Looking for disk to non-disk transitions in TNG50

Pablo Galan de Anta

Hi,

I'm looking for non-disk (at z = 0) subhaloes in two haloes of TNG50 which could have been disks in the past. To achieve this, I initially identify non-diks by using the circularity parameter CircAbove07Frac in the suplementary data catalogs at z=0. Then, I consider all those subhaloes with circulatiry fraction < 0.4 as non-disks. For the two identified haloes, by using this method I found 138 non-disks in one halo and 78 (both at z = 0) in the other one. Also, I'm neglecting all those subhaloes with M<1.0e8 solar masses. With all these I got the IDs of all these subhalos, because later on I like to use these IDs to follow the circularity of these non-disks backward in time. In essence, I'm using the IDs of the identified non-disk subhaloes in these two haloes to following the evolution of the circularity of these subhaloes back in time, as I consider that a non-disk was a disk when CircAbove07Frac > 0.4 for a specific redshift. The problem appears when I do this experiment I found that only 12 subhaloes were disks in the past for the halo with 138 non-disks at redshift = 0, and 1 non-disk subhalo for the halo with 78 non-disks at redshift = 0. This makes no sense to me as when I analyse the total number of discs vs redshift for the two haloes the number of disks I get is completely different (see the figure attached in the link).
https://drive.google.com/file/d/1ouoMlljnFgGckSz4AOIGpj8SvXnLfx4M/view?usp=sharing

Am I using the wrong parameter to estimate the 'diskiness' of a subhalo or am I understanding something in the wrong way?

Thanks in advance,
Pablo

Dylan Nelson
  • 4 Feb

Hi Pablo,

The approach you describe seems ok, i.e. following the CircAbove07Frac backwards along the main progenitor branch of satellite galaxies which are non-disky at z=0. Afraid I can't suggest much other than to double-check your codes for possible issues.

Pablo Galan de Anta
  • 4 Feb

Thanks Dylan!

I will take a look again to double-check.

Cheers,
Pablo

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