Image of a filament in gamma-rays produced via synchrotron emission, integrated over E_γ = 1−100   GeV. We chose an “anisotropic” distribution of the magnetic field with normalization B₀ = 1 nG. Left: the filament is observed along its axis from a distance of 100 Mpc and the embedded source has a cosmic-ray luminosity of L_E,19 = 10⁴⁴ erg s^-1. Right: the filament is observed along its axis from a distance of 1 Gpc and the embedded source has a luminosity of L_E,19 = 10⁴⁶ erg s^-1. The color bar indicates the logarithm of the flux in GeV cm^-2 s^-1. White contours indicate a flux level of 10^-10   GeV cm^-2 s^-1.