Day 733

Friday.

1408.6608
Detection of the universal effect of the large scale velocity shear on they fall directions of the galactic satellites
Lee, Choi

Report a detection of the universal effect on the large-scale velocity shear on the infall directions of the galactic satellites into their hosts.  Identifying the isolated galactic systems each of which consists of a single host galaxy and its satellites from SDSS DR7 and using the velocity shear field recently reconstructed by Lee+ in the local universe, investigate the alignments between the relative positions of the satellites from their isolated haloes and the principal axes of the local velocity shear tensors.  Find a clear signal that the galactic satellites in isolated systems are located preferentially along the directions of the minor principal axes of the local velocity shears smoothed on the scale of 10 Mpc/h.  Those galactic satellites which are fainter and located at larger distances from the hosts are shown to yield stronger alignments.  It is also shown that the alignment strength is quite insensitive to the cosmic web environment as well as to the luminosity, mass, richness sand a morphology of the isolated hosts and their satellites, which is consistent with the recent prediction of Libeskind+ based on a N-body sim that the velocity shear effect on the satellite infall direction is universal.

1408.6611
The effective cross-sections of a lensing-galaxy: singular isothermal sphere with external shear
Lee, Kim

Numerical studies on the imaging and caustic properties of the SIS under a wide range of external shear (from 0.0 to 2.0) are presented.  Using a direct inverse-mapping formula for this lens system, investigate various lensing properties under both a low and high shear case: image separations, total or individual magnifications, flux ratios of 2 images, maximum number of images, and lensing cross-sections.  Systematically analyze the effective lending cross-sections of double-lensing and quad-lensing systems based on the radio luminosity function obtained by JVAS and CLASS.  Find that the limit of a survey selection bias (i.e., between a brighter- and a fainter-image) preferentially reduces the effective lensing cross-sections of 2-image lensing systems.  By considering the effects of survey selection bias, demonstrate that the long standing anomaly on the high Quads-to-Doubles ratios (JVAS & CLASS : 50-70%) can be explained by the moderate effective shear of 0.16-0.18, which is half of previous estimates.  The derived inverse mapping formula could facilitate the SIS+shear lens model to be useful for galaxy-lensing simulations.