The Compton Y- parameter and the X-Ray temperature can both be used to estimate these objects' masses.
The redMaPPer algorithm is a photometric way of detecting these objects. The Compton Y- parameter and the X-Ray temperature can both be used to estimate these objects' masses. They appear as negative point sources on high-res CMB maps due to their strong thermal Sunyaev-Zeldovich effect and the kinematic SZ effect was used to determine a coherent peculiar velocity of these objects, the "Dark Flow". Properties of these objects are measured at "R sub 200c," the virial (*) radius at which their density drops to 200 times the mean universe density. An 8 sigma offset between the baryonic and lensing mass of the Bullet one of these objects definitively proved the existence of dark matter. The Abell catalog contains examples of these objects and Fritz Zwicky first detected dark matter in the Coma one. For 10 points, name this type of object, a collection of galaxies larger than a group.
The redMaPPer algorithm is a photometric way of detecting these objects.
galaxy cluster [prompt on cluster until 'galaxies' is read, accept afterwards, DO NOT ACCEPT OR PROMPT ON "galaxy"]