2020MNRAS.496.3381R

We report the discovery of a remnant radio active galactic nucleus (AGN) J1615+5452 in the field of ELAIS-N1. GMRT continuum observations at 150, 325, and 610 MHz combined with archival data from the 1.4 GHz NVSS survey were used to derive the radio spectrum of the source. At a redshift z ∼ 0.33, J1615+5452 has a linear size of ∼100 kpc and spectral indices ranging between α¹⁴⁰⁰₆₁₀ < -1.5 and α³²⁵₁₅₀ = -0.61 ±0.12. While the source has a diffuse radio emission at low frequencies, we do not find evidence of core, jets, or hotspots in the 1.4 GHz VLA data of ∼5 arcsec angular resolution. Such morphological properties coupled with a curved radio spectrum suggest that the AGN fueling mechanisms undergo a shortage of energy supply which is typical of a dying radio AGN. This is consistent with the observed steep curvature in the spectrum Δα ≃ -1, the estimated synchrotron age of t_s=76.0 ^+7.4_–8.7 Myr and a t_off/t_s ratio of ∼0.3.