Day 1268

Monday.

1706.02704
The abundance of ultra-diffuse galaxies from groups to clusters: UDGs are relatively more common in more massive haloes
van der Burg, Hoekstra, et al

In recent years, multiple studies have reported substantial populations of large, low-surface-brightness galaxies in local galaxy clusters.  Various theories that aim to explain the presence of such UDGs have since been proposed.  A key question that will help to differentiate between models is whether UDGs have counterparts in lower-mass host haloes, and what their abundance as a function of halo mass is.  In this study, extend the previous study of UDGs in galaxy clusters to galaxy groups.  Measure the abundance of UDGs in 325 spectroscopically-selected groups from GAMA.   Make use of the overlapping image from KiDS, from which galaxies can be identified with mean surface brightnesses within their effective radii down to ~25.5 mag/arcsec^2 in the r-band.  Able to measure a significant overdensity of UDGs (with sizes r_eff>1.5 kpc) in galaxy groups down to M200=1e12 Msun, a regime where approximately only 1 in 10 groups contains a UDG that can be detected.  Combine measurements of the abundance of UDGs in haloes that cover 3 orders of magnitude in halo mass, finding that their numbers scale quite steeply with halo mass; N_UDG (R<R200) ~ M200^(1.11±0.07). To better interpret this, also measure the mass-richness relation for brighter galaxies down to M*_r +2.5 in the same GAMA groups, and find a much shallower relation of N_Bright (R<R200) ~ M200^(0.78±0.05).  This shows that UDGs are relatively more abundant, compared to bright galaxies, in massive clusters than in groups.  Discuss implications, but whether this difference is related to a higher destruction rate of UDGs in groups, or whether massive haloes have a positive effect on their formation, is not yet clear.


1706.02892
KiDS-450: The tomographic weak lensing power spectrum and constraints on cosmological parameters
Köhlinger, Viola, Joachimi, Hoekstra, van Uitert, et al

Present measurements of the WL shear power spectrum based on 450 sq. deg. of imaging data from KiDS.  Employ a quadratic estimator in 2 and 3 z bins and extract band powers of z auto-correlation and cross-correlation spectra in the multipole range 76<ell<1310.  The cosmo interpretation of the measured shear PS is performed in a Bayesian framework assuming a LCDM model with spatially flat geometry, while accounting for small residual uncertainties in the shear calibration and redshift distributors as well as marginalizing over intrinsic alignments, baryon feedback and an excess-noise power model.  Moreover, massive neutrinos are included in the modeling.  The cosmo main result is expressed in terms of the parameter combination S8=sigma_8xsqrt(Omega_m/0.3) yielding S8=0.651±0.058 (3 z-bins), confirming the recently reported tension in this parameter with constraints from Planck at 3.2 sigma (3 z-bins).  Cross-check the results of the 3 z-bin analysis with the weaker constraints from the 2 z-bin analysis and find them to be consistent.  The high-level data products of this analysis, such as the band power measurements, covariance matrices, z distributions, and likelihood evaluation changes are available at http://kids.strw.leidenuniv.nl/.