Should I contact a Caterpillar core member to use the data?
For using the merger tree and halo catalogs, no, you now no longer need to contact a core member. That being said however, we do encourage you to contact a core member as certain efforts may have been undertaken by groups either internally and externally and we can put you in direct contact with them to coordinate efforts.
Why aren't the particle snapshots public?
This is primarily because unlink many other simulation suites, the particle resolution and snapshot resolution make it expensive to 100% host on public servers (e.g. Google Cloud Platform). Should you want more than the z = 0 snapshot, please get in touch so we can find the best path forward for your project.