Research Note

From galaxy-scale fueling to nuclear-scale feedback

The merger-state of radio galaxies 3C 293, 3C 305, and 4C 12.50

¹ Centro de Astrobiología (INTA-CSIC), Ctra de Torrejón a Ajalvir, km 4, 28850 Torrejón de Ardoz Madrid, Spain
e-mail: bjornemonts@gmail.com
² ASTRON, The Netherlands Institute for Radio Astronomy, Postbus 2, 7990 AA Dwingeloo, The Netherlands
³ Kapteyn Astronomical Institute, University of Groningen, PO Box 800, 9700 AV Groningen, The Netherlands
⁴ Astro-UAM, UAM, Unidad Asociada CSIC, Facultad de Ciencias, Campus de Cantoblanco, 28049 Madrid, Spain
⁵ Korea Astronomy and Space Science Institute, 776 Daedeokdae-ro, Yuseong-gu, 34055 Daejeon, Korea
⁶ Academic Services Group, University of Canterbury, Christchurch, Private Bag 4800, 8140 Christchurch, New Zealand
⁷ Department of Physics and Astronomy, University of Sheffield, Sheffield S3 7RH, UK
⁸ Sydney Institute for Astronomy, School of Physics A28, University of Sydney, NSW 2006, Australia
⁹ ARC Centre of Excellence for All-Sky Astrophysics (CAASTRO), Australia

Received: 25 March 2016
Accepted: 12 August 2016

Abstract

Powerful radio galaxies are often associated with gas-rich galaxy mergers. These mergers may provide the fuel to trigger starburst and active galactic nuclear (AGN) activity. In this Research Note, we study the host galaxies of three seemingly young or re-started radio sources that drive fast outflows of cool neutral hydrogen (H i) gas, namely 3C 293, 3C 305 and 4C 12.50 (PKS 1345+12). Our aim is to link the feedback processes in the central kpc-scale region with new information on the distribution of stars and gas at scales of the galaxy. For this, we use deep optical V-band imaging of the host galaxies, complemented with H i emission-line observations to study their gaseous environments. We find prominent optical tidal features in all three radio galaxies, which confirm previous claims that 3C 293, 3C 305, and 4C 12.50 have been involved in a recent galaxy merger or interaction. Our data show the complex morphology of the host galaxies and identify the companion galaxies that are likely involved in the merger or interaction. The radio sources appear to be (re-)triggered at a different stage of the merger; 4C 12.50 is a pre-coalescent and possibly multiple merger, 3C 293 is a post-coalescent merger that is undergoing a minor interaction with a close satellite galaxy, while 3C 305 appears to be shaped by an interaction with a gas-rich companion. For 3C 293 and 3C 305, we do not detect H i beyond the inner ~30−45 kpc region, which shows that the bulk of the cold gas is concentrated within the host galaxy, rather than along the widespread tidal features.