Day 780

Thursday.

1411.1074
Cosmological implications of baryon acoustic oscillation (BAO) measurements
Aubourg, et al

From BOSS, BAO, combined with CMB and SNIa.  Use SDSS-III BAO measurements from LyaF and galaxy clustering.  BAO alone show evidence of DE; combined with CMB further imply a nearly flat universe.  Combining BAO and SN into an inverse distance ladder yields a 1.7% measurement of H0=67.3pm1.1 km/s/Mpc.  This measurement assumes standard pre-recombination physics but is insensitive to assumptions about DE or space curvature, so agreement with CMB-based estimates that assume a flat LCDM cosmology is an important corroboration of this minimal cosmological model.  For open LCDM, the BAO+SN+CMB combination yields Omega_m=0.301pm0.008 and curvature Omega_k=-0.003 pm 0.003.  When allowed more general forms of evolving DE, the BAO+SN+CMB parameter constraints remain consistent with flat LCDM.  While the overall chi2 of model fits is satisfactory, the LyaF BAO measurements are in moderate (2-2.5 sigma) tension with model predictions.  Models with early DE that tracks the dominant energy component at high redshifts remain consistent with the constraints, but models where dark matter decays into radiation are sharply limited.  Expansion history alone yields an upper limit of 0.56 eV on the summed mass of neutrino species, improving to 0.26 eV if Planck CMB lensing is included.  Standard DE models constrained by the data predict a level of matter clustering that is high compared to most, but not all, observational estimates.

1411.1094
Calibrating the cosmic distance scale ladder: the role of the sound horizon scale and the local expansion rate as distance anchors
Cuesta, Verde, Reiss, Jiminez

Exploit the cosmological-model independent measurements of the expansion history of the Universe to provide a cosmic distance ladder.  These are SNIa used as standard candles (0.01<z<1.3) and BAO (0.1<z<0.8) as standard rulers.  Calibrate (anchor) the ladder in two ways: first using the local H0 value as an anchor at z=0 (effectively calibrating the standard candles) and secondly using the CMB-inferred sound-horizon scale as an anchor (giving the standard ruler length) as an inverse distance ladder.  Both methods are consistent, but the uncertainty in the expansion history H(z) is smaller if the sound horizon scale is used.  Present inferred values for the sound horizon at radiation drag r_d which do not rely on assumptions about the early expansion history nor on CMB measurements but on the cosmic distance ladder and BAO measurements.  Also present derived values of H0 from the inverse distance ladder and show that they are in very good agreement with the derived value from the CMB data for a LCDM model.

1411.1265
Extensive light profile fitting of galaxy-scale strong lenses
Brault, Gavazzi

Investigate the merits of a massive forward modeling of ground-based optical imaging as a diagnostic for the SL nature of ETGs, in the light of which blurred and faint Einstein rings can hide.  Model space- and ground-based conditions of an exponential disk around a FB deVauc light profile whose lensing potential is described by a singular isothermal ellipsoid.  Then fit for the lensed light distribution with sl_fit after having subtracted the FG light emission off (ideal case) and also after having fitted the deflector's light with gal fit.  By setting thresholds in the output parameter space, can decide the lens/not-a-lens status of each system.  Finally apply strategy to a sample of 517 lens candidates present in the CFHTLS data to test the consistency of the selection approach.  The efficiency of the fast modeling method at recovering the main lens parameters like Einstein radius, total magnification or total lensed flux, is quite comparable under CFHT and HST conditions when the deflector is perfectly subtracted off (only possible in simulations), fostering a sharp distinction between the good and the bad candidates.  Conversely, for a more realistic subtraction, a substantial fraction of the lensed light is absorbed into the deflector's model, which biases the subsequent fitting of the rings and then disturbs the selection process.  Quantify completeness and purity of the lens finding method in both cases.  This suggests that the main limitation currently resides in the subtraction of the FG light.  Provided further enhancement of the latter, the direct forward modeling of large numbers of gg SLs thus appears tractable and could constitute a competitive lens finder in the next generation of wide-field imaging surveys.