The Declined Activity in the Nucleus of NGC 1316

Abstract

NGC 1316 (Fornax A) is a radio galaxy with prototypical double lobes, where the magnetic field intensity is accurately measured via the inverse-Compton technique. The radio-emitting electrons in the lobes are inferred to have a synchrotron life time of 0.1 Gyr. Considering the lobe energetics, we estimate the past nuclear X-ray luminosity of NGC 1316 to be at least 4 times 10^{34} W (4 times 10^{41} erg s^{-1}). Thus, the nucleus was rather active at least 0.1 Gyr ago. In contrast, we confirmed with ASCA and ROSAT that the nucleus of NGC 1316 is very faint in X-rays at present, with the 2--10 keV luminosity of any AGN-like hard component being < 2 times 10^{33} W (2 times 10^{40} erg s^{-1}) even assuming a nuclear obscuration up to 10^{28} m^{-2} (10^{24} cm^{-2}). This is at least an order of magnitude lower than the estimated past activity, indicating that the nucleus is presently very inactive. From these two results, we conclude that the nucleus of NGC 1316 has become dormant during the last 0.1 Gyr. This suggests the possible abundance of ``dormant'' quasars in nearby galaxies.

arXiv comment7 pages, 2 figures, to be published in the Astrophysical Journal Letters

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Cited by in corpus (24)

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• X-ray source populations in galaxies
• The subarcsecond mid-infrared view of local active galactic nuclei: I. The N- and Q-band imaging atlas
• Chandra X-ray Observations of NGC 1316 (Fornax A)
• The Fornax Deep Survey with VST. II. Fornax A: a two-phase assembly caught on act
• Ultra-high energy cosmic rays from shocks in the lobes of powerful radio galaxies
• The supermassive black hole of Fornax A
• Fornax A, Centaurus A and other radio galaxies as sources of ultra-high energy cosmic rays
• Modelling of the Spectral Energy Distribution of Fornax A: Leptonic and Hadronic Production of High Energy Emission from the Radio Lobes
• Constraining the Outburst Properties of the SMBH in Fornax A through X-ray, Infrared, and Radio Observations
• The flickering nuclear activity of Fornax A
• The globular cluster system of NGC1316. I. Wide-field photometry in the Washington system
• Hard X-Ray Spectrum from West Lobe of Radio Galaxy Fornax A Observed with Suzaku
• Broadband radio polarimetry of Fornax A, I: Depolarized patches generated by advected thermal material from NGC 1316
• X-ray measurements of the field and particle energy distributions in the west lobe of the radio galaxy NGC 1316 (Fornax A)
• Suzaku observation of the giant radio galaxy 3C 326
• Mid-infrared dust in two nearby radio galaxies, NGC 1316 (Fornax A) and NGC 612 (PKS 0131-36)
• Particle acceleration in radio galaxies with flickering jets: GeV electrons to ultrahigh energy cosmic rays
• Complex distribution and velocity field of molecular gas in NGC 1316 as revealed by Morita Array of ALMA
• Abundance Patterns in the Interstellar Medium of the S0 Galaxy NGC 1316 (Fornax A) Revealed with Suzaku
• Suzaku diagnostics of the energetics in the lobes of the giant radio galaxy 3C 35
• Suzaku measurement of electron and magnetic energy densities in the east lobe of the giant radio galaxy DA 240
• Suzaku Detection of Thermal X-Ray Emission Associated with the Western Radio Lobe of Fornax A
• Study of the Long-Term X-Ray Variability of a Possible Quasar RX J0957.9+6903 with ASCA