High Galactic latitudeFermisources ofγ-rays with energies above 100 GeV

Abstract

Aims. We present a catalog of sources of very high energy (E > 100 GeV) γ-rays detected by the Large Area Telescope (LAT) onboard the Fermi Gamma-Ray Space Telescope at Galactic latitudes |b| ≥ 10 • . Methods. We cross-correlate the directions of individual photons with energies above 100 GeV detected by Fermi /LAT with the first year Fermi catalog of sources detected at lower energies. We find a significant correlation between the arrival directions of the highest energy photons and positions of Fermi sources, with the possibility of chance coincidences at the level of 10 −45 . We present a list of Fermi sources contributing to the correlation signal. A similar analysis is performed to cross-correlate the catalog of BL Lac objects with the highest energy photons detected by Fermi. Results. We produce a catalog of high Galactic latitude Fermi sources visible at 100−300 GeV energies. The catalog is divided into two parts. The first part contains a list of 50 higher significance sources among which there can be three possible false detections. The second part of the catalog contains a list of 25 lower significance sources, among which six are possibly false detections. Finally we identify eight additional sources from the cross-correlation analysis with the BL Lac catalog. The reported sources of E > 100 GeV γ-rays span a broad range of redshifts, up to z ∼ 1. Most of the sources are BL Lac type objects. Only 17 out of 83 objects in our list were previously reported as VHE γ-ray sources.

Minimal variability time scale – central black hole mass relation of theγ-ray loud blazars

“…However, the observed fast variability of the blazar γ-ray emission -down to (sub-)hour time scales (Aharonian et al 2007;Albert et al 2007;Neronov et al 2008;Abramowski et al 2010;Foschini et al 2011;Neronov & Vovk 2011;Sbarrato et al 2011;Vovk & Neronov 2013) -suggests that the gammaray emission region is very compact, much smaller than the transverse size of the jet at parsec distances from the SMBH.…”

Very high-energyγ-ray emission from high-redshift blazars

“…This analysis is similar to one done for the 1 FGL catalogue by Neronov et al (2011), where a catalogue of 75 objects with E > 100 GeV was obtained. There are 1359 front and 1135 back converted photons at high Galactic latitude |b| > 10 • and E > 100 GeV in the selected data.…”

“…The size of the 68% containment circle for the event classes 65 311 and 32 543 is 0.08 • for front photons and 0.21 • for back photons with energies above 100 GeV. In order to keep the analysis methods consistent with those used by Neronov et al (2011), we use 0.1 • and 0.2 • distance bins for correlation analysis using front and back photons.…”

“…However, an extremely low level of the background (including the residual cosmic ray background and Galactic/extragalactic γ-ray background) makes even signal from only a few photons in the energy band above 100 GeV significant. This fact has been used by Neronov et al (2010Neronov et al ( , 2011 for the search of extragalactic VHE γ-ray sources via the analysis of clustering of VHE γ-rays on the sky, based on the method first proposed by Gorbunov et al (2005). In this paper we use the correlation of arrival directions of VHE γ-rays detected by Fermi with the positions of high-redshift blazars to identify highredshift sources of VHE γ-rays and to study their spectral characteristics.…”

Application of the MST clustering to the high energy γ $\gamma$ -ray sky. I—New possible detection of high-energy γ $\gamma$ -ray emission associated with BL Lac objects

“…MST was already applied in preparing the 1FHL and the 1FGL (Abdo et al 2010) and 2FGL (Nolan et al 2012) catalogues of the Fermi -LAT collaboration. Other clustering methods have been applied to γ-ray source searches in the Fermi -LAT sky images such that by Neronov et al (2011), and DBSCAN by Tramacere and Vecchio (2013).…”