Day 790

Thursday.

1411.4983
Probing the galaxy-halo connection in UltraVISTA to $z\sim2$
McCracken, et al

Use %-level precision photo-z in UltraVISTA-DR1 NIR survey to investigate the changing relationship between galaxy M* and the DM haloes hosting them to z~2.  Achieve this by measuring the clustering properties and abundances of a series of volume-limited galaxy samples selected by stellar mass and SF activity.  Interpret these results in the framework of a phenomenological halo model and numerical simulations.  Measurements span a uniquely large range in stellar mass and z and reach below the characteristic stellar mass to z~2.  Results are: 1. At fixed z and scale, clustering amplitude depends monotonically on sample M* threshold; 2. at fixed angular scale, the projected clustering amplitude decreases with z but the co-moving correlation length remains constant; 3. characteristic halo masses and galaxy bias increase with increasing median stellar mass of the sample; 4. the slope of these relationships is modified in lower mass haloes; 5. concerning the passive galaxy population, characteristic halo masses are consistent with a simply less-abundant version of the full galaxy sample, but at lower z the fraction of satellite galaxies in the passive population is very different from the full galaxy sample; 6. find that the ratio between the characteristic halo mass and median stellar mass at each redshift bin reaches a peak at log(Mh/Msun)~12.2 and the position of this peak remains constant out to z~2.  The behavior of the full and passively evolving galaxy samples can be understood qualitatively by considering the slow evolution of the characteristic M* in the z range probed by the survey.

1411.5022
The fastest unbound stars in the universe
Guillochon, Loeb

Hypervelocity stars (HVS) can (theoretically) frequently ejected with v_inf>1e4 km/s, and occasionally with ~1e5 km/s (c/3) in an interaction with massive BH with M>1e5 Msun.  Depending on MBH interactions, the space density of fast-moving (>1e4 km/s) semi-relativistic hypervelocity stars, unbound to any galaxy, can be as large as 1e3 per Mpc^3.  Hundreds of the SHS will be giant stars that could be detected by WFIRST or Euclid and proper motion surveys such as LSST, with spectroscopic follow-up being possible with JWST.

1411.5030
Observational cosmology with semi-relativistic stars
Loeb, Guillochon

Tracing the stars to their part galaxies as a function of speed and age will provide a novel test of the equivalence principle and the standard cosmological parameters.  Semi-relativistic stars could also flag BH binaries as gravitational wave sources for the future eLISA observatory.