Effects of feedback on galaxies in the VELA simulations: elongation, clumps and compaction

TL;DR

This study compares two feedback models in high-redshift galaxy simulations, revealing how feedback strength influences galaxy shape, clump formation, and the star formation history, aligning results with observational data.

Contribution

It introduces a comparative analysis of feedback mechanisms in cosmological simulations, highlighting their impact on galaxy morphology and star formation processes.

Findings

Stronger feedback reduces stellar mass and improves halo mass relation.

Galaxies are more elongated at fixed stellar mass with stronger feedback.

Giant clumps form in massive, star-forming discs regardless of feedback strength.

Abstract

The evolution of star-forming galaxies at high redshifts is very sensitive to the strength and nature of stellar feedback. Using two sets of cosmological, zoom-in simulations from the VELA suite, we compare the effects of two different models of feedback: with and without kinetic feedback from the expansion of supernovae shells and stellar winds. At a fixed halo mass and redshift, the stellar mass is reduced by a factor of 1-3 in the models with stronger feedback, so the stellar-mass-halo-mass relation is in better agreement with abundance matching results. On the other hand, the three-dimensional shape of low-mass galaxies is elongated along a major axis in both models. At a fixed stellar mass, Ms<10^10 Msun, galaxies are more elongated in the strong-feedback case. More massive, star-forming discs with high surface densities form giant clumps. However, the population of round, compact, old (age_c > 300 Myr), quenched, stellar (or gas-poor) clumps is absent in the model with strong feedback. On the other hand, giant star-forming clumps with intermediate ages (age_c= 100 - 300 Myr) can survive for several disc dynamical times, independently of feedback strength. The evolution through compaction followed by quenching in the plane of central surface density and specific star-formation rate is similar under the two feedback models.