Disentangling Stellar Mass and Environmental Effects on eROSITA AGN Activity using multi-wavelength data from GAMA, WISE, GALEX, and DESI Legacy Survey

arXiv:2609.16333 · astro-ph.GA · Submitted 2026-09-14 · Read on arXiv

astro-ph.GA

Submitted: 2026-09-14

Updated: 2026-09-14

Project page: http://www.gama-survey.org

License: http://creativecommons.org/licenses/by/4.0/

The gist: We use a stellar-mass complete sample of about 36, 000 galaxies from GAMA/eFEDS to test whether AGN activity depends on environment independent of stellar mass.

Terminology

Abstract

We use a stellar-mass complete sample of about 36, 000 galaxies from GAMA/eFEDS to test whether AGN activity depends on environment independent of stellar mass. To isolate this effect, we introduce δ rank, a novel local overdensity metric defined within narrow stellar mass bins. Our main result is that X-ray-selected AGNs show a clear environmental trend, the AGN fraction rises from about 4% in low-density regions to about 6% in high-density regions, with a sharp transition at δ rank about 0.4. This environmental dependence is absent for WISE-selected and broad-line AGN, and Eddington ratios show no variation across environments. We also found that for galaxies with SFR > 15,M, yr-1, X-ray AGN fraction is approximately 5%, 60% and 20% in low, mid and high δ rank galaxies. We show that relationship between AGN fraction and SFR varies dramatically with both environment and selection method. We conclude that environment on scales of about 5h-1, Mpc regulates X-ray AGN triggering efficiency.

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