Correlation Analysis for γ-ray and Broad Line Emissions of Fermi Blazars
摘要：In a standard model of active galactic nuclei (AGNs), there is a supermassively
central black hole surrounded by an accretion disk with the jet coming out perpendic-ularly 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 cor-relation 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 corre-lation 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. We obtained a strong positive correlation between γ-ray and broad-line emission and between radio and broad-line emis-sion for the 202 blazars; It’s worth noting that the correlation still exists after removing redshift effect. For the 66 sources with Doppler factors, there is also a strong positive correlation between γ-rays and broad-line emission after remov-ing the Doppler factors, as well as that between radio and broadlineemission.Ouranalysissuggestthat1. Therearestrongcorrelationsbetween
theγ-rayandthe broad line emission for the whole blazar sample and their subclasses. The correlations exist when the redshift effect is removed for the whole sample and their subclasses,confirming the results by Ghisellini et al. (2014) and Chen (2018). 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 also obtained between radio and broad-line emission. 3. Our analysis suggests a robust connection between the accretion process and the jet.