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Observational studies of gas in protoplanetary disks [Elektronische Ressource] / presented by Andrés Carmona Gonzalez

116 pages
Dissertationsubmitted to theCombined Faculties for the Natural Sciences and for Mathematicsof the Ruperto-Carola University of Heidelberg, Germanyfor the degree ofDoctor of Natural Sciencespresented byDiplom-Ingenieur, MSc, MA, Andres´ Carmona Gonzalezborn in Bogota,´ ColombiaOral examination: 25 July 2007Observational Studies of Gasin Protoplanetary DisksReferees: Prof. Dr. Thomas HenningDr. Mario E. van den AnckerAbstract – ZusammenfassungO      The gas dominates the mass and dynamics of protoplanetary disks. However, very few observational constraints existabout the physical properties of the gas in the planet forming region of the disks. This thesis presents an ensemble of newobservational projects aimed at studying the gas in the disks of selected nearby Herbig Ae/Be stars (HAEBES) and clas-sical T Tauri stars (CTTS). In the first chapter we present a search for CO 4.7µm ro-vibrational emission from HAEBESusing ISAAC, ESO’s first generation VLT near-infrared spectrograph. In the second chapter, we describe a project inwhich we intended to probe the outer cold gas of protoplanetary disks, by measuring gas absorption features of the disksuperimposed on the optical spectra of close (<1.5”) visual companions of nearby HAEBES utilizing FORS2, ESO’s VLToptical spectrograph. In the third chapter, we present a large observational effort to detect H fundamental rotational2emission at 12.278 and 17.
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Dissertation
submitted to the
Combined Faculties for the Natural Sciences and for Mathematics
of the Ruperto-Carola University of Heidelberg, Germany
for the degree of
Doctor of Natural Sciences
presented by
Diplom-Ingenieur, MSc, MA, Andres´ Carmona Gonzalez
born in Bogota,´ Colombia
Oral examination: 25 July 2007Observational Studies of Gas
in Protoplanetary Disks
Referees: Prof. Dr. Thomas Henning
Dr. Mario E. van den AnckerAbstract – Zusammenfassung
O      
The gas dominates the mass and dynamics of protoplanetary disks. However, very few observational constraints exist
about the physical properties of the gas in the planet forming region of the disks. This thesis presents an ensemble of new
observational projects aimed at studying the gas in the disks of selected nearby Herbig Ae/Be stars (HAEBES) and clas-
sical T Tauri stars (CTTS). In the first chapter we present a search for CO 4.7µm ro-vibrational emission from HAEBES
using ISAAC, ESO’s first generation VLT near-infrared spectrograph. In the second chapter, we describe a project in
which we intended to probe the outer cold gas of protoplanetary disks, by measuring gas absorption features of the disk
superimposed on the optical spectra of close (<1.5”) visual companions of nearby HAEBES utilizing FORS2, ESO’s VLT
optical spectrograph. In the third chapter, we present a large observational effort to detect H fundamental rotational2
emission at 12.278 and 17.035µm from HAEBES employing VISIR, ESO’s new high-resolution mid-infrared spectro-
graph. In the fourth chapter, we describe the first results of a sensitive search for near-infrared H ro-vibrational emission2
at 2.1218, 2.2233 and 2.2477µm in the CTTS LkHα 264 and the debris disk 49 Cet using CRIRES, ESO’s new VLT
near-infrared high-resolution spectrograph. From our observations (detections and non-detections), we derive important
constraints on the physical properties of the studied disks (e.g. mass, column density, temperature, age, excitation mech-
anism, inclination). We show that high-resolution infrared spectroscopy is a crucial tool for future studies of the structure
of protoplanetary disks.
B  G   S
Gas dominiert die Masse und Dynamik von protoplanetaren Scheiben. Dennoch sind durch Beobachtungen erst sehr
wenige Erkenntnisse uber¨ die physikalischen Eigenschaften des Gases in den Planetenentstehungsgebieten der Scheiben
gewonnen worden. In dieser Arbeit prasentieren¨ wir eine Anzahl von neuen Beobachtungsprojekten, die das Gas in den
Scheiben ausgewahlter¨ Herbig Ae/Be Sterne (HAEBES) and klassischer T Tauri Sterne (CTTS) untersuchen. Im ersten
Kapitel wird die Suche nach CO Emission (Rotations- und Schwingungsuber¨ gange¨ bei 4.7µm) von HAEBES mit Hilfe
von ISAAC, ESO’s Nahinfrarot-Spektrographen der ersten Generation am VLT, erlautert.¨ Im zweiten Kapitel beschreiben
wir ein Projekt welches versucht, das aussere,¨ kalte Gas der protoplanetaren Scheiben zu untersuchen. Dies wird erreicht
durch die Messung der absorption durch Gas in der Scheibe. Die Absorption ist mit dem mit dem Spektrum eines engen
(<1.5”) visuellen Begleiters naher HAEBES uberlagert.¨ Fur¨ die Messungen wurde FORS2 benutzt, ein optischer Spektro-
graph am VLT. Im dritten Kapitel prasentieren¨ wir ein grosses Beobachtungsprojekt zur Detektion der H Emission (Rota-2
tionsuber¨ gang bei 12.278 und 17.035µm) von HAEBES mit Hilfe von ESO’s neuem, hochauflosenden¨ Spektrographen fur¨
das mittlere Infrarot, VISIR. Im vierten Kapitel beschreiben wir erste Resultate einer sensitiven Suche nach Nahinfrarot-
H -Emission (Rotations- und Schwingungsuber¨ gange¨ bei 2.1218, 2.2233 und 2.2477µm) in der CTTS Scheibe LkHα 2642
und der “debris disk” 49 Cet unter Verwendung des neuen VLT-Instruments CRIRES, eines hochauflosenden¨ Nahinfrarot-
Spektrographen. Basierend auf unseren Beobachtungsresultaten (Detektionen sowie auch gegebenfalls abgeleitete Ober-
grenzen fur¨ gewisse Parameter) konnen¨ wir wichtige physikalische Eigenschaften der beobachteten Scheiben (z. B. Masse,
S¨ aulendichte, Temperatur, Alter, Anregungsbedingungen, Scheibenneigung) entscheidend eingrenzen. Wir zeigen, daß
Infrarot-Spektroskopie ein unerlassliches¨ Werkzeug fur¨ zukunftige¨ Studien zur Struktur protoplanetarer Scheiben ist.
vA la memoria de Beatriz Gonzalez,´ mi madre, quien
desafortunadamente fallecio´ justo antes de finalizar esta tesis.
A mi padre Jose´ Emerio Carmona y su permanente apoyo.Contents
1 Introduction: From Clouds to Disks to Planets 3
1.1 How did we arrive at idea that planets form in disks? . . . ............ 4
1.2 Star Formation ........................... 5
1.3 Pre-main sequence stars............... 8
1.3.1 T Tauri and Herbig Ae/Be stars . . ............ 9
1.4 Planet Formation . . . ....................... 12
1.4.1 Terrestrial Planet Formation............ 12
1.4.2 Giant Planet Formation . . . ................ 13
1.4.3 Some additional open issues............ 14
1.5 The observational study of protoplanetary disks . ............. 15
1.5.1 Modeling of the Spectral Energy Distribution . . ..... 15
1.5.2 The disk dissipation time scale . . . .................... 17
1.5.3 The disk’s mass............... 18
1.5.4 Direct evidence for disks . ..................... 18
1.5.5 Disk dust composition and mineralogy . ..... 19
1.5.6 The study of the gas . . . . ........................ 20
1.5.7 This Thesis . . ........... 28
1.6 References . . . ............................... 29
2 Upper limits on CO 4.7µm emission from disks around five Herbig Ae/Be stars 33
2.1 Introduction . . ................................... 33
2.2 Observations ........ 35
2.2.1 Data Reduction ............................... 35
2.3 Results . ............... 36
2.4 Discussion . . ................................ 37
2.5 References . . . ........... 40
3 Optical spectroscopy of close companions to nearby Herbig Ae/Be and T Tauri stars 43
3.1 Preface ....................................... 43
3.2 Introduction . ........ 44
3.3 Observations & data reduction . . . ........................ 45
ix1
3.3.1 Observations . ............................... 45
3.3.2 Data reduction....... 46
3.4 Results . ....................................... 48
3.4.1 Spectral classification . . . ..... 48
3.4.2 Luminosity determination . ........................ 53
3.4.3 Primaries and companions in the HR diagram . . ..... 55
3.5 Discussion . . . ................................... 57
3.6 References . . ........ 59
4 A Search for MIR Molecular Hydrogen Emission from Protoplanetary Disks 63
4.1 Introduction . . ................................... 63
4.2 Observations ........ 65
4.3 Data Reduction ................................... 66
4.4 Results . ........... 67
4.5 Discussion . . . ................................... 72
4.5.1 Comparison with the gas mass of a 2-layer disk model . . . . .. 72
4.5.2 Derivation of expected S(1) and S(2) H emission from the two-layer disk2
model. ................................... 73
4.5.3 The effect of the disk inclination . ..... 77
4.6 Summary and Conclusions . . . . . ........................ 79
4.7 References . . . ............... 81
4.8 Appendix. A study for the H2EX mission . .................... 82
5 NIR Molecular Hydrogen Emission in the CTTS LkHα 264 and the debris disk 49
Cet 85
5.1 Introduction . . ................................... 85
5.2 Observations ........ 87
5.2.1 Data Reduction ............................... 87
5.3 Results . ............... 89
5.3.1 Upper flux limits to H emission in 49 Cet . ................ 892
5.3.2 Molecular Hydrogen Emission in LkHα264 ....... 89
5.3.3 Mass of hot H in LkHα264and49Cet.................. 902
5.4 Discussion . . . ....................... 91
5.4.1 The excitation mechanism of the H line in LkHα264.......... 912
5.4.2 The inclination of the disk around LkHα264........... 92
5.4.3 H NIR ro-vibrational emission in LkHα 264 and other T Tauri disks . . 942
5.4.4 49 Cet disk . . ............................... 97
5.5 Conclusions . . ........... 98
5.6 References . . ................................ 99
6 Conclusion and Perspectives 101