Saturday. Didn't get any significant work done yesterday... Aaron made hamburger last night, and it was very delicious.
1110.2517
On point spread function modelling: towards optimal interpolation
Berge, Price, Amara, Rhodes
PSF modeling: important for measuring shapes (WL). Pipeline in two steps: (1) assess shapes on stars, (2) interpolate it to any position. Focus on interpolation schemes (incl. polynomial, radial basis functions, Delaunay trangulation, Kriging). Simulation of PSF fields based on PCA of real ground-based images. Kringing gives the most reliable interpolation; much better than polynomial. Although a Kriging interpolation on individual images is enough to control systematics at the level necessary to current WL surveys, more elaborate tecniques will have to be developed to reach future ambitious surveys' requirements.
1110.2525
The complementarity of the redshift drift
Moraes, Polarski
Redshift drift: a direct signature of acceleration or deceleration; some DE properties can be retrieved from it [duh]. Some DE models will show redshift drift while no signature present in the luminosity distance: a sudden change of w at low z, oscillating DE and w with spikes at low z. Accurate z drift measurements would provide complementary probes for some of these models and for models with varying gravitational coupling. The z drift would efficiently constrain models with a spike at z~1; signature of the z drift for models with large variations at very low z < 0.1 would be unobservable, allowing a large arbitrariness in the present expansion of the universe.
1110.2536
Disentangling baryons and dark matter in the spiral gravitational lensg B1933+503
Suyu, Hensel, McKean, Fasssnacht, Treu, Halkola, Norbury, Jackson, Schneider, Thompson, Auger, Koopmans, Matthews
Relative mass contributions of luminous and DM in spiral galaxies is necessary for understanding their formation and evolution. Combine galaxy rotation curve and SL to break disk-halo degeneracy inherent in each of the methods individually. Analysis of the 10-image radio spiral lens B1933+503 at z_l=0.755 (new VLBI, AO K-band imaging, spectro for lens rotation curve and source redshift observations). Construct 3d axisymmetric mass distribution with 3 components--exponential profile for the disk, point mass for the bulge, NFW for halo. Mass model is simultaneously fitted to kinematics and lensing data. Suggests baryons are effective at making the halos oblate near the center. Lensing and kinematics probe the inner ~10 kpc of the galaxy; obtain lower limit on the halo scale radius of 16 kpc (95%cl). DM fraction inside a sphere with radius of 2.2 disk scale lengths is f_{DM, 2.2}=0.43\pm0.1. Contribution of the disk to the total circular velocity at 2.2 disk scale lengths is 0.76\pm0.05; suggests disk is marginally submaximal. Stellar mass of disk from modeling is log10(M*/Msun) = 11.06\pm0.1 assuming cold gas contributes ~20% of the total disk mass. In comparison to the stellar masses estimated from SPS models, the stellar initial mass function of Chabrier is preferred to that of Salpeter by a factor of 7.2.
* have SL (radio), rotation curve (spectra)
* DM fraction inside 2.2R = 0.43
* Disk contribution to circular velocity: 0.76 (submaximal)
* Stellar mass of disk = 1e11
1110.2786
A first estimate of radio halo statistics from LSS cosmo simulation
Sutter, Ricker
First estimate of galaxy cluster radio halo counts (expected from low-frequency radio surveys). Estimate based on FLASH simulation of LCDM model; assigning radio power to clusters via model that relates radio emissivity to cluster magnetic field strength, intracluster turbulence, and density. Vary several free parameters of this model, find radio halo number counts vary by a factor of 2 for average magnetic fields ranging from 0.2 to 3.1 uG. However, predict significantly fewer low-frequency radio halos than expected from previous SAM; find upcoming surveys will have difficulty distinguishing models because of large uncertainties and low number counts. Find expected number counts can be degenerate in both re-acceleration and hardronic secondary models of CR generation. Find that relations between radio power and mass and X-ray luminosity may be used to distinguish models; building mock radio sky maps and demonstrate surveys such as LOFAR may have sufficient resolution and sensitivity to break this model degeneracy by imaging many individual clusters.
1110.2854
Triaxial strong-lensing analysis of z>0.5 MACS clusters: the mass-concentration relation
Sereno, Zitrin
High concentration derived for several SL clusters present inconsistency between LCDM expencation and measurements. Triaxiality and orientation biases origin of this disagreement (clusters elongated along the LOS would have a relatively higher projected mass density, boosting resulting lensing properties. Analysis of statistical samples can probe these effects and reduce biases. Perform fully triaxial SL analysis of the 12 macs clusters at z>0.5, X-ray selected sample, and fully account for the impact of intrinsic 3d shapes on their SL properties. First construct SL mass models for each cluster based on multiple images and fit projected ellipsoidal NFW haloes with arbitrary orientations to each mass distribution. Then invert the measured surface mass densities using Bayesian statistics. Einstein radii of this sample are significantly larger than predicted by LCDM, but find that mass-concentration relation in full agreement with N-body sims. The z>0.5 MACS clusters suffer from a moderate form of orientation bias as may be expected for X-ray selected samples. Mostly unrelaxed at relatively high z, with high X-ray luminosity and noticeable substructures, these clusters may lie outside the standard concentration-Einstein radius relation. Results remark the importance of triaxiality and properly selected samples for understanding galaxy cluster properties, and suggest that higher-z, unrelaxed low-concentration clusters form a different class of prominent SL. Arc redshift confirmation and WL data in the outer region needed to further refine analysis.
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