Self-consistent feedback-free-burst triggering criterion

Derive a self-consistent feedback-free-burst triggering criterion within SAGE26 by using the model’s own cloud-scale conditions and timescale comparison rather than an externally imposed halo mass–redshift threshold.

Background

SAGE26 models feedback-free bursts (FFBs) using a halo mass–redshift threshold adopted from external prescriptions by Dekel et al. and Li et al. This threshold determines when galaxies switch to an enhanced star-formation efficiency, allowing the model to reproduce the observed abundance of massive galaxies at very high redshift.

The authors note that SAGE26 tracks cooling times natively but does not derive the FFB condition directly from its own cloud-scale physics. An unresolved task is therefore to replace the externally imposed threshold with a self-consistent criterion based on the physical conditions and timescales represented within the model, so that the burst phase emerges from the model rather than being assigned phenomenologically.

References

The FFB implementation (see #1{FFBs_method}) adopts the halo mass-redshift threshold of and rather than deriving it within SAGE26 by comparing timescales directly, as the model tracks cooling times natively. Deriving the criterion self-consistently, so that the burst phase is triggered by the model's own cloud-scale conditions rather than by an externally imposed threshold, is left to future work, to which we refer the reader to Bradley et al., in prep. for a fuller discussion.

— SAGE26 Paper I: Modelling the baryon cycle from cosmic dawn to the present day  (2610.09564 - Bradley et al., 7 Oct 2026) in Section 8, “Feedback-Free Bursts”; Section 9.2, “Physical Assumptions and Limitations”