We have a question about the Nelson et al 2024 paper on the intracluster medium's properties in the TNG-Cluster simulation. Specifically, in Fig. 7, we did not see any TNG-Cluster z=0 halos with M_(gas, 500c) / M_500c < 0.10. However, if we do a simple calculation of (M_gas / M_500c) on the z=0 halos, which gives an upper bound on the gas fraction within R_500c, we find many with gas fraction below 0.10. For example, halo 17469184 has GroupMassType/0 = 1.392 x 10^13 Msun and Mcrit500 = 4.1195 x 10^14 Msun, so its R500c gas fraction should be lower than 0.04, but we do not find this data point on Fig. 7.
upper bound set by M_gas / M_500c:
We also tried to calculate M_(gas, 500c) / M_500c directly via
In the TNG-Cluster Catalog, you will find fgas_r500. These are the values used in Nelson+24. The definition of this is fgas_r500 = Mgas_r500 / Mhalo_r500 where the denominator is the Group_M_Crit500 (i.e. total mass spherical-overdensity value) from the group catalogs.
For reference, I checked halo 18083780 (at z=0) and found 3082613 (of 5125570 in the FoF) gas cells within r500c. They have a mass sum of 13.578 (log msun). For m500c of 14.413 (log msun), this gives fgas = 0.146, as in the catalog, but not in your plot (which has ~0.04). Perhaps there is some minor bug in your code?
The Mgas / Mhalo_r500 upper bound on fgas_r500 is particularly intriguing for us as it can be directly obtained by dividing two values in the halo info page without writing any code. Do you mind checking halo 18083789?
Dylan Nelson
12h
This seems like the problem, or at least a problem.
Halo 18083780 is a primary zoom target of TNG-Cluster (snapshot 99), i.e. it can be analyzed.
Halo 18083789 is not - this is not a valid halo to consider.
Odd that the numbers are so similar, perhaps it indicates a minor bug somewhere?
Please see the documentation e.g. about GroupPrimaryZoomTarget.
I see, I think the GroupPrimaryZoomTarget flag is what we are missing. We had adapted the example script meant for TNG-100 to download the TNG-Cluster halos, which looks at the parent halos of the 100 most massive subhalos in TNG-Cluster, but I suppose there are some non-zoomed halos in there -- we did not check the GroupPrimaryZoomTarget flag. I think we will instead download the halos directly from TNG-Cluster Catalog. Thank you so much!
We have a question about the Nelson et al 2024 paper on the intracluster medium's properties in the TNG-Cluster simulation. Specifically, in Fig. 7, we did not see any TNG-Cluster z=0 halos with M_(gas, 500c) / M_500c < 0.10. However, if we do a simple calculation of (M_gas / M_500c) on the z=0 halos, which gives an upper bound on the gas fraction within R_500c, we find many with gas fraction below 0.10. For example, halo 17469184 has GroupMassType/0 = 1.392 x 10^13 Msun and Mcrit500 = 4.1195 x 10^14 Msun, so its R500c gas fraction should be lower than 0.04, but we do not find this data point on Fig. 7.
upper bound set by M_gas / M_500c:
We also tried to calculate M_(gas, 500c) / M_500c directly via
which gave this plot. We do see a lot of halos with fgas ~ 0.14, but there are still many with abnormally low fgas.
We are wondering how fgas was calculated in the Nelson et al 2024 paper, and if our calculations might be incorrect?
Thank you!
In the TNG-Cluster Catalog, you will find
fgas_r500. These are the values used in Nelson+24. The definition of this isfgas_r500 = Mgas_r500 / Mhalo_r500where the denominator is theGroup_M_Crit500(i.e. total mass spherical-overdensity value) from the group catalogs.For reference, I checked halo
18083780(at z=0) and found 3082613 (of 5125570 in the FoF) gas cells within r500c. They have a mass sum of 13.578 (log msun). For m500c of 14.413 (log msun), this gives fgas = 0.146, as in the catalog, but not in your plot (which has ~0.04). Perhaps there is some minor bug in your code?Hi Dylan,
Thanks for checking! I think there was a typo -- our plot shows
18083789, not18083780? Per our code,18083780hasNgas_r500 / Ngas = 3083612 / 5125570,Mgas_r500 / Mhalo_r500 = 0.14618<Mgas / Mhalo_r500 = 0.243, agreeing with you, while18083789hasNgas_r500 / Ngas = 43350 / 47739,Mgas_r500 / Mhalo_r500 = 0.03888<Mgas / Mhalo_r500 = 0.039The
Mgas / Mhalo_r500upper bound onfgas_r500is particularly intriguing for us as it can be directly obtained by dividing two values in the halo info page without writing any code. Do you mind checking halo18083789?This seems like the problem, or at least a problem.
Halo 18083780 is a primary zoom target of TNG-Cluster (snapshot 99), i.e. it can be analyzed.
Halo 18083789 is not - this is not a valid halo to consider.
Odd that the numbers are so similar, perhaps it indicates a minor bug somewhere?
Please see the documentation e.g. about
GroupPrimaryZoomTarget.I see, I think the GroupPrimaryZoomTarget flag is what we are missing. We had adapted the example script meant for TNG-100 to download the TNG-Cluster halos, which looks at the parent halos of the 100 most massive subhalos in TNG-Cluster, but I suppose there are some non-zoomed halos in there -- we did not check the GroupPrimaryZoomTarget flag. I think we will instead download the halos directly from TNG-Cluster Catalog. Thank you so much!