1606.00008
Cosmological parameters, shear maps and power spectra from CFHTLenS using Bayesian hierarchical inference
Alsing, Heavens, Jaffe
Apply two Bayesian hierarchical inference schemes to infer shear power spectra, shear mass and cosmo parameters from the CFHTLenS WL survey -- the first application of this method to data. In the first approach, sample the joint posterior distribution of the shear maps and power spectra by Gibbs sampling, with minimal model assumptions. In the second approach, sample the joint posterior of the shear maps and cosmo parameters, providing a new, accurate and principled approach to cosmo parameter inference from cosmic shear data. As a first demonstration on data, perform a 2-bin tomographic analysis to constrain cosmo parameters and investigate the possibility of photometric z bias in the CFHTLenS data. Under the baseline LCDM model, constrain S8=sigma_8(Omega_m/0.3)^0.5 = 0.67 ±0.03 (68%), consistent with previous CFHTLenS analysis by in tension with Planck. Adding neutrino mass as a free parameter, able to constrain Sigma m_nu<4.6 eV (95%) using CFHTLenS data alone. Including a linear redshift dependent photo-z bias Delta z=p_2(z-p_1), find p_1 = -0.25±0.6 and p_2=-0.15 ±0.15, and tension with Planck is only alleviated under very conservative prior assumptions. Neither the non-minimal neutrino mass or photo-z bias models are significantly preferred by the CFHTLenS(2-bin tomography) data.
1606.00017
H0LiCOW I. H0 lenses in COSMOGRAIL's Wellspring: program overview
Sulu, Bonvin, Corbin, Fassnacht, Rush, Sluse, Treu, ..Hilbert, Marshall .. Tewes, ... Blandford, et al
SL systems with time delays between the multiple images are a powerful probe of cosmo and astrophysics. In particular, the time-delay distance from such a system is primarily sensitive to the Hubble Constant that is key to probing DE, neutrino physics, and the spatial curvature of the Universe, as well as discovering new physics. Present H0LiCOW, a program that aims to measure H0 with <3.5% uncertainty in precision and accuracy from 5 lens systems. Acquired or are in the process of acquiring (1) time delays through COSMOGRAIL and VLA monitoring, (2) high-resolution HST imaging for the lens mass modeling, (3) wide-field imaging and spectroscopy to characterize the lens environment, and (4) moderate-resolution spectroscopy for obtaining the stellar velocity dispersion of the lenses and, thus, to further constrain the lens mass models. Expect to measure, with the data set for the five lenses, H0 and better than 3.5% in most cosmological models. Furthermore, would measure spatial curvature Omega_k to 0.004, w to 0.14, and the effective number of neutrino species to 0.2 (1sigma) when combined with current CMB experiments, which are a factor of ~15, ~2 and ~1.5 tighter than CMB aline. The data set will further enable to study the dark matter distribution of lens galaxies, the stellar initial mass function of the lens galaxies, and the co-evolution of supermassive BHs and their host (source) galaxies. This program will provide a foundation for extracting robustly cosmo distances from the hundreds of time-delay lenses that are expected to be discovered in current and future surveys.
1606.00043
Perturbative approach to covariance matrix of the matter power spectrum
Mohammed, Seljak, Vlah
Evaluate the cov matrix of the matter PS using perturbation theory up to dominant terms at 1-loop order and compare it to numerical simulations. Decompose the cov matrix into the disconnected (Gaussian) part, trispectrum from the modes outside the survey (beat coupling or super-sample variance), and trispectrum from the modes inside the survey, and show how the different components contribute to the overall covariance matrix. Find the agreement with the simulations is at a 10% level up to k~1h/Mpc. Show that all the connected components are dominated by the large-scale models (k<0.1 h/Mpc), regardless of the value of the wavelvectors k,k' of the cov matrix, suggesting that one must be careful in applying the jackknife or bootstrap methods to the cov matrix. Perform an eigen mode decomposition of the connected part of the cov matrix, showing that at higher k it is dominated by a single eigenmode. The full cov matrix can be approximated as the disconnected part only, with the connected part being treated as an external nuisance parameter with a known scale dependence, and a known prior on its variance for given survey volume. Finally, provide a prescription for how to evaluate the cov matrix from small box simulations without the need to simulated large volumes.
1606.00184
Constraining $f(R)$ gravity theory using CHFTLenS Weak Lensing Peak statistics
Liu, et al
Report the observational constraints on the Hu-Sawicki f(R) theory derived from WL peak abundances, which are closely related to the MF of massive halos. In comparison with studies using optical or X-ray clusters of galaxies, WL peak analyses have the advantages of not relying on mass-baryonic observable calibration. From CFHTLenS, peak analysis give rise to a tight constant on the model parameter |f_R0| for n=1. The 95% CL limit is log_10|f_R0|<-4.82 given WMAP9 priors on (Omega_m, A_s). With Planck15 priors, the corresponding result is log_10|f_R0|<-5.16.
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