Day 611

Wednesday.

1403.4241
WFIRST ultra-recise astrometry I: Kuiper belt objects
Gould

Show that the WFIRST microlensing survey will enable detection and precision orbit determination of KBOs down to H_vega=28.2 over an effective area of about 17 sq deg.  Typical fractional period errors will be 1.5% X 1e{0.4(H-28.2)} with similar errors in other parameters for roughly 5000 KBOs.  Binary companions to detected KBOs can be detected to even fainter limits, H_vega=29, corresponding to R~31 and effective diameters D~7.5 km.  This will provide an unprecedented probe of orbital resonance and KBO mass measurements.

1403.4245
Cosmic reionization on computers I> design and calibration of simulations
Gnedin

CROC is a long-term program of numerical sims on cosmic reionization.  Its goal is to model fully self-consistently (albeit not necessarily from the first principles) all relevant physics, from radiative transfer to gas dynamics and SF, in simulation volumes of up to 100 comoving Mpc, and with spatial resolution approaching 100 pc in physical units.  In this method paper, describe numerical method, the design of simulations, and calibration of numerical parameters.  Using several sets (ensembles) of simulations in 20 Mpc/h and 40 Mpc/h boxes with spatial resolution reaching 125 pc at z=6, able to match the observed galaxy UV luminosity functions at all redshifts between 6 and 10, as well as obtain reasonable agreement with the observational measurements of the Gunn-Peterson optical depth at z<6.  

1403.4295
UV luminosity functions at redshifts z~4 to z~10: 11000 galaxies from HST legacy fields
Bouwends et al

Evolution of UV LF from z~10 to 4.  6k, 3k, 940, 598, 225, and 6 galaxy candidates at z~4,5,6,7,8 and 10, respectively from 1000 arcmin^2 covered by the datasets.  New LF results strengthen the earlier findings to 4.5 sigma significance for a steeper UV LF at z>4, with alpha evolving from alpha=-1.6 at z~4 to -2.06 at z~7.  The observed steepening of the UV LF is consistent with that expected from the evolution of the halo MF.  Improved constraints at the bright end, find less evolution in the characteristic luminosity M* over the range 4<z<7 consistent with current models; the observed evolution in the LF is now largely represented by changes in phi*.  With the much larger sample of bright galaxies, find no evidence for the LF having a non-Schechter-like form at z~4-8.  A simple conditional LF model based on halo growth and a modest evolution in the M/L of haloes provides a good representation of the evolution of the UV LF.

1403.4339
The nature of damped Lyman-{\alpha} and MgII absorbers explored with their dust contents
Fukugita, Ménard

Estimate the abundance of dust in damped Lya absorbers (DLA) by statistically measuring the excess reddening they induce on their background quasars.  Detect systematic reddening behind DLA consistent with the SMC type reddening curve, but is inconsistent with the MW type reddening.  Find that metallicity derived from the dust abundance, on average, anti correlates with the column density of neutral hydrogen, <Z>~1/N, meaning that the column density of metals HI is constant irrespective of the column density of hydrogen.  This indicates that the prime origin of metals seen in damped Lya absorbers is not by in situ SF, with which <Z>~N^0.4 is HI expected from the empirical SF law, contrary to observations.  Interpret the metals observed in absorbers being deposited dominantly from nearby galaxies by galactic winds ubiquitous in intergalactic space.  Find that this metallicity HI column density relation for damped Lya clouds extrapolates to Mg II clouds.

1403.4573
The strongest gravitational lenses: III. the order statistics of the largest Einstein radii
Waizmann, Redlich, Meneghetti, Bartelmann

The Einstein radius (ER) of a gravitational lens encodes information about decisive quantities such as halo mass, concentration, triaxiality, and orientation with respect to the observer.  Thus, the largest Einstein radii can potentially be utilized to test the predictions of the LCDM model.  Hitherto, studies have focussed on the single largest observed ER.  Extend those studies by employing order statistics to formulate exclusion criteria based on the n largest Einstein radii and apply these criteria to the strong lensing analysis of 12 MACS clusters at z>0.5.  Obtain the order statistics of Einstein radii by a MC approach, based on the SAM of the halo population on the past light cone.  After sampling the order statistics, fit a GEV distribution to the first-order distribution, which allows us to derive analytic relations for the order statistics of the Einstein radii. Find that the Einstein radii of the 12 MACS clusters are not in conflict with the LCDM expectations.  Exclusion criteria indicate that, in order to exhibit tension with the concordance model, one would need to observe approximately 20 Einstein radii > 30", ten >35", or five >42" in the range 0.5<z<1.0 on the full sky.  Furthermore, find that, with increasing order, the haloes with the largest Einstein radii are on average less aligned along the LoS and less triaxial.  In general, the cumulative distribution functions steepen for higher orders, giving them better constraining power.