Day 765

Thursday.

1410.3883
Comparing dense galaxy cluster redshift surveys with weak lensing maps
Hwang, Geller, et al

9 galaxy clusters at z~0.2; cover with spectroscopic samples within region of WL maps of high (70-89%) and uniform completeness.  With these dense redshift surveys, construct galaxy number density maps using several galaxy subsamples.  The shape of the main cluster concentration in the WL maps is similar to the global morphology of the number density maps based on cluster members alone, mainly dominated by red members.  Cross correlate the galaxy number density maps with the WL maps.  The cross correlation signal when FG and BG galaxies at 0.5 z_cl < z <2 z_cl is included is 10-23% larger than for cluster members alone at the cluster virial radius.  The excess can be as high as 30% depending on the cluster.  Cross correlating the galaxy number density and WL maps suggests that superimposed structures close to the cluster in z space contribute more significantly to the excess cross correlation signal than unrelated LSS along the LoS.  The WL mass profiles are not well constrained for clusters with the largest cross correlation signal excesses (>20%).  The fractional excess in the cross correlation signal including FG and BG structures could be a useful proxy for assessing the reliability of WL cluster mass estimates.

1410.4061
The origin of spin in galaxies: clues from simulations of atomic cooling halos
Prieto, Jiminez, Haiman, González

From Hydro sims from cosmological IC:  The main conclusion is that the spin orientation and magnitude is initially well described by tidal torque linear theory, but later on is determined by the merging and accretion history of each halo.  Provide evidence that the topology of the merging region, i.e., the number of colliding filaments, gives an accurate prediction for the spin of DM and gas: halos at the center of knots will have low spin while those in the center of filaments will have high spin.