The environmental dependence of X-ray AGN activity at z ∼0.4

E. Noordeh, R. E.A. Canning, A. King, S. W. Allen, A. Mantz, R. G. Morris, S. Ehlert, A. Von Der Linden, W. N. Brandt, B. Luo, Y. Q. Xue, P. Kelly

Research output: Contribution to journalArticlepeer-review

6 Scopus citations


We present an analysis of the X-ray active galactic nucleus (AGN) population in a sample of seven massive galaxy clusters in the redshift range 0.35 < z < 0.45. We utilize high-quality Chandra X-ray imaging to robustly identify AGN and precisely determine cluster masses and centroids. Follow-up VIsible Multi-Object Spectrograph optical spectroscopy allows us to determine which AGN are cluster members. Studying the subset of AGN with 0.5-8 keV luminosities >6.8 × 1042 erg s-1, within r ≤ 2r500 (approximately the virial radius), we find that the cluster AGN space density scales with cluster mass as ∼ M-2.0+0.8-0.9. This result rules out zero mass dependence of the cluster X-ray AGN space density at the 2.5σ level. We compare our cluster X-ray AGN sample to a control field with identical selection and find that the cluster AGN fraction is significantly suppressed relative to the field when considering the brightest galaxies with V < 21.5. For fainter galaxies, this difference is not present. Comparing the X-ray hardness ratios of cluster member AGN to those in the control field, we find no evidence for enhanced X-ray obscuration of cluster member AGN. Lastly, we see tentative evidence that disturbed cluster environments may contribute to enhanced AGN activity.

Original languageEnglish (US)
Pages (from-to)4095-4108
Number of pages14
JournalMonthly Notices of the Royal Astronomical Society
Issue number3
StatePublished - Nov 1 2020

All Science Journal Classification (ASJC) codes

  • Astronomy and Astrophysics
  • Space and Planetary Science


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