scholarly journals Reconstructing the gravitational lensing potential from the Lyman-α forest

2020 ◽  
Vol 642 ◽  
pp. A122
Author(s):  
R. Benton Metcalf ◽  
Nicolas Tessore ◽  
Rupert A. C. Croft
Keyword(s):  
Gravitational Lensing ◽  
Real Space ◽  
Weak Lensing ◽  
High Fidelity ◽  
Noise Levels ◽  
Microwave Background ◽  
Intensity Mapping ◽  
Source Density ◽  
Optimal Estimator ◽  
Relative Absorption

We demonstrate a method for reconstructing the weak lensing potential from the Lyman-α forest data. We derive an optimal estimator for the lensing potential on the sky based on the correlation between pixels in real space. This method effectively deals with irregularly spaced data, holes in the survey, missing data, and inhomogeneous noise. We demonstrate an implementation of the method with simulated spectra and weak lensing. It is shown that with a source density of ≳0.5 per square arcmin and ∼200 pixels in each spectrum (λ/Δλ = 1300) the lensing potential can be reconstructed with high fidelity if the relative absorption in the spectral pixels is signal dominated. When noise dominates the measurement of the absorption in each pixel the noise in the lensing potential is higher, but for reasonable numbers of sources and noise levels and a high fidelity map the lensing potential is obtainable. The lensing estimator could also be applied to lensing of the cosmic microwave background, 21 cm intensity mapping, or any case in which the correlation function of the source can be accurately estimated.

scholarly journals Calibrating the Planck cluster mass scale with CLASH

2017 ◽  
Vol 604 ◽  
pp. A89 ◽  
Author(s):  
M. Penna-Lima ◽  
J. G. Bartlett ◽  
E. Rozo ◽  
J.-B. Melin ◽  
J. Merten ◽  
...  
Keyword(s):  
Gravitational Lensing ◽  
Mass Scale ◽  
Model Fit ◽  
Weak Lensing ◽  
Selection Function ◽  
Microwave Background ◽  
True Cluster ◽  
Cluster Mass ◽  
Constant Bias ◽  
Analysis Strategy

We determine the mass scale of Planck galaxy clusters using gravitational lensing mass measurements from the Cluster Lensing And Supernova survey with Hubble (CLASH). We have compared the lensing masses to the Planck Sunyaev-Zeldovich (SZ) mass proxy for 21 clusters in common, employing a Bayesian analysis to simultaneously fit an idealized CLASH selection function and the distribution between the measured observables and true cluster mass. We used a tiered analysis strategy to explicitly demonstrate the importance of priors on weak lensing mass accuracy. In the case of an assumed constant bias, bSZ, between true cluster mass, M500, and the Planck mass proxy, MPL, our analysis constrains 1−bSZ = 0.73 ± 0.10 when moderate priors on weak lensing accuracy are used, including a zero-mean Gaussian with standard deviation of 8% to account for possible bias in lensing mass estimations. Our analysis explicitly accounts for possible selection bias effects in this calibration sourced by the CLASH selection function. Our constraint on the cluster mass scale is consistent with recent results from the Weighing the Giants program and the Canadian Cluster Comparison Project. It is also consistent, at 1.34σ, with the value needed to reconcile the Planck SZ cluster counts with Planck’s base ΛCDM model fit to the primary cosmic microwave background anisotropies.

scholarly journals KiDS+VIKING-450 and DES-Y1 combined: Cosmology with cosmic shear

2020 ◽  
Vol 638 ◽  
pp. L1 ◽  
Author(s):  
S. Joudaki ◽  
H. Hildebrandt ◽  
D. Traykova ◽  
N. E. Chisari ◽  
C. Heymans ◽  
...  
Keyword(s):  
Dark Energy ◽  
Cosmic Microwave Background ◽  
Gravitational Lensing ◽  
Error Model ◽  
Calibration Error ◽  
Microwave Background ◽  
Weak Gravitational Lensing ◽  
Dark Energy Survey ◽  
Cosmic Shear ◽  
Energy Survey

We present a combined tomographic weak gravitational lensing analysis of the Kilo Degree Survey (KV450) and the Dark Energy Survey (DES-Y1). We homogenize the analysis of these two public cosmic shear datasets by adopting consistent priors and modeling of nonlinear scales, and determine new redshift distributions for DES-Y1 based on deep public spectroscopic surveys. Adopting these revised redshifts results in a 0.8σ reduction in the DES-inferred value for S​8, which decreases to a 0.5σ reduction when including a systematic redshift calibration error model from mock DES data based on the MICE2 simulation. The combined KV450+DES-Y1 constraint on S8 = 0.762−0.024+0.025 is in tension with the Planck 2018 constraint from the cosmic microwave background at the level of 2.5σ. This result highlights the importance of developing methods to provide accurate redshift calibration for current and future weak-lensing surveys.

Gravitational Lensing Studies of High Resolution Cluster Simulations

2005 ◽  
Vol 201 ◽  
pp. 476-477
Author(s):  
Lindsay King ◽  
Douglas Clowe ◽  
Peter Schneider ◽  
Volker Springel
Keyword(s):  
High Resolution ◽  
Gravitational Lensing ◽  
Particle Mass ◽  
Weak Lensing ◽  
Reconstruction Technique ◽  
Ongoing Work ◽  
Non Parametric

In our ongoing work, we use high resolution cluster simulations to study gravitational lensing. These simulations have a softening length of 0.7 h-1 kpc and a particle mass of 4.68 × 107M⊙ (Springel 1999). Questions that can be addressed include the accuracy with which substructure on various scales can be recovered using the information from lensing. This is very important in determining the power of lensing in studying the evolution of cluster substructure as a function of redshift. We briefly consider how a weak lensing non-parametric reconstruction technique and the Map-statistic can be applied to the simulations.

scholarly journals A gravitational puzzle

2011 ◽  
Vol 369 (1957) ◽  
pp. 4998-5002
Author(s):  
Robert R. Caldwell
Keyword(s):  
Gravitational Lensing ◽  
Large Scale ◽  
Current Data ◽  
Cosmic Acceleration ◽  
Late Time ◽  
Microwave Background ◽  
Scale Free ◽  
Cosmological Observations ◽  
Stress Energy ◽  
The Relationship

The challenge to understand the physical origin of the cosmic acceleration is framed as a problem of gravitation. Specifically, does the relationship between stress–energy and space–time curvature differ on large scales from the predictions of general relativity. In this article, we describe efforts to model and test a generalized relationship between the matter and the metric using cosmological observations. Late-time tracers of large-scale structure, including the cosmic microwave background, weak gravitational lensing, and clustering are shown to provide good tests of the proposed solution. Current data are very close to proving a critical test, leaving only a small window in parameter space in the case that the generalized relationship is scale free above galactic scales.

scholarly journals Full-sky maps for gravitational lensing of the cosmic microwave background

2008 ◽  
Vol 388 (4) ◽  
pp. 1618-1626 ◽  
Author(s):  
Carmelita Carbone ◽  
Volker Springel ◽  
Carlo Baccigalupi ◽  
Matthias Bartelmann ◽  
Sabino Matarrese
Keyword(s):  
Cosmic Microwave Background ◽  
Gravitational Lensing ◽  
Microwave Background

scholarly journals A New Model to Predict Weak Lensing Peak Counts

2014 ◽  
Vol 10 (S306) ◽  
pp. 107-109 ◽  
Author(s):  
Chieh-An Lin ◽  
Martin Kilbinger
Keyword(s):  
Gravitational Lensing ◽  
Mass Function ◽  
Weak Lensing ◽  
High Signal ◽  
Dark Matter Halos ◽  
Signal To Noise ◽  
New Approach ◽  
Promising Tool ◽  
Peak Abundance ◽  
Good Agreement

AbstractPeak statistics from weak gravitational lensing have been shown to be a promising tool for cosmology. Here we propose a new approach to predict weak lensing peak counts. For an arbitrary cosmology, we draw dark matter halos from the halo mass function, and calculate the number of peaks from the projected halo mass distribution. This procedure is much faster than time-consuming N-body simulations. By comparing these “fast simulations” to N-body runs, we find that the peak abundance is in very good agreement. Furthermore, our model is able to discriminate cosmologies with different sets of parameters, using high signal-to-noise peaks (≳ 4). This encourages us to examine the optimal combinations of parameters to this approach in the future.

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