The Relation Between AGN and Host Galaxy Properties in the JWST Era: II. The merger-driven evolution of Seyferts at Cosmic Noon

Nina Bonaventura, Jianwei Lyu, George H. Rieke, Andrew J. Bunker, Chris J. Willott, Christopher N. A. Willmer

First listed 2025-10-13 | Last updated 2025-10-14

Abstract

In Paper I, we exploited the unsurpassed resolution and depth of JWST/NIRCam imagery to investigate the relationship between AGN and host-galaxy properties in the JWST era, finding a correlation between the level of spatial disturbance (as measured by shape asymmetry, $A_S$) and obscuration ($N_H$). Here in Paper II, we report an expansion of our X-ray and infrared analysis of Seyfert-luminosity host galaxies with four additional metrics to the single-metric morphology analysis of Paper I, as well as new samples of inactive control galaxies. This expanded study of one of the largest and most complete, multi-wavelength samples of AGN detected at $0.6<z<2.4$ in the GOODS-South and North fields, confirms that mergers surprisingly play a significant role in obscured, sub-quasar AGN host galaxies. Additionally, the pattern of morphological disturbances observed amongst the X-ray- and mid-IR-selected AGN suggests that these represent different phases of AGN evolution tied to a major-merger timeline, as opposed to distinct populations of AGN. These results indicate that mergers are important in triggering sub-quasar AGN at these redshifts.

Short digest

Paper II expands the JWST/NIRCam morphology work by adding four metrics to shape asymmetry and introducing matched inactive controls for 425 Seyfert-luminosity AGN at 0.6<z<2.4 in GOODS-N/S. The analysis classifies major versus minor mergers and finds a high merger fraction among obscured, sub‑quasar hosts, with major mergers dominant and rising toward higher redshift. Disturbance patterns differ for X-ray- versus mid-IR-selected AGN, consistent with sequential phases in a major‑merger timeline (mid‑IR/X‑ray‑faint preceding X‑ray‑bright). These results argue that mergers are an important trigger of Seyfert activity at Cosmic Noon.

Key figures to inspect

• Figure 1 — Verify that the control samples (CANDELS near-IR, MIRI-selected, and X-ray-selected) are well matched in stellar mass and redshift to the AGN, ensuring morphology contrasts are not driven by selection effects.
• Figure 2 — Inspect F150W cutouts illustrating major, minor, and non‑merger labels; look for tidal tails, wisps, edges, and multiple nuclei that underpin the combined indicator-based staging of the merger sequence.
• Figure 3 — Read off the major, minor, and total merger fractions versus redshift (and N_H color-coding, including simulated CT mid‑IR AGN); note the dominance of major mergers and the rise of total merger incidence with redshift.
• Figure 4 — From Paper I, examine how shape asymmetry increases with obscuration and redshift; the clustering at high A_S and high N_H highlights the early, chaotic stage of mergers relevant to this sample.