Day 625

Thursday.

1404.2280
The properties of cosmic velocity fields
Hahn, Angulo, Abel

Understanding the velocity field is very important to modern cosmology: it gives insights to structure formation in general, and also its properties are crucial ingredients in modeling z-space distortions and in interpreting measurements of the kinetic SZ effect.  Unfortunately, characterizing the velocity field in cosmo N-body sims is inherently complicated by two facts: i) the velocity field becomes manifestly multi-valued after shell-crossing and has discontinuities at caustics.  This is due to the collision less nature of DM.  ii) N-body sims sample the velocity field only at a set of discrete locations, with poor resolution in low-density regions.  In this paper, discuss how the associated problems can be circumvented by using a phase-space interpolation technique.  This mouthed provides extremely accurate estimates of the cosmic velocity fields and its derivatives, which can be properly defined without the need of the arbitrary "coarse-graining" procedure commonly used.  Explore in detail the configuration-space properties of the cosmic velocity field on very large scales and in the highly NL regime.  In particular, characterize the divergence and curl of the velocity field, present their one-point statistics, analyze the Fourier-space properties and provide fitting formulae for the velocity divergence bias relative to the non-linear matter PS.  Furthermore contrast some of the interesting differences in the velocity fields of warm and cold DM models.  Anticipate that the high-precision measurements carried out here will help to understand in detail the dynamics of DM and the structures it forms.

1404.2297
Close companions to two high-redshift quasars
McGreer, Fan, Strauss, Haiman, Richards, … Schneider, et al

Serendipitous discoveries of companion galaxies to two high-z quasars.  11kpc projected distance for the z=4.79 quasar; 7kpc projected for the z=6.25 quasar.  Observations of close companions are rare; if major mergers are primarily responsible for high-z quasar fueling, then the phase when progenitor galaxies can be observed as bright companions is relatively short.

1404.2552
The solar system and the exoplanet orbital eccentricity - multiplicity relation
Limbach, Turner

Te known population of exoplanets exhibits a much wider range of orbital eccentricities than SS planets and has a much higher average eccentricity.  These facts have been widely interpreted to indicate that the SS is an atypical member of the overall population of planetary systems.  Report here on a strong anti-correlation of orbital eccentricity with multiplicity (number of planets in the system) among catalogued RV systems.  The mean, median and rough distribution of eccentricities of SS planets fits an extrapolation of this anti-correlation to the eight planet case rather precisely.  Thus, the SS is not anomalous among known exoplanetary systems wrt eccentricities when its multiplicity is taken into account.  Specifically, as the multiplicity of a system increases the eccentricity decreases roughly as a power law of index -1.20.  A simple and plausible but ad hoc model of this relationship implies that approximately 80% of the one planet and 25% of the two planet systems in the sample have additional, as yet undiscovered, members.  If low eccentricities favor high multiplicities, habitability may be more common in systems with a larger number of planets.