For much of its development history, yt took the approach of bundling as many analysis modules as possible in the primary repository.
This provided the advantage of having all work be centralized, and ensuring that each download or installation of yt was a fully-featured system for analyzing a large swath of data, but it brought with it the development overhead of the entire yt package for what in many cases were isolated pieces of functionality with separable responsibilities.
As a result of the slowing in speed of development as a result of review requirements (and limited personnel to conduct those reviews), some of the analysis modules that were bundled with yt have been "spun out" into their own repository, yt_astro_analysis.
This repository, which is developed, released and installed separately from yt, includes modules for cosmological observation (upon which Triden, which is discussed in @sec:trident, is based), dark matter halo finding and analysis, tools for interacting with position-position-velocity cubes, and a system for exporting from yt to RADMC-3D [@ascl:1202.015].