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Chemistry in evolving protoplanetary disks Jonkheid, Bastiaan Johan

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Citation

Jonkheid, B. J. (2006, June 28). Chemistry in evolving protoplanetary disks. Retrieved from https://hdl.handle.net/1887/4451

Version: Corrected Publisher’s Version

License: Licence agreement concerning inclusion of doctoral thesisin the Institutional Repository of the University of Leiden Downloaded from: https://hdl.handle.net/1887/4451

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Contents

1 Introduction 1

1.1 Low mass star formation . . . 1

1.2 Disk evolution and planet formation . . . 1

1.2.1 Global evolution . . . 1

1.2.2 Dust evolution . . . 3

1.3 Photodissociation regions . . . 6

1.4 Disk chemistry . . . 7

1.5 Outline of the thesis . . . 9

1.6 Main results of the thesis . . . 11

2 A PDR code comparison study 15 2.1 Introduction . . . 16

2.2 The physics of PDRs . . . 17

2.3 Modeling of PDRs . . . 18

2.4 Description of sensitivities and pitfalls . . . 20

2.4.1 Model geometry . . . 20

2.4.2 Chemistry . . . 21

2.4.3 Heating and cooling . . . 25

2.4.4 Grain properties . . . 26

2.4.5 Radiative transfer . . . 27

2.4.6 Ionization rate . . . 27

2.5 Description of the benchmark models . . . 29

2.5.1 PDR code characteristics . . . 29

2.5.2 Benchmark frame and input values . . . 31

2.6 Results . . . 33

2.6.1 Models with constant temperature F1-F4 . . . 34

2.6.2 Models with variable temperature V1-V4 . . . 39

2.6.3 Further thermal balance tests . . . 43

2.7 Concluding remarks . . . 45

3 The gas temperature in flaring disks around pre-main sequence stars 53 3.1 Introduction . . . 53

3.2 Calculating the gas temperature . . . 55

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3.2.2 Chemistry . . . 57 3.2.3 Thermal balance . . . 59 3.2.4 Dust settling . . . 59 3.3 Results . . . 62 3.3.1 Temperature . . . 62 3.3.2 Chemistry . . . 66 3.3.3 Line intensities . . . 69 3.4 Discussion . . . 69

3.4.1 Limitations of the 1+1-D model . . . 69

3.4.2 Effects of gas-dust coupling . . . 70

3.4.3 Effects of the radiation field . . . 70

3.5 Conclusions . . . 71

Appendix . . . 75

A. Heating processes . . . 75

B. Cooling processes . . . 77

4 Modeling the chemistry of the HD 141569A transitional disk 79 4.1 Introduction . . . 79 4.2 Model . . . 81 4.2.1 Input . . . 81 4.2.2 Treatment of dust . . . 85 4.3 Results . . . 86 4.3.1 Chemistry . . . 86 4.3.2 Temperature . . . 90

4.4 Constraining the gas mass . . . 91

4.4.1 CO lines . . . 91

4.4.2 Other emission lines . . . 94

4.4.3 Gas/dust ratio . . . 94

4.4.4 Second generation gas? . . . 95

4.5 Conclusions . . . 95

5 Chemistry and line emission from evolving Herbig Ae disks 99 5.1 Introduction . . . 99

5.2 Model . . . 101

5.3 Results and discussion . . . 106

5.3.1 Gas temperature . . . 106

5.3.2 Chemistry . . . 107

5.3.3 Column densities . . . 111

5.3.4 Atomic and molecular lines . . . 113

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Contents

Nederlandse samenvatting 123

Curriculum Vitae 129

Nawoord 131

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