Are luminous radio-loud active galactic nuclei triggered by galaxy interactions?
Article first published online: 21 OCT 2011
© 2011 The Authors Monthly Notices of the Royal Astronomical Society © 2011 RAS
Monthly Notices of the Royal Astronomical Society
Volume 419, Issue 1, pages 687–705, January 2012
How to Cite
Ramos Almeida, C., Bessiere, P. S., Tadhunter, C. N., Pérez-González, P. G., Barro, G., Inskip, K. J., Morganti, R., Holt, J. and Dicken, D. (2012), Are luminous radio-loud active galactic nuclei triggered by galaxy interactions?. Monthly Notices of the Royal Astronomical Society, 419: 687–705. doi: 10.1111/j.1365-2966.2011.19731.x
- Issue published online: 13 DEC 2011
- Article first published online: 21 OCT 2011
- Accepted 2011 August 29. Received 2011 August 16; in original form 2011 July 14
- galaxies: active;
- galaxies: elliptical and lenticular, cD;
- galaxies: evolution;
- galaxies: interactions;
- galaxies: nuclei
We present the results of a comparison between the optical morphologies of a complete sample of 46 southern 2 Jy radio galaxies at intermediate redshifts (0.05 < z < 0.7) and those of two control samples of quiescent early-type galaxies: 55 ellipticals at redshifts z ≤ 0.01 from the Observations of Bright Ellipticals at Yale (OBEY) survey, and 107 early-type galaxies at redshifts 0.2 < z < 0.7 in the Extended Groth Strip (EGS). Based on these comparisons, we discuss the role of galaxy interactions in the triggering of powerful radio galaxies (PRGs). We find that a significant fraction of quiescent ellipticals at low and intermediate redshifts show evidence for disturbed morphologies at relatively high surface brightness levels, which are likely the result of past or on-going galaxy interactions. However, the morphological features detected in the galaxy hosts of the PRGs (e.g. tidal tails, shells, bridges, etc.) are up to 2 mag brighter than those present in their quiescent counterparts. Indeed, if we consider the same surface brightness limits, the fraction of disturbed morphologies is considerably smaller in the quiescent population (53 per cent at z < 0.2 and 48 per cent at 0.2 ≤ z < 0.7) than in the PRGs (93 per cent at z < 0.2 and 95 per cent at 0.2 ≤ z < 0.7 considering strong-line radio galaxies only). This supports a scenario in which PRGs represent a fleeting active phase of a subset of the elliptical galaxies that have recently undergone mergers/interactions. However, we demonstrate that only a small proportion (≲20 per cent) of disturbed early-type galaxies are capable of hosting powerful radio sources.