Kavli Affiliate: Andrey Kravtsov
| First 5 Authors: Yue Pan, Andrey Kravtsov, , ,
| Summary:
We investigate the impact of bursty star formation on several galaxy scaling
relations of dwarf galaxies using the $texttt{GRUMPY}$ galaxy formation model.
While this model reproduces the star formation rate (SFR)-stellar mass, stellar
mass-gas mass, and stellar mass-metallicity relations, the scatter of these
relations in the original model is smaller than observed. We explore the
effects of additional stochasticity of SFR on the scaling relations using a
model that reproduces the level of SFR burstiness in high-resolution zoom-in
simulations. The additional SFR stochasticity increases the scatter in the
SFR-stellar mass relation to a level similar to that exhibited by most nearby
dwarf galaxies. The most extreme observed starbursting dwarfs, however, require
higher levels of SFR stochasticity. We find that bursty star formation
increases the scatter in the colour-magnitude distribution (CMD) for brighter
dwarf galaxies $(M_V < -12)$ to the observed level, but not for fainter ones
for which scatter remains significantly smaller than observed. This is due to
the predominant old stellar populations in these faint model galaxies and their
generally declining SFR over the past 10 Gyrs, rather than quenching caused by
reionization. We examine the possibility that the colour scatter is due to
scatter in metallicity, but show that the level of scatter required leads to an
overestimation of scatter in the metallicity-mass relation. This illustrates
that the scatter of observed scaling relations in the dwarf galaxy regime
represents a powerful constraint on the properties of their star formation.
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