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Marusa Bradac (KIPAC)Doug Clowe (Ohio U.)
Anthony Gonzalez (U. Florida)
Maxim Markevitch (CfA)Christine Jones (CfA)
Phil Marshall (KIPAC)Scott Randall (CfA)Tim Schrabback (AlFA, Bonn)
William Forman (CfA)
Dennis Zaritsky (U. Arizona)
Bradac et al., 2006, ApJ, 652,937Clowe et al., 2006, ApJL, 648,108
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Zwicky (1933) : Coma Cluster (400x observed mass)Smith (1936) : Virgo Cluster
The Case for Dark Matter
H.D. Babcock (1938; PhD - unpublished) M 31, M/L ~ 50
Kahn & Woltjer (1959): Local Group Timing
argument
de Blok et al. 2001
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MOND (Milgrom)
The PROBLEM : Coincidence of Baryons & Dark Matter
Sanders & McGaugh 2002
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Gonzalez, Zaritsky, Zabludoff 2006
We see all the baryons!
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Dark Matter (mass)
Gas
Galaxies
Scenario 1: ‘New’ Gravity - mass follows gas
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Dark Matter (mass)
Gas
Galaxies
Scenario II: Collisionless DM
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Dark Matter (mass)
Gas
Galaxies
Scenario III: Self-Interacting DM
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1E0657-56 (The Bullet Cluster)
• Supersonic merger• z=0.30 (3.35 Gyr ago, or 1.2 Gpc away)
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Weak lensing by cluster at z ~ 0.5
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1E0657-56 (The Bullet Cluster)
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8 sigma offsets from X-ray peaks
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Bradac et al. Strong + weak lensing
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Conclusions
Rare high-v, face-on merger provides unique opportunity
plasma dominates baryons (lensing signal seen)
galaxies/dark matter separated from plasma
other “lumpy” clusters have X-ray/mass co-centered
data at http://flamingos.astro.ufl.edu/1e0657/public_html