Day 775

Thursday.

1410.7768
Effect of primordial non-Gaussianities on the far-UV luminosity function of high-redshift galaxies: implications for cosmic reionization
Chevallard, Silk, Nishimichi, Habouzit, Mamon, Peirani

IGM reionization at z>6 depend on FUV LF.  Run 5 N-body sims with Gaussian and scale-dependent non-Gaussian IC, all consistent with Planck constraints.  Compute the FUV galaxy luminosity function down to M_UV=-14 at 7<z<15.  Find that models with strong primordial non-Gausisnities on <Mpc scales show a FUV LF significantly enhanced in low-mass galaxies.  Adopt a reionization model calibrated from state-of-the-art hydrodynamical simulations and show that such non-Gaussianities leave a clear imprint on the Universe reionization history and electron Thomson scattering optical depth tau_E.  Although current uncertainties in the physics of reionization and on the determination of tau_E still dominate the signatures of non-Gauassianities, results suggest that tau_E could ultimately be used to constrain the statistical properties of initial density fluctuations.

1410.7770
Measuring angular diameter distances of strong gravitational lenses
Jee, Komatsu, Suyu

Show that measurements of positions and time delays of strongly lensed images of a background galaxy, as well as those of the velocity dispersion and mass profile of a lens galaxy, can be combined to extract the angular diameter distance of the lens galaxy.  Physically, as the velocity dispersion and the time delay give a gravitational potential (GM/r) and a mass (GM) of the lens, respectively, dividing them gives a physical size (r) of the lens.  Comparing the physical size with the image positions of a lensed galaxy gives the angular diameter distance to the lens.  A mismatch between the exact locations at which these measurements are made can be corrected by measuring a local slope of the mass profile.  Expand on the original idea put forward by Paraficz and Hjorth, who analyzed singular isothermal lenses, by allowing for an arbitrary slope of a power-law spherical mass density profile, and external convergence, and an anisotropic velocity dispersion.  Find that the effect of external convergence cancels out when dividing the time delays and velocity dispersion measurements.  Derive a formula for the uncertainty in the angular diameter distance in terms of the uncertainties in the observables.  As an application, use two existing SL systems to show that the uncertainty in the inferred angular diameter distances is dominated by that in the velocity dispersion, sigma^2, and its anisotropy.  Find that the current data on these systems should yield about 16% uncertainty in DA per object.  This improves to 13% when sigma^2 is measured at the so-called sweet-sopt radius.  Achieving 7% is possible if sigma^2 is determined with 5% precision.

1410.7778
A new spin on disks of satellite galaxies
Cautun, Wang, Frenk, Sawala

The excess of satellites on opposite sides of their primaries having anti correlated radial velocities, found by Ibata+ in SDSS, is sensitive to small changes in the sample selection criteria, which can significantly reduce its significance.  In addition, find no evidence for correspondingly correlated velocities for satellites observed on the same side of their primaries, which would be expected for rotating disks of satellites.  Conclude that the detection of coherent rotation in satellite population in current observational samples is not robust.  Compare data to the LCDM Millennium sims populated with galaxies according to the SAM of Guo+.  Find excellent agreement with the spatial distribution of satellites in the SDSS data and the lack of strong signal from coherent rotation.

1410.7839
Weak lensing with sizes, magnitudes and shapes
Alsing, Kirk, Heavens, Jaffe

Galaxy shapes probe the shear field whilst size, magnitude and number density probe the convergence field.  Both contain cosmo information.  Use magnification of size and magnitude of individual galaxies as probe of cosmic convergence.  Develop a Bayesian approach for inferring the convergence field from a measured size, magnitude and redshift and demonstrate that the inference on convergence requires detailed knowledge of the joint distribution of intrinsic sizes and magnitudes.  Build a simple parameterized model for the size-magnitude distribution and estimate this distribution for CFHTLenS galaxies.  In light of the measured distribution, show that the typical dispersion on convergence estimation is ~0.8, compared to ~0.38 for shear.  Discuss the possibility of physical systematics for magnification (similar to IA for shear) and compute the expected gains in DE FoM from combining magnification with shear for different scenarios regarding systematics: when accounting for IA but no systematics on the magnification signal, including magnification could improve the FoM by unto a factor of ~2.5, whilst when accounting for physical systematics in both shear and magnification anticipate a gain between ~25% and 65%.  In addition to the statistical gains, the fact that cosmic shear and magnification are subject to different systematics makes magnification an attractive complement to ay cosmic shear analysis.

1410.7946
Three Einstein rings: explicit solution and numerical simulation
Bannikova, Kotvytskiy

As the title says.