MUFASA: Galaxy Formation Simulations With Meshless Hydrodynamics

TL;DR

MUFASA presents advanced cosmological galaxy formation simulations using meshless hydrodynamics, accurately matching observed galaxy stellar mass functions and star formation histories across cosmic time, with insights into feedback and resolution effects.

Contribution

This work introduces the MUFASA simulation suite employing meshless finite mass hydrodynamics, achieving unprecedented agreement with observed galaxy properties and analyzing methodological impacts.

Findings

GSMF matches observations from z=4 to 0 within <1.2sigma.

Cosmic star formation history aligns with data, showing downsizing.

Hydrodynamics method influences GSMF by a factor of two.

Abstract

We present the MUFASA suite of cosmological hydrodynamic simulations, which employs the GIZMO meshless finite mass (MFM) code including H2-based star formation, nine-element chemical evolution, two-phase kinetic outflows following scalings from the Feedback in Realistic Environments zoom simulations, and evolving halo mass-based quenching. Our fiducial (50 Mpc/h)^3 volume is evolved to z=0 with a quarter billion particles, The predicted galaxy stellar mass functions (GSMF) reproduce observations from z=4-0 to <1.2sigma in cosmic variance, providing an unprecedented match to this key diagnostic. The cosmic star formation history and stellar mass growth show general agreement with data, with a strong archaeological downsizing trend such that dwarf galaxies form the majority of their stars after z~1. We run 25 Mpc/h and 12.5 Mpc/h volumes to z=2 with identical feedback prescriptions, the latter resolving all hydrogen-cooling halos, and the three runs display fair resolution convergence. The specific star formation rates broadly agree with data at z=0, but are underpredicted at z~2 by a factor of three, re-emphasizing a longstanding puzzle in galaxy evolution models. We compare runs using MFM and two flavours of Smoothed Particle Hydrodynamics, and show that the GSMF is sensitive to hydrodynamics methodology at the ~x2 level, which is sub-dominant to choices for parameterising feedback.