The physical properties of γ-ray-quiet flat-spectrum radio quasars: why are they undetected by Fermi-LAT?

• Published in: Monthly notices of the Royal Astronomical Society 2021-10, Vol.506 (4), p.5764-5773
• Main Authors: Deng, Xue-Jiao, Xue, Rui, Wang, Ze-Rui, Xi, Shao-Qiang, Xiao, Hu-Bing, Du, Lei-Ming, Xie, Zhao-Hua
• Format: Article
• Language: English
• ISSN: 0035-8711; 1365-2966
• DOI: 10.1093/mnras/stab2095

ABSTRACT During a decade of operation of the Fermi-Large Area Telescope (LAT), thousands of blazars have been detected in the γ-ray band. However, there are still numbers of blazars that have not been detected in the γ-ray band. In this work, we focus on investigating why some flat-spectrum radio quasars (FSRQs) are undetected by Fermi-LAT. By cross-matching the Candidate Gamma-ray Blazars Survey catalogue with the Fourth Catalog of Active Galactic Nuclei Detected by the Fermi-LAT, we select 11 γ-ray-undetected (γ-ray-quiet) FSRQs as our sample and collect their quasi-simultaneous multiwavelength data. In the framework of the conventional one-zone leptonic model, we investigate their underlying physical properties and study the possibility that they are undetected in the γ-ray by modelling their quasi-simultaneous spectral energy distributions. In contrast to a smaller bulk Lorentz factor suggested by previous works, our results suggest that the dissipation region located relatively far away from the central super-massive black hole is more likely to be the reason why some γ-ray-quiet FSRQs are undetected by Fermi-LAT.