> There's no reason for any dark matter to be distributed in a halo. This was one of the more eye-catching statements in this thread. To be blunt, you're wron

> There's no reason for any dark matter to be distributed in a halo. This was one of the more eye-catching statements in this thread. To be blunt, you're wrong. A straightforward and almost inevitable dynamical explanation has been available (and explored in ever greater detail) since at least the mid-1990s, driven in part by the Saskatoon experiment and subsequently supported by BOOMERanG's observation of the first acoustic peak, and many others lines of evidence since then (see [1] for a less-heavy explanation than what follows). You may wish to check this chapter from a forthcoming graduate-level textbook in galactic dynamics from well-known galactic astrophysicist Jo Bovy <http://astro.utoronto.ca/~bovy/ http://astro.utoronto.ca/~bovy/>, which you can read for free at his site: <https://galaxiesbook.org/chapters/IV-01.-Formation-DM-Halos.html https://galaxiesbook.org/chapters/IV-01.-Formation-DM-Halos....>. There are of course other already-completed textbooks. For example, one can find an excellent pedagogic (if advanced) treatment of primordial Gaussian Random Fields[2] as applied to halo formation in chapter 7 of Mo, van den Bosch & White (2010) <https://www.cambridge.org/core/books/abs/galaxy-formation-and-evolution/formation-and-structure-of-dark-matter-halos/36C7784367F6CC9B5C072F9950B841A6 https://www.cambridge.org/core/books/abs/galaxy-formation-an...> (you can find the chapter on scy hob via its DOI if you don't have institutional or otherwise affordable access). - -- [1] https://lweb.cfa.harvard.edu/~deisenst/acousticpeak/acoustic_physics.html https://lweb.cfa.harvard.edu/~deisenst/acousticpeak/acoustic... from <https://astronomy.fas.harvard.edu/people/daniel-eisenstein https://astronomy.fas.harvard.edu/people/daniel-eisenstein> [2] If you're more visually inclined and can't find the illustrated version of Mo et al., see the diagrams on p.3-5 of this slide deck on GRFs <https://www.astro.rug.nl/~weygaert/tim1publication/lss2016/lss2016.gaussian_fields.handout2.pdf https://www.astro.rug.nl/~weygaert/tim1publication/lss2016/l...> from Rien van de Weijgaert of the Kapteyn Institute at the University of Groningen.