Day 685

Wednesday.

1406.6056
The distribution of satellites around massive galaxies at 1<z<3 in ZFOURGE/CANDELS: dependence on star formation activity
Kawinwanichakij, et al

Deep NIR data select satellites down to log(M/Msun)>9 at z<3.  The radial satellite distribution around centrals is consistent with a projected NFW profiles.  Massive quiescent centrals have ~2x the number of satellites compared to SF centrals with a significance of 2.7 sigma even after accounting for differences in the centrals' stellar-mass distributions.  Find no statistical difference in the satellite distributions of intermediate-mass quiescent and SF centrals (10.48-10.78 for log(M/Msun)).  Comparing to the Guo2011 SAM, the excess number of satellites indicates that quiescent centrals have halo masses 0.3 dex larger than SF centrals, even when the stellar-mass distributions are fixed.  Use a simple toy model that relates halo mass and quenching, which roughly reproduces the observed quenched fractions and the differences in halo mass between SF and quenched galaxies only if galaxies have a quenching probability that increases with halo mass from ~0 for log (Mh/Msun)~11 to ~1 for log(Mh/Msun)~13.5.  A single halo-mass quenching threshold is unable to reproduce the quiescent fraction and satellite distribution of centrals.  Therefore, while halo quenching may be an important mechanism, it is unlikely to be the only factor driving quenching.  It remains unclear why a high fraction of centrals remain star-forming even in relatively massive haloes.

1406.6062
Co-orbiting planes of sub-aloes are similarly unlikely around paired and isolated hosts
Pawlowski, McGaugh

Sub-haloes in DM cosmo sims tend to be distributed approximately isotropically around their host; the observed VPOS (vast polar structure) of satellites around MW and M31 is a possible problem for cosmo models.  Perhaps the pair is an environmental consideration.  Search for VPOS analogs in the ELVIS suite of cosmo sims, which consists of 24 paired and 24 isolated host halos.  Do not find significant differences between the properties of sub-halo distributions around paired and isolated hosts.  The observed flattening and the observed orbital alignment are each reproduced by only 0.2 to 2% of paired and isolated systems incorporating the obscuration of satellites by randomly oriented galactic discs.  Only one of all 4800 analyzed realizations (0.02%) reproduces both parameters simultaneously, but the average orbital pole of this sub-halo system does not align as well with the normal to the plane fit as observed.  That the MW is part of a galaxy pair thus does not help in explaining the existence of the VPOS if the satellite galaxies are identified with sub-haloes found in dissipationless simulations.

1406.6152
Can one determine cosmological parameters from multi-plane strong lens systems?
Schneider

Strong gravitational lensing of sources with different redshifts has been used to determine cosmological distance ratios, which in turn depend on the expansion history.  Hence, such systems are viewed as potential tools for constraining cosmological parameters.  Show that in lens systems with two distance source redshifts, of which the nearest one contributes to the light deflection towards the more distant one, there exists and invariance transformation which leaves all SL observables unchanged (except the product of time delay and H0), generalizing the well-known mass-sheet transformation in single plane lens systems.  The transformation preserves the relative distribution of mass and light, so that a 'mass-follows-light' assumption does not fix the MST [?].  All time delays (from sources on both planes) scale with the same factor -- time-delay ratios are therefore invariant under the MST.  Changing cosmological parameters, and thus distance ratios, is essentially equivalent to such a mass-sheet transformation.  As an example, discuss the double source plane system DSSSJ0946+1006, which has been recently studied gy Colett and Auger, and show that variations of cosmo params within reasonable ranges lead to only a small mass-sheet transformation in both lens planes.  Hence the ability to extract cosmo information from such systems depends heavily on the ability to break the mass-sheet degeneracy.