thesis - IRS, The Infrared Spectrograph

More documents

Recommendations

Info

46 CHAPTER 3: An ISO and IUE study of Planetary Nebula NGC 2440Table 3.9–. Comparison of the abundance ratios of C, N and O.NGC 2440 NGC 7027 1 Sun O StarsN/O 1.2 0.39 0.15 0.15C/O 1.9 1.5 0.48 0.42(C+N+O)H1.5(-3) 1.2(-3) 1.2(-3) 6.6(-4)1 From Bernard Salas et al. (2001).argon abundances agree with those of this paper. The neon and sulfur abundances are lowerthan the present study, but agree better than those of the models. The nitrogen abundancefrom Perinotto & Corradi (1998) is much higher but they only measured N II, and used ahighly uncertain ICF. From the C, N, O elements, only oxygen is less abundant than in theSun and O, B stars. Maybe some oxygen has been converted into carbon and nitrogen viathe CNO cycle. Neon and argon are similar to O, B stars which could mean that the nebulahasn’t formed any of these elements during its evolution. It is interesting to compare the ratioof carbon, oxygen and/or nitrogen. This is shown in Table 3.9.The N/O ratio is 3 times bigger than in NGC 7027 and 9 times bigger than in the Sun andO, B stars. A less pronounced difference occurs for the C/O ratio. Probably the oxygen hasbeen converted into nitrogen and to some extent into carbon as well. The (C+N+O)/H ratio istwice as large as in any other source. The progenitor star of NGC 2440 must be much moremassive than the Sun or NGC 7027. This is also supported by the helium abundance which isalso larger than any of these comparison sources.3.7 ConclusionsThe combined use of ISO, IUE and optical data is a powerful tool to derive NGC 2440’selemental abundances.The density seems to be constant (see Table 3.5) across the nebula because line ratios ofions with different IP that are probably formed in different regions give the same electrondensity. The nebula’s size is expected to increase with time as more layers are ejected. Inorder to keep a constant density in an expanding nebula, the ejection should occur at continuouslylower rates. The electron temperature increases with ionization potential (see Fig.3.2). This has previously been detected for NGC 7027 (Bernard Salas et al. 2001, chapter2), NGC 6302 (Pottasch & Beintema 1999) and NGC 6537 (Pottasch et al. 2000). A simplepicture of a planetary nebula is that close to the central star there exist more high energyUV photons than in the outer regions. Thus high IP ions are formed close to the central staronly and in an environment of high temperature. Low stages of ionization require lower UVphotons and consequently give lower temperature. From Table 3.9 it is clear that the CNOcycle has converted much of the oxygen into nitrogen and to some extent into carbon. The(C+N+O)/H ratio is larger than that of the Sun and NGC 7027. Therefore NGC 2440’s progenitormust have been more massive than NGC 7027. This is supported by the fact that thecarbon, nitrogen and oxygen abundances (Table 3.8) are, although lower, close to those ofmore massive O, B stars.
3.7. Conclusions 47AcknowledgementsWe are grateful to the referee, Prof. M. Perinotto whose comments have result in an improvement ofthe paper. IA3 is a joint development of the SWS consortium. Contributing institutes are SRON, MPE,KUL and the ESA Astrophysics Division.
Page 1 and 2:
RIJKSUNIVERSITEIT GRONINGENPhysics
Page 3 and 4: To my parents
Page 5 and 6: Contents1 Introduction 11.1 Evoluti
Page 7 and 8: CONTENTSvii5 Probing AGB nucleosynt
Page 9 and 10: 1IntroductionPLANETARY NEBULAE are
Page 11 and 12: 1.1. Evolution of low and intermedi
Page 13 and 14: 1.2. Planetary Nebulae 5Flash−Dri
Page 15 and 16: 1.3. Physics in PNe 7their whole li
Page 17 and 18: 1.3. Physics in PNe 95.35 eVO IIIλ
Page 19 and 20: 1.4. Studying PNe in the infrared 1
Page 21 and 22: 2The ISO-SWS Spectrum ofPlanetary N
Page 23 and 24: 2.3. Data reduction 15Table 2.1-. C
Page 25 and 26: 2.4. Line flux discussion 17Table 2
Page 27 and 28: 2.5. The visual and the ultraviolet
Page 29: 2.6. Analysis 21Table 2.5-. Electro
Page 32 and 33: 24 CHAPTER 2: The ISO-SWS Spectrum
Page 39 and 40: 3An ISO and IUE study of PlanetaryN
Page 41 and 42: 3.3. Corrections to line fluxes 33[
Page 43 and 44: 3.4. Line fluxes 35Table 3.1-. Comp
Page 45 and 46: Table 3.3-. IUE intensities, fluxes
Page 47 and 48: 3.5. Physical parameters 393.4.3 Op
Page 49 and 50: 3.5. Physical parameters 41Table 3.
Page 51 and 52: 3.6. Chemical abundances 43Table 3.
Page 53: 3.6. Chemical abundances 45Table 3.
Page 58 and 59: 50 CHAPTER 4: Abundances of Planeta
Page 77 and 78: 5Probing AGB nucleosynthesis viaacc
Page 79 and 80: 5.1. Introduction 71about the synth
Page 81 and 82: Table 5.2-. Radius, Zanstra tempera
Page 83 and 84: 5.3. Accurate abundances of ISO-obs
Page 85 and 86: 5.3. Accurate abundances of ISO-obs
Page 87 and 88: 5.4. Nucleosynthesis in low- and in
Page 89 and 90: 5.5. Synthetic TP-AGB calculations
Page 91 and 92: 5.6. Comparison between models and
Page 105 and 106:
5.6. Comparison between models and
Page 107 and 108:
Page 109 and 110:
Page 111 and 112:
5.7. Summary and conclusions 103Fig
Page 113 and 114:
5.7. Summary and conclusions 105A s
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 129 and 130:
Page 131 and 132:
Page 133 and 134:
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 and 150:
141• PNe with He/H > 0.14. The st
Page 151 and 152:
143HERSCHEL The launch of this sate
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,
show all

thesis - IRS, The Infrared Spectrograph

Create successful ePaper yourself

Delete template?

Save as template?