Protruding bullet heads indicating dark matter pull
Abstract
A clump moving through the intracluster medium of a galaxy cluster can drive a bow shock trailed by a bullet-like core. In some cases, such as in the prototypical Bullet cluster, X-rays show a gas bullet with a protruding head and pronounced shoulders. We point out that these features, while difficult to explain without dark matter (DM), naturally arise as the head of the slowed-down gas is gravitationally pulled forward toward its unhindered DM counterpart. X-ray imaging thus provides a unique, robust probe of the offset, collisionless DM, even without gravitational lensing or other auxiliary data. Numerical simulations and a toy model suggest that the effect is common in major mergers, is often associated with a small bullet-head radius of curvature, and may lead to distinct bullet morphologies, consistent with observations.
- Publication:
-
Monthly Notices of the Royal Astronomical Society
- Pub Date:
- December 2021
- DOI:
- 10.1093/mnras/stab2808
- arXiv:
- arXiv:2101.06271
- Bibcode:
- 2021MNRAS.508.3455K
- Keywords:
-
- hydrodynamics;
- magnetic fields;
- galaxies: clusters: general;
- galaxies: clusters: intracluster medium;
- X-rays: galaxies: clusters;
- Astrophysics - Cosmology and Nongalactic Astrophysics
- E-Print:
- 9 pages, 3 figures, comments welcome