The Radio/Gamma Connection of Blazars from High to Low Radio Frequencies

Abstract We construct a large sample of γ -ray blazars with low-frequency radio data using the recently released TGSS AD1 catalog at 150 MHz. The radio/gamma connections of blazars are compared from 143 GHz to 150 MHz. The radio flux density at all radio frequencies shows strong correlation with γ -ray flux for blazars, as well as for the two subclasses, flat-spectrum radio quasars (FSRQs) and BL Lacs. But the correlations get worse from high to low radio frequencies, which indicates that the low-frequency radio emission is the mixture of extended and core components for blazars. In addition, we find that the correlation between 150 MHz radio flux density and γ -ray flux is more significant for BL Lacs than that for FSRQs. The slope for the luminosity correlation between radio and γ -ray flux also gets flatter than unity at 150 MHz. These results indicate that the core dominance at 150 MHz for BL Lacs is larger than that for FSRQs. We also compare the radio luminosity from direct TGSS observations and the extended radiation at 150 MHz for blazars. The results show that the ratio between core and extended components at 150 MHz is about 1:1 on average.