When downloading a cutout of a halo in TNG-Cluster using the API, my understanding is that the cutout captures the "inner fuzz" in addition to the subhalos of the FoF halo, but does not include the "outer fuzz". I believe this is the case because I am seeing a very steep drop-off in baryon density beyond R200c in the halo cutout. Is this the correct interpretation, and is it possible to download the outer fuzz without downloading the entire last chunk of the snapshot?
Thanks!
Dylan Nelson
17 Mar
That is correct, the FoF-scope cutouts include the inner fuzz by definition.
Note that (i) the outer fuzz is not only in the last snapshot chunk, it definitely spans more than one chunk, (ii) the outer fuzz is very large. As a rough approximation, only half of all matter is inside halos by z=0, so the outer fuzz could be around ~50% of the entire snapshot.
You can obtain the starting index of the outer fuzz by starting from the particle offset (by type) of the last halo (plus its length). This will tell you the first chunk containing fuzz. You can then either analyze (in the Lab) or download (via the API) this subset of the particles.
Dylan Nelson
17 Mar
My comments above are in general, i.e. for the TNG boxes.
For TNG-Cluster, you are correct that since there are exactly two chunks per original zoom simulation (the first containing all halos), then the second chunk contains all outer fuzz. Because this is a zoom simulation, the outer fuzz is not enormous, and would be rather simple to just download/look at this chunk.
When downloading a cutout of a halo in TNG-Cluster using the API, my understanding is that the cutout captures the "inner fuzz" in addition to the subhalos of the FoF halo, but does not include the "outer fuzz". I believe this is the case because I am seeing a very steep drop-off in baryon density beyond R200c in the halo cutout. Is this the correct interpretation, and is it possible to download the outer fuzz without downloading the entire last chunk of the snapshot?
Thanks!
That is correct, the FoF-scope cutouts include the inner fuzz by definition.
Note that (i) the outer fuzz is not only in the last snapshot chunk, it definitely spans more than one chunk, (ii) the outer fuzz is very large. As a rough approximation, only half of all matter is inside halos by z=0, so the outer fuzz could be around ~50% of the entire snapshot.
You can obtain the starting index of the outer fuzz by starting from the particle offset (by type) of the last halo (plus its length). This will tell you the first chunk containing fuzz. You can then either analyze (in the Lab) or download (via the API) this subset of the particles.
My comments above are in general, i.e. for the TNG boxes.
For TNG-Cluster, you are correct that since there are exactly two chunks per original zoom simulation (the first containing all halos), then the second chunk contains all outer fuzz. Because this is a zoom simulation, the outer fuzz is not enormous, and would be rather simple to just download/look at this chunk.