Unveiling the AGN in IC 883: discovery of a parsec-scale radio jet

Romero-Canizales, C. et. al.
IC 883 is a luminous infrared galaxy (LIRG) classified as a starburst- active galactic nucleus (AGN) composite. In a previous study, we detected a low- luminosity AGN (LLAGN) radio candidate. Here, we report on our radio follow- up at three frequencies that provides direct and unequivocal evidence of the AGN activity in IC 883. Our analysis of archival X-ray data, together with the detection of a transient radio source with luminosity typical of bright supernovae, gives further evidence of the ongoing star formation activity, which dominates the energetics of the system. At sub- parsec scales, the radio nucleus has a core-jet morphology with the jet being a newly ejected component showing a subluminal proper motion of 0.6-1 c. The AGN contributes less than 2 per cent of the total IR luminosity of the system. The corresponding Eddington factor is similar to 10(-3), suggesting this is a low-accretion rate engine, as often found in LLAGNs. However, its high bolometric luminosity (similar to 10(44) erg s(-1)) agrees better with a normal AGN. This apparent discrepancy may just be an indication of the transition nature of the nucleus from a system dominated by star formation, to an AGN-dominated system. The nucleus has a strongly inverted spectrum and a turnover at similar to 4.4 GHz, thus qualifying as a candidate for the least luminous (L(5.0)GHz similar to 6.3 x 10(28) erg s(-1) Hz(-1)) and one of the youngest (similar to 3 x 10(3) yr) gigahertz-peaked spectrum (GPS) sources. If the GPS origin for the IC 883 nucleus is confirmed, then advanced mergers in the LIRG category are potentially key environments to unveil the evolution of GPS sources into more powerful radio galaxies. © 2017 The Authors. Published by Oxford University Press on behalf of the Royal Astronomical Society.
We acknowledge financial support by the Ministry of Economy, Development, and Tourism's Millennium Science Initiative through grant IC120009, awarded to The Millennium Institute of Astrophysics, MAS, Chile (CR-C, FEB), from CONICYT through FONDECYT grants 3150238 (CR-C), 1140304 (PA), 1141218 and 1151408, from the CONICYT-Chile grants 'EMBIGGEN' Anillo ACT1101, Basal-CATA PFB-06/2007 and the China-CONICYT fellowship (CR, FEB), as well as funding from the SpanishMinistry of Economy and Competitiveness under grants AYA2012-38491CO2-02 and AYA2015-63939-C2-1-P, which are partly funded by the FEDER programme (AA, MAP-T, RH-I). The European VLBI Network is a joint facility of independent European, African, Asian and North American radio astronomy institutes. Scientific results from data presented in this publication are derived from the EVN project code ER030. The research leading to these results has received funding from the European Commission Seventh Framework Programme (FP/2007-2013) under grant agreement no. 283393 (RadioNet3). The National Radio Astronomy Observatory is a facility of the National Science Foundation operated under cooperative agreement by Associated Universities, Inc.