Description of Simulations

Overview of CAMELS-SAM

A complete description of the suite, its creation, and application can be found in Perez, Genel, et al. (2023, in press as of July 2023): https://arxiv.org/abs/2204.02408 .

The backbone of CAMELS-SAM are the 1,000+ N-body only AREPO simulations we generated across 100 snapshots between \(z=127\) to \(z=0\) across the broad cosmological parameter space of CAMELS. Each simulation was run through ROCKSTAR to generate halo catalogs at each snapshot, and then ConsistentTrees to generate merger trees. We feed this finely sampled merger tree history into the Santa Cruz semi-analytic model (SC-SAM, hence CAMELS-SAM) for galaxy formation. The parameters we vary across the suite are \(\Omega_{\rm M}\), \(\sigma_{8}\), \(A_{\rm SN1}\), \(A_{\rm SN2}\), and \(A_{\rm AGN}\). The later 3 are pre-factors to three SC-SAM parameters controlling, respectively, the amplitude and rate of mass outflow from massive stars out of a galaxy, and the strength of the radio jet mode of AGN.

In this documentation, simulation indicates that there exists an N-body only simulation (i.e. snapshots) that generated the product; simulation products refers to the ROCKSTAR and ConsistentTrees products generated from the simulations; and galaxy catalog refers to the output halo and subhalo/galaxy catalogs that the Santa Cruz SAM generated. The raw simulations are enormously large (>450TB after compression), and are therefore not able to be publically released as the CAMELS snapshots are. Please contact the CAMELS team to discuss access to the CAMELS-SAM snapshots, and otherwise refer to the CAMELS data acess instructions for how to access everything else: https://camels.readthedocs.io/en/latest/data_access.html.

Simulation sets within the suite

Within CAMELS-SAM, these are these three sets of products publically released:

  • LH. This set contains 1,000 simulation products and galaxy catalogs. Each simulation has a different value of the cosmological and astrophysical parameters, are arranged in a latin-hypercube. Each simulation has a different value of the initial random seed. This set represents the main CAMELS-SAM dataset. LH stands for Latin-Hypercube. These can be found within camels/PUBLIC_RELEASE/SCSAM/LH_? .
  • CV. This set contains 5 simulation products and galaxy catalogs. All the simulations share the value of the cosmological and astrophysical parameters, and they only differ in the value of their initial random seed. This set is typically used to study the effect of cosmic variance due to the simulated volume size. CV stands for Cosmic Variance. These can be found within camels/PUBLIC_RELEASE/SCSAM/CV_? .
  • 1P. This set contains 12 galaxy catalogs. In this set, the SC-SAM was run at the smallest and largest value of each SAM parameter for two of the CV simulations (\(0,1\)). The value of the random seed is the same in all galaxy catalogs generated atop the same CV simulation. This set can be used to study the change induced by the astrophysical SC-SAM parameters in a given quantity. 1P stands for 1-parameter at a time. (We emphasize this differs from the CAMELS 1P set, which more finely samples the parameter space and also focus on the cosmological parameters.) These can be found within These can be found within camels/PUBLIC_RELEASE/SCSAM/CV_0 and CV_1, in folders named e.g. Asn1x0p25-sc-sam .

Characteristics

The CAMELS-SAM simulations follow the evolution of \(640^3\) dark matter particles within a periodic comoving volume of \((100~h^{-1}{\rm cMpc})^3\) from \(z=127\) down to \(z=0\). All simulations share the value of these cosmological parameters:

\(\Omega_{\rm b}\)

\(h\)

\(n_s\)

\(w\)

\(M_\nu\)

\(\Omega_k\)

0.049

0.6711

0.9624

-1

0.0 eV

0.0

CAMELS-SAM has been designed to sample the parameter space of cosmology (by varying \(\Omega_{\rm M}\) and \(\sigma_8\)) and of the feedback astrophysics in the SC-SAM model (by varying \(A_{\rm SN1}\), \(A_{\rm SN2}\), and \(A_{\rm AGN}\)). The physical meaning of these parameters is such:

Parameter

Meaning

Parameter coverage

\(\Omega_{\rm m}\)

Fraction of energy density in matter (dark matter + baryons)

[0.1,0.5] linearly, fid.=0.3

\(\sigma_8\)

Variance of the linear field on \(8~h^{-1}{\rm Mpc}\) at \(z=0\)

[0.6,1.0] linearly, fid.=0.8

\(A_{\rm SN1}\)

Multiplicative factor for the normalization of mass outflow rate of cold gas due to SN winds & SN feedback efficiency (Somerville et al. 2015, Eq. 2)

[0.25,4.0] logarithmically, fid.=1.0

\(A_{\rm SN2}\)

Additive factor to the power-law slope of mass outflow rate; SN feedback slope (Somerville et al. 2015, Eq. 2)

[-2.0,2.0] linearly, fid.=1.0

\(A_{\rm AGN}\)

Multiplicative factor for the n Normalization of ‘radio mode’ AGN feedback (Somerville et al. 2008, Eq. 20)

[0.25,4.0] logarithmically, fid.=1.0

We note that each simulation’s file describing their parameter, CosmoAstro_params.txt, lists the for the astrophysical parameters the convolution with the base fiducial SC-SAM value. Each file will list: \(\Omega_{\rm m}\) , \(\sigma_8\) , \(A_{\rm SN1} \times 1.7\), \(A_{\rm SN2} + 3\), \(A_{\rm AGN} \times 0.002\), and a vestigial parameter set to 0.5. These are the parameters that went directly into creating each CAMELS-SAM N-body simulation and SC-SAM catalog. For those who are curious, this comes from how the latin hypercube was created: the minimum/lower and maximum/upper bounds are, respectively: \(\Omega_{\rm m}=[0.1, 0.6]\) , \(\sigma_8=[0.6, 1.0]\) , \(A_{\rm SN1}=[0.25, 4.0] \times 1.7\), \(A_{\rm SN2}=[-2,2] + 3\), \(A_{\rm AGN}=[0.25, 4.0] \times 0.002\)

Redshifts

The CAMELS-SAM simulations were generated over 100 snapshots between z=20 and z=0, following the same steps as IllustrisTNG:

Click to expand/collapse this very large table of snapshot number | redshifts | age of universe | lookback time

Snapshot[#]

Redshift

Age [Gyr]

Lookback time [Gyr]

0

20.05

0.179

13.624

1

14.99

0.271

13.532

2

11.98

0.370

13.433

3

10.98

0.418

13.385

4

10.00

0.475

13.328

5

9.39

0.517

13.286

6

9.00

0.547

13.256

7

8.45

0.596

13.207

8

8.01

0.640

13.163

9

7.60

0.687

13.116

10

7.24

0.732

13.071

11

7.01

0.764

13.039

12

6.49

0.844

12.959

13

6.01

0.932

12.871

14

5.85

0.965

12.838

15

5.53

1.036

12.767

16

5.23

1.112

12.691

17

5.00

1.177

12.626

18

4.66

1.282

12.521

19

4.43

1.366

12.437

20

4.18

1.466

12.337

21

4.01

1.540

12.263

22

3.71

1.689

12.115

23

3.49

1.812

11.991

24

3.28

1.944

11.859

25

3.01

2.145

11.658

26

2.90

2.238

11.565

27

2.73

2.384

11.419

28

2.58

2.539

11.264

29

2.44

2.685

11.118

30

2.32

2.839

10.964

31

2.21

2.981

10.823

32

2.10

3.129

10.674

33

2.00

3.285

10.519

34

1.90

3.447

10.356

35

1.82

3.593

10.210

36

1.74

3.744

10.059

37

1.67

3.902

9.901

38

1.60

4.038

9.766

39

1.53

4.206

9.597

40

1.50

4.293

9.510

41

1.41

4.502

9.301

42

1.36

4.657

9.147

43

1.30

4.816

8.987

44

1.25

4.980

8.823

45

1.21

5.115

8.688

46

1.15

5.289

8.514

47

1.11

5.431

8.372

48

1.07

5.577

8.226

49

1.04

5.726

8.077

50

1.00

5.878

7.925

51

0.95

6.073

7.730

52

0.92

6.193

7.610

53

0.89

6.356

7.447

54

0.85

6.522

7.281

55

0.82

6.692

7.111

56

0.79

6.822

6.981

57

0.76

6.998

6.805

58

0.73

7.132

6.671

59

0.70

7.314

6.489

60

0.68

7.453

6.350

61

0.64

7.642

6.161

62

0.62

7.786

6.017

63

0.60

7.932

5.872

64

0.58

8.079

5.724

65

0.55

8.280

5.523

66

0.52

8.432

5.371

67

0.50

8.587

5.216

68

0.48

8.743

5.060

69

0.46

8.902

4.901

70

0.44

9.062

4.741

71

0.42

9.225

4.578

72

0.40

9.389

4.414

73

0.38

9.556

4.247

74

0.36

9.724

4.079

75

0.35

9.837

3.966

76

0.33

10.009

3.794

77

0.31

10.182

3.621

78

0.30

10.299

3.504

79

0.27

10.535

3.269

80

0.26

10.654

3.149

81

0.24

10.834

2.969

82

0.23

11.016

2.787

83

0.21

11.138

2.665

84

0.20

11.323

2.480

85

0.18

11.509

2.294

86

0.17

11.635

2.169

87

0.15

11.824

1.979

88

0.14

11.951

1.852

89

0.13

12.143

1.660

90

0.11

12.337

1.466

91

0.10

12.467

1.336

92

0.08

12.663

1.140

93

0.07

12.795

1.008

94

0.06

12.993

0.810

95

0.05

13.127

0.676

96

0.03

13.328

0.475

97

0.02

13.463

0.340

98

0.01

13.667

0.136

99

0.00

13.803

0.000

*ages and lookback time from IllustrisTNG300 documentation, and therefore their assumed cosmology .. raw:: html

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