# Tutorial on designing your own model of the galaxy-halo connection¶

By following this tutorial, you will learn how to use the Halotools framework to design your own model of the galaxy-halo connection. The empirical_models factories come in two different types, HOD-style models and subhalo-based models. In HOD-style models, there is no connection between the abundance of satellite galaxies in a host halo and the number of subhalos in that host halo. In these models, satellite abundance in each halo is determined by a Monte Carlo realization of some analytical model. Examples of this approach to the galaxy-halo connection include the HOD, CLF and CSMF, as well as extensions of these that include additional features such as color-dependence.

By contrast, in subhalo-based models there is a one-to-one correspondence between subhalos and satellite galaxies. In these models, every host halo in the simulation is connected to a central galaxy, and every subhalo is connected a satellite. Examples include traditional abundance matching, age matching, and parameterized stellar-to-halo mass models such as Behroozi et al. (2010) and Moster et al. (2010).

The implementation of these two different approaches to the galaxy-halo connection is sufficiently different that the modeling for each is done by a separate factory. The HodModelFactory builds HOD-style models, and the SubhaloModelFactory builds subhalo-based models. Choose which class of model you are most interested in and follow the link to the appropriate tutorial: