Clumpy high-z galaxies as a testbed for feedback-regulated galaxy formation

TL;DR

This study investigates how different feedback models and hydrodynamical methods affect galaxy disk fragmentation at high redshift, revealing that feedback physics critically influence the formation of massive star-forming clumps.

Contribution

It compares the effects of blastwave and superbubble supernova feedback in galaxy simulations, highlighting their impact on disk fragmentation and clump formation.

Findings

Blastwave feedback produces numerous star-forming clumps with masses $10^7-10^8 M_{\u2299}$.

Superbubble feedback prevents formation of massive bound clumps, leading to unbound, short-lived overdensities.

The results challenge the idea that observed high-z clumps are solely due to gravitational instability.

Abstract

We study the dependence of fragmentation in massive gas-rich galaxy disks at $z > 1$ on feedback model and hydrodynamical method, employing the GASOLINE2 SPH code and the lagrangian mesh-less code GIZMO in finite mass mode. We compare non-cosmological galaxy disk runs with standard blastwave supernovae (SN)feedback, which introduces delayed cooling in order to drive winds, and runs with the new superbubble SN feedback, which produces winds naturally by modelling the detailed physics of SN-driven bubbles and leads to efficient self-regulation of star formation. We find that, with blastwave feedback, massive star forming clumps form in comparable number and with very similar masses in GASOLINE2 and GIZMO. The typical masses are in the range $10^7-10^8 M_{\odot}$, lower than in most previous works, while giant clumps with masses above $10^9 M_{\odot}$ are exceedingly rare. With superbubble feedback, instead, massive bound star forming clumps do not form because galaxies never undergo a phase of violent disk instability. Only sporadic, unbound star forming overdensities lasting only a few tens of Myr can arise that are triggered by perturbations of massive satellite companions. We conclude that there is a severe tension between explaining massive star forming clumps observed at $z > 1$ primarily as the result of disk fragmentation driven by gravitational instability and the prevailing view of feedback-regulated galaxy formation. The link between disk stability and star formation efficiency should thus be regarded as a key testing ground for galaxy formation theory.