Surveying dark matter deficient galaxies ( those with dark matter mass to stellar mass ratio M _ { dm } / M _ { star } < 1 ) in the Illustris simulation of structure formation in the flat- \Lambda CDM cosmogony , we find M _ { star } \approx 2 \times 10 ^ { 8 } M _ { \sun } galaxies that have properties similar to those ascribed by \citet vanDokkumetal2018a to the ultra-diffuse galaxy NGC1052-DF2 .
The Illustris simulation also contains more luminous dark matter deficient galaxies .
Illustris galaxy subhalo 476171 is a particularly interesting outlier , a massive and very compact galaxy with M _ { star } \approx 9 \times 10 ^ { 10 } M _ { \sun } and M _ { dm } / M _ { star } \approx 0.1 and a half-stellar-mass radius of \approx 2 kpc .
If the Illustris simulation and the \Lambda CDM model are accurate , there are a significant number of dark matter deficient galaxies , including massive luminous compact ones .
It will be interesting to observationally discover these galaxies , and to also more clearly understand how they formed , as they are likely to provide new insight into and constraints on models of structure formation and the nature of dark matter .