The gamma-ray emitting region in low synchrotron peak blazars Testing self-synchrotron Compton and external Compton scenarios

Autor(es)

Arsioli, B. ^{[1, 2, 3]} ; Chang, Y-L. ^{[4, 2, 5]}

Afiliação do(s) autor(es)

^[1] CBPF, ICRANet Rio, Rua Dr Xavier Sigaud 150, BR-22290180 Rio De Janeiro - Brazil

^[2] SSDC, ASI, Sci Data Ctr, Rome - Italy

^[3] Univ Estadual Campinas, Inst Fis Gleb Wataghin, Rua Sergio B de Holanda 777, BR-13083859 Campinas, SP - Brazil

^[4] ICRANet, Pzza Repubbl 10, I-65122 Pescara - Italy

^[5] Sapienza Univ Roma, Dipartimento Fis, Piazzale Aldo Moro 5, I-00185 Rome - Italy

• Tipo de documento: Artigo Científico
• Fonte: Astronomy & Astrophysics; v. 616, AUG 17 2018.
• Citações Web of Science: 1

Resumo

Aims. From the early days in gamma-ray astronomy, locating the origin of GeV emission within the core of an active galactic nucleus (AGN) persisted as an open question; the problem is to discern between near-and far-site scenarios with respect to the distance from the super massive central engine. We investigate this question under the light of a complete sample of low synchrotron peak (LSP) blazars which is fully characterized along many decades in the electromagnetic spectrum, from radio up to tens of GeV. We consider the high-energy emission from bright radio blazars and test for synchrotron self-Compton (SSC) and external Compton (EC) scenarios in the framework of localizing the gamma-ray emission sites. Given that the inverse Compton (IC) process under the EC regime is driven by the abundance of external seed photons, these photons could be mainly ultraviolet (UV) to X-rays coming from the accretion disk region and the broad-line region (BLR), therefore close to the jet launch base; or infrared (IR) seed photons from the dust torus and molecular cloud spine-sheath, therefore far from jet launch base. We investigate both scenarios, and try to reveal the physics behind the production of gamma-ray radiation in AGNs which is crucial in order to locate the production site. Methods. Based on a complete sample of 104 radio-selected LSP blazars, with 37 GHz flux density higher than 1 Jy, we study broadband population properties associated with the nonthermal jet emission process, and test the capability of SSC and EC scenarios to explain the overall spectral energy distribution (SED) features. We use SEDs well characterized from radio to gamma rays, considering all currently available data. The enhanced available information from recent works allows us to refine the study of Syn to IC peak correlations, which points to a particular gamma-ray emission site. Results. We show that SSC alone is not enough to account for the observed SEDs. Our analysis favors an EC scenario under the Thomson scattering regime, with a dominant IR external photon field. Therefore, the far-site (i.e., far from the jet launch) is probably the most reasonable scenario to account for the population properties of bright LSP blazars in cases modeled with a pure leptonic component. We calculate the photon energy density associated with the external field at the jet comoving frame to be U'(ext) = 1.69 x 10(-2) erg cm(-3), finding good agreement to other correlated works. (AU)

• Processo FAPESP: 17/00517-4 - Busca por novas fontes extragalácticas de radiação-gamma GeV visando estudos de correlação com neutrinos astrofísicos e raios cósmicos
• Beneficiário: Bruno Sversut Arsioli
• Modalidade de apoio: Bolsas no Brasil - Pós-Doutorado