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The Cluster-Merger Shock in 1E 0657–56: Faster than a Speeding Bullet?

Milosavljević, Miloš and Koda, Jun and Nagai, Daisuke and Nakar, Ehud and Shapiro, Paul R. (2007) The Cluster-Merger Shock in 1E 0657–56: Faster than a Speeding Bullet? Astrophysical Journal Letters, 661 (2). L131-L134. ISSN 2041-8205. doi:10.1086/518960.

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Shock waves driven in the intergalactic medium during the merging of galaxy clusters have been observed in X-ray imaging and spectroscopy. Fluid motions inferred from the shock strength and morphology can be compared to the cold dark matter (CDM) distribution inferred from gravitational lensing. A detailed reconstruction of the CDM kinematics, however, must take into account the nontrivial response of the fluid intracluster medium to the collisionless CDM motions. We have carried out two-dimensional simulations of gas dynamics in cluster collisions. We analyze the relative motion of the clusters, the bow shock wave, and the contact discontinuity, and relate these to X-ray data. We focus on the Bullet Cluster, 1E 0657-56, a near-head-on collision of unequal-mass clusters, for which the gas density and temperature jumps across the prominent bow shock imply a high shock velocity, 4700 km s^(-1). The velocity of the fluid shock has been widely interpreted as the relative velocity of the CDM components. This need not be the case, however. An illustrative simulation finds that the present relative velocity of the CDM halos is ~16% lower than that of the shock. While this conclusion is sensitive to the detailed initial mass and gas density profile of the colliding clusters, such a decrease of the inferred halo relative velocity would increase the likelihood of finding 1E 0657-56 in a ΛCDM universe.

Item Type:Article
Related URLs:
URLURL TypeDescription
Nagai, Daisuke0000-0002-6766-5942
Nakar, Ehud0000-0002-4534-7089
Additional Information:© 2007 The American Astronomical Society. Received 2007 March 8; accepted 2007 April 19; published 2007 May 16. Research was supported in part by the Sherman Fairchild Foundation and NASA Astrophysical Theory Program grant NNG 04-G177G. The software used in this work was developed in part by the DOE-supported ASC/Alliance Center for Astrophysical Thermonuclear Flashes at the University of Chicago.
Funding AgencyGrant Number
Sherman Fairchild FoundationUNSPECIFIED
Department of Energy (DOE)UNSPECIFIED
Subject Keywords:dark matter; galaxies : clusters : general; galaxies : clusters : individual (1E 0657-56); intergalactic medium; shock waves; X-rays : galaxies : clusters
Issue or Number:2
Record Number:CaltechAUTHORS:20091116-132411622
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Official Citation:The Cluster-Merger Shock in 1E 0657–56: Faster than a Speeding Bullet? Miloš Milosavljević, Jun Koda, Daisuke Nagai, Ehud Nakar, and Paul R. Shapiro 2007 ApJ 661 L131-L134 doi: 10.1086/518960
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:16717
Deposited By: Tony Diaz
Deposited On:25 Nov 2009 21:32
Last Modified:08 Nov 2021 23:29

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