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

doi:10.48550/arxiv.1905.10771

Cited by 3 publications

(3 citation statements)

References 45 publications

(45 reference statements)

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“…All the other sources have PowerLaw spectra. We have chosen to adopt a PowerLaw spectrum as a base for Table 1: γ-ray detected radio galaxies in the 4LAC [10]. Coordinates, redshift and radio flux have been collected from the NASA/IPAC Extragalactic Database (NED), while the γ-ray properties are from the 4FGL [ the CTA simulations for 3C 120 and PKS 2153−69 as well, since these are faint sources where the curvature is not as well determined as for NGC 1275 and NGC 6251.Given that it is quite unrealistic to expect that a spectrum without curvature would extend from the LAT energy range down to 150 TeV (in the case of LAT sources with a Pow-erLaw spectrum), we have simulated different scenarios to account for spectral curvature, following [8].…”

Section: Cta Simulated Observationsmentioning

confidence: 99%

Revisiting the TeV detection prospects for radio galaxies

Angioni

2020

Astroparticle Physics

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Radio galaxies host relativistic jets oriented away from our line of sight, making them challenging targets for Very High Energy (VHE, E>100 GeV) γ-ray detectors. Indeed, out of ∼ 100 extragalactic sources detected at E > 100 GeV, only six are radio galaxies, while the great majority are blazars hosting aligned jets. The new Cherenkov Telescope Array (CTA) will provide order-of-magnitude improvements in sensitivity and spectral resolution with respect to the present generation of ground-based γ-ray observatories, opening new frontiers for high-energy studies of radio galaxies. In a previous paper, we studied the detection prospects of misaligned jets with the CTA for a sample of sources from the Third Fermi-LAT catalog (3FGL). In this work, we complement this study taking advantage of the expanded sample from the Fourth Fermi-LAT catalog (4FGL), which includes roughly double the number of sources. We simulate CTA observations of 41 γ-ray radio galaxies, extrapolating their Fermi-LAT spectrum into the TeV energy range assuming different spectral shapes. We predict that the CTA will detect eleven new TeV radio galaxies with an observational campaign of 50 hours per source, under the realistic assumption of a spectral cutoff at 0.5 TeV. This would increase the sample of VHE radio galaxies by a factor of three, and result in the first detection of FR II radio galaxies at these energies. By simulating CTA observations with 5 hours exposure, we predict that two Fermi-LAT radio galaxies should already be well within reach of current TeV observatories. Finally we have investigated the prospects for a CTA detection of extended VHE emission from the lobe-dominated FR I Fornax A, and predict that such a detection will be possible for integration times 50 hours. We conclude that, in line with our previous findings, the CTA will significantly impact our understanding of misaligned jets at TeV energies, allowing us to perform population studies, as well as a comparison between the two main radio galaxy subclasses for the first time in this energy band.

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Section: Cta Simulated Observationsmentioning

confidence: 99%

Revisiting the TeV detection prospects for radio galaxies

Angioni

2020

Astroparticle Physics

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“…their spectral index becomes steeper. The Blazar Sequence, established originally with 132 objects out of which only 33 were detected in high energy 𝛾-rays, was supplemented with the launch of Fermi and the discovery of more than 5000 𝛾-ray Blazars as recorded in the 4th Fermi Blazar Catalog [2]. This compilation provided novel correlations that replaced those of the original Blazar Sequence.…”

Section: Introductionmentioning

confidence: 99%

A two-zone emission model for Blazars and the role of Accretion Disk MHD winds

S.¹,

Mastichiadis²,

Kazanas³

2021

Preprint

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Blazars are a sub-category of radio-loud active galactic nuclei with relativistic jets pointing towards the observer. They exhibit non-thermal variable emission, which practically extends over the whole electromagnetic spectrum. Despite the plethora of multi-wavelength observations, the origin of the emission in blazar jets remains an open question. In this work, we construct a twozone leptonic model: particles accelerate in a small region and lose energy through synchrotron radiation and inverse Compton Scattering. Consequently, the relativistic electrons escape to a larger area where the ambient photon field, which is related to Accretion Disk MHD Winds, could play a central role in the gamma-ray emission. This model explains the Blazar Sequence and the broader properties of blazars, as determined by Fermi observations, by varying only one parameter, the mass accretion rate onto the central black hole. Flat Spectrum Radio Quasars have a strong ambient photon fields and their gamma-ray emission is dominated by the more extensive zone, while in the case of BL Lac objects, the negligible ambient photons make the smaller, i.e. acceleration, zone dominant.

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“…Sources considered for Fermi-LAT (left) and FACT (right) with the corresponding logarithm of the position of the synchrotron peak frequency 𝜈 syn and the redshift 𝑧 taken from 4LAC[10] and[1].…”

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confidence: 99%

Statistical properties of flux variations in blazar light curves at GeV and TeV energies

Wagner,

Burd,

Dorner

et al. 2021

Preprint

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Despite numerous detections of individual flares, the physical origin of the rapid variability observed from blazars remains uncertain. Using Bayesian blocks and the Eisenstein-Hut HOP algorithm, we characterize flux variations of high significance in the 𝛾-ray light curves of two samples of blazars. Daily binned long-term light curves of TeV-bright blazars observed with the First G-APD Cherenkov Telescope (FACT) are compared to those of GeV-bright blazars observed with the Large Area Telescope on board the Fermi Gamma-ray Space Telescope (Fermi-LAT). We find no evidence for systematic asymmetry of the flux variations based on the derived rise and decay time scales. Additionally, we show that the daily-binned blazar light curves can be described by an exponential stochastic Ornstein-Uhlenbeck process with parameters depending on energy. Our analysis suggests that the flux variability in both samples is a superposition of faster fluctuations. This is, for instance, challenging to explain by shock-acceleration but expected for magnetic reconnection.

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

Cited by 3 publications

References 45 publications

Revisiting the TeV detection prospects for radio galaxies

Revisiting the TeV detection prospects for radio galaxies

A two-zone emission model for Blazars and the role of Accretion Disk MHD winds

Statistical properties of flux variations in blazar light curves at GeV and TeV energies

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