We report the discovery of large-scale diffuse radio emission from what
appears to be a large-scale filamentary network of galaxies in the region of
cluster ZwCl 2341.1+0000, and stretching over an area of at least 6h50−1 Mpc in diameter. Multicolour CCD observations yield photometric
redshifts indicating that a significant fraction of the optical galaxies in
this region is at a redshift of z=0.3. This is supported by spectroscopic
measurements of 4 galaxies in the SDSS survey at a mean z=0.27. We present VLA
images at 20 cm (NVSS) and 90 cm wavelengths, showing the detailed radio
structure of the filaments. Comparison with the VLA high resolution FIRST radio
survey shows that the diffuse emission is not due to known individual point
sources. The diffuse radio-emission has a spectral index α≲−0.5, and is most likely synchrotron emission from relativistic charged
particles in an inter-galactic magnetic field. Furthermore, this optical/radio
structure is detected in X-rays by the ROSAT all-sky survey. It has a 0.1--2.4
keV luminosity of about 1044 erg s−1 and shows an extended highly
non-relaxed morphology. These observations suggest that ZwCl 2341.1+0000 is
possibly a proto-cluster of galaxies in which we are witnessing the process of
structure formation. We show (both analytically and by numerical simulations)
that the energetics of accretion shocks generated in forming large-scale
structures are sufficient to produce enough high energy cosmic-ray (CR)
electrons required to explain the observed radio emission, provided a magnetic
field of strength of about 1 micro Gauss is present there.Thus it is the first
evidence of cosmic-ray particle acceleration and magnetic fields occuring on a
super-cluster scale. (Abridged)Comment: Replaced with the published version. The published paper can be
accessed from http://www.elsevier.com/gej-ng/10/33/29/71/56/53/article.htm