The fourth catalog of active galactic nuclei (AGNs) detected by the Fermi Gamma-ray Space Telescope Large Area Telescope (4LAC) between 2008 August 4 and 2016 August 2 contains 2863 objects located at high Galactic latitudes (|b| > 10°). It includes 85% more sources than the previous 3LAC catalog based on 4 yr of data. AGNs represent at least 79% of the high-latitude sources in the fourth Fermi-Large Area Telescope Source Catalog (4FGL), which covers the energy range from 50 MeV to 1 TeV. In addition, 344 gamma-ray AGNs are found at low Galactic latitudes. Most of the 4LAC AGNs are blazars (98%), while the remainder are other types of AGNs. The blazar population consists of 24% Flat Spectrum Radio Quasars (FSRQs), 38% BL Lac-type objects, and 38% blazar candidates of unknown types (BCUs). On average, FSRQs display softer spectra and stronger variability in the gamma-ray band than BL Lacs do, confirming previous findings. All AGNs detected by ground-based atmospheric Cerenkov telescopes are also found in the 4LAC.
The Astrophysical Journal
- Pub Date:
- April 2020
- Astrophysics - High Energy Astrophysical Phenomena
- Fits tables can be found at https://www.ssdc.asi.it/fermi4lac/table_4LAC.fits and https://www.ssdc.asi.it/fermi4lac/table_lowlat_sample.fits. About 200 counterpart names have changed relative to the earlier version and match the entries in the 4FGL-DR2 catalog (https://fermi.gsfc.nasa.gov/ssc/data/access/lat/10yr_catalog/)