The Second Catalog of Active Galactic Nuclei Detected by the Fermi Large Area Telescope

The second catalog of active galactic nuclei (AGNs) detected by the Fermi Large Area Telescope (LAT) in two years of scientific operation is presented. The Second LAT AGN Catalog (2LAC) includes 1017 γ-ray sources located at high Galactic latitudes (|b| > 10) that are detected with a test statistic (TS) greater than 25 and associated statistically with AGNs. However some of these are affected by analysis issues and some are associated with multiple AGNs. Consequently we define a clean sample which includes 886 AGNs, comprising 395 BL Lacertae objects (BL Lacs), 310 flat-spectrum radio quasars (FSRQs), 157 candidate blazars of unknown type (i.e., with broad-band blazar characteristics but with no optical spectral measurement yet), eight misaligned AGNs, four narrow-line Seyfert 1 (NLS1s), 10 AGNs of other types and two starburst galaxies. Where possible, the blazars have been further classified based on their spectral energy distributions (SEDs) as archival radio, optical, and X-ray data permit. While almost all FSRQs have a synchrotron-peak frequency 1015 Hz. The 2LAC represents a significant improvement relative to the First LAT AGN Catalog (1LAC), with 52% more associated sources. The full characterization of the newly detected sources will require more broad-band data. Various properties, such as γ-ray fluxes and photon power law spectral indices, redshifts, γ-ray luminosities, variability, and archival radio luminosities—and their correlations are presented and discussed for the different blazar classes. The general trends observed in 1LAC are confirmed. Subject headings: gamma rays: observations — galaxies: active — galaxies: jets — BL Lacertae objects: general bruck, A-6020 Innsbruck, Austria Max-Planck-Institut fur Kernphysik, D-69029 Heidelberg, Germany Space Sciences Division, NASA Ames Research Center, Moffett Field, CA 94035-1000, USA NYCB Real-Time Computing Inc., Lattingtown, NY 11560-1025, USA Department of Chemistry and Physics, Purdue University Calumet, Hammond, IN 46323-2094, USA Solar-Terrestrial Environment Laboratory, Nagoya University, Nagoya 464-8601, Japan Institucio Catalana de Recerca i Estudis Avancats (ICREA), Barcelona, Spain NASA Postdoctoral Program Fellow, USA Consorzio Interuniversitario per la Fisica Spaziale (CIFS), I-10133 Torino, Italy Dipartimento di Fisica, Universita di Roma “Tor Vergata”, I-00133 Roma, Italy Praxis Inc., Alexandria, VA 22303, resident at Naval Research Laboratory, Washington, DC 20375