General description

As of March 2025, CAMELS host more than 2 petabytes of data from 16,960 cosmological simulations: 7,208 N-body and 9,752 hydrodynamic simulations. This project is the result of a large, collaborative effort and represents the most extensive suite of cosmological hydrodynamic simulations ever conducted.

The simulations are run with different codes (suites), cover different volumes and number of particles (generations), and sample different points in parameter space (sets), defined as the space formed from cosmological and astrophysical parameters and different initial conditions.

All CAMELS simulations share a few characteristics:

• All simulations start at redshift \(z=127\) and finish at \(z=0\).

• All simulations have the same mass and spatial resolution.

• For each simulation we store multiple snapshots, halo/subhalo catalogs, and summary statistics (e.g. power spectra) see Data organization.

• The N-body simulations only model the spatial phase-space distribution of total matter under the influence of gravity.

• The hydrodynamic simulations account for gravity + (magento-)hydrodynamics + astrophysical processes (e.g. supernova and AGN feedback).

Organization

The simulations can be classified into:

• Suites: depending on the code and subgrid physics model used to run them. CAMELS has 9 suites:

Suite	Code	Subgrid Physics Model
IllustrisTNG	AREPO	IllustrisTNG
SIMBA	GIZMO	SIMBA
Astrid	MP-Gadget	Astrid
Magneticum	OpenGadget	Magneticum-like
Swift-EAGLE	Swift	EAGLE
Ramses	Ramses	—
Enzo	Enzo	—
CROCODILE	Gadget4-Osaka	CROCODILE
Obsidian	GIZMO	Obsidian

• Generations: depending on the volume and number of particles in the simulations. CAMELS has 3 generations:

Generation	Description
First generation	\(256^3\) dark matter + \(256^3\) initial fluid elements in a 25 Mpc/h box
Second generation	\(512^3\) dark matter + \(512^3\) initial fluid elements in a 50 Mpc/h box
Third generation	\(1024^3\) dark matter + \(1024^3\) initial fluid elements in a 100 Mpc/h box

• Sets: depending on how their cosmological and astrophysical parameters, and initial random seed values are organized. CAMELS has 6 sets:

Set	Description
SB	Variations in cosmology, astrophysics, and initial conditions
LH	Variations in cosmology, astrophysics, and initial conditions
1P	Variations on a single cosmological or astrophysical parameter. Initial conditions fixed
CV	Fixed cosmology and astrophysics. Variations in initial conditions
EX	Fixed cosmology and initial conditions. Extreme variations in astrophysics
BE	Fixed cosmology, astrophysics, and initial conditions

See Organization for further details.

Simulations available

The tables below shows the number of available hydrodynamic and N-body simulations:

First generation hydrodynamic simulations
	Set
Suite	SB	LH	1P	CV	EX	BE	Total
IllustrisTNG	2048 (28 params)	1000 (6 params)	113 (28 params)	27	4	27	3219
SIMBA		1000 (6 params)	113 (28 params)	27	4	27	1171
Astrid	1024 (7 params)	1000 (6 params)	25 (6 params)	27	4		2080
Magneticum		50 (6 params)		27			77
Swift-EAGLE		1000 (6 params)	25 (6 params)	27			1052
Ramses	512 (5 params)	–	13 (5 params)	27			552
Enzo		–	5	1			6
CROCODILE	128 (6 params)	–	25 (6 params)	27			180
Obsidian		–		27			27
All	3712	4050	319	217	12	54	8364

Second generation hydrodynamic simulations
	Set
Suite	SB	1P	CV	EX	BE	Total
IllustrisTNG	1024 (35 params)	141 (35 params)	27			1192
SIMBA
Astrid
Magneticum
Swift-EAGLE
Ramses		21 (5 params)	27			48
Enzo
CROCODILE	16	105 (26 params)	27			148
Obsidian
All	1040	267	81			1388

First generation N-body simulations
	Set
Suite	SB	LH	1P	CV	EX	BE	Total
IllustrisTNG	2048 (5 params)	1000 (2 params)	9 (5 params)	27	1	27	3112
SIMBA		1000 (2 params)					1064
Astrid	1024 (3 params)	1000 (2 params)					2088
Magneticum							64
Swift-EAGLE							64
Ramses		–					64
Enzo		–					64
CROCODILE		–					64
Obsidian		–					64
All	3072	3000	9	27	1	27	6136

Second generation N-body simulations
	Set
Suite	SB	1P	CV	EX	BE	Total
IllustrisTNG	1024 (5 params)	21 (5 params)	27			1072
SIMBA
Astrid
Magneticum
Swift-EAGLE
Ramses
Enzo
CROCODILE
Obsidian
All	1024	21	27			1072

Note

CAMELS is designed so that each hydrodynamic simulation has a N-body counterpart. However, several hydrodynamic simulations may have the same N-body simulation. For instance, in the 1P set, simulations that only vary astrophysical parameters, will have the same N-body counterpart. This is the reason why in the above table, the number of N-body simulations may be lower than the corresponding number of hydrodynamic simulations.

The value of the cosmological, astrophysical, and initial random seed of the different simulations can be found Parameters.

Codes

All N-body simulations have been run with the Gadget-III code, while the hydrodynamic simulations have been run with different codes: AREPO, GIZMO, MP-Gadget, OpenGadget, Swift, Ramses, Gadget4-Osaka, and Enzo. See Codes for details on the different codes and subgrid physics models available in CAMELS.

Redshifts

Important

A reorganization of the data was performed in 2024 in order to enhance its uniformity and simplicity. This will require slight changes to existing codes that access the data.

• Snapshot numbers in the IllustrisTNG and SIMBA suites, where simulations have only 34 snapshots, have been updated to match the numbering in the Astrid suite (and some TNG simulations) that have 91 snapshots. For example, where 33 used to be the z=0 snapshot, now it is 90 uniformly for all suites.

All simulations have 91 snapshots. This file contains the scale factors of the snapshots. The user can click below to see the redshift, scale factor, and snapshot number for the different snapshots:

Click here to see the relation between the snapshot number and the redshift

Redshift	Scale Factor	34 snapshots	91 snapshots
14.99	0.063	—	000
13.34	0.070	—	001
11.98	0.077	—	002
11.20	0.082	—	003
10.48	0.087	—	004
9.69	0.094	—	005
9.00	0.100	—	006
8.49	0.105	—	007
8.01	0.111	—	008
7.60	0.116	—	009
7.24	0.121	—	010
6.89	0.127	—	011
6.56	0.132	—	012
6.28	0.137	—	013
6.01	0.143	000	014
5.75	0.148	—	015
5.50	0.154	—	016
5.23	0.161	—	017
5.00	0.167	001	018
4.80	0.172	—	019
4.61	0.178	—	020
4.45	0.183	—	021
4.30	0.189	—	022
4.15	0.194	—	023
4.01	0.200	002	024
3.87	0.205	—	025
3.73	0.211	—	026
3.62	0.216	—	027
3.49	0.223	003	028
3.36	0.229	—	029
3.24	0.236	—	030
3.12	0.242	—	031
3.01	0.249	004	032
2.90	0.257	—	033
2.80	0.263	005	034
2.72	0.269	—	035
2.63	0.276	006	036
2.54	0.282	—	037
2.46	0.289	007	038
2.38	0.296	—	039
2.30	0.303	008	040
2.22	0.310	—	041
2.15	0.318	009	042
2.07	0.325	—	043
2.00	0.333	010	044
1.93	0.341	—	045
1.86	0.349	011	046
1.80	0.358	—	047
1.73	0.366	012	048
1.67	0.375	—	049
1.60	0.384	013	050
1.54	0.393	—	051
1.48	0.403	014	052
1.43	0.412	—	053
1.37	0.422	015	054
1.30	0.434	—	055
1.26	0.443	016	056
1.20	0.455	—	057
1.14	0.466	017	058
1.09	0.478	—	059
1.05	0.489	018	060
1.00	0.501	—	061
0.95	0.513	019	062
0.90	0.525	—	063
0.86	0.538	020	064
0.82	0.550	—	065
0.77	0.564	021	066
0.73	0.577	—	067
0.69	0.591	022	068
0.65	0.605	—	069
0.61	0.620	023	070
0.58	0.635	—	071
0.54	0.650	024	072
0.50	0.665	—	073
0.47	0.681	025	074
0.43	0.698	—	075
0.40	0.714	026	076
0.37	0.731	—	077
0.34	0.749	027	078
0.30	0.771	—	079
0.27	0.789	028	080
0.24	0.808	—	081
0.21	0.827	029	082
0.18	0.847	—	083
0.15	0.867	030	084
0.13	0.888	—	085
0.10	0.910	031	086
0.07	0.931	—	087
0.05	0.954	032	088
0.02	0.977	—	089
0.00	1.000	033	090

Note

The exact redshifts of a given snapshot may be slighty different to the above ones. For instance, there are small differences between the exact redshifts of the snapshots in the Astrid and SIMBA suites. In the simulations of the IllustrisTNG suite these numbers can also be slightly different, since AREPO can only write snapshots in the highest time steps in the hierarchy.

Warning

We have moved some snapshots to tape. If you need these please reach out.