The observed radio/gamma-ray emission correlation for blazars with the
  Fermi-LAT and the RATAN-600 data
  We study the correlation between gamma-ray and radio band radiation for 123
blazars, using the Fermi-LAT first source catalog (1FGL) and the RATAN-600 data
obtained at the same period of time (within a few months). We found an apparent
positive correlation for BL Lac and flat-spectrum radio quasar (FSRQ) sources
from our sample through testing the value of the Pearson product-moment
correlation coefficient. The BL Lac objects show higher values of the
correlation coefficient than FSRQs at all frequencies, except 21.7 GHz, and at
all bands, except $10-100$ GeV, typically at high confidence level (> 99%). At
higher gamma-ray energies the correlation weakens and even becomes negative for
BL Lacs and FSRQs. For BL Lac blazars, the correlation of the fluxes appeared
to be more sensitive to the considered gamma-ray energy band, than to the
frequency, while for FSRQ sources the correlation changed notably both with the
considered radio frequency and gamma-ray energy band. We used a data
randomization method to quantify the significance of the computed correlation
coefficients. We find that the statistical significance of the correlations we
obtained between the flux densities at all frequencies and the photon flux in
all gamma-ray bands below 3 GeV is high for BL Lacs (chance probability $\sim
10^{-3} - 10^{-7}$). The correlation coefficient is high and significant for
the $0.1-0.3$ GeV band and low and insignificant for the $10-100$ GeV band for
both types of blazars for all considered frequencies.
