Day 1102

Thursday.

1605.07620
II. Apples to apples $A^2$: cluster selection functions for next-generation surveys
Ascaso, Mei, Bartlett, Benítez

Present the cluster selection function for 3 of the largest next-generation stage-IV surveys in the optical in IR: Euclid-Optimistic, Euclid-Pessimistic and the LSST.  To simulate test surveys, use the realistic mock catalogues introduced in the first paper of this series.  Detected galaxy clusters using Bayesian Cluster Finder (BCF) in the mock catalogues.  Then model and calibrate the total cluster stellar mass observable-theoretical mass (M*_CL-M_h) relation using a power law model, including a possible redshift evolution term.  Find a moderate scatter of sigma_{M*_CL | M_h} of 0.124, 0.135 and 0.136 dex for the 3 cases, respectively, comparable to other work over more limited ranges and redshift.  Moreover, the 3 datasets are consistent with negligible evolution with redshift, in agreement with observational and simulation results in the literature.  Find that Euclid-Optimistic will be able to detect clusters with >80% completeness and purity down to 8e13 Msun up to z<1.  At higher redshifts, the same completeness and purity are obtained with the larger mass threshold of 2e14 Msun up to z=2.  The Euclid-Pessimistic selection function has a similar shape with ~10% higher mass limit.  LSST shows ~5% higher mass limit than Euclid-Optimistic up to z<0.7 and increases afterwards, reaching values of 2e14 Msun at z=1.4.  Similar selection functions with only 80% completeness threshold have been also computed.  The complementarity of these results with selection functions for surveys in other bands is discussed.


1605.07621
Lens models under the microscope: comparison of Hubble Frontier Field Cluster Magnification Maps
Price, Williams, Liesenborgs, Coe, Rodney

Using the power of gravitational lensing magnification by massive galaxy clusters, the HFF provide views of 6 patches of the high-z universe.  The combination of deep Hubble imaging and exceptional lensing strength has revealed the greatest numbers of multiply-imaged galaxies available to constrain models of cluster mass distributions.  However, even with O(100) images per cluster, the uncertainties associated with the reconstructions are not negligible.  The goal of this paper is to present a quantitative and visual impression of the diversity of model magnification predictions.  Examine 7 and 9 mass models of Abell 2744 and MCS J0416, respectively, submitted to the Mikulski Archive for Space Telescopes for public distribution in September 2015.  The dispersion between model predictions increases from 20% at common low magnifications (mu~2) to 70% at rare high magnifications (mu~40).  MACS J0416 exhibits smaller dispersions than Abell 2744 for 2<mu<10.  Show that magnification map based on different lens inversion techniques typically differ from each other by more than their quoted statistical errors.  This suggests that some models probably underestimate the true uncertainties, which are primary due to various lensing degeneracies.  Though the exact mass sheet degeneracy is broken, its approximate counterpart is not broken at least in Abell 2744.  Other, local degeneracies are also present in both clusters.  The comparison of models in this paper is complementary to the exercise of comparing reconstructions of known synthetic mass distributions.  By focusing here on a comparison of actual observed clusters, we can identify the clusters that are best constrained, and therefore provide the clearest view of the distant Universe.