Public Data Access Overview / Discussion Forum

Dear Dylan,

In TNG-Cluster, there is a zoom cluster (335 at z=0) whose star formation rate (sum of the individual star formation rates of all gas cells within R200c of this cluster) is 0. This seems to defy physical intuition.

GroupPrimaryZoomTarget = il.groupcat.loadHalos(basePath,snapNum,fields='GroupPrimaryZoomTarget')
cut_cluster = GroupPrimaryZoomTarget > 0

haloID_zoom = np.arange(len(GroupPrimaryZoomTarget),dtype=np.int32)[cut_cluster]

haloID = haloID_zoom[335]

halo_fields = il.groupcat.loadSingle(basePath, snapNum, haloID=haloID)
Group_R_Crit200 = halo_fields['Group_R_Crit200']
GroupPos = halo_fields['GroupPos']

gas_pos = il.snapshot.loadOriginalZoom(basePath, snapNum, haloID, 'gas', 'Coordinates')
SFR = il.snapshot.loadOriginalZoom(basePath, snapNum, haloID, 'gas', 'StarFormationRate')

radius = np.linalg.norm((gas_pos-GroupPos), axis=1)

cut_r200 = radius < Group_R_Crit200

np.sum(SFR[cut_r200])
0.0

Could you please check it?

Thank you and best wishes.

Similar to the TNG-Cluster catalog entries for SFR (that are meant to be the central BCGs), such values of absolute zero are possible, and should be considered as upper limits of ~1e-3 Msun/yr.

Such a threshold on the smallest representable SFR arises due to numerical resolution - see Donnari+19 (Appendix A) for discussion.

I see. Thank you so much.