1603.04441
Revealing the z~2.5 cosmic web with 3d Lyman-Alpha forest tomography: a deformation tensor approach
Lee, White
Studies of cosmological objects should take into account their positions within the cosmic web of LSS. Unfortunately, the cosmic web has only been extensively mapped at low-redshifts (z<1), using galaxy redshifts as tracers of the underlying density field. At z>1, the required galaxy densities are inaccessible for the foreseeable future, but 3d reconstructions of alpha forest absorption in closely-separated background QSOs and SF galaxies already offer a detailed window in to z~2-3 large-scale structure. Quantify the utility of such maps for studying the cosmic web by using realistic z-2.5 Lya forest simulations matched to observational properties of upcoming surveys. A deformation tensor-based analysis is used to classify voids, sheets, filaments and nodes in the flux, which is compared to those determined from the underlying DM field. Find an extremely good correspondence, with 70% of the volume in the flux maps correctly classified relative to the DM web, and 99% classified to within 1 eigenvalue. This compares favorably to the performance of galaxy-based classifiers with even the highest galaxy densities at low-redshift. Find that narrow survey geometries can degrade the cosmic web recovery unless the survey is >60 Mpc/h or >1 deg on the sky. Also examine halo abundances as a function of the cosmic web, and find a clear dependence as a function of flux overdensity, but little expect dependence on the cosmic web. These methods will provide a new window on cosmo environments of galaxies at this special time in galaxy formation, "high noon", and on overall properties of cosmological structures at this epoch.
1603.04536
Oxygen isotopic evidence for vigorous mixing during the Moon-forming Giant Impact
Young, et al
Earth and Moon are shown to be composed of O isotope reservoirs that are indistinguishable, with a difference in Detla ^17O of -1±5ppm (2se). Based on these data and the new planet formation simulations that include a realistic model for O isotopic reservoirs, the results favor vigorous mixing during the giant impact and therefore a high-energy high- angular-momentum impact. The results indicate that the late veneer impactors had an average Delta ^17O within approximately 1 per mil of the terrestrial value, suggesting that these impactors were water rich.
1603.04696
Weak lensing study of 16 DAFT/FADA clusters: substructures and filaments
Martinet et al
While the current cosmological model places galaxy clusters at the nodes of a filament network, we still struggle to detect these filaments at high redshifts. Perform a WL study for a sample of 16 massive, medium-high redshift (0.4<<0.9) galaxy clusters from the DAFT/FADA survey, that are imaged in at least 3 optical bands with Subaru/Suprime-Cam or CFHT/MegaCam. Estimate the cluster masses using a NFW fit to the shear profile measured in a KSB-like method, adding the contribution to the calibraiton of the observable-mass relation required for cluster abundance cosmo studies. Compute convergence maps and select structures within, securing their detection with noise re-sampling techniques. Taking advantage of the large field of view of the data, study cluster environment, adding information from galaxy density maps at the cluster redshift and from X-ray images when available. Find that clusters show a large variety of WL maps at large scales and that they may all be embedded in filamentary structures at Mpc scale. Classify them in 3 categories according to the smoothness of their WL contours and to the amount of substructures: relaxed (~7%), past mergers (~21.5%), recent or present mergers (~71.5%). The fraction of clusters undergoing merging events observationally supports the hierarchical scenario of cluster growth, and implies that massive clusters are strongly evolving at the studied redshifts. Finally, report the detection of unusually elongated structures in CLJ0152, MACSJ0454, MACSJ0717, A851, BMW1226, MACSJ1621, and MS1621.
1603.04698
Roulettes: a weak lensing formalism for strong lensing - I. Overview
Clarkson
Present a new perspective on gravitational lensing. Describe a new extension of the WL formalism capable of describing strongly lensed images. By integrating the non-linear geodesic deviation equation, the amplification matrix of WL is generalized to a sum over independent amplification tensors of increasing rank. Show how an image distorted by a generic lens may be constructed as a sum over 'roulettes', which have the natural curves associated with the independent spin modes of the amplification tensors. Highly distorted images can be constructed even for large sources observed near or within the Einstein radius of a lens where the shear and convergence are large. The amplitude of each roulette is formed from a sum over appropriate derivatives of the lensing potential. Consequently, measuring these individual roulette is formed from a sum over appropriate derivatives of the lensing potential. Consequently, measuring these individual roulettes for images around a lens gives a new way to reconstruct a strong lens mass distribution without requiring a lens model. This formalism generalists the convergence, shear and flexion of WL to arbitrary order, and provides a unified bridge between the strong and weak lensing regimes. This overview paper is accompanied by a much more detailed Paper II.
1603.04784
Radio weak lensing shear measurement in the visibility domain - I. Methodology
Rivi, Miller, Makhathini, Abdalla
Present an adaptation to radio data of "lensfit". Simulations show additive and multiplicative bias values that are comparable to SKA1 requirements for SNR>18 and SNR>30. The multiplicative bias for SNR>10 is comparable to that found in ground-based optical surveys such as CFHTLenS, and it is anticipated that similar shear measurement calibration strategies for those red for optical surveys may be used to good effect in the analysis of SKA radio interferometer data.
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