with the latest large-scale structure constraints from large spectroscopic surveys such as the SDSS Data Release 7 (DR7) and WiggleZ. We also find that systematic-corrected power spectra give consistent constraints on cosmological models when compared with pre-systematic correction power spectra in the angular scales of interest. The SDSS-III Data Release 8 (SDSS-III DR8) Angular Clustering Data allow a wide range of investigations into the cosmological model, cosmic expansion (via BAO), Gaussianity of initial conditions, and neutrino masses. Here, we refer to our companion papers for further investigations using the clustering data. Our calculation of the survey selection function, systematics maps, and likelihood function for the COSMOMC package will be released at http://portal.nersc.gov/project/boss/galaxy/photoz/.
Keywords: cosmological parameters; dark energy; dark matter; distance scale
|