Loading the main descendant branch

Qin PENG
  • 25 Dec '24

Hi Dylan,

I want to load the main descendant branches of some subhaloes in TNG100-1. I used the loadTree function of illustris_python package and set the option onlyMDB=True, but I get several branches not a single branch. The results are as below,

tree = il.sublink.loadTree(basePath=basePath,snapNum=80,id=1,fields=['SnapNum','SubfindID'],onlyMDB=True)
tree
{'count': 67358,
 'SnapNum': array([99, 98, 97, ..., 82, 81, 80], dtype=int16),
 'SubfindID': array([17187, 17210, 17030, ..., 12244, 12127,     1], dtype=int32)}

len(tree['SnapNum'])
67358

Could you tell me why it is?
Thank you very much.

All the best and merry Christmas.

Dylan Nelson
  • 26 Dec '24

I suspect this is as described in the documentation:

"If onlyMDB, then only the 'main descendant branch' is loaded, which is a single
tree branch if and only if this subhalo lies on the MPB of its z=0 descendant, while if not,
then the return is the full descendant merger tree which contains as its first entry the z=0
descendant of this subhalo."

If you want a different behavior, or to load other data, then you can extract it from the full trees.

Qin PENG
  • 27 Dec '24

Thank you. The MPB of this subhalo has no descendant at z=0.

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