3 years ago

A comparison of the excess mass around CFHTLenS galaxy-pairs to predictions from a semi-analytic model using galaxy-galaxy-galaxy lensing.

P. Schneider, P. Simon, S. Hilbert, C. Boever, H. Saghiha

Galaxy-galaxy-galaxy lensing (G3L) is a probe of the matter environment of average galaxy pairs, which is a strong test for galaxy models. Using G3L we map out the distribution of correlated excess-mass around galaxy pairs in the Canada-France-Hawaii Telescope Lensing Survey (CFHTLenS) in a reanalysis of the data. We compare the maps to predictions by a recent semi-analytic model (SAM) which is implanted on the Millennium Simulation. Our target galaxies span a range of stellar masses between $10^9-10^{11}\,{\rm M}_\odot$ and have redshifts below $z\lesssim0.6$ in two redshift bins; the projected separation between galaxies pairs is chosen between $\approx170-300\,h^{-1}\,\rm kpc$ in two separation bins. Compared to an earlier G3L study with CFHTLenS galaxies, we make more efficient use of the data. In addition, we verify the accuracy of our refined stacking technique for the map construction with simulated data and provide a detailed description of the methodology. For a better interpretation of the maps, we discuss the impact of chance pairs, i.e., galaxy pairs that appear close to each other in projection only, and we introduce an alternative correlation map that is less affected by projection effects but has a lower signal-to-noise ratio (S/N). For all maps, we obtain significant measurements of the excess-mass distribution for all galaxy samples and an overall good agreement with the SAM predictions. There is, however, tentative evidence for a bulge-like feature in the distribution of excess mass that is not predicted by the SAM and similar models. Although we have no strong indications for systematic errors in the maps, this feature may be related to a residual B-mode pattern visible in the average of all maps. Alternatively, misaligned galaxy pairs inside matter halos or lensing by a misaligned distribution of the intra-cluster gas might also cause a bulge.

Publisher URL: http://arxiv.org/abs/1710.09902

DOI: arXiv:1710.09902v1

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