FARADAY ROTATION MEASURE DUE TO THE INTERGALACTIC MAGNETIC FIELD

Studying the nature and origin of the intergalactic magnetic field (IGMF) is an outstanding problem of cosmology. Measuring Faraday rotation would be a promising method to explore the IGMF in the large-scale structure (LSS) of the universe. We investigated the Faraday rotation measure (RM) due to the IGMF in filaments of galaxies using simulations for cosmological structure formation. We employed a model IGMF based on turbulence dynamo in the LSS of the universe, it has an average strength of < B > similar to 10 nG and a coherence length of several x 100 h(-1) kpc in filaments. With the coherence length smaller than the path length, the inducement of RM would be a random walk process, and we found that the density peak along the line of sight dominantly contributes to the resultant RM. The root mean square of RM through filaments at the present universe was predicted to be similar to 1 rad m(-2). In addition, we predicted that the probability distribution function of vertical bar RM vertical bar through filaments follows the lognormal distribution, and the power spectrum of RM in the local universe peaks at a scale of similar to 1 h(-1) Mpc. Our prediction of RM could be tested with future instruments.