Starbursts and black hole masses in X-shaped radio galaxies: Signatures of a merger event?

TL;DR

This study investigates X-shaped radio galaxies, revealing they have higher black hole masses and older starburst histories than typical radio galaxies, supporting the merger scenario for their formation.

Contribution

It provides new spectroscopic data for 12 X-shaped radio galaxies, extending the sample and analyzing their starburst and black hole properties in relation to mergers.

Findings

X-shaped radio galaxies have higher black hole masses.

They show older starburst episodes.

Enhanced star formation supports merger origins.

Abstract

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 Astron\'omico Nacional at San Pedro M\'artir, M\'exico. 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.