Bound Domains

Abstract How much energy is required to unbind baryons from the cosmological structures that originally bind them? This tutorial article explains why trying to answer this question using just a halo model can be misleading. Instead, it recommends parsing the universe into “bound domains,” which are the gravitationally bound structures that ultimately become widely separated islands as the universe evolves. It explains why a bound domain’s potential well was about as deep ∼1 Gyr after the Big Bang as it is now, and it outlines how future research might take advantage of a bound-domain approach to make progress on some open questions about the baryon distributions in and around galaxy groups and clusters.