On the spine-layer scenario for the very high-energy emission of NGC 1275

Understand

We discuss the $\gamma$-ray emission of the radiogalaxy NGC 1275 (the central galaxy of the Perseus Cluster), detected by Fermi-LAT and MAGIC, in the framework of the "spine-layer" scenario, in which the jet is assumed to be characterized by a velocity structure, with a fast spine surrounded by a slower layer.

• The existence of such a structure in the parsec scale jet of NGC 1275 has been recently proved through VLBI observations.
• We discuss the constraints that the observed spectral energy distribution imposes to the parameters and we present three alternative models, corresponding to three different choices of the angles between the jet and the line of sight ($\theta_{\rm v}=6^{\circ}, 18^{\circ}$ and 25$^{\circ}$).
• While for the the case with $\theta_{\rm v}=6^{\circ}$ we obtain an excellent fit, we consider this solution unlikely, since such small angles seems to be excluded by radio observations of the large-scale jet.