Kavli Affiliate: Andrey Kravtsov
| First 5 Authors: Andrey Kravtsov, , , ,
| Summary:
I compare the dark matter content within stellar half-mass radius expected in
a $Lambda$CDM-based galaxy formation model with existing observational
estimates for the observed dwarf satellites of the Milky Way and ultra-diffuse
galaxies (UDGs). The model reproduces the main properties and scaling relations
of dwarf galaxies, in particular their stellar mass-size relation. I show that
the model also reproduces the relation between the dark matter mass within the
half-mass radius, $M_{rm dm}(<r_{1/2})$, and stellar mass exhibited by the
observed dwarf galaxies. The scatter in the $M_{rm dm}(<r_{1/2})-M_star$
relation is driven primarily by the broad range of sizes of galaxies of a given
stellar mass. I also show the $M_{rm dm}(<r_{1/2})$ of UDGs are within the
range expected in the model for their stellar mass, but they tend to lie above
the median relation due to their large sizes. The upper limits on $M_{rm
dm}(<r_{1/2})$ for the dark matter deficient UDGs are also consistent with the
range of dark matter masses expected in the model. The most dark
matter-deficient galaxies of a given size correspond to halos with the smallest
concentrations and the largest ratios of $M_star/M_{rm 200c}$. Conversely,
the most dark matter-dominated galaxies are hosted by the highest concentration
halos with the smallest $M_star/M_{rm 200c}$ ratios. Results presented in
this paper indicate that dark matter content of observed UDGs may represent a
tail of the expected dark matter profiles, especially if the effect of feedback
on these profiles is taken into account. Nevertheless, the unusually rich GC
populations in some UDG galaxies do indicate unusual evolution. Our results
simply indicate that with the current accuracy of the velocity dispersion
measurements their $M_{rm dm}(<r_{1/2})$ are consistent with the range
expected in the $Lambda$CDM model.
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