Neutrino and gamma-ray emissions from NGC 1068

IceCube has recently reported the detection of <a:math xmlns:a="http://www.w3.org/1998/Math/MathML" display="inline"> <a:mrow> <a:mo>∼</a:mo> <a:mn>1</a:mn> <a:mi>–</a:mi> <a:mn>10</a:mn> <a:mtext> </a:mtext> <a:mtext> </a:mtext> <a:mi>TeV</a:mi> </a:mrow> </a:math> neutrinos from the nearby active galaxy, NGC 1068. The lack of TeV-scale emission from this source suggests that these neutrinos are generated in the dense corona that surrounds NGC 1068’s supermassive black hole. In this paper, we present a physical model for this source, including the processes of pair production, pion production, synchrotron, and inverse Compton scattering. We have also performed a new analysis of -LAT data from the direction of NGC 1068, finding that the gamma-ray emission from this source is very soft but bright at energies below <c:math xmlns:c="http://www.w3.org/1998/Math/MathML" display="inline"> <c:mo>∼</c:mo> <c:mn>1</c:mn> <c:mtext> </c:mtext> <c:mtext> </c:mtext> <c:mi>GeV</c:mi> </c:math> . Our model can predict a gamma-ray spectrum that is consistent with Fermi-LAT observations when the magnetic field within the corona of this active galactic nucleus (AGN) is quite high, namely <e:math xmlns:e="http://www.w3.org/1998/Math/MathML" display="inline"> <e:mi>B</e:mi> <e:mo>≳</e:mo> <e:mn>6</e:mn> <e:mtext> </e:mtext> <e:mtext> </e:mtext> <e:mi>kG</e:mi> </e:math> . To explain the observed neutrino emission, this source must accelerate protons with a total power that is comparable to its intrinsic x-ray luminosity. In this context, we consider two additional nearby active galaxies, NGC 4151 and NGC 3079, which have been identified as promising targets for IceCube.