Gamma-ray observations of low-luminosity active galactic nuclei

Journal Article · Thu Jan 16 00:00:00 EST 2020 · Monthly Notices of the Royal Astronomical Society

DOI:https://doi.org/10.1093/mnras/staa083· OSTI ID:1595848

de Menezes, Raniere ^[1]; Nemmen, Rodrigo ^[2]; Finke, Justin D.  ^[3]; Almeida, Ivan  ^[2]; Rani, Bindu ^[4]

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1. Departamento de Astronomia, Instituto de Astronomia, Universidade de São Paulo,Geofísica e Ciências Atmosféricas, São Paulo, SP 05508-090, Brazil, Dipartimento di Fisica, Università degli Studi di Torino, via Pietro Giuria 1, I-10125 Torino, Italy
2. Departamento de Astronomia, Instituto de Astronomia, Universidade de São Paulo,Geofísica e Ciências Atmosféricas, São Paulo, SP 05508-090, Brazil
3. U.S. Naval Research Laboratory, Code 7653, 4555 Overlook Ave. SW, Washington, DC, 20375-5352, USA
4. Southeastern Universities Research Association, Washington, DC 20005, USA, NASA Goddard Space Flight Center, Greenbelt, MD 20771, USA, Center for Research and Exploration in Space Sciences and Technology, NASA/GSFC, Greenbelt, MD 20771, USA, Korea Astronomy and Space Science Institute, Daejeon 34055, Republic of Korea

ABSTRACT The majority of the activity around nearby (z ≈ 0) supermassive black holes is found in low-luminosity active galactic nuclei (LLAGN), the most of them being classified as low-ionization nuclear emission regions. Although these sources are well studied from radio up to X-rays, they are poorly understood in γ-rays. In this work, we take advantage of the all sky-surveying capabilities of the Large Area Telescope on board Fermi Gamma-ray Space Telescope to study the whole Palomar sample of LLAGN in γ-rays. Precisely, the four radio-brightest LLAGN in the sample are identified as significant γ-ray emitters, all of which are recognized as powerful Fanaroff–Riley I galaxies. These results suggest that the presence of powerful radio jets is of substantial importance for observing a significant γ-ray counterpart even if these jets are misaligned with respect to the line of sight. We also find that most of the X-ray-brightest LLAGN do not have a significant γ-ray and strong radio emission, suggesting that the X-rays come mainly from the accretion flow in these cases. A detailed analysis of the spectral energy distributions (SEDs) of NGC 315 and NGC 4261, both detected in γ-rays, is provided where we make a detailed comparison between the predicted hadronic γ-ray emission from a radiatively inefficient accretion flow (RIAF) and the γ-ray emission from a leptonic jet-dominated synchrotron self-Compton (SSC) model. Both SEDs are better described by the SSC model, while the RIAF fails to explain the γ-ray observations.

• Sponsoring Organization: USDOE
• Grant/Contract Number: AC02-76SF00515
• OSTI ID: 1595848
• Journal Information: Monthly Notices of the Royal Astronomical Society, Journal Name: Monthly Notices of the Royal Astronomical Society Vol. 492 Journal Issue: 3; ISSN 0035-8711
• Publisher: Oxford University Press
• Country of Publication: United Kingdom
• Language: English