Public Data Access Overview / Discussion Forum

I am trying to determine the time at which mergers take place using the merger trees for the TNG100-3 data. However, from the documentation I can't find any other way to determine the cosmic scale factor (or redshift would work) of a snapshot other than using il.groupcat.loadHeader(basePath, SnapNum)['Time'] which requires you to have the group catalogue files downloaded for that specific snapshot right?

Any help would be much appreciated.

• James

Hi James,

You could (i) grab this from the table on the download page for each simulation, or (ii) use the Lab service and write a few lines of python to dump this to a text file.

This was pretty quick, so in fact I just put this below here, which is valid for all TNG50, TNG100, and TNG300 simulation runs:

0 0.04751385731723353 20.046492
1 0.06254232185960246 14.989173
2 0.07704033726307313 11.980213
3 0.0835028220872966 10.975643
4 0.09093727638618128 9.996591
5 0.09625777625677749 9.388771
6 0.09997660230807648 9.00234
7 0.10582597113143531 8.449476
8 0.11096103385965722 8.012173
9 0.11634526374841153 7.595107
10 0.12141409319190727 7.236276
11 0.1249154186751753 7.005417
12 0.13348287593567293 6.4915977
13 0.1426379400030906 6.0107574
14 0.1460576011655903 5.846614
15 0.1531448539427487 5.5297656
16 0.16057599188495353 5.227581
17 0.16677970069945375 4.9959335
18 0.17653753086762708 4.664518
19 0.18422877077628394 4.428034
20 0.1931682173348771 4.176835
21 0.19968270176155556 4.007945
22 0.21236948944535833 3.7087743
23 0.22267442866700524 3.4908614
24 0.23347939860645056 3.2830331
25 0.2494928417280737 3.008131
26 0.2566876704050959 2.895785
27 0.26787082715568816 2.7331426
28 0.2795411937809858 2.5772903
29 0.2903410117450141 2.4442258
30 0.30155807372567695 2.3161108
31 0.3117279319272405 2.2079256
32 0.3222407770833193 2.1032696
33 0.3331081270506525 2.0020282
34 0.3443419963056933 1.9040896
35 0.35427207728348925 1.8226893
36 0.36448852904603996 1.7435706
37 0.37499958649323284 1.6666696
38 0.38398998658924743 1.6042346
39 0.39506344010324784 1.531239
40 0.4007193508817026 1.4955121
41 0.4142333455994403 1.4140983
42 0.424164371298754 1.3575766
43 0.43433346708950876 1.3023784
44 0.4447463637011901 1.2484726
45 0.4532561348050735 1.206258
46 0.46412267530841617 1.1546028
47 0.47300321740670026 1.1141505
48 0.4820536525674852 1.0744579
49 0.49127726872915933 1.0355104
50 0.50067735458945 0.99729425
51 0.5126808103265549 0.95053136
52 0.5200205811062965 0.9230008
53 0.529970660087538 0.8868969
54 0.5401111120160957 0.8514709
55 0.5504455871348378 0.81671
56 0.5583260139333776 0.79106826
57 0.5690090145577201 0.7574414
58 0.5771552197301775 0.73263615
59 0.5881984859123771 0.7001064
60 0.5966194159086837 0.6761104
61 0.6080351295320676 0.6446418
62 0.6167400285114983 0.6214287
63 0.6255695473219727 0.5985433
64 0.6345254798014763 0.57598084
65 0.6466664785703571 0.5463922
66 0.6559244537389011 0.5245658
67 0.6653149569656572 0.5030475
68 0.6748398995431867 0.48183295
69 0.6845012084491502 0.4609178
70 0.6943008389108709 0.44029784
71 0.7042407596769785 0.41996893
72 0.7143229812971729 0.39992696
73 0.7245495424831069 0.38016787
74 0.7349225260710267 0.36068764
75 0.7419202073475998 0.34785384
76 0.7525418594057561 0.32882974
77 0.7633155896705354 0.31007412
78 0.7705836233453013 0.2977177
79 0.7853279761145784 0.27335334
80 0.7928055933351884 0.26134327
81 0.8041557594230563 0.24354018
82 0.815668410678142 0.22598839
83 0.8234349302691203 0.21442504
84 0.8352235995893931 0.19728418
85 0.8471810284186769 0.18038526
86 0.8552476006018109 0.16925204
87 0.867491713381367 0.15274876
88 0.8757516751105947 0.1418762
89 0.8882893264625089 0.12575933
90 0.9010064712048776 0.10986994
91 0.9095855567458574 0.0994018
92 0.9226075858599464 0.08388443
93 0.9313923478473856 0.07366139
94 0.9447265767754882 0.058507323
95 0.9537219481614782 0.04852363
96 0.9673758573574026 0.03372437
97 0.9765868880131308 0.023974428
98 0.9905681401139916 0.009521667
99 1.0 0.0

Thanks!