1605.08472
Strong lensing in the inner halo of galaxy clusters
Saez, et al
Probabilities for finding gravitational arcs in galaxy clusters are calculated and compared for two DM halo profiles: NFW and non-singular isothermal sphere (NSIS). KS test allows establishment of limits on the values of the concentration parameter for the NFW profile (c_Delta) and the core radius for the NSIS profile (rc), which are related to the lowest cluster redshift (z_cut) where strong arcs can be observed. For NFW DM profiles, infer cluster haloes with concentrations that are consistent to those predicted by LCDM simulations. As for NSIS DM profiles, find only upper limits for the clusters core radii and thus do not rule out a purely SIS model. For alternative mass profiles the formulation provides constraints through z_cut on the parameters that control the concentration of mass in the inner region of the clusters haloes. Find that z_cut is expected to lie in the 0.0-0.2 redshift, highlighting the need to include very low-z clusters in samples to study the cluster mass profiles.
1605.08784
Precise strong lensing mass profile of the CLASH galaxy cluster MACS 2129
Monna, et al
Present a detailed SL mass reconstruction of the core of the galaxy cluster MACS 2129 at z_cl=0.589, obtained by combining high-resolution HST photometry from the CLASH survey with new spectra observations from CLASH-VLT survey. A BG bright red passive galaxy at z_sp=1.36, sextuply lensed in the cluster core, has four radial lensed images located over the 3 central cluster members. Further 19 BG lensed galaxies are spectroscopically confirmed by the VLT survey, including 3 additional multiple systems. A total of 27 multiple images are used in the lensing analysis. This allows to trace with high precision the total mass profile of the cluster in its very inner region (R<100 kpc). The final lensing mass model reproduces the multiple images systems identified in the cluster core with high accuracy of 0.4". This translates in an high precision mass reconstruction of MACS 2129, which is constrained at level of 3%. The cluster has Einstein radius theta_E=(15±2)", for a source at z_s=1.36 and a projected total mass of M_tot(<theta_E) = (3.4±0.1)e13 Msun within such radius. Together with the cluster mass profile, provide here also the complete spectroscopic dataset for the cluster members and lensed images measured with VLT/VIMOS within the CLASH-VLT survey.
** 1605.09056
Cosmic shear as a probe of galaxy formation physics
Foreman, Becker, Wechsler
Evaluate the potential for current and future cosmic shear measurements from large galaxy surveys to constrain the impact of baryonic physics on the matter power spectrum. Do so by using a model-independent parameterization that describes deviations for the patter power spectrum from the DM-only case as a set of principal components that are localized in wavenumber and redshift. Perform forecasts for a variety of current and future datasets, and find that at least ~90% of the constraining power of these datasets is contained in no more than none principal components. The constraining power of different surveys can be quantified using a figure of merit defined relative to currently available surveys. With this metric, find that the final DES dataset and the Hyper Supreme Cam survey will be roughly an order of magnitude more powerful than existing dat in constraining baryonic effects. Upcoming stage IV surveys (LSST, Euclid, and WFIRST) will improve upon this by a further factor for a few. Show that his conclusion is robust to marginalization over several key systematics at small (sub-arcminute) scales. If these systematics can be sufficiently controlled, cosmic shear measurements from DES and other future surveys have the potential to provide a very clean probe of galaxy formation and to strongly constrain a wide range of predictions from modern hydrodynamical simulations.
*** 1605.09130
Cosmic shear bias and calibration in cosmic shear studies
Taylor, Kitching
With the advent of large-scale weak lensing surveys there is a need to understand how realistic, scale-dependent systematics bias cosmic shear and DE measurements, and how they can be removed. Describe how spatial variations in the amplitude and orientation of realistic image distortions convolve with the measured shear field, mixing the even-parity convergence and odd-parity modes, and bias the shear power spectrum. Many of these biases can be removed by calibraion to external data, the survey itself, or by modeling in simulations. The uncertainty in the calibration must be marginalized over; calculate how this propagates in to parameter estimation, degrading the DE FoM. Find that noise-like biases affect DE measurements the most, while spikes in the bias power have the least impact, reflecting their correlation with the effect of cosmological parameters. Argue that in order to remove systematic biases in cosmic shear surveys and maintain statistical power, effort should be put into improving the accuracy of the bias calibration rather than minimizing the size of the bias. In general, this appears to be a weaker condition for bias removal. Also investigate how to minimize the size of the calibration set for a fixed reduction in the FoM. These results can be used to model the effect of biases and calibration on a cosmic shear survey accurately, assess their impact on the measurement of modified gravity and DE models, and to optimize surveys and calibration requirements.
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