Evidence from gravitational lensing for a non-thermal pressure support in the cluster of galaxies A2218
Jun, 199412 pages
Published in:
- Astrophys.J.Lett. 435 (1994) L109-L112
e-Print:
- astro-ph/9406030 [astro-ph]
DOI:
Report number:
- CFA-3930
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Abstract: (arXiv)
The central mass distribution of clusters of galaxies can be inferred from gravitationally lensed arcs with known redshifts. For the Abell cluster 2218, this method yields a core mass which is larger by a factor of than the value deduced from X-ray observations, under the assumptions that the gas is supported by thermal pressure and that the cluster is spherical. We show that a non-thermal pressure support is the most plausible explanation for this discrepancy. Such a pressure can be naturally provided by strong turbulence and equipartition magnetic fields (G) that are tangled on small spatial scales (<10 kpc). The turbulent and magnetic pressures do not affect the measured Sunyaev-Zel'dovich effect for this cluster. Intracluster magnetic fields with a comparable magnitude (G) have already been detected by Faraday rotation in other clusters. If generic, a small-scale equipartition magnetic field should affect the structure of cooling flows and must be included in X-ray determinations of cluster masses.Note:
- 12 pages, Postcript file
- GALAXY CLUSTERS
- MAGNETIC FIELDS
- DARK MATTER
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