2fhl: The Second Catalog of Hard Fermi-Lat Sources

Abstract

We present a catalog of sources detected above 50 GeV by the Fermi-Large Area Telescope (LAT) in 80 months of data. The newly delivered Pass8 event-level analysis allows the detection and characterization of sources in the 50 GeV-2 TeV energy range. In this energy band, Fermi-LAT has detected 360 sources, which constitute the second catalog of hard Fermi-LAT sources (2FHL). The improved angular resolution enables the precise localization of point sources (∼1 7 radius at 68% C.L.) and the detection and characterization of spatially extended sources. We find that 86% of the sources can be associated with counterparts at other wavelengths, of which the majority (75%) are active galactic nuclei and the rest (11%) are Galactic sources. Only 25% of the 2FHL sources have been previously detected by Cherenkov telescopes, implying that the 2FHL provides a reservoir of candidates to be followed up at very high energies. This work closes the energy gap between the observations performed at GeV energies by Fermi-LATon orbit and the observations performed at higher energies by Cherenkov telescopes from the ground.

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

“…In a previous analysis of the region above 10 GeV using Fermi-LAT data (Acero et al 2013), HESS J1420−607 and HESS J1418−609 were detected as two point sources with different spectral shapes: a hard spectrum for the first one (suggesting a PWN origin), and a soft spectrum with an energy cutoff at a few GeV for the second one, suggestive of pulsar emission and thus likely due to contamination from PSR J1418−6058. It was then detected as a very extended source 64 of 0°.33 covering both PWNe in Ackermann et al (2016). In our new analysis, HESS J1420−607 is detected as an extended source with a disk radius of 0°.12, in good agreement with the TeV size, while HESS J1418−609 remains pointlike.…”

“…In the right panel, statistical errors are indicated in black, while the quadrature sum of systematic and statistical errors is reported in red. 64 A typo was recently discovered in the disk extension value reported in Table 5 of Ackermann et al (2016) and in its associated fits file. An erratum is being prepared quoting a value of 0°.…”

“…1. The SNR γ Cygni (FGES J2020.8+4026): γ Cygni (SNR G78.2+2.1) is a nearby (∼1.7 kpc) middle-aged SNR already detected by Fermi-LAT in different energy bands (Ackermann et al 2016;Acero et al 2016b). Our analysis is in perfect agreement with previous publications of the SNR.…”

“…This paper used two analysis pipelines similar to those employed in Ackermann et al (2016). The primary one is presented in Section 3.3.…”

“…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.…”