Using diffuse radio emission in clusters of galaxies to probe the cosmic
  web, cosmic rays and dark matter
  The study of diffuse radio sources is essential to our knowledge of the
physical conditions in clusters of galaxies and of the role that large scale
magnetic fields play in the propagation of the relativistic particles in the
intracluster medium (ICM). Due to dissipative processes, the thermal plasma of
the ICM contains useless information about the formation of structures and CRs.
Such past and current information is carried intact by its non-thermal emission
caused by highly relativistic particles spiraling in large-scale magnetic
fields. The diffuse radio emission is not associated with the active galactic
nucleus phenomenon and has no optical counterpart. Instead it is associated
with the ICM and it is characterized by steep spectrum. The low surface radio
brightness features are thought to be formed via re-acceleration of a relic
population of relativistic electrons, or proton-proton collisions with the ICM.
Diffuse radio sources are classified typically as `relics', `halos',
'mini-halos' and 'radio-ghosts'. We use a sample of 67 nearby clusters of
galaxies at redshift, 0.02 < z < 0.1, to tackle the relation between the
diffuse radio emission and the large scale structure (cosmic web), dark matter
(DM) and cosmic rays (CRs). Our sample of clusters at low redshift containing
areas of radio flux below the Jy level is well suited for the study of DM. DM
halos can substantially contribute to the counts of sources at low brightness.
We report on the work in progress.
