Mathilde Jauzac

The behaviour of dark matter associated with four bright cluster galaxies in the 10 kpc core of Abell 3827

Galaxy cluster Abell 3827 hosts the stellar remnants of four almost equally bright elliptical galaxies within a core of radius 10 kpc. Such corrugation of the stellar distribution is very rare, and suggests recent formation by several simultaneous mergers. We map the distribution of associated dark matter, using new Hubble Space Telescope imaging and Very Large Telescope/Multi-Unit Spectroscopic Explorer integral field spectroscopy of a gravitationally lensed system threaded through the cluster core. We find that each of the central galaxies retains a dark matter halo, but that (at least) one of these is spatially offset from its stars. The best-constrained offset is 1.62(-0.49)(+0.47) kpc, where the 68 per cent confidence limit includes both statistical error and systematic biases in mass modelling. Such offsets are not seen in field galaxies, but are predicted during the long infall to a cluster, if dark matter self-interactions generate an extra drag force. With such a small physical separation, it is difficult to definitively rule out astrophysical effects operating exclusively in dense cluster core environments - but if interpreted solely as evidence for self-interacting dark matter, this offset implies a cross-section sigma(DM)/(m) similar to (1.7 +/- 0.7) x 10(-4) cm(2) g(-1) x (t(infall)/10(9) yr)(-2), where t(infall) is the infall duration.

NEW CONSTRAINTS ON THE FAINT-END OF THE UV LUMINOSITY FUNCTION AT Z 7 8 USING THE GRAVITATIONAL LENSING OF THE HUBBLE FRONTIER FIELDS CLUSTER A2744 †

Exploiting the power of gravitational lensing, the Hubble Frontier Fields (HFF) program aims at observing six massive galaxy clusters to explore the distant Universe far beyond the depth limits of blank field surveys. Using the complete Hubble Space Telescope observations of the first HFF cluster Abell 2744, we report the detection of 50 galaxy candidates at

ARE ULTRA-FAINT GALAXIES AT z=6-8 RESPONSIBLE FOR COSMIC REIONIZATION? COMBINED CONSTRAINTS FROM THE HUBBLE FRONTIER FIELDS CLUSTERS AND PARALLELS

z \sim 7

HUBBLE SPACE TELESCOPE OBSERVATIONS OF A SPECTACULAR NEW STRONG-LENSING GALAXY CLUSTER: MACS J1149.5+2223 AT z = 0.544

and eight candidates at

The Herschel Lensing Survey (HLS): Overview

z \sim 8

Hubble Frontier Fields: A High-Precision Strong-Lensing Analysis of Galaxy Cluster MACSJ0416.1-2403 Using 200 Multiple Images

in a total survey area of 0.96 arcmin

A weak lensing mass reconstruction of the large-scale filament feeding the massive galaxy cluster MACS J0717.5+3745

^{2}

Strong lensing by a node of the cosmic web - The core of MACS J0717.5+3745 at z = 0.55

in the source plane. Three of these galaxies are multiply-imaged by the lensing cluster. Using an updated model of the mass distribution in the cluster we were able to calculate the magnification factor and the effective survey volume for each galaxy in order to compute the ultraviolet galaxy luminosity function at both redshifts 7 and 8. Our new measurements extend the

Hubble Frontier Fields: a high-precision strong-lensing analysis of the massive galaxy cluster Abell 2744 using ∼180 multiple images

z \sim 7

Probing the z > 6 universe with the first Hubble Frontier Fields cluster A2744.

UV LF down to an absolute magnitude of