Interferometric observations of pre-main sequence disks - Caltech ...

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18 Scientific overview Figure 1.3: From Natta et al. (2006). Opacity indexβfor grains with a size distribution n(a)∝ a −q between amin and amax. The indexβis computed between 1 and 7 mm for compact segregated spheres of olivine, organic materials, water ice (Pollack et al., 1994), and plotted as function of amax. Different curves correspond to different values of q, as labelled. In all cases, amin≪ 1 mm. The dotted curve showsβfor grains with single size amax. The histogram on the right shows the distribution of the values ofβderived from millimeter observations. About 60% of the objects haveβ≤1, and amax > ∼ 1 cm. flux is expressed by the power law Fν ∝ λ −α . Using Eq. 1.3 and Eq. 1.4 it can be demonstrated using that in this caseα=β+2. This simple relation allow to translate the observed value ofαinto the opacity power low indexβ. To verify the fundamental assumption that the millimetric disk emission is optically thin, the emission itself must be spatially resolved and the disk size measured (Testi et al., 2001 and 2003). There are at present several disks whose millimeter emission has been resolved with interferometers (Natta et al., 2004; Rodmann et al., 2006) and in Chapter 7 we will present new multi-wavelengths observations of the HAe star HD 163296. The obtained
1.4 Outline and aims of the thesis 19 values ofβvaries from 1.6 (very similar to the interstellar medium and Class 0/I objects) to 0.5, with most of the objects withβ< ∼ 1, corresponding to the presence of centimeter size grains (Natta et al., 2004; Draine, 2006). In order to constrain dust growth models, the next step is to check for variations of the dust properties as a function of the radius. Our observation of HD 163296 are the first attempt to obtain the multi wavelengths high angular resolution and high sensitivity observations required for such analysis and we refer to the Chapter 7 for the results. The major actual limitation to understand planetary formation is that none of the discussed techniques is sensitive to bodies larger than few centimeters. In principle, planetesimals of few kilometers in size could be detected through the dynamical pertur- bations exerted on the surrounding material. Particularly interesting is the discovery of clumps in the dust density distribution in the disk around the close-by HAe star AB Aur (Corder et al., 2005; Pietú et al., 2005). On the other hand, the detection of meter-size bodies is at the moment practically impossible. 1.4 Outline and aims of the thesis The aim of this thesis is to study the structure of circumstellar disks around pre-main sequence stars. Taking advantage of high spatial resolution interferometric observations we have focused our attention on the gas and dust properties both in the inner disk, at fractions of AU from the central star, and in the outer disk regions, at R>50 AU. The thesis is divided into five parts: a general introduction and a general review of astronomical interferometry (this Chapter and Chapter 2), a study of the dust in the inner disk (Chapter 3, 4, 5), a study of the gas in the inner disk (Chapter 6), a study of gas and dust in the outer disk (Chapter 7) and the final remarks (Chapter 8 and 9). Chapter 2 describes the basis of interferometry, similarities and differences between the near-infrared and millimeter interferometry and a presentation of the modelling techniques used to analyse interferometric observations. In Chapter 3 we describe the structure of the innermost part of circumstellar disks.
Page 1: Università degli Studi di Milano F
Page 5 and 6: CONTENTS I Introduction 1 1 Scienti
Page 7 and 8: CONTENTS v 4.5 Comparison with prev
Page 9: Part I Introduction
Page 12 and 13: 4 Scientific overview the critical
Page 14 and 15: 6 Scientific overview Log νFν Log
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Page 28 and 29: 20 Scientific overview We propose a
Page 31 and 32: CHAPTER 2 2.1 A bit of history Intr
Page 33 and 34: 2.1 A bit of history 25 measure ste
Page 35 and 36: 2.2 Basic principle of astronomical
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Page 51 and 52: 3.1 Introduction 43 Tauri stars (Ei
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Page 55 and 56: 3.2 Model description 47 log(δR/R
Page 57 and 58: 3.2 Model description 49 the pressu
Page 59 and 60: 3.3 Results 51 Photospherical heigh
Page 61 and 62: 3.3 Results 53 ever, is sufficientl
Page 63 and 64: 3.3 Results 55 Sec. 3.3.1 (see Fig.
Page 65 and 66: 3.4 Discussion 57 the value ofǫ, t
Page 67 and 68: 3.4 Discussion 59 sample of Fig. 3.
Page 69 and 70: 3.5 Summary and conclusions 61 R in
Page 71 and 72: 3.6 Appendix 63 However, the bright
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68 Large dust grains in the inner r
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Face-on disk image Baseline (m) V 2
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V 2 1 0.8 0.6 0.4 0.2 0 0 50 100 15
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V 2 1 0.8 0.6 0.4 0.2 0 0 50 100 15
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CHAPTER 5 More on the “puffed-up
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5.1 Fuzzy and sharp rims 97 opacity
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5.2 New shapes for the rim 99 grain
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5.3 New observational results 101 (
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5.3 New observational results 103 w
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CHAPTER 6 Constraining the wind lau
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6.1 Introduction 109 λ Fλ (erg cm
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6.2 Observations and data reduction
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6.3 Results and discussions 113 V V
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6.4 Conclusions 115 note however th
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Part IV The structure of the outer
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120 The keplerian disk of HD 163296
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Part V Conclusions and future prosp
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152 Summary and Conclusions ∼1 an
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154 Summary and Conclusions disk in
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CHAPTER 9 Future developments As my
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9.1 Gas in the inner disk of Herbig
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9.2 Probing planet formation throug
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Published papers • Isella, A.; Te
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172 BIBLIOGRAPHY [2000] Bodenheimer
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174 BIBLIOGRAPHY [2004] Gail H.-P.,
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176 BIBLIOGRAPHY Arizona Press, Tuc
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178 BIBLIOGRAPHY [2001] Thompson A.
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