The role of major mergers in triggering super-Eddington accretion

@misc{caleno2026role,
  title = {{The role of major mergers in triggering super-Eddington accretion}},
  author = {Riccardo Caleno and Tommaso Zana and Raffaella Schneider and Alessandro Lupi and Pedro R. Capelo and Lucio Mayer and Alessandro Trinca and Rosa Valiante and Marta Volonteri},
  howpublished = {arXiv},
  year = {2026},
  month = oct,
  doi = {10.48550/arxiv.2606.04081},
  eprint = {2606.04081},
  archivePrefix = {arXiv},
  url = {https://arxiv.org/abs/2606.04081},
}

TY  - UNPB
TI  - The role of major mergers in triggering super-Eddington accretion
AU  - Riccardo Caleno
AU  - Tommaso Zana
AU  - Raffaella Schneider
AU  - Alessandro Lupi
AU  - Pedro R. Capelo
AU  - Lucio Mayer
AU  - Alessandro Trinca
AU  - Rosa Valiante
AU  - Marta Volonteri
PY  - 2026
DA  - 2026/10/21
PB  - arXiv
DO  - 10.48550/arxiv.2606.04081
UR  - https://arxiv.org/abs/2606.04081
AB  - JWST observations have opened a new era in the exploration of the high-redshift Universe, revealing black holes (BHs) with masses of several million solar masses already at z>8, challenging our understanding of their growth mechanisms. In this context, super-Eddington (SE) accretion has emerged as a promising solution and has been widely adopted in both numerical simulations and semi-analytical models. In this work, we investigate whether a major merger between two relatively low-mass halos (M_halo∼10^9 M_⊙) at high redshift can trigger episodes of sustained SE accretion, with particular focus on the role of BH feedback. We employ state-of-the-art, high-resolution cosmological zoom-in simulations of a major merger at z∼11. We explore different prescriptions for BH seeding and feedback, including physically motivated radiative and kinetic models (winds and jets) across the three main accretion regimes: advection-dominated accretion flows (ADAF), radiatively efficient sub-Eddington accretion, and SE accretion. For the relatively low-mass halos studied here, our feedback prescription efficiently suppresses gas accretion, preventing substantial BH growth. We find that, although the merger drives gas inflows towards the central regions, this is not sufficient to trigger sustained SE accretion. Post-merger SE accretion episodes are observed only when BH feedback is entirely switched off. Amongst the feedback channels considered, kinetic feedback is the primary mechanism regulating BH growth. Moreover, the only significant SE accretion episodes occur immediately after BH seeding, while the merger itself does not produce a substantial enhancement of the accretion rate.
ER  -