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pynbody / tangos

The Agile Numerical Galaxy Organisation System
BSD 3-Clause "New" or "Revised" License
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Is it possible to calculate quantities for trackers that depend on their host halo properties? #195

Open Martin-Rey opened 2 years ago

Martin-Rey commented 2 years ago

Hi,

I have a question on the best-use of trackers and whether it is possible to compute properties for them that depends on other halo properties.

For example, I have identified a stellar sub-population with specific kinematics at z=0 that I am interested in. I then defined a tracker object to identify it over the galaxy's history, and would like to compute its phase space over time (velocities, radii, orbital energy etc).

This works very well for mass, but a lot of quantities like velocities are frame-dependent and most meaningful when defined against the entire stellar population of the galaxy. That means accessing e.g. the shrink_center and faceon orientation of the total host halo, rather than calculating it from the particles solely available inside the tracker.

Is there a way to natively link trackers to a parent halo (maybe using the link infrastructure) , and to access the host properties to define any subsequent trackers' properties?

Martin

apontzen commented 2 years ago

I don’t believe this is currently supported, but the way I’d recommend doing it is to extend the idea of crosslinking to be able to identify tracker host halos through the particles in common. It might be worth checking how black holes find their host_halo link, though I suspect it’s simpler in that case as it’s only one particle.