The ATLAS^3D Project - XXXI. Nuclear radio emission in nearby early-type galaxies

Kristina Nyland , Lisa M. Young , Joan M. Wrobel , Marc Sarzi , Raffaella Morganti , Katherine Alatalo , Leo Blitz , Frédéric Bournaud (1) , Martin Bureau , Michele Cappellari , Alison F. Crocker , Roger L. Davies , Timothy A. Davis , P. T. de Zeeuw , Pierre-Alain Duc (1) , Eric Emsellem (2) , Sadegh Khochfar , Davor Krajnović , Harald Kuntschner , Richard M. Mcdermid , Thorsten Naab , Tom Oosterloo , Nicholas Scott , Paolo Serra , Anne-Marie Weijmans

1 AIM (UMR_7158 / UMR_E_9005 / UM_112) - Astrophysique Interprétation Modélisation
2 CRAL - Centre de Recherche Astrophysique de Lyon

We present the results of a high-resolution, 5 GHz, Karl G. Jansky Very Large Array study of the nuclear radio emission in a representative subset of the ATLAS^3D survey of early-type galaxies (ETGs). We find that 51 ± 4 per cent of the ETGs in our sample contain nuclear radio emission with luminosities as low as 10¹⁸ W Hz^-1. Most of the nuclear radio sources have compact (≲25-110 pc) morphologies, although ∼10 per cent display multicomponent core+jet or extended jet/lobe structures. Based on the radio continuum properties, as well as optical emission line diagnostics and the nuclear X-ray properties, we conclude that the majority of the central 5 GHz sources detected in the ATLAS^3D galaxies are associated with the presence of an active galactic nucleus (AGN). However, even at subarcsecond spatial resolution, the nuclear radio emission in some cases appears to arise from low-level nuclear star formation rather than an AGN, particularly when molecular gas and a young central stellar population is present. This is in contrast to popular assumptions in the literature that the presence of a compact, unresolved, nuclear radio continuum source universally signifies the presence of an AGN. Additionally, we examine the relationships between the 5 GHz luminosity and various galaxy properties including the molecular gas mass and - for the first time - the global kinematic state. We discuss implications for the growth, triggering, and fuelling of radio AGNs, as well as AGN-driven feedback in the continued evolution of nearby ETGs.

Mots clés: galaxies: active; galaxies: nuclei; radio continuum: galaxies; Astrophysics - Astrophysics of Galaxies

Domaines: Planète et Univers [physics]; Astrophysique [astro-ph]

Kristina Nyland, Lisa M. Young, Joan M. Wrobel, Marc Sarzi, Raffaella Morganti, et al.. The ATLAS^3D Project - XXXI. Nuclear radio emission in nearby early-type galaxies. Monthly Notices of the Royal Astronomical Society, 2016, 458, pp.2221-2268. ⟨10.1093/mnras/stw391⟩. ⟨insu-03746217⟩