I'm tracking the merger trees of many galaxies, from TNG50, and saving data from those mergers that originate from a cosmic source. To do this, I'm using the "SubhaloFlag" for each NextProgenitor.
Additionally, I would like to recover the orbits of those progenitors.
The problem arises when I notice that some NextProgenitor only exists during 1 or 2 snapshot but their SubhaloFlag is set to True.
As an example, for the galaxy with SubfindID = 557721, I printed the snapshots in which its NextProgenitors (with StellarMass > 0) exist, along with their corresponding SubhaloFlag values.
The first NextProgenitors Snaps shown only exist in snap 71 yet it is marked as cosmic origin.
Can I rely on these NextProgenitors as actual subhalos with a cosmic origin? Or is there something else happening in these cases?
Dylan Nelson
7 Mar
The SubhaloFlag is a good starting point, but perhaps you want to go further (i.e. be more restrictive).
It sounds like you are interested in mergers, where the secondary (incoming) subhalo started outside the host halo, accreted across the virial radius, and perhaps eventually merged. You could make a criterion to identify the orbits of such events, requiring that those orbits cross the virial radius (R200c). If they never cross, i.e. were always inside the host, then it probably isn't the type of event you are interested to analyze.
Hi !!!
I'm tracking the merger trees of many galaxies, from TNG50, and saving data from those mergers that originate from a cosmic source. To do this, I'm using the "SubhaloFlag" for each NextProgenitor.
Additionally, I would like to recover the orbits of those progenitors.
The problem arises when I notice that some NextProgenitor only exists during 1 or 2 snapshot but their SubhaloFlag is set to True.
As an example, for the galaxy with SubfindID = 557721, I printed the snapshots in which its NextProgenitors (with StellarMass > 0) exist, along with their corresponding SubhaloFlag values.
The first NextProgenitors Snaps shown only exist in snap 71 yet it is marked as cosmic origin.
Can I rely on these NextProgenitors as actual subhalos with a cosmic origin? Or is there something else happening in these cases?
The
SubhaloFlagis a good starting point, but perhaps you want to go further (i.e. be more restrictive).It sounds like you are interested in mergers, where the secondary (incoming) subhalo started outside the host halo, accreted across the virial radius, and perhaps eventually merged. You could make a criterion to identify the orbits of such events, requiring that those orbits cross the virial radius (R200c). If they never cross, i.e. were always inside the host, then it probably isn't the type of event you are interested to analyze.