Into Darkness: what the MARVEL-ous dwarf simulations can tell us about the physics of first star formation
Abstract
The existence of ultra-faint dwarf (UFD) galaxies highlights the need to push our theoretical understanding of galaxies to extremely low mass. Using two identical volumes from the high-resolution, fully cosmological MARVEL-ous dwarf galaxy simulation suite, we examine the formation of dwarf galaxies and their UFD satellites. The volumes have identical initial conditions, and vary only in how they form stars: one uses a temperature-density threshold for star formation in combination with metal line cooling, while the other replaces the temperature-density threshold with an H$_{2}$-based sub-grid star formation model. We find that the total number of dwarf galaxies that form is different by a factor of 2 between the two runs, but most of these are satellites, leading to a factor of 5 difference in the number of luminous UFD companions around more massive, isolated dwarfs. These results emphasize that predictions for UFD properties made using hydrodynamic simulations, in particular regarding the frequency of satellites around dwarf galaxies, the slope of the stellar mass function at low masses, as well as the properties of ultra-faint galaxies occupying the smallest halos, are extremely sensitive to the subgrid physics of star formation contained within the simulation.
- Publication:
-
American Astronomical Society Meeting Abstracts #233
- Pub Date:
- January 2019
- Bibcode:
- 2019AAS...23335121M