Denition. For halos that continuously amass matter, material close to its rst apocenter piles up next to the edge of the multi-stream region, where collapsed and infalling material meets (Xxxxxxxx et al., 2014). A sudden drop in density, i.e. the feature visible in the proles of Figure 4.1, is associated with this process. This intuitive picture leads to three characterizations of the splashback radius, de- pending on the approach used to measure or model it:
