Day 554

Wednesday.

1311.5936
The effects of structure anisotropy on lensing observables in an exact general relativistic setting for precision cosmology
Troxel Ishak, Peel

Study of relativistic, higher order and NL effects necessary for precision cosmology; develop and apply a framework to study GL in exact models in GR that are not restricted to homogeneity and isotropy, and where full NL and relativistic effects included.  Apply framework to a specific, anisotropic galaxy cluster model based on modified NFW profile and described by Szekeres metric.  Examine the effects of increasing levels of anisotropy in the galaxy cluster on lensing observables like the convergence and shear for various lensing geometries, finding a strong NL response in both the convergence and shear for rays passing through anisotropic regions of the cluster.  Deviation from the expected values in a spherically symmetric structure are asymmetric with respect to path direction and thus will persist as a statistical effect when averaged over some ensemble of such clusters.  The resulting relative difference in various geometries can be as large as 2,8, and 24% in the measure of convergence for levels of anisotropy of 5,10, and 15%, respectively, as a fraction of total cluster mass.  FOr the total magnitude of shear, the relative difference can grow near the structure to be as large as 15,32 and 44% for the same levels of anisotropy, averaged over the two extreme geometries.  The convergence is impacted most strongly for rays which pass in directions along the axis of maximum dipole anisotropy in the structure, while the shear is most strongly impacted for rays which pass in directions orthogonal to this axis, as expected.  These effects due to anisotropic structures will affect lensing measurements and must be fully examined in an era of precision cosmology.

1311.6200
First measurement of the cross-correlation of CMB lensing and galaxy lensing
Hand, Leauthaud, Das, Sherwin, … Heymans, Devlin, Erben, Hildebrandt, Kneib, … et al

Measure the X-correlation of CMB lensing convergence maps from ACT with galaxy lensing convergence maps from CHFTLenS Stripe82 survey.  The CMB-galaxy lensing cross PS is measured for the first time with 3.2 sigma, which correspond to 16% constraint on the amplitude of density fluctuations at redshifts ~0.9.  With upcoming improved lensing data, this novel type of measurement will become a powerful cosmological probe, providing a precise measurement of the mass distribution at intermediate redshifts and serving as a calibrator for systematic biases in WL measurements.

1311.6344
The host galaxies of Type Ia supernovae discovered by the Palomar Transient Factory
Pan, … Nugent, … Cenko, .. Fakhouri, … Gal-Yam, … et al

Present spectroscopic observations of 82 host galaxies of low-z SNeIa discovered, discovered by PTF.  Strong correlations between SNIa light-curve width (stretch) and the host age/mass/metallicity found: fainter, faster-declining events tend to be hosted by older/massive/metal-rich galaxies.  There is some evidence that redder SNeIa explode in higher metallicity galaxies, but found no relation between the SN color and host galaxy extinction based on the Balmer decrement, suggesting that the color variation of these SNe does not primarily arise from [extinction].  SNeIa in higher-mass/metallicity galaxies also appear brighter after stretch/color corrections than their counterparts in lower mass hosts, and the stronger correlation is with gas-phase metallicity suggesting this may be the more important variable.  Also compared the host stellar mass distribution to that in galaxy targeted SN surveys and the high-z untargeted SNLS.  SNLS has more low mass galaxies, while the targeted searches have fewer. THis can be explained by an evolution in the galaxy stellar mass function, coupled with a SN delay-time distribution proportional to t^-1.  Finally, found no significant difference in the mass-metallicity relation of the SN Ia hosts compared to field galaxies, suggesting any metallicity effect on the SN Ia rate is small.

1311.6383
Magnification bias as a novel probe for primordial magnetic fields
Camera, Fedeli, Moscardini

Intermediate to small scales would experience further substantial matter clustering, were a cosmological magnetic field present prior to recombination.  Explore the constraining potential of the density fluctuation bias induced by gravitational lensing magnification onto the galaxy-galaxy angular power spectrum.  Such an effect is known as magnification bias.  Compared to the usual galaxy clustering approach, magnification bias helps in lifting the pathological degeneracy present amongst PS normalization and galaxy bias.  This is because magnification bias cross-correlates galaxy number density fluctuations of nearby objects with WL distortions of high-z sources.  Thus, it takes advantage of the gravitational deflection of light, which is insensitive to galaxy bias but powerful in constraining the density fluctuation amplitude.  To scrutinize the potentiality of this method, adopt a deep and wide-field spectroscopic galaxy survey.  Show that magnification bias does contain important information on primordial magnetism, which will be useful in combination with galaxy clustering and shear.  Find can rule out 95.4% CL amplitudes of PMFs larger than 0.0005 nG for values of the PMF power spectral index ~0.