Much work regarding the formation and early evolution of galaxies seems to assume that galaxies form based on clumps dark matter.
The following observations indicate that some galaxies started with and/or have little or no dark matter.
- R. Genzel, N. M. Forster Schreiber, H. Ubler, et al. Strongly baryon-dominated disk galaxies at the peak of galaxy formation ten billion years ago. Nature, 543(7645):397_401, March 2017.
- Pieter van Dokkum, Shany Danieli, Yotam Cohen, et al. A galaxy lacking dark matter. Nature, 555(7698):629_632, March 2018.
- Pieter van Dokkum, Shany Danieli, Roberto Abraham, et al. A second galaxy missing dark matter in the NGC 1052 group. ApJ Letters, 874(1):L5, March 2019.
Possibly, the following observations point to possibilities that some galaxies (that start with little or no dark matter) accumulate dark matter.
- Peter Behroozi, Risa Wechsler, Andrew Hearin, and Charlie Conroy. UniverseMachine: The correlation between galaxy growth and dark matter halo assembly from z=0-10. June 2018. (See, for example, figure 7.)
Possibly, given observations noted above, the following observations also point to the notion that some galaxies (that start with little or no dark matter) accumulate dark matter.
- J. Jimenez-Vicente, E. Mediavilla, C. S. Kochanek, and J. A. Munoz. Dark matter mass fraction in lens galaxies: New estimates from microlensing. The Astrophysical Journal, 799(2):149, 2015.
For purposes of discussion, perhaps it would be best to ignore "dark matter galaxies" (such as Dragonfly 44), collisions between galaxies, and so forth. To the extent one thinks of results that people generate by simulations, perhaps it would be best to note (and try to support by results of observations) assumptions underlying the simulations.