I think this is where the debate is. I’m not a physicist but my understanding of the current dark matter models is that it doesn’t interact with itself in a way that could be thought of as “energy transfer” (ie. like particles that collide), but only gravitationally. This would mean there’s no real way for a dark matter “particle” to transfer momentum to another particle, and thus no real way for “heat” to exist as such.
I think this is where the debate is. I’m not a physicist but my understanding of the current dark matter models is that it doesn’t interact with itself in a way that could be thought of as “energy transfer” (ie. like particles that collide), but only gravitationally. This would mean there’s no real way for a dark matter “particle” to transfer momentum to another particle, and thus no real way for “heat” to exist as such.