Journal
ASTROPHYSICAL JOURNAL
Volume 687, Issue 2, Pages 959-967Publisher
UNIV CHICAGO PRESS
DOI: 10.1086/591246
Keywords
dark matter; galaxies: clusters: individual (MACS J0025.4-1222); gravitational lensing
Categories
Funding
- NASA [HST-GO-11100, NAS5-26555, NNX08AD79G, HST-HF-01206.01]
- Space Telescope Science Institute
- AURA, Inc
- NSF [0642621]
- Sloan Foundation through a Sloan Research
- Packard Foundation
- STFC
- STFC [PP/E006450/1]
- US Department of Energy [AC0276SF00515]
- X-Ray Center (CXC)
- California Institute of Technology, the University of California
- National Aeronautics and Space Administration
- Keck Foundation
- NASA [NNX08AD79G, 103019] Funding Source: Federal RePORTER
- Science and Technology Facilities Council [PP/E006450/1] Funding Source: researchfish
- STFC [PP/E006450/1] Funding Source: UKRI
- Division Of Astronomical Sciences
- Direct For Mathematical & Physical Scien [807458] Funding Source: National Science Foundation
- Division Of Astronomical Sciences
- Direct For Mathematical & Physical Scien [0642621] Funding Source: National Science Foundation
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We constrain the physical nature of dark matter using the newly identified massive merging galaxy cluster MACS J0025.4-1222. As was previously shown by the example of the Bullet Cluster (1E 0657-56), such systems are ideal laboratories for detecting isolated dark matter and distinguishing between cold dark matter (CDM) and other scenarios (e.g., self-interacting dark matter, alternative gravity theories). MACS J0025.4-1222 consists of two merging subclusters of similar richness at z = 0.586. We measure the distribution of X- ray-emitting gas from Chandra X-ray data and find it to be clearly displaced from the distribution of galaxies. A strong (information from highly distorted arcs) and weak (using weakly distorted background galaxies) gravitational lensing analysis based on Hubble Space Telescope observations and Keck arc spectroscopy confirms that the subclusters have near-equal mass. The total mass distribution in each of the subclusters is clearly offset (at >4 sigma significance) from the peak of the hot X-ray-emitting gas (the main baryonic component) but aligned with the distribution of galaxies. We measure the fractions of mass in hot gas (0.09(-0.03)(+0.07)) and stars (0.10(-0.04)(+0.07)) consistent with those of typical clusters, finding that dark matter is the dominant contributor to the gravitational field. Under the assumption that the subclusters experienced a head-on collision in the plane of the sky, we obtain an order-of-magnitude estimate of the dark matter self-interaction cross section of sigma/m < 4 cm(2) g(-1), reaffirming the results from the Bullet Cluster on the collisionless nature of dark matter.
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