Best way to find interacted pair in SubLink merger tree

Minyong Jung

5 Mar '20

Dear All,

I have difficulty in finding interacted pair in the SubLink merger tree.

A subhalo may not in a single snapshot because the subhalo is overlapped with other galaxy and the Subfind algorithm could not find it. So the SubLink merger tree jumps the snapshot if this subhalo is found in the next snapshot. I wonder that there is an efficient way to find which subhalo is interacted (or overlapped) with this subhalo.

I first try to find the nearest subhalo in before and after the missing snapshot. But this needs a long computation time to use my research.
I wonder there is another way to find the interacted pair I mentioned.

Thanks for reading my question!
Minyong.

Dylan Nelson

9 Mar '20

Hello Minyong,

I think the most likely scenario is that, for the two snapshots where the subhalo is identified (with one skipped in the middle), it resides within the same FoF halo.

One idea would be: find this FoF halo (SubhaloGrNr) before or after the skip, then find the central subhalo of it (GroupFirstSub), and use the merger tree of that subhalo to find the FoF halo ID at the skipped snapshot. Then all of the subhalos of this interaction/complexity are most likely contained within this FoF, and there are just a few, so easy to look through.

Minyong Jung

12 Mar '20

Dear Nelson,

Thanks for the insightful suggestion!
I'll try the method you said.

Dear All,

I have difficulty in finding interacted pair in the SubLink merger tree.

A subhalo may not in a single snapshot because the subhalo is overlapped with other galaxy and the Subfind algorithm could not find it. So the SubLink merger tree jumps the snapshot if this subhalo is found in the next snapshot. I wonder that there is an efficient way to find which subhalo is interacted (or overlapped) with this subhalo.

I first try to find the nearest subhalo in before and after the missing snapshot. But this needs a long computation time to use my research.

I wonder there is another way to find the interacted pair I mentioned.

Thanks for reading my question!

Minyong.

Hello Minyong,

I think the most likely scenario is that, for the two snapshots where the subhalo is identified (with one skipped in the middle), it resides within the same FoF halo.

One idea would be: find this FoF halo (

`SubhaloGrNr`

) before or after the skip, then find the central subhalo of it (`GroupFirstSub`

), and use the merger tree of that subhalo to find the FoF halo ID at the skipped snapshot. Then all of the subhalos of this interaction/complexity are most likely contained within this FoF, and there are just a few, so easy to look through.Dear Nelson,

Thanks for the insightful suggestion!

I'll try the method you said.

Minyong