University of Hertfordshire

From the same journal

From the same journal

By the same authors

Delayed triggering of radio Active Galactic Nuclei in gas-rich minor mergers in the local Universe

Research output: Contribution to journalArticlepeer-review


  • Stanislav Shabala
  • Adam Deller
  • Sugata Kaviraj
  • Enno Middelberg
  • Ross Turner
  • Yuan-Sen Ting
  • James Allison
  • Tim Davis
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Original languageEnglish
Pages (from-to)4706-4720
Number of pages16
JournalMonthly Notices of the Royal Astronomical Society
Early online date5 Oct 2016
Publication statusPublished - 1 Feb 2017


We examine the processes triggering star formation and Active Galactic Nucleus (AGN) activity in a sample of 25 low redshift ($z 10^7$ K) brightness temperature required for an mJIVE-20 detection allows us to unambiguously identify the radio AGN in our sample. We find three such objects. Our VLBI AGN identifications are classified as Seyferts or LINERs in narrow line optical diagnostic plots; mid-infrared colours of our targets and the comparison of H$\alpha$ star formation rates with integrated radio luminosity are also consistent with the VLBI identifications. We reconstruct star formation histories in our galaxies using optical and UV photometry, and find that these radio AGN are not triggered promptly in the merger process, consistent with previous findings for non-VLBI samples of radio AGN. This delay can significantly limit the efficiency of feedback by radio AGN triggered in galaxy mergers. We find that radio AGN hosts have lower star formation rates than non-AGN radio-selected galaxies at the same starburst age. Conventional and VLBI radio imaging shows these AGN to be compact on arcsecond scales. Our modeling suggests that the actual sizes of AGN-inflated radio lobes may be much larger than this, but these are too faint to be detected in existing observations. Deep radio imaging is required to map out the true extent of the AGN, and to determine whether the low star formation rates in radio AGN hosts are a result of the special conditions required for radio jet triggering, or the effect of AGN feedback.


This article has been accepted for publication in Monthly Notices of the Royal Astronomical Society © : 2016 [S. S. Shabala, a. Deller, S. Kaviraj, E. Middelberg, R. J. Turner, Y. S. Ting, J. R. Allison, T. A Davis, 'Delayed triggering of radio active galactic nucle in gas-rich minor mergers in the local Universe', MNRAS (2016) 464(4): 4706-4720]. The final, published version is available online via doi: Published by Oxford University Press on behalf of the Royal Astronomical Society. All rights reserved.

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