Lance Miller

Abstract:

This paper presents the first application of 3D cosmic shear to a wide-field weak lensing survey. 3D cosmic shear is a technique that analyses weak lensing in three dimensions using a spherical harmonic approach, and does not bin data in the redshift direction. This is applied to CFHTLenS, a 154 square degree imaging survey with a median redshift of 0.7 and an effective number density of 11 galaxies per square arcminute usable for weak lensing. To account for survey masks we apply a 3D pseudo-Cℓ approach on weak lensing data, and to avoid uncertainties in the highly non-linear regime, we separately analyse radial wavenumbers k ≤ 1.5 and 5.0 h Mpc-1, and angular wavenumbers ℓ ≈ 400-5000. We show how one can recover 2D and tomographic power spectra from the full 3D cosmic shear power spectra and present a measurement of the 2D cosmic shear power spectrum, and measurements of a set of 2-bin and 6-bin cosmic shear tomographic power spectra; in doing so we find that using the 3D power in the calculation of such 2D and tomographic power spectra from data naturally accounts for a minimum scale in the matter power spectrum. We use 3D cosmic shear to constrain cosmologies with parametersωM,ωB, σ8, h, ns, w0 and wa. For a non-evolving dark energy equation of state, and assuming a flat cosmology, lensing combined with Wilkinson Microwave Anisotropy Probe 7 results in h= 0.78 ± 0.12, ΩM = 0.252 ± 0.079, σ8 = 0.88 ± 0.23 and w=-1.16 ± 0.38 using only scales k ≤ 1.5 h Mpc-1. We also present results of lensing combined with first year Planck results, where we find no tension with the results from this analysis, but we also find no significant improvement over the Planck results alone. We find evidence of a suppression of power compared to Lambda cold dark matter (LCDM) on small scales 1.5 < k ≤ 5.0 h Mpc-1 in the lensing data, which is consistent with predictions of the effect of baryonic feedback on the matter power spectrum. © 2014 The Authors. Published by Oxford University Press on behalf of the Royal Astronomical Society.

Abstract:

We present evidence for the rapid variability of the high-velocity iron K-shell absorption in the nearby (z = 0.184) quasar PDS 456. From a recent long Suzaku observation in 2013 (1 Ms effective duration), we find that the equivalent width of iron K absorption increases by a factor of 5 during the observation, increasing from <105 eV within the first 100 ks of the observation, toward a maximum depth of 500 eV near the end. The implied outflow velocity of 0.25 c is consistent with that claimed from earlier (2007, 2011) Suzaku observations. The absorption varies on timescales as short as 1 week. We show that this variability can be equally well attributed to either (1) an increase in column density, plausibly associated with a clumpy time-variable outflow, or (2) the decreasing ionization of a smooth homogeneous outflow which is in photo-ionization equilibrium with the local photon field. The variability allows a direct measure of absorber location, which is constrained to within r = 200-3500 r g of the black hole. Even in the most conservative case, the kinetic power of the outflow is ≳ 6% of the Eddington luminosity, with a mass outflow rate in excess of 40% of the Eddington accretion rate. The wind momentum rate is directly equivalent to the Eddington momentum rate which suggests that the flow may have been accelerated by continuum scattering during an episode of Eddington-limited accretion. © 2014. The American Astronomical Society. All rights reserved..

Abstract:

Charge-coupled device (CCD) detectors, widely used to obtain digital imaging, can be damaged by high energy radiation. Degraded images appear blurred, because of an effect known as Charge Transfer Inefficiency (CTI), which trails bright objects as the image is read out. It is often possible to correct most of the trailing during post-processing, by moving flux back to where it belongs. We compare several popular algorithms for this: quantifying the effect of their physical assumptions and tradeoffs between speed and accuracy. We combine their best elements to construct a more accurate model of damaged CCDs in the Hubble Space Telescope's Advanced Camera for Surveys/Wide Field Channel, and update it using data up to early 2013. Our algorithm now corrects 98 per cent of CTI trailing in science exposures, a substantial improvement over previous work. Further progress will be fundamentally limited by the presence of read noise. Read noise is added after charge transfer so does not get trailed-but it is incorrectly untrailed during post-processing. © 2014 The Authors Published by Oxford University Press on behalf of the Royal Astronomical Society.

Abstract:

Higher order, non-Gaussian aspects of the large-scale structure carry valuable information on structure formation and cosmology, which is complementary to second-order statistics. In this work, we measure second- and third-order weak-lensing aperture-mass moments from the Canada-France-Hawaii Lensing Survey (CFHTLenS) and combine those with cosmic microwave background (CMB) anisotropy probes. The third moment is measured with a significance of 2σ. The combined constraint on Σ8 = σ8(Ωm/0.27)α is improved by 10 per cent, in comparison to the second-order only, and the allowed ranges for Ωm and σ8 are substantially reduced. Including general triangles of the lensing bispectrum yields tighter constraints compared to probing mainly equilateral triangles. Second- and third-order CFHTLenS lensing measurements improve Planck CMB constraints on Ωm and σ8 by 26 per cent for flat Λ cold dark matter. For a model with free curvature, the joint CFHTLenS-Planck result is Ωm = 0.28 ± 0.02 (68 per cent confidence), which is an improvement of 43 per cent compared to Planck alone. We test how our results are potentially subject to three astrophysical sources of contamination: source-lens clustering, the intrinsic alignment of galaxy shapes, and baryonic effects. We explore future limitations of the cosmological use of third-order weak lensing, such as the non-linear model and the Gaussianity of the likelihood function. © 2014 The Authors. Published by Oxford University Press on behalf of the Royal Astronomical Society.