Dwarf diversity in $\Lambda$CDM with baryons

Abstract

Observed rotation curves of dwarf galaxies exhibit significant diversity at fixed halo mass, challenging galaxy formation within the Cold Dark Matter (CDM) model. Previous cosmological galaxy formation simulations with baryonic physics fail to reproduce the full diversity of rotation curves, suggesting either that there is a flaw in baryonic feedback models, or that an alternative to CDM must be invoked. In this work, we use the Marvelous Massive Dwarf zoom-in simulations, a suite of high-resolution dwarf simulations with $M_{200}~\sim 10^{10}-10^{11}$ ${\rm M}_{\odot}$ and $M_{*}\sim 10^{7}-10^{9}$ ${\rm M}_{\odot}$, designed to target the mass range where galaxy rotation curve diversity is maximized, i.e., between $V_{\rm max} \sim 70-100~ {\rm km/s}$. We add to this a set of low-mass galaxies from the Marvel Dwarf Zoom Volumes to extend the galaxy mass range to lower values. Our fiducial star formation and feedback models produce simulated dwarfs with a broader range of rotation curve shapes, similar to observations. These are the first simulations that can both create dark matter cores via baryonic feedback, reproducing the slower rising rotation curves, while also allowing for compact galaxies and steeply rising rotation curves. Our simulated dwarfs also reproduce the observed size$-M_*$ relation, including scatter, producing both extended and compact dwarfs for the first time in simulated field dwarfs. We explore star formation and feedback models and conclude that previous simulations may have had feedback that was too strong to produce compact dwarfs.