Day 1116

Wednesday.

1606.01014
Integrated approach to cosmology: combining CMB, large-scale structure and weak lensing
Nicola, Refregier, Amara

Recent observational progress has led to the establishment of the standard LCDM model for cosmology.  This development is based on different cosmological probes that are usually combined through their likelihoods at the latest stage in the analysis.  Implement here an integrated scheme for cosmo probes, which are combined in a common framework starting at the map level.  This treatment is necessary as the probes are generally derived from overlapping maps and are thus not independent.  It also allows for a thorough test of the cosmo model and of systematics through the consistency of different physical tracers.  As a first application, combine current measurements of CMB from Planck, and galaxy clustering from SDSS.  Consider the spherical harmonic power spectra of these probes including all six auto- and cross-correlations along with the associated full gaussian covariance matrix.  This provides an integrated treatment of different analyses usually performed separately including CMB anisotropies, cosmic shear, galaxy clustering, gg lensing and the ISW effect with galaxy and shear tracers.  Derive constraints on LCDM parameters which are compatible with existing constraints and highlight tensions between data sets, which become apparent in this integrated treatment.  Discuss how this approach provides a complete and powerful integrated framework for probe combination and how it can be extended to include the tracers in the context of current and future wide field cosmo surveys.


1607.01047
H0LiCOW III. Quantifying the effect of mass along the line of sight to the gravitational lens HE 0435-1223 through weighted galaxy counts
Rusu, et al

Based on spectra and multi band wide-field observations of the gravitationally lensed quasar HE 0435-1223, determine the probability distribution function of the external convergence kappa_ext for this system.  Measure the under/overdensity of the LoS towards the lens system and compare it to the average LoS throughout the universe, determined by using the CFHTLenS as a control field.  Aiming to constrain kappa_ext as tightly as possible, determine under/overdensities using various combinations of relevant informative weighing schemes for the galaxy counts, such as projected distance to the lens, redshift, and stellar mass.  Then convert the measured under/overdensities into a kappa_ext distribution, using ray-tracing through the Millennium sims.  Explore several limiting magnitudes and apertures, and account for systematic and statistical uncertainties relevant to the quality of the observational data, which is further tested through simulations.  The most robust estimate of kappa_ext has a median value kappa_ext^med=0.004 and a standard deviation of sigma_kappa=0.025.  The measured sigma_kappa corresponds to 2.5% uncertainty on the time delay distance, and hence the Hubble constant H0 inference from this system.  The median kappa_ext^med value is robust to ~0.005 (i.e. ~0.5% on H0) regardless of the adopted aperture radius, limiting magnitude and wighting scheme, as long as the latter incorporates galaxy number counts, the projected distance to the main lens, and a prior on the external shear obtained from mass modeling.  The availability of a well-constrained kappa_ext makes the quad a valuable system for measuring cosmo params using SL time delays.


1607.01189
The SuperCOSMOS all-sky galaxy catalogue
Peacock, Humbly, Bilicki, MacGillivray, Miller, Read, Tritton

Describe the construction of an all-sky galaxy catalogue, using SueprCOSMOS scans of Schmidt photographic plates from the UKST and POSS2 surveys.  The photographic photometry is calibrated using SDSS data, with results that are linear to 2% or better.  All-sky photometric uniformity is achieved by matching plate overlaps and also by requiring homogeneity in optical-to-2MASS colors, yielding zero points that are uniform to 0.03 mag or better.  The typical AB depths achieved are B_J<21, R_F<19.5, and I_N<18.5, with little difference between hemispheres.  In practice, the I_N plates are shallower than the B_J & R_F plates, so for most purposes advocate the use of a catalogue selected in these two latter bands.  At high Galactic latitudes, this catalogues is approximately 90% complete with 5% stellar contamination, quantify how the quality degrades towards the Galactic plane.  At low latitudes, there are many spurious galaxy candidates resulting from stellar blends: these approximately match the surface density of true galaxies at |b|=30 deg.  Above this latitude, the catalogue limited in B_J & R_F contains in total about 20M galaxy candidates, of which 75% are real.  This contamination can be removed, and the sky coverage extended, by matching with additional datasets.  This SuperCOSMOS catalogue has been matched with 2MASS and with WISE, yielding quasi-allsky samples of respectively 1.5 million and 18.5 million galaxies, to median redshifts of 0.08 and 0.20.  This legacy dataset thus continues to offer a valuable resource for large-angle cosmo investigations.