PKS 0347+05: a radio-loud/radio-quiet double active galactic nucleus system triggered in a major galaxy merger

Abstract

We present optical, infrared (IR) and radio observations of the powerful Fanaroff–Riley type II (FR II) radio source PKS 0347+05 (z = 0.3390), and demonstrate that it is a rare example of a radio‐loud/radio‐quiet double active galactic nucleus (AGN) system, comprising a weak‐line radio galaxy (WLRG) separated by 25 kpc (in projection) from a Seyfert 1 nucleus at the same redshift. Our deep Gemini optical images show a highly disturbed morphology, with a warped dust lane crossing through the halo and nuclear regions of the radio galaxy host, tidal tails and a bridge connecting the radio galaxy to the Seyfert 1 nucleus. Spectral synthesis modelling of our Gemini optical spectrum of the radio galaxy shows evidence for a reddened young stellar population of age ≤100 Myr. Further evidence for recent star formation activity in this source is provided by the detection of strong polycyclic aromatic hydrocarbon features in mid‐IR Spitzer/IRS spectra. Together, these observations support a model in which both AGN have been triggered simultaneously in a major galaxy merger. However, despite the presence of a powerful FR II radio source, and the apparently plentiful supply of fuel provided by the merger, the nucleus of the radio galaxy shows only weak, low‐ionization emission‐line activity. We speculate that the fuel supply to nuclear regions of the radio galaxy has recently switched off (within the last ∼106 yr), but the information about the resulting decrease in nuclear AGN activity has yet to reach the extended lobes and hotspots of the FR II radio source. Based on this scenario, we derive a lower limit on the typical lifetimes of powerful, intermediate‐redshift FR II radio sources of τ FR II ≳5×106 yr. Overall, our observations emphasize that the fuelling of AGN activity in major galaxy mergers is likely to be highly intermittent.

Galaxies hosting an active galactic nucleus: a view from the CALIFA survey

“…Studies on AGN lifetime agree that it lasts between 10 5 to 10 9 years, depending what is consider to constrain the AGN activity (ratio between the number of RG/GV/SFG populations, period of X-ray being emitted by a central event, length of radio jets, statistics in function of redshift, etc). Tadhunter et al (2012) studied a dual radio-loud/radio-quiet AGN system. Through the assumption that both AGN were triggered at same time by a major galaxy merge, they observe radio emission from hot spots away from the nucleus even not observing emission from the narrow-line region of one of the AGNs.…”

Does the Jet Production Efficiency of Radio Galaxies Control Their Optical Agn Types?

“…Eventually, the scenario I propose implies an evolution from Seyfert 2s to LINERs and Seyfert 1 galaxies caused by an increase in jet production efficiency. I note that the rather clear separation of the Seyfert 2s from the rest of the sample suggests that the transition in efficiency happens relatively fast compared to the characteristic life times of galactic radio jets, meaning 10 6 years (cf., e.g., Tadhunter et al 2012).…”

Circumnuclear and infalling H i gas in a merging galaxy pair at z = 0.123

“…Several authors have found evidence for connection between the merger process and the AGN activity for both radio-loud and radio-quiet AGNs (e.g. Combes et al 2009;Ellison et al 2011;Ramos Almeida et al 2012;Villar-Martín et al 2012;Tadhunter et al 2012; Khabiboulline et al 2014). However, there are also studies that find no relationship between the AGN activity and mergers (e.g.…”