Possible jet contribution to the γ-ray luminosity in NGC 1068
Artikel i vetenskaplig tidskrift, 2024

NGC 1068 is a nearby, widely studied Seyfert II galaxy presenting radio, infrared, X-ray, and γ-ray emission, along with strong evidence for high-energy neutrino emission. Recently, the evidence for neutrino emission was explained in a multimessenger model, whereby the neutrinos originate from the corona of the active galactic nucleus. In this environment, γ-rays are strongly absorbed, so that an additional contribution is necessary, for instance, from the circumnuclear starburst ring. In this work, we discuss whether the radio jet can be an alternative source of the γ-rays between about 0.1 and 100 GeV, as observed by Fermi-LAT. In particular, we include both leptonic and hadronic processes, namely, accounting for inverse Compton emission and signatures from pp as well as pγ interactions. In order to constrain our calculations, we used VLBA and ALMA observations of the radio knot structures, which are spatially resolved at different distances from the supermassive black hole. Our results show that the best leptonic scenario for the prediction of the Fermi-LAT data is provided by the radio knot closest to the central engine. For that to be the case, a magnetic field strength of ∼mG is needed as well as a strong spectral softening of the relativistic electron distribution at (1a∼10)aγ GeV. However, we show that neither such a weak magnetic field strength, nor such a strong softening is expected for that knot. A possible explanation for the ≥14;10 GeV γ-rays could potentially be provided by hadronic pion production in case of a gas density a104a cm3. Nonetheless, this process is not found to contribute significantly to the low-energy end of the Fermi-LAT range. We conclude that the emission sites in the jet are not sufficient to explain the γ-rays across the whole Fermi-LAT energy band.

X-rays: galaxies

Galaxies: Seyfert

Gamma rays: general

Författare

S. Salvatore

Ruhr-Universität Bochum

Ruhr Astroparticle and Plasma Physics Center (RAPP Center)

B. Eichmann

Ruhr-Universität Bochum

Ruhr Astroparticle and Plasma Physics Center (RAPP Center)

X. Rodrigues

Ruhr-Universität Bochum

Ruhr Astroparticle and Plasma Physics Center (RAPP Center)

European Southern Observatory (ESO)

R. -J. Dettmar

Ruhr-Universität Bochum

Ruhr Astroparticle and Plasma Physics Center (RAPP Center)

Julia Tjus

Ruhr Astroparticle and Plasma Physics Center (RAPP Center)

Chalmers, Rymd-, geo- och miljövetenskap, Astronomi och plasmafysik

Ruhr-Universität Bochum

Astronomy and Astrophysics

0004-6361 (ISSN) 1432-0746 (eISSN)

Vol. 687 A139

Ämneskategorier

Subatomär fysik

Astronomi, astrofysik och kosmologi

DOI

10.1051/0004-6361/202348447

Mer information

Senast uppdaterat

2024-07-26