Making Galaxies in a Cosmological Context: The Need for Early Stellar Feedback

TL;DR

This paper presents the MaGICC simulation program, demonstrating that early stellar feedback combined with supernova feedback produces more realistic galaxy formation models that align with observational data across cosmic time.

Contribution

The study introduces a novel implementation of early stellar feedback in galaxy simulations, improving the match to observed galaxy properties and evolution.

Findings

Early stellar feedback heats gas to >10^6 K, influencing star formation.

Galaxies with combined feedback have realistic rotation curves and surface brightness profiles.

The inside-out formation process matches observed galaxy growth patterns.

Abstract

We introduce the Making Galaxies in a Cosmological Context (MaGICC) program of smoothed particle hydrodynamics (SPH) simulations. We describe a parameter study of galaxy formation simulations of an L* galaxy that uses early stellar feedback combined with supernova feedback to match the stellar mass--halo mass relationship. While supernova feedback alone can reduce star formation enough to match the stellar mass--halo mass relationship, the galaxy forms too many stars before z=2 to match the evolution seen using abundance matching. Our early stellar feedback is purely thermal and thus operates like a UV ionization source as well as providing some additional pressure from the radiation of massive, young stars. The early feedback heats gas to >10^6 K before cooling to 10^4 K. The pressure from this hot gas creates a more extended disk and prevents more star formation prior to z=1 than supernovae feedback alone. The resulting disk galaxy has a flat rotation curve, an exponential surface brightness profile, and matches a wide range of disk scaling relationships. The disk forms from the inside-out with an increasing exponential scale length as the galaxy evolves. Overall, early stellar feedback helps to simulate galaxies that match observational results at low and high redshifts.