The evolving velocity field around protostars
Brinch, C.
Citation
Brinch, C. (2008, October 22). The evolving velocity field around protostars.
Retrieved from https://hdl.handle.net/1887/13155
Version: Corrected Publisher’s Version
License: Licence agreement concerning inclusion of doctoral thesis in the Institutional Repository of the University of Leiden
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The evolving velocity field around protostars
PROEFSCHRIFT
ter verkrijging van
de graad van Doctor aan de Universiteit Leiden
op gezag van de Rector Magnificus prof. mr. P. F. van der Heijden volgens besluit van het College voor Promoties
te verdedigen op woensdag 22 oktober 2008 klokke 16.15 uur
door
Christian Brinch
geboren te Rødovre (Kopenhagen), Denemarken in 1977
Promotiecommisie
Promotor: Prof. dr. E. F. van Dishoeck Co-promotor: Dr. M. R. Hogerheijde
Referent: Prof. dr. A. Burkert (Universitäts-Sternwarte München) Overige leden: Dr. C. P. Dullemond (Max-Planck-Institut für Astronomie)
Prof. dr. F. P. Israel Prof. dr. K. Kuijken Prof. dr. H. V. J. Linnartz
Table of contents
1 Introduction 1
1.1 The birth of stars . . . 1
1.2 The study of molecular emission lines . . . 4
1.2.1 Line formation . . . 5
1.2.2 Modeling of line profiles . . . 6
1.2.3 Submillimeter observations . . . 8
1.3 Thesis outline . . . 9
1.4 Conclusions . . . 11
2 Structure and dynamics of the Class I young stellar object L1489 IRS 15 2.1 Introduction . . . 16
2.2 Observations and model description . . . 17
2.2.1 Single-dish observations . . . 17
2.2.2 The model . . . 18
2.2.3 Molecular excitation and line radiative transfer . . . 23
2.2.4 Modeling the neighboring cloud core . . . 24
2.2.5 Optimizing the fit . . . 25
2.2.6 Error estimates . . . 27
2.3 Results . . . 29
2.3.1 Quality of the best fit . . . 32
2.3.2 Comparison to other observations . . . 34
2.4 Discussion . . . 38
2.5 Summary . . . 41
3 Characterizing the velocity field in a hydrodynamical simulation of low-mass star formation using spectral line profiles 45 3.1 Introduction . . . 46
3.2 Simulations and models . . . 47
3.2.1 Hydrodynamical collapse . . . 47 iii
Contents
3.2.2 Parameterized model . . . 51
3.2.3 Obtaining the best fit . . . 52
3.3 Line profiles and the velocity field . . . 54
3.3.1 Low resolution spectra . . . 59
3.3.2 High resolution spectra . . . 60
3.4 Results . . . 61
3.4.1 Single-dish simulations . . . 61
3.4.2 Interferometric simulations . . . 65
3.5 Discussion . . . 67
3.6 Conclusion . . . 70
4 A deeply embedded young protoplanetary disk around L1489 IRS ob- served by the Submillimeter Array 75 4.1 Introduction . . . 76
4.2 Observations and data reduction . . . 78
4.3 Results . . . 79
4.4 Analysis . . . 82
4.4.1 Introducing a disk model . . . 85
4.4.2 Modeling the continuum emission . . . 88
4.4.3 Modeling the HCO+emission . . . 89
4.5 Discussion . . . 93
4.6 Conclusion . . . 96
5 Time-dependent CO chemistry during the formation of protoplane- tary disks 99 5.1 Introduction . . . 100
5.2 Tracing chemistry during disk formation . . . 101
5.2.1 The physical model . . . 101
5.2.2 Freeze-out and evaporation . . . 104
5.3 Results . . . 106
5.3.1 Model 1: Drop abundance . . . 107
5.3.2 Model 2: Variable freeze-out . . . 109
5.3.3 Model 3: Dynamical evolution . . . 109
5.3.4 Cosmic ray desorption and increased binding energy . . . 112
5.3.5 Comparison to observations . . . 115
5.3.6 Emission lines . . . 118
5.4 Discussion . . . 121
5.5 Conclusion . . . 122
Contents
6 The kinematics of NGC1333-IRAS2A – a true Class 0 protostar 127
6.1 Introduction . . . 128
6.2 Observations . . . 129
6.3 Results . . . 130
6.4 Analysis . . . 133
6.4.1 Model fit . . . 134
6.4.2 Outflow . . . 138
6.5 Discussion . . . 139
6.6 Summary and outlook . . . 141
7 Advances in line radiation transfer modeling 143 7.1 Introduction . . . 143
7.2 Solution method . . . 144
7.2.1 The molecular level population equilibrium . . . 144
7.2.2 Photon transport . . . 145
7.2.3 Raytracing . . . 149
7.2.4 Interface . . . 150
7.3 Performance . . . 150
7.4 Examples . . . 152
7.4.1 Comparison toRATRAN . . . 152
7.4.2 Misaligned disk/envelope system . . . 154
7.4.3 Complex structured disks . . . 155
7.5 Outlook . . . 158
Nederlandse samenvatting 161
Curriculum vitae 165
Acknowledgements 167
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