Investigating the Effect of Galaxy Interactions on the Enhancement of Active Galactic Nuclei at 0.5 < z < 3.0

Ekta A. Shah, Jeyhan S. Kartaltepe, Christina T. Magagnoli, Isabella G. Cox, Caleb T. Wetherell, Brittany N. Vanderhoof, Antonello Calabro, Nima Chartab, Christopher J. Conselice, Darren J. Croton, Jennifer Donley, Laura De Groot, Alexander De La Vega, Nimish P. Hathi, Olivier Ilbert, Hanae Inami, Dale D. Kocevski, Anton M. Koekemoer, Brian C. Lemaux, Kameswara Bharadwaj ManthaStefano Marchesi, Marie Martig, Daniel C. Masters, Elizabeth J. McGrath, Daniel H. McIntosh, Jorge Moreno, Hooshang Nayyeri, Belen Alcalde Pampliega, Mara Salvato, Gregory F. Snyder, Amber N. Straughn, Ezequiel Treister, Madalyn E. Weston

Research output: Contribution to journalArticlepeer-review

30 Scopus citations


Galaxy interactions and mergers are thought to play an important role in the evolution of galaxies. Studies in the nearby universe show a higher fraction of active galactic nuclei (AGNs) in interacting and merging galaxies than in their isolated counterparts, indicating that such interactions are important contributors to black hole growth. To investigate the evolution of this role at higher redshifts, we have compiled the largest known sample of major spectroscopic galaxy pairs (2381 with ΔV < 5000 km s-1) at 0.5 < z < 3.0 from observations in the COSMOS and CANDELS surveys. We identify X-ray and IR AGNs among this kinematic pair sample, a visually identified sample of mergers and interactions, and a mass-, redshift-, and environment-matched control sample for each in order to calculate AGN fractions and the level of AGN enhancement as a function of relative velocity, redshift, and X-ray luminosity. While we see a slight increase in AGN fraction with decreasing projected separation, overall, we find no significant enhancement relative to the control sample at any separation. In the closest projected separation bin (< 25 kpc, ΔV < 1000 km s-1), we find enhancements of a factor of for X-ray and IR-selected AGNs, respectively. While we conclude that galaxy interactions do not significantly enhance AGN activity on average over 0.5 < z < 3.0 at these separations, given the errors and the small sample size at the closest projected separations, our results would be consistent with the presence of low-level AGN enhancement.

Original languageEnglish (US)
Article number107
JournalAstrophysical Journal
Issue number2
StatePublished - Dec 1 2020
Externally publishedYes

Bibliographical note

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© 2020. The American Astronomical Society. All rights reserved..


  • Active galactic nuclei (16)
  • Extragalactic astronomy (506)
  • Galaxy interactions (600)
  • Galaxy mergers (608)
  • Galaxy pairs (610)
  • High-redshift galaxies (734)
  • Interacting galaxies (802)


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