thesis - IRS, The Infrared Spectrograph

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142 CHAPTER 7: Conclusions and future workWhat we still don’t know...Some questions have not been answered in this thesis or have arisen as a consequence of thisresearch. These are:• How can the difference between nebular abundances and the central star abundancesbe explained?• Why are low metallicity models needed to reproduce the abundances of intermediatemass stars?• Is there a relationship between the characteristics of the dust emission features and thenucleosynthetic history of the progenitor star?These questions stimulate research lines that should be followed up in the future.Future workISO has provided an excellent opportunity to study in detail the Planetary Nebula phase in ourown Milky Way. It will be very interesting to extend this study to other galaxies (i.e. LMCand SMC) for two reasons: 1) Distances are better known. This will allow deriving elementalabundances and ionization gradients as a function of metallicity of the progenitor star. Inparticular, because all objects will be at the same distance, the nucleosynthetic enrichmentcan be studied as a function of the location in the Hertzsprung-Russel diagram (eg., as afunction of the core mass). 2) The metallicity content differs from that of the Milky Way.This offers the possibility of comparing the abundances in such environments with our owngalaxy.The profile and peak position of dust features vary from source to source and this maybe linked to local chemical modification of the carriers. Correlating these variations with theelemental abundances of the objects can give insight in the carriers of these features. This canbe complemented with a study of these features on PNe in galaxies with different metallicitycomposition.Hard X-ray emission (peaking from 0.5-1.0 keV) has been detected in several nebulaewith Wolf-Rayet central stars. This emission is probably produced by the interaction of themass loss from the central star and the nebular material. Studying PNe in X-rays can giveimportant clues to better understand the chemical evolution of the ejected material.A large number of observatories currently in use, or available in the near future, areable to study PNe in other galaxies or in another wavelength regions addressing some of thequestions listed in the previous section.SIRTF This satellite will be operational from Autumn 2003 and carries a 85 cm mirror. TheInfrared Spectrograph (IRS) on board this satellite will provide spectral coverage in therange of 5 to 40 µm with a superb sensitivity. This sensitivity will enable the study ofPNe in the LMC, SMC and perhaps in the galactic center. Because of the metallicitydifference, changes can be expected and a comparison of the abundances found in theseenvironments is a very interesting issue that could be addressed. SIRTF’s resolutionand wavelength coverage is ideal as well to study dust features.
143HERSCHEL The launch of this satellite is scheduled for 2007. It will carry a 3.5 metertelescope and a high resolution spectrometer (HIFI) covering the range from 150 to600 µm. This will be ideal to study the rotational lines of CO and other moleculesoriginating in the photo-dissociation regions associated with PNe.SOFIA This stratospheric airborne observatory will carry a 2.7 meter telescope and willbe operational early in 2004. On board there is a Mid-IR camera (FORCAST) thatprovides imaging from 5-40 µm with an angular resolution of 0.75 ′′ /pixel. This willbe extremely useful to locate the emission of the different ions and learn about theionization gradient in the nebula.XMM-Newton This Multi-mirror X-ray satellite was launched in December 1999. Thespectral range covered by the satellite is 0.1 to 12 keV (120-1 nm). The resolutionof the RGS spectrograph is able to resolve narrow recombination lines arising fromthe hot X-ray emitting region in PNe. This can give us a better understanding of theinteraction of the mass loss from the central star with the nebular material.
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RIJKSUNIVERSITEIT GRONINGENPhysics
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To my parents
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Contents1 Introduction 11.1 Evoluti
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CONTENTSvii5 Probing AGB nucleosynt
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1IntroductionPLANETARY NEBULAE are
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1.1. Evolution of low and intermedi
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1.2. Planetary Nebulae 5Flash−Dri
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1.3. Physics in PNe 7their whole li
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1.3. Physics in PNe 95.35 eVO IIIλ
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1.4. Studying PNe in the infrared 1
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2The ISO-SWS Spectrum ofPlanetary N
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2.3. Data reduction 15Table 2.1-. C
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2.4. Line flux discussion 17Table 2
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2.5. The visual and the ultraviolet
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2.6. Analysis 21Table 2.5-. Electro
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24 CHAPTER 2: The ISO-SWS Spectrum
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3An ISO and IUE study of PlanetaryN
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3.3. Corrections to line fluxes 33[
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3.4. Line fluxes 35Table 3.1-. Comp
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Table 3.3-. IUE intensities, fluxes
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3.5. Physical parameters 393.4.3 Op
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3.5. Physical parameters 41Table 3.
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3.6. Chemical abundances 43Table 3.
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3.6. Chemical abundances 45Table 3.
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3.7. Conclusions 47Acknowledgements
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50 CHAPTER 4: Abundances of Planeta
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5Probing AGB nucleosynthesis viaacc
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5.1. Introduction 71about the synth
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Table 5.2-. Radius, Zanstra tempera
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5.3. Accurate abundances of ISO-obs
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5.3. Accurate abundances of ISO-obs
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5.4. Nucleosynthesis in low- and in
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5.5. Synthetic TP-AGB calculations
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5.6. Comparison between models and
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Page 111 and 112: 5.7. Summary and conclusions 103Fig
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Page 115 and 116: 6Physical Conditions in PDRs around
Page 117 and 118: 6.2. Observations 109are not promin
Page 119 and 120: 6.4. General parameters of the PNe
Page 121 and 122: 6.4. General parameters of the PNe
Page 123 and 124: Table 6.3-. Radius, Zanstra tempera
Page 125 and 126: 6.6. Lines fluxes 117Figure 6.2-. S
Page 127 and 128: 6.7. Physical conditions of the PDR
Page 135 and 136: 6.8. PDRs versus Shocks 127Figure 6
Page 137 and 138: 6.10. Atomic, ionized and molecular
Page 139 and 140: 6.10. Atomic, ionized and molecular
Page 141 and 142: 6.11. General discussion 133Table 6
Page 143 and 144: 6.11. General discussion 135Figure
Page 145 and 146: 6.12. Summary and Conclusions 137su
Page 147 and 148: 7Conclusions and future workTHE res
Page 149: 141• PNe with He/H > 0.14. The st
Page 153 and 154: Nederlandse SamenvattingSTERREN wor
Page 155 and 156: Nederlandse Samenvatting 147Figuur
Page 157 and 158: Nederlandse Samenvatting 149PHOTOIO
Page 159 and 160: Nederlandse Samenvatting 151Figuur
Page 161 and 162: Nederlandse Samenvatting 153infraro
Page 163 and 164: English SummarySTARS are born, live
Page 165 and 166: English Summary 157Figure 2-. Two e
Page 167 and 168: English Summary 159PHOTOIONIZATIONR
Page 169 and 170: English Summary 161Figure 5-. Spect
Page 171 and 172: English Summary 163all) stages of i
Page 173 and 174: BibliographyAcker A., Marcout J., O
Page 175 and 176: BIBLIOGRAPHY 167Henry R.B.C., Kwitt
Page 177 and 178: BIBLIOGRAPHY 169Pottasch S.R., Bern
Page 179 and 180: List of PublicationsPublications in
Page 181 and 182: AcknowledgementsI could easily writ
Page 183: Acknowledgements 175sense of humor,
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