Current constraints from bullet clusters on the cross-section of particulate dark matter are 18
orders of magnitude larger than that required to distinguish between plausible particle-physics dark matter
candidates (for example from supersymmetric extensions to the standard model). In order to
investigate a physically interesting régime of dark matter cross-section, and provide smaller
error bars, many more individual bullet clusters are required. However collisions between two
massive progenitors are rare and ultimately the total observable number of such systems may be
inadequate.
In [643], a method for using every individual infalling substructure in every cluster has been proposed. For each piece of infalling substructure, a local vector from the dark matter peak (identified using weak lensing analysis) and the baryonic mass peak (from X-rays) – dubbed ‘bulleticity’ – can be defined
where the radial In Figure 35 a result from full hydrodynamical simulations of dark and baryonic matter within clusters
in shown. [643] have used these simulations to show that the measurement of a net bulleticity consistent
with the cold dark matter used in the simulations is possible.
Finally, a Fisher matrix calculation has shown that, under the assumption that systematic effects can be
controlled, Euclid could use such a technique to constrain the relative particulate cross-sections to
.
The raw bulleticity measurement would constrain the relative cross-sections of the baryon-baryon interaction and the dark matter-dark matter interaction. However, since we know the baryonic cross-section relatively well, we can infer the dark matter-dark matter cross-section. The dark matter-dark matter interaction probed by Euclid using this technique will be complementary to the interactions constrained by direct detection and accelerator experiments where the primary constraints will be on the dark matter-baryon interaction.
http://www.livingreviews.org/lrr-2013-6 |
Living Rev. Relativity 16, (2013), 6
![]() This work is licensed under a Creative Commons License. E-mail us: |