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.