Discovery of a suspected giant radio galaxy with the KAT-7 array

Abstract

We detect a new suspected giant radio galaxy (GRG) discovered by KAT-7. The GRG core is identified with the Wide-field Infrared Survey Explorer source J013313.50-130330.5, an extragalactic source based on its infrared colours and consistent with a misaligned active galactic nuclei-type spectrum at z ≈ 0.3. The multi-ν spectral energy distribution (SED) of the object associated with the GRG core shows a synchrotron peak at ν ≈ 1014 Hz consistent with the SED of a radio galaxy blazar-like core. The angular size of the lobes are ∼4 arcmin for the NW lobe and ∼1.2 arcmin for the SE lobe, corresponding to projected linear distances of ∼1078 kpc and ∼324 kpc, respectively. The best-fitting parameters for the SED of the GRG core and the value of jet boosting parameter δ = 2, indicate that the GRG jet has maximum inclination θ ≈ 30 deg with respect to the line of sight, a value obtained for δ = Γ, while the minimum value of θ is not constrained due to the degeneracy existing with the value of Lorentz factor Γ. Given the photometric redshift z ≈ 0.3, this GRG shows a core luminosity of P1.4 GHz ≈ 5.52 × 1024 W Hz−1, and a luminosity P1.4 GHz ≈ 1.29 × 1025 W Hz−1 for the NW lobe and P1.4 GHz ≈ 0.46 × 1025 W Hz−1 for the SE lobe, consistent with the typical GRG luminosities. The radio lobes show a fractional linear polarization ≈9 per cent consistent with typical values found in other GRG lobes