Constraining stellar assembly and AGN feedback at the peak epoch of star formation

TL;DR

This study uses hydrodynamic simulations to investigate stellar assembly and AGN feedback during the peak epoch of star formation (z=1-2), comparing results with observations to understand galaxy evolution.

Contribution

It introduces a detailed AGN feedback model in simulations and compares predicted galaxy colours and masses with observations at z=1-2.

Findings

AGN feedback broadens galaxy colour agreement with observations

Simulated massive galaxies match observed stellar mass functions

Residual star formation in models exceeds observational estimates

Abstract

We study stellar assembly and feedback from active galactic nuclei (AGN) around the epoch of peak star formation (1<z<2), by comparing hydrodynamic simulations to rest-frame UV-optical galaxy colours from the Wide Field Camera 3 (WFC3) Early-Release Science (ERS) Programme. Our Adaptive Mesh Refinement simulations include metal-dependent radiative cooling, star formation, kinetic outflows due to supernova explosions, and feedback from supermassive black holes. Our model assumes that when gas accretes onto black holes, a fraction of the energy is used to form either thermal winds or sub-relativistic momentum-imparting collimated jets, depending on the accretion rate. We find that the predicted rest-frame UV-optical colours of galaxies in the model that includes AGN feedback is in broad agreement with the observed colours of the WFC3 ERS sample at 1<z<2. The predicted number of massive galaxies also matches well with observations in this redshift range. However, the massive galaxies are predicted to show higher levels of residual star formation activity than the observational estimates, suggesting the need for further suppression of star formation without significantly altering the stellar mass function. We discuss possible improvements, involving faster stellar assembly through enhanced star formation during galaxy mergers while star formation at the peak epoch is still modulated by the AGN feedback.