Fermi Large Area Telescope Detection of Gamma Rays from the NGC 6251 Radio Lobe

Yu, Yu-Wei; Zhang, Hai-Ming; Gan, Ying-Ying; Hu, Xin-Ke; Wu, Tan-Zheng; Zhang, Jin

doi:10.3847/1538-4357/ad2e07

Cited by 3 publications

(2 citation statements)

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“…It is well known that γ-rays of blazars are predominantly produced by their core jets and are strongly amplified due to the Doppler boosting effect, while their radio radiations originate from more extended regions. These nonblazars have lower ratios of L γ to L 1.4 GHz due to the weakly relativistic effect or the lobe-dominated γ-ray emission (e.g., Stawarz & Petrosian 2008;Abdo et al 2010a;Ackermann et al 2016;Migliori et al 2016;Principe et al 2020Principe et al , 2021Gan et al 2024;Yu et al 2024). Although it has been confirmed that radio galaxies Cen A, Fornax A, and NGC 6251 are lobe-dominated γ-ray-emitting AGNs (Abdo et al 2010a;Ackermann et al 2016;Yu et al 2024), in general, the origin of γ-rays in radio galaxies is still believed to be from the core-jet (Abdo et al 2009a(Abdo et al , 2009bAleksić et al 2014;Fukazawa et al 2015;Xue et al 2017).…”

Section: Discussionmentioning

confidence: 99%

“…These nonblazars have lower ratios of L γ to L 1.4 GHz due to the weakly relativistic effect or the lobe-dominated γ-ray emission (e.g., Stawarz & Petrosian 2008;Abdo et al 2010a;Ackermann et al 2016;Migliori et al 2016;Principe et al 2020Principe et al , 2021Gan et al 2024;Yu et al 2024). Although it has been confirmed that radio galaxies Cen A, Fornax A, and NGC 6251 are lobe-dominated γ-ray-emitting AGNs (Abdo et al 2010a;Ackermann et al 2016;Yu et al 2024), in general, the origin of γ-rays in radio galaxies is still believed to be from the core-jet (Abdo et al 2009a(Abdo et al , 2009bAleksić et al 2014;Fukazawa et al 2015;Xue et al 2017). The radio luminosity of PKS 1007+142 surpasses that of most γ-ray-emitting radio galaxies but is lower than that of the seven γ-ray-emitting CSSs.…”

Section: Discussionmentioning

confidence: 99%

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Study of γ-Ray Emission from a Compact Radio Galaxy with the Fermi Large Area Telescope

Wu,

Yu,

Gan

et al. 2024

ApJ

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The radio galaxy PKS 1007+142 is classified as a compact steep-spectrum source (CSS) and belongs to the class of young active galactic nuclei (AGNs). In this paper, we investigate the γ-ray emission from this CSS by conducting a comprehensive analysis of the 15 yr Fermi Large Area Telescope (Fermi-LAT) observation data. The Fermi-LAT latest Source Catalog, 4FGL-DR4, includes an unassociated γ-ray source, 4FGL J1010.0+1416, located at 0.°24 away from the radio position of PKS 1007+142. Using the 15 yr Fermi-LAT observation data, we reestimate the best-fit position of the γ-ray source and find that PKS 1007+142 is in close proximity to the γ-ray source and falls within its 68% error circle. Therefore, we conclude that PKS 1007+142 is the most plausible counterpart to the unassociated LAT source with detection test statistics ∼ 43.4 (∼6.6σ). PKS 1007+142 exhibits a steep power-law spectrum in the 0.1–300 GeV band, with a photon spectral index (Γ γ ) of 2.86 ± 0.17. The average flux in the considered time interval is (2.14 ± 0.34) × 10−12 erg cm−2 s−1. Comparing PKS 1007+142 with other γ-ray emitting AGNs in both the L γ –Γ γ and L γ –L 1.4 GHz planes, it shows a softer γ-ray spectrum and lower luminosity compared to other γ-ray emitting CSSs. Furthermore, the possible origins of γ-ray in PKS 1007+142 are also discussed.

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Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Study of γ-Ray Emission from a Compact Radio Galaxy with the Fermi Large Area Telescope

Wu,

Yu,

Gan

et al. 2024

ApJ

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On the Nature of the Radio Calibrator and Gamma-Ray Emitting NLS1 Galaxy 3C 286 and Its Multiwavelength Variability

Komossa,

Yao,

Grupe

et al. 2024

Universe

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The quasar 3C 286, a well-known calibrator source in radio astronomy, was found to exhibit exceptional multiwavelength properties. Its rich and complex optical emission-line spectrum revealed its narrow-line Seyfert 1 (NLS1) nature. Given its strong radio emission, this makes 3C 286 one of the radio-loudest NLS1 galaxies known to date. 3C 286 is also one of very few known compact steep-spectrum (CSS) sources detected in the gamma-ray regime. Observations in the X-ray regime, rarely carried out so far, revealed evidence for variability, raising the question whether it is driven by the accretion disk or jet. 3C 286 is also well known for its damped Lyman alpha system from an intervening absorber at z = 0.692, triggering a search for the corresponding X-ray absorption along the line-of-sight. Here, we present new observations in the radio, X-ray, optical, and UV bands. The nature of the X-ray variability is addressed. Spectral evidence suggests that it is primarily driven by the accretion disk (not the jet), and the X-ray spectrum is well fit by a powerlaw plus soft excess model. The radio flux density and polarization remain constant at the Effelsberg telescope resolution, reconfirming the use of 3C 286 as radio calibrator. The amount of reddening/absorption along the line-of-sight intrinsic to 3C 286 is rigorously assessed. None is found, validating the derivation of a high Eddington ratio (L/LEdd ∼ 1) and of the very high radio-loudness index of 3C 286. Based on the first deep Chandra image of 3C 286, tentative evidence for hard X-ray emission from the SW radio lobe is reported. A large variety of models for the gamma-ray emission of 3C 286 are briefly discussed.

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Origin of the Very High Energy Gamma Rays in the Low-luminosity Active Galactic Nucleus NGC 4278

Lian,

Li,

et al. 2024

ApJ

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NGC 4278, a low-luminosity active galactic nucleus, is generally classified as a low-ionization nuclear emission-line region (LINER). Recently, it has been reported to be associated with a very high energy γ-ray source 1LHAASO J1219+2915 in the first Large High Altitude Air Shower Observatory source catalog. However, no associated counterpart has been detected by analyzing the data collected by the Large Area Telescope on board the Fermi Gamma-ray Space Telescope. By analyzing its X-ray observation data from Swift-XRT, we find that NGC 4278 is in a high-flux state on MJD 59546, with the X-ray flux more than one order of magnitude higher than that observed ∼11.7 yr earlier by Chandra. Interestingly, this Swift-XRT observation was conducted during the active phase of the γ-ray source 1LHAASO J1219+2915. We propose that the detection of very high energy γ-rays from NGC 4278 may be attributed to the presence of an active nucleus in its center. To reproduce the spectral energy distribution (SED) of NGC 4278, we employ a one-zone leptonic model, typically used for fitting broadband SEDs of BL Lacs, and find that a smaller magnetic field strength is required than that of typical TeV BL Lacs. Furthermore, NGC 4278 exhibits significantly lower luminosity in both radio and TeV bands when compared with typical TeV BL Lacs. In the radio luminosity versus Eddington ratio plane, NGC 4278 shows greater similarity to Seyfert galaxies and LINERs than to BL Lacs; however, it still roughly follows the extension toward lower luminosity seen in BL Lacs.

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Fermi Large Area Telescope Detection of Gamma Rays from the NGC 6251 Radio Lobe

Cited by 3 publications

References 44 publications

Study of γ-Ray Emission from a Compact Radio Galaxy with the Fermi Large Area Telescope

Study of γ-Ray Emission from a Compact Radio Galaxy with the Fermi Large Area Telescope

On the Nature of the Radio Calibrator and Gamma-Ray Emitting NLS1 Galaxy 3C 286 and Its Multiwavelength Variability

Origin of the Very High Energy Gamma Rays in the Low-luminosity Active Galactic Nucleus NGC 4278

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