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duncandc / intrinsic_alignments

project to measure and model the intrinsic alignments of galaxies in both observations and simulations
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code up a satellite alignment model that works with SubhaloPhaseSpace() #10

Closed duncandc closed 6 years ago

duncandc commented 6 years ago

It would be useful for the satellite alignment models to work with the halotools SubhaloPhaseSpace models. This would be good to check for the effects of the NFW phase space model on alignments.

duncandc commented 6 years ago

I suspect this would be particularly interesting to @ssamuroff and @aphearin

duncandc commented 6 years ago

well, that was easy. Nothing needed to be changed. The example is now included in the ia model demo notebook.

aphearin commented 6 years ago

Ha! Yes, you beat me to it. This is already supported if you just carry over the necessary keys.

Note that the existing infrastructure also supports transferring over subhalo orientations relative to the parent halo eigenvector and/or relative to the original radial position vector. Doing things this way, these vectors could then just be added to the corresponding vector of the HOD-assigned halo, which will do a better job of preserving shape-position correlations.

Another approach would be to populate systems of subhalos together, matched on richness and host mass, rather than drawing one-by-one from the subhalo table. That would do more to preserve the impact of satellite planarity on the one-halo term. To do this, I think the GalSampler kernels are the ones that are needed, rather than the ones in SubhaloPhaseSpace. Those would be easy to adapt for this purpose if you want to go down that road.