FERMI LARGE AREA TELESCOPE THIRD SOURCE CATALOG

Abstract

We present the third Fermi Large Area Telescope (LAT) source catalog (3FGL) of sources in the 100 MeV-300 GeV range. Based on the first 4 yr of science data from the Fermi Gamma-ray Space Telescope mission, it is the deepest yet in this energy range. Relative to the Second Fermi LAT catalog, the 3FGL catalog incorporates twice as much data, as well as a number of analysis improvements, including improved calibrations at the event reconstruction level, an updated model for Galactic diffuse γ-ray emission, a refined procedure for source detection, and improved methods for associating LAT sources with potential counterparts at other wavelengths. The 3FGL catalog includes 3033 sources above 4σ significance, with source location regions, spectral properties, and monthly light curves for each. Of these, 78 are flagged as potentially being due to imperfections in the model for Galactic diffuse emission. Twenty-five sources are modeled explicitly as spatially extended, and overall 238 sources are considered as identified based on angular extent or correlated variability (periodic or otherwise) observed at other wavelengths. For 1010 sources we have not found plausible counterparts at other wavelengths. More than 1100 of the identified or associated sources are active galaxies of the blazar class; several other classes of non-blazar active galaxies are also represented in the 3FGL. Pulsars represent the largest Galactic source class. From source counts of Galactic sources we estimate that the contribution of unresolved sources to the Galactic diffuse emission is ∼3% at 1 GeV.

Search for Extended Sources in the Galactic Plane Using Six Years of Fermi-Large Area Telescope Pass 8 Data above 10 GeV

“…In this work, we report a significant extension at a position coincident with SNR G298.6−0.0 and with a size including G298.5−0.3, as can be seen in Figure 18. The soft γ-ray spectrum is consistent with the fact that these sources have a spectral break around a few GeV (Acero et al 2015(Acero et al , 2016b, which is similar to most SNRs interacting with MCs. The higher flux reported in this analysis can be explained by the fact that we are adding the flux of both SNRs.…”

“…The possible interaction with a high-density medium from the direction of these two SNRs was reported by Reach et al (2006), making these sources excellent targets for GeV observations. Indeed, the GeV detection of a point source coincident with the shell of G298.6−0.0 and G298.5−0.3 was reported by Acero et al (2015Acero et al ( , 2016b. Recently, X-ray observations by Suzaku revealed a center-filled structure inside the radio shell (Bamba et al 2016).…”

“…2. Only 3FGL sources that were identified (as defined in Acero et al 2015) with a multiwavelength counterpart were retained in the initial region models used in the…”

“…The Second Fermi-LAT Point Source Catalog (2FGL; Nolan et al 2012) contained 12 extended sources. The number of extended sources increased to 22 in the First Fermi-LAT Hard Source Catalog, covering nearly 3 yr of data in the range 10-500 GeV (1FHL; Ackermann et al 2013a); then to 25 in the Third Fermi-LAT Point Source Catalog, with 48 months of data in the range 100 MeV-300 GeV (3FGL; Acero et al 2015); and to 31 in the Second Fermi-LAT Hard Source Catalog, with 80 months of data above 50 GeV (2FHL; Ackermann et al 2016). The addition of data and, in the case of the hard source catalogs, the focus on higher energies where photons are better localized and backgrounds are reduced have amplified the excellent capability of the Fermi-LAT to spatially resolve GeV γ-ray sources.…”

Two new high-energy γ-ray blazar candidates

“…To date, the Fermi collaboration has published three catalogues of sources detected above 100 MeV, the most recent of which (3FGL catalogue, Acero et al 2015) is based on the first 4 years of data, and two catalogues of high energy sources above 10 GeV (1FHL, Ackermann et al 2013) and 50 GeV (2FHL, Ackermann et al 2016), the latter covering a time interval of 80 months. In addition, some specific catalogues for selected classes of objects such as pulsars (Abdo et al 2013) and Supernova Remnants (Acero et al 2016) have also been published.…”