It seems that not all snapshots released contain all particle fields like Potential or others.
I tried the command :
wget -nd -nc -v -e robots=off -l 1 -r -A hdf5 --content-disposition --header="API-Key: d13840959d4671f94dbe88ba0daa9f3a" "http://www.tng-project.org/api/TNG300-1/files/snapshot-98.0.hdf5?gas=Potential"
To make execute cutout queries for specific fields, but I get API response 400 Bad request.
Did I understand correctly ? or I must change my command ?
This is unfortunately true for TNG, see the beginning of the snapshot docs, where it starts "Note that, unlike in Illustris, TNG contains two different types of snapshots: 'full' and 'mini'. "