The Connection between Radio and Gamma Ray Emission in Fermi/LAT Blazars

TL;DR

This study analyzes the relationship between radio and gamma-ray emissions in blazars, revealing correlations and variability patterns that depend on gamma-ray energy and source type, providing insights into emission mechanisms.

Contribution

It provides a comprehensive statistical analysis of radio-gamma connections in blazars using quasi-simultaneous data, highlighting how correlations vary with gamma-ray energy and source classification.

Findings

Positive radio-gamma correlations confirmed, weakening at higher gamma-ray energies.

Gamma-ray variability linked to internal emission region changes, not external photon density.

Different variability behaviors observed between FSRQs and BL Lac objects.

Abstract

We collect the 2LAC and MOJAVE quasi-simultaneous data to investigate the radio-gamma connection of blazars. The cross sample contains 166 sources. The statistic analysis based on this sample confirms positive correlations between these two bands, but the correlations become weaker as the gamma-ray energy increases. The statistic results between various parameters show negative correlations of gamma-ray photon spectral index with gamma-ray loudness for both FSRQs and BL Lacertae objects, positive correlations of gamma-ray variability index with the gamma-ray loudness for FSRQs, a negative correlation of the gamma-ray variability index with the gamma-ray photon spectral index for FSRQs, and negative correlations of gamma-ray photon spectral index with gamma-ray luminosity for FSRQs. These results suggest that the gamma-ray variability may be due to changes inside the gamma-ray emission region like the injected power, rather than changes in the photon density of the external radiation fields, and the variability amplitude tends to be larger as the gamma-rays are closer to the high energy peak of spectral energy distribution. No correlation of variability index found for BL Lacertae objects implies that variability behavior may differ below and above the peak energy.