Timing and Lensing of the Colliding Bullet Clusters: barely enough time and gravity to accelerate the bullet

Understand

We present semi-analytical constraint on the amount of dark matter in the merging bullet galaxy cluster using the classical Local Group timing arguments.

• We consider particle orbits in potential models which fit the lensing data.
• {\it Marginally consistent} CDM models in Newtonian gravity are found with a total mass M_{CDM} = 1 x 10^{15}Msun of Cold DM: the bullet subhalo can move with V_{DM}=3000km/s, and the "bullet" X-ray gas can move with V_{gas}=4200km/s.
• These are nearly the {\it maximum speeds} that are accelerable by the gravity of two truncated CDM halos in a Hubble time even without the ram pressure.