Abstract
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^{+0.47}_{-0.49} 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 σDM/m ˜ (1.7 ± 0.7)
× 10-4 cm2 g-1 ×
(tinfall/109 yr)-2, where
tinfall is the infall duration.
Original language | English |
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Pages (from-to) | 3393-3406 |
Journal | Monthly Notices of the Royal Astronomical Society |
Volume | 449 |
Publication status | Published - 1 Jun 2015 |
Keywords
- astroparticle physics
- gravitational lensing: strong
- galaxies: clusters: individual: Abell 3827
- dark matter