Day 999

Monday.


1510.08852
Measuring the distance-redshift relation with the baryon acoustic oscillations of galaxy clusters
Veropalumbo, et al

Analyse the largest spectra samples of galaxy clusters to date, and provide observational constraints on the distance-redshift relation from BAO.  The cluster samples considered in this work have been extracted from SDSS at 3 median redshifts, z=0.2, 0.3 and 0.5.  The number of objects is 12910, 42215, and 11816, respectively.  Detect the peak of BAO for all the 3 samples.  The derived distance constraints are: r_s/D_V(z=0.2)=0.18±0.01, (z=0.3): 0.124±0.004, and (z=0.5): 0.080±0.002.  Combining these measurements, obtain robust constraints on cosmo parameters.  Results are in agreement with the standard LCDM.  Specifically, constrain the Hubble constant in a LCDM model, H0=64±14-9 km/s/Mpc, the density of curvature energy, in the oLCDM context, Omega_K=-0.015±0.35, and finally the parameter of the DE EoS in owCDM case, w=-1.01±0.44.  This is the first time the distance-redshift relation has been constrained using only the peak of BAO of galaxy clusters.


1510.09118
Analysis of luminosity distributions and shape parameters of strong gravitational lensing elliptical galaxies
Biernaux, et al

Luminosity profiles of galaxies acting as SL can be tricky to study.  SL images display several lensed components, both point-like and diffuse, around the lensing galaxy.  Those objects limit the study of the galaxy luminosity to its inner parts.  Therefore, the usual fitting methods perform rather badly on such images.  Previous studies of SL luminosity profiles using software such as GALFIT or IMFITFITS and various PSF-determining methods have resulted in discrepant results.  The present work aims at investigating the causes of those discrepancies, as well as at designing more robust techniques for studying the morphology of early-type lensing galaxies with the ability to subtract a lensed signal from their luminosity profiles.  Design a new method to independently measure each shape parameter, namely, the position angle, ellipticity, and HLR of the galaxy.  The HLR measurement method is based on an innovative scheme for computing isophotes that is well suited to measuring the morphological properties of gravitational lensing galaxies.  Its robustness regarding various specific aspects of gravitational lensing image processing is analyzed and tested against GALFIT.  It is applied to a sample of systems from CASTLES database.  Simulations show that when restricted to small, inner parts of the lensing galaxy, the technique presented here is more trustworthy than GALFIT.  It gives more robust results than GALFIT, which shows instabilities regarding the fitting region, the value of the Sersic index, and the S/N ratio.  It is therefore better suited than GALFIT for gravitational lensing galaxies.  It is also able to study lensing galaxies that are not much larger than the PSF.  New values for the HLR of the objects in the sample are presented and compared to previous works.