J1615+5452: a remnant radio galaxy in the ELAIS-N1 field

Abstract

ABSTRACT 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 $\alpha ^{1400}_{610} \lt -1.5$ and $\alpha ^{325}_{150} = -0.61 \pm 0.12$. 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 $t_{\rm s}=76.0\, ^{+7.4}_{-8.7}$ Myr and a toff/ts ratio of ∼0.3.