Questions on matching a specific halo and its mock images.

Nan Li
  • 1
  • 20 Feb '16

Hi there,

I am writing to ask some questions on looking for the mock image for a given halo. I am using sunpy to extract fits files from illustris database, so as is shown in the instruction, I need to input the subhaloID to specify the image. Say here is a Halo (haloID = 2), how could I find the FOF image of this halo? I assume that the subhaloID of the this image should be the subhaloID of the first subhalo of this halo, so I use the code below to read out the subhaloID :

GroupFirstSub = il.groupcat.loadHalos(basePath,135,fields=['GroupFirstSub'])

When HaloID=2, GroupFirstSub=1030. But sunpy can not find the image of subhalo-1030. I think I must misunderstand something. Could you please instruct me to figure it out?

PS: One more native question, "the SubfindDensity in dm class shows the the local total comoving mass density", the "total" means all the components ( dm+stars/wind+gas+.....), right? If I want to calculate the total density map of a halo, I can just load in the SubfindDensity then perform linear interpolation, do I understand right?

If you could help me out about these questions, I really appreciate it. Thank you so much!

All the best, Nan Li

Dylan Nelson
  • 29 Feb '16

Hi Nan Li,

  • The mock images only exist for Illustris-1 (the highest resolution), and not for Illustris-2 or Illustris-3. It seems you were looking at Illustris-3, where HaloID=2 has GroupFirstSub=1030. In Illustris-1, Halo=2 has GroupFirstSub=30430, which you can view here in the galaxy observatory.
  • Yes 'total' does mean all components. If you are wanting to make a 2D image of total density, I suppose this might work, although I've never tried this. You will still only have these density values at the positions of the individual particles, so you will need to distribute/smooth them onto a 2D image grid.

Let me know if I can clarify anything further

Nan Li
  • 29 Feb '16

Hi Dylan,

Thank you so much for your reply, it is pretty clear to me now, and extremely helpful. really appreciate it.

All the best, Nan Li

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