Correlation Analysis for γ -ray and Broad Line Emissions of Fermi Blazars

In a standard model of active galactic nuclei (AGNs), there is a supermassive central black hole surrounded by an accretion disk with the jet coming out perpendicularly to the disk plane. Theoretical works suggest that there is a connection between the jet and the accretion disk. To investigate such a connection, people use the correlation between the radio emission (or γ-ray emission) and the broad line emission. However, it is well known that the radio (or γ-ray) emission is strongly beamed in blazars. In this sense, we should consider the beaming effect when we discuss the jet-accretion disk connection. In this work, we compiled a sample of 202 Fermi/LAT blazars with available broad line emissions. Out of the 202 sources, 66 have known Doppler factors. The correlation between γ-ray and broad-line emission, and that between radio and broad-line emission are investigated by removing the effects of redshift and beaming boosting for the whole sample and the subclasses, flat spectrum radio quasars (FSRQs) and BL Lacertae objects (BL Lacs) respectively. Our analysis suggests that (1) There are strong correlations between the γ-ray and the broad line emission for the whole blazar sample and their subclasses. The correlations exist after the redshift effect is removed for the whole sample and their subclasses, confirming the results in the literatures. (2) For the 66 blazars with available Doppler factors, a strong correlation between the broad line emission and the Doppler factor is found. The correlation between the γ-ray and the broad line emission exists after the Doppler factor effect is removed. Similar results for 1 and 2 are also obtained between radio and broad-line emission. (3) Our analysis suggests a robust connection between the accretion process and the jet.