| variable name | data type | meaning |
|---|---|---|
| x,y,z | double | position of particle |
| w | float | speed of particle |
| mass | float | mass of particle |
| id | long | particle’s unique id |
| dm | long | dark matter |
| star | long | a star particle |
| ap | float | particle formation time |
| zp | float | particle metallicity |