Starbursts and black hole masses in X-shaped radio galaxies: Signatures of a merger event?
1 Max Planck Institute for Radio Astronomy, Auf dem Hügel 69, 53121 Bonn, Germany
2 Instituto de Astrofísica de Canarias, vía Láctea S/N, 38200 La Laguna, Tenerife, Spain
3 Dept. Astrofísica, Universidad de La Laguna (ULL), 38206 La Laguna, Tenerife, Spain
4 Instituto Nacional de Astrofísica, Óptica y Electrónica, Apdo. Postal 51, 72000 Puebla, México
5 Aalto University Metsähovi Radio Observatory, Metsähovintie 114, 02540 Kylmälä, Finland
Received: 18 July 2011
Accepted: 20 June 2012
We present new spectroscopic identifications of 12 X-shaped radio galaxies and use the spectral data to derive starburst histories and masses of the nuclear supermassive black holes in these galaxies. The observations were done with the 2.1-m telescope of the Observatorio Astronómico Nacional at San Pedro Mártir, México. The new spectroscopic results extend the sample of X-shaped radio galaxies studied with optical spectroscopy. We show that the combined sample of the X-shaped radio galaxies has statistically higher black-hole masses and older episodes of star formation than a control sample of canonical double-lobed radio sources with similar redshifts and luminosities. The data reveal enhanced star-formation activity in the X-shaped sample on the timescales expected in galactic mergers. We discuss the results obtained in the framework of the merger scenario.
Key words: galaxies: kinematics and dynamics / galaxies: formation / galaxies: nuclei / black hole physics
© ESO, 2012