A Significant Excess in Major Merger Rate for AGNs with the Highest Eddington Ratios at z < 0.2

Victor Marian, Knud Jahnke, Irham Andika, Eduardo Baados, Vardha N. Bennert, Seth Cohen, Bernd Husemann, Melanie Kaasinen, Anton M. Koekemoer, Mira Mechtley, Masafusa Onoue, Jan Torge Schindler, Malte Schramm, Andreas Schulze, John D. Silverman, Irina Smirnova-Pinchukova, Arjen Van Der Wel, Carolin Villforth, Rogier A. Windhorst

Research output: Contribution to journalArticlepeer-review

Abstract

Observational studies are increasingly finding evidence against major mergers being the dominant mechanism responsible for triggering an active galactic nucleus (AGN). After studying the connection between major mergers and AGNs with the highest Eddington ratios at z = 2, we here expand our analysis to exploring the same AGN parameter space. Using ESO VLT/FORS2 and color images, we examine the morphologies of 17 galaxies hosting AGNs with Eddington ratios and 25 mass- A nd redshift-matched control galaxies. To match the appearance of the two samples, we add synthetic point sources to the inactive comparison galaxies. The combined sample of AGN and inactive galaxies was independently ranked by 19 experts with respect to the degree of morphological distortion. We combine the resulting individual rankings into multiple overall rankings, from which we derive the respective major merger fractions of the two samples. With a best estimate of f m,agn = 0.41 ± 0.12 for the AGN host galaxies and f m,ina = 0.08 ± 0.06 for the inactive galaxies, our results imply that our AGN host galaxies have a significantly higher merger rate, regardless of the observed wavelength or applied methodology. We conclude that although major mergers are an essential mechanism to trigger local high Eddington ratio AGNs at the origin of this specific AGN subpopulation still remains unclear.

Original languageEnglish (US)
Article number79
JournalAstrophysical Journal
Volume904
Issue number1
DOIs
StatePublished - Nov 23 2020

Keywords

  • Active galactic nuclei (16)
  • AGN host galaxies (2017)
  • Galaxy evolution (594)
  • Galaxy mergers (608)
  • Quasars (1319)
  • Supermassive black holes (1663)

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science

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