From major merger to radio galaxy: low surface-brightness stellar counterpart to the giant HI ring around B2 0648+27

Abstract

We present the detection of a low surface-brightness stellar counterpart to an enormous (190 kpc) ring of neutral hydrogen (HI) gas that surrounds the nearby radio galaxy B2 0648+27. This system is currently in an evolutionary stage between major merger and (radio-loud) early-type galaxy. In a previous paper we investigated in detail the timescales between merger, starburst and AGN activity in B2 0648+27, based on its unusual multi-wavelength properties (large-scale HI ring, dominating post-starburst stellar population and infra-red luminosity). In this Research Note we present deep optical B- and V-band imaging that provides further evidence for the merger origin of B2 0648+27. The host galaxy shows a distorted optical morphology and a broad tidal arm is clearly present. A low surface-brightness stellar tail or partial ring curls around more than half the host galaxy at a distance of up to 55 kpc from the centre of the galaxy, following the large-scale, ring-like HI structure that we detected previously around this system. The gas and stars in this ring are most likely tidally expelled material that slowly fell back onto the host galaxy after the merger event. There also appear to be sites of star formation in the HI ring that may have formed within the gaseous tidal debris after the merger. We argue that the observed properties of the gas and stars in B2 0648+27, as well as the apparent time-delay between the merger and the starburst event, may be the logical result of a merger between two gas-rich disk galaxies with a prominent bulge, or of a merger between an elliptical and a gas-rich spiral galaxy. There also appears to be a significant time-delay between the merger/starburst event and the current episode of radio-AGN activity.

arXiv comment4 pages, 2 figures, accepted by Astronomy & Astrophysics (Research Notes)

References in corpus (13)

• Energy input from quasars regulates the growth and activity of black holes and their host galaxies
• Modeling feedback from stars and black holes in galaxy mergers
• Gasdynamics and Starbursts in Major Mergers
• Black Holes in Galaxy Mergers: Evolution of Quasars
• Star Formation Thresholds in Galactic Disks
• Star formation efficiency in galaxy interactions and mergers: a statistical study
• Formation of gas disks in merging galaxies
• Keck Absorption-Line Spectroscopy of Galactic Winds in Ultraluminous Infrared Galaxies
• UV Morphology and Star Formation in the Tidal Tails of NGC 4038/39
• Star formation rates and mass distributions in interacting galaxies
• Low Power Compact Radio Galaxies at High Angular Resolution
• Timescales of merger, starburst and AGN activity in radio galaxy B2 0648+27
• B2 0648+27: a radio galaxy in a major merger

Cited by in corpus (7)

• Radio AGN in the local universe: unification, triggering and evolution
• Starburst radio galaxies: general properties, evolutionary histories and triggering
• Taking snapshots of the jet-ISM interplay: The case of PKS0023-26
• Large-scale HI in nearby radio galaxies (II): the nature of classical low-power radio sources
• Centrally Concentrated H I Distribution Enhances Star Formation in Galaxies
• Classical radio source propagating into outer HI disc in NGC 3801
• The core fundamental plane of B2 radio galaxies