LeMMINGs VII: 5 GHz, 50 mas <i>e</i> -MERLIN observations of a statistically complete sample of nearby AGN

Abstract We present 5 GHz e-MERLIN radio images at 50 mas resolution of the nuclear regions of the Legacy e-MERLIN Multi-band Imaging of Nearby Galaxy survey (LeMMINGs): the deepest, statistically complete radio-band survey of the local Universe (&amp;lt;120 Mpc), consisting of 280 galaxies spanning all morphological and nuclear types. We detect nuclear radio emission above a median 5σ threshold of 0.33 mJy beam−1 in 68/280 sources (24 per cent), with core luminosities 1035–1041.9 erg s−1. The radio emission is attributed to active galactic nuclei (AGN), circumnuclear star formation, or – in the case of NGC 3690 – a tidal disruption event. The brightest radio nuclei, with brightness temperatures ≥106 K, reside in optically ‘active’ galaxies – LINERs and Seyferts. The detection rate for ‘inactive’ systems (H ii and absorption-line galaxies), which may host low-luminosity AGN (LLAGN), is 8 per cent. Most detections (78 per cent) are compact (&amp;lt;10 pc), while the remaining 22 per cent show extended, jet-like features (up to 380 pc). Compared to 1.5 GHz LeMMINGs data, the 5 GHz observations’ superior resolution and spatial filtering resolve out large-scale structures, isolating genuine nuclear emission. Our results suggests that LLAGN are the primary manifestation of black-hole activity in the local Universe in the form of compact jets and cores, with a preference for early-type hosts. The two LeMMINGs campaigns show that up to 30 per cent of the local galaxy population host a radio-active nucleus, highlighting the necessity of high-resolution, high-sensitivity imaging for uncovering nuclear emission at the lowest luminosities.