153 research outputs found
The Skewness of the Aperture Mass Statistic
We present simple formulae for calculating the skewness and kurtosis of the
aperture mass statistic for weak lensing surveys which is insensitive to
masking effects of survey geometry or variable survey depth. The calculation is
the higher order analog of the formula given by Schneider et al (2002) which
has been used to compute the variance of the aperture mass from several lensing
surveys. As our formula requires the three-point shear correlation function, we
also present an efficient tree-based algorithm for measuring it. We show how
our algorithm would scale in computing time and memory usage for future lensing
surveys. Finally, we apply the procedure to our CTIO survey data, originally
described in Jarvis et al (2003). We find that the skewness is positive
(inconsistent with zero) at the 2 sigma level. However, the signal is too noisy
from this data to usefully constrain cosmology.Comment: 16 pages, accepted by MNRAS. Minor revisions; this replacement
matches the accepted versio
The Born and Lens-Lens Corrections to Weak Gravitational Lensing Angular Power Spectra
We revisit the estimation of higher order corrections to the angular power
spectra of weak gravitational lensing. Extending a previous calculation of
Cooray and Hu, we find two additional terms to the fourth order in potential
perturbations of large-scale structure corresponding to corrections associated
with the Born approximation and the neglect of line-of-sight coupling of two
foreground lenses in the standard first order result. These terms alter the
convergence (), the lensing shear E-mode (),
and their cross-correlation () power spectra on large angular
scales, but leave the power spectra of the lensing shear B-mode ()
and rotational () component unchanged as compared to previous
estimates. The new terms complete the calculation of corrections to weak
lensing angular power spectra associated with both the Born approximation and
the lens-lens coupling to an order in which the contributions are most
significant. Taking these features together, we find that these corrections are
unimportant for any weak lensing survey, including for a full sky survey
limited by cosmic variance.Comment: Added references, minor changes to text. 9 pages, 2 figure
Weak lensing, dark matter and dark energy
Weak gravitational lensing is rapidly becoming one of the principal probes of
dark matter and dark energy in the universe. In this brief review we outline
how weak lensing helps determine the structure of dark matter halos, measure
the expansion rate of the universe, and distinguish between modified gravity
and dark energy explanations for the acceleration of the universe. We also
discuss requirements on the control of systematic errors so that the
systematics do not appreciably degrade the power of weak lensing as a
cosmological probe.Comment: Invited review article for the GRG special issue on gravitational
lensing (P. Jetzer, Y. Mellier and V. Perlick Eds.). V3: subsection on
three-point function and some references added. Matches the published versio
Weak Lensing and CMB: Parameter forecasts including a running spectral index
We use statistical inference theory to explore the constraints from future
galaxy weak lensing (cosmic shear) surveys combined with the current CMB
constraints on cosmological parameters, focusing particularly on the running of
the spectral index of the primordial scalar power spectrum, . Recent
papers have drawn attention to the possibility of measuring by
combining the CMB with galaxy clustering and/or the Lyman- forest. Weak
lensing combined with the CMB provides an alternative probe of the primordial
power spectrum. We run a series of simulations with variable runnings and
compare them to semi-analytic non-linear mappings to test their validity for
our calculations. We find that a ``Reference'' cosmic shear survey with
and galaxies per steradian can reduce the
uncertainty on and by roughly a factor of 2 relative to the
CMB alone. We investigate the effect of shear calibration biases on lensing by
including the calibration factor as a parameter, and show that for our
Reference Survey, the precision of cosmological parameter determination is only
slightly degraded even if the amplitude calibration is uncertain by as much as
5%. We conclude that in the near future weak lensing surveys can supplement the
CMB observations to constrain the primordial power spectrum.Comment: 12 pages, 10 figures, revtex4. Final form to appear in Phys Rev
Dark Energy Survey Year 1 Results: A Precise H0 Measurement from DES Y1, BAO, and D/H Data
We combine Dark Energy Survey Year 1 clustering and weak lensing data with baryon acoustic oscillations and Big Bang nucleosynthesis experiments to constrain the Hubble constant. Assuming a flat ΛCDM model with minimal neutrino mass (Σm υ = 0.06 eV), we find H 0 = 67.4 -1.2+1.1 km s -1 Mpc -1 (68 per cent CL). This result is completely independent of Hubble constant measurements based on the distance ladder, cosmic microwave background anisotropies (both temperature and polarization), and strong lensing constraints. There are now five data sets that: (a) have no shared observational systematics; and (b) each constrains the Hubble constant with fractional uncertainty at the few percent level. We compare these five independent estimates, and find that, as a set, the differences between them are significant at the 2.5σ level (χ 2 /dof = 24/11, probability to exceed = 1.1 per cent). Having set the threshold for consistency at 3σ, we combine all five data sets to arrive at H 0 = 69.3 -0.6+0.4 km s -1 Mpc -
Weak-lensing mass calibration of redMaPPer galaxy clusters in dark energy survey Science verification data
The DES Science Verification weak lensing shear catalogues
We present weak lensing shear catalogues for 139 square degrees of data taken during the Science Verification (SV) time for the new Dark Energy Camera (DECam) being used for the Dark Energy Survey (DES). We describe our object selection, point spread function estimation and shear measurement procedures using two independent shear pipelines, IM3SHAPE and NGMIX, which produce catalogues of 2.12 million and 3.44 million galaxies respectively. We detail a set of null tests for the shear measurements and find that they pass the requirements for systematic errors at the level necessary for weak lensing science applications using the SV data. We also discuss some of the planned algorithmic improvements that will be necessary to produce sufficiently accurate shear catalogues for the full 5-year DES, which is expected to cover 5000 square degrees
Dark energy survey year 1 results: a precise H-0 estimate from DES Y1, BAO, and D/H data
FINEP - FINANCIADORA DE ESTUDOS E PROJETOSFAPERJ - FUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DO RIO DE JANEIROCNPQ - CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICOMCTIC - MINISTÉRIO DA CIÊNCIA, TECNOLOGIA, INOVAÇÕES E COMUNICAÇÕESWe combine Dark Energy Survey Year 1 clustering and weak lensing data with baryon acoustic oscillations and Big Bang nucleosynthesis experiments to constrain the Hubble constant. Assuming a flat Lambda CDM model with minimal neutrino mass (Sigma m(v), = 0.06 eV), we find H-0 = 67.4(-1.2)(+1.1) km s(-1) Mpc(-1) (68 per cent CL). This result is completely independent of Hubble constant measurements based on the distance ladder, cosmic microwave background anisotropies (both temperature and polarization), and strong lensing constraints. There are now five data sets that: (a) have no shared observational systematics; and (b) each constrains the Hubble constant with fractional uncertainty at the few-per cent level. We compare these five independent estimates, and find that, as a set, the differences between them are significant at the 2.5 sigma level (chi(2)/dof = 24/11, probability to exceed = 1.1 per cent). Having set the threshold for consistency at 30 sigma we combine all five data sets to arrive at H-0 = 69.3(-0.6)(+0.4) km s(-1) Mpc(-1).480338793888FINEP - FINANCIADORA DE ESTUDOS E PROJETOSFAPERJ - FUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DO RIO DE JANEIROCNPQ - CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICOMCTIC - MINISTÉRIO DA CIÊNCIA, TECNOLOGIA, INOVAÇÕES E COMUNICAÇÕESFINEP - FINANCIADORA DE ESTUDOS E PROJETOSFAPERJ - FUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DO RIO DE JANEIROCNPQ - CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICOMCTIC - MINISTÉRIO DA CIÊNCIA, TECNOLOGIA, INOVAÇÕES E COMUNICAÇÕESSem informaçãoSem informaçãoSem informaçãoSem informaçãoAgências de fomento estrangeiras apoiaram essa pesquisa, mais informações acesse artig
Weak-lensing mass calibration of redMaPPer galaxy clusters in Dark Energy Survey Science Verification data
We use weak-lensing shear measurements to determine the mean mass of optically selected galaxy clusters in Dark Energy Survey Science Verification data. In a blinded analysis, we split the sample of more than 8000 redMaPPer clusters into 15 subsets, spanning ranges in the richness parameter 5 ≤ λ ≤ 180 and redshift 0.2 ≤ z ≤ 0.8, and fit the averaged mass density contrast profiles with a model that accounts for seven distinct sources of systematic uncertainty: shear measurement and photometric redshift errors; clustermember contamination; miscentring; deviations from the NFW halo profile; halo triaxiality and line-of-sight projections. We combine the inferred cluster masses to estimate the joint scaling relation between mass, richness and redshift, M(λ, z) ∝ M0λF (1 + z) G. We find M0 ≡ (M200m | λ = 30, z = 0.5) = [2.35 ± 0.22 (stat) ± 0.12 (sys)] × 1014 M., with F = 1.12 ± 0.20 (stat) ± 0.06 (sys) and G = 0.18 ± 0.75 (stat) ± 0.24 (sys). The amplitude of the mass–richness relation is in excellent agreement with the weak-lensing calibration of redMaPPer clusters in SDSS by Simet et al. and with the Saro et al. calibration based on abundance matching of SPT-detected clusters. Our results extend the redshift range over which the mass–richness relation of redMaPPer clusters has been calibrated with weak lensing from z ≤ 0.3 to z ≤ 0.8. Calibration uncertainties of shear measurements and photometric redshift estimates dominate our systematic error budget and require substantial improvements for forthcoming studies
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