Determine the dominant feedback mechanism driving the CRISTAL-02 outflow

Determine whether the outflow in the z ≈ 5.3 galaxy CRISTAL-02 is primarily driven by active galactic nucleus feedback or by star formation-driven stellar feedback, thereby establishing the dominant mechanism regulating its Lyman-alpha escape.

Background

CRISTAL-02 exhibits extended Lyman-alpha emission aligned with a [C II]-identified outflow. The spatial distribution of Lyman-alpha, H-alpha, and UV emission is consistent with feedback-driven gas clearing and anisotropic low-opacity channels that facilitate Lyman-alpha escape.

Although broad H-alpha components identify Clumps A and B as possible AGN candidates, the available emission-line diagnostics and multiwavelength data do not provide definitive evidence for AGN activity. Independent analyses favor stellar feedback as an energetically sufficient and likely primary driver of the outflow, but an AGN contribution cannot be excluded. Consequently, the relative roles of AGN and star formation-driven feedback remain unresolved and require higher-quality spatially resolved multiwavelength observations.

References

The current observational evidence is most consistent with the presence of an outflow, while the mechanism driving it remains uncertain, as the available data do not uniquely distinguish between AGN and star formation-driven feedback. Future spatially resolved multiwavelength IFU observations combining Lyα, Hα, and [C ii] emission will be essential to disentangling these scenarios and establishing the dominant feedback mechanism.

— Tracing Lyman alpha escape in the CRISTAL-02 galaxy at z~5.3  (2608.19439 - Ali et al., 19 Aug 2026) in Abstract; Conclusions, item 4