A filament of dark matter between two clusters of galaxies
Abstract
It is a firm prediction of the concordance cold-dark-matter cosmological model that galaxy clusters occur at the intersection of large-scale structure filaments. The thread-like structure of this `cosmic web' has been traced by galaxy redshift surveys for decades. More recently, the warm-hot intergalactic medium (a sparse plasma with temperatures of 105 kelvin to 107 kelvin) residing in low-redshift filaments has been observed in emission and absorption. However, a reliable direct detection of the underlying dark-matter skeleton, which should contain more than half of all matter, has remained elusive, because earlier candidates for such detections were either falsified or suffered from low signal-to-noise ratios and unphysical misalignments of dark and luminous matter. Here we report the detection of a dark-matter filament connecting the two main components of the Abell 222/223 supercluster system from its weak gravitational lensing signal, both in a non-parametric mass reconstruction and in parametric model fits. This filament is coincident with an overdensity of galaxies and diffuse, soft-X-ray emission, and contributes a mass comparable to that of an additional galaxy cluster to the total mass of the supercluster. By combining this result with X-ray observations, we can place an upper limit of 0.09 on the hot gas fraction (the mass of X-ray-emitting gas divided by the total mass) in the filament.
- Publication:
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Nature
- Pub Date:
- July 2012
- DOI:
- 10.1038/nature11224
- arXiv:
- arXiv:1207.0809
- Bibcode:
- 2012Natur.487..202D
- Keywords:
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- Astrophysics - Cosmology and Extragalactic Astrophysics
- E-Print:
- Nature, in press