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H.D. Babcock (1938; PhD - unpublished) M 31, M/L ~ 50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
MOND (Milgrom)
The PROBLEM : Coincidence of Baryons & Dark Matter
Sanders & McGaugh 2002
Dark Matter (mass)
Gas
Galaxies
Gonzalez, Zaritsky, Zabludoff 2006
We see all the baryons!
Dark Matter (mass)
Gas
Galaxies
Scenario 1: ‘New’ Gravity - mass follows gas
Dark Matter (mass)
Gas
Galaxies
Scenario II: Collisionless DM
Dark Matter (mass)
Gas
Galaxies
Scenario III: Self-Interacting DM
1E0657-56 (The Bullet Cluster)
• Supersonic merger• z=0.30 (3.35 Gyr ago, or 1.2 Gpc away)
Gravitational Lensing
We see all the matter!
Strong lensing
Weak lensing
Weak lensing by cluster at z ~ 0.5
1E0657-56 (The Bullet Cluster)
8 sigma offsets from X-ray peaks
Bradac et al. Strong + weak lensing
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