Which came first: supermassive black holes or galaxies? Insights from JWST

Abstract: Insights from JWST observations suggest that AGN feedback evolved from a short-lived, high redshift phase in which radiatively cooled turbulence and/or momentum-conserving outflows stimulated vigorous early star formation (``positive'' feedback), to late, energy-conserving outflows that depleted halo gas reservoirs and quenched star formation. The transition between these two regimes occurred at $z\sim 6$, independently of galaxy mass, for simple assumptions about the outflows and star formation process. Observational predictions provide circumstantial evidence for the prevalence of massive black holes at the highest redshifts hitherto observed, and we discuss their origins.

• The paper presents evidence that early positive AGN feedback boosts star formation in compact high-redshift host galaxies independent of galaxy mass.
• It identifies a transition at z~6 where energy-conserving outflows shift to negative feedback, quenching star formation.
• Observations reveal SMBHs with high mass relative to stellar content, suggesting rapid black hole growth prior to full galaxy assembly.

Insights into High-Redshift Galaxy Formation and Supermassive Black Holes from JWST Observations

This paper examines the intricate relationship between high-redshift galaxy formation and supermassive black holes (SMBHs), utilizing data from the James Webb Space Telescope (JWST) to offer new insights into this complex astrophysical process. The researchers provide an analysis of how active galactic nuclei (AGNs) feedback mechanisms may have transitioned from an epoch of positive star formation feedback to negative feedback leading to star formation quenching, largely dependent on redshift and galaxy evolution stages.

Positive and Negative Feedback Mechanisms

The paper identifies two distinct feedback regimes dictated by AGN activity. Initially, at high redshifts, radiatively cooled turbulence and momentum-conserving outflows from AGNs are shown to enhance star formation in their host galaxies, a process the authors term "positive feedback." This phase is characterized by rapid cooling in ultracompact AGN host galaxies, resulting in shock-boosted star formation. Notably, this initial phase is independent of galaxy mass.

As the universe evolves, the paper describes a transition to energy-conserving AGN outflows by redshift $z \sim 6$. In this regime, the feedback becomes predominantly negative, characterized by the depletion of gas reservoirs that ultimately quenches star formation. This transition marks a significant point in galaxy evolution, highlighting a shift from galaxy-building processes to those that inhibit further stellar birth.

Observational Evidence and Predictions

The study substantiates its claims with data showing that compact AGN host galaxies at high redshifts possess unusually high black hole masses relative to their stellar mass content. These observations suggest that many SMBHs existed even before their host galaxies had fully formed their stellar populations. The researchers argue that this compactness contributes to effective cooling, thus triggering star formation, which aligns with observed chemical signatures in distant galaxies that mimic those of massive star clusters and quasar emission line regions.

Transition Redshift and SMBH Scaling

A key contribution of the paper is the identification of a transition in feedback regimes occurring around redshift $z\sim 6$, leading to changes in SMBH scaling laws as the universe evolves. The authors hypothesize that the early, compact galaxy structures facilitate rapid cooling and SBMH growth while later stages see reduced cooling efficiency, allowing for energy-conserving outflows that expand and deplete the galaxy's gas content.

Theoretical Implications and Future Directions

Theoretically, this research suggests new models for SMBH evolution that account for early feedback mechanisms driving rapid star formation and SMBH growth. The model provides a framework for understanding the observed discrepancies in SMBH-host galaxy masses at different epochs and suggests potential pathways for the early formation of massive black hole seeds, considering factors like primordial density fluctuations and the initial conditions of early universe gas dynamics.

Future developments in AI and astrophysical modeling could leverage these findings to refine simulations of galaxy evolution, particularly in accurately reproducing the early universe conditions where SMBH and galaxy coevolution are critically intertwined. Enhanced observational capabilities, possibly from future sensitive X-ray missions or radio observations with facilities such as SKA, could further elucidate these intricate cosmic processes.

In summary, the research showcases the transformative potential of JWST's observations in unraveling the complex history of galaxy and black hole formation. By effectively combining observational data with theoretical models, the study advances our understanding of the fundamental processes governing the early universe.