thesis - IRS, The Infrared Spectrograph

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40 CHAPTER 3: An ISO and IUE study of Planetary Nebula NGC 2440Table 3.4–. Optical line fluxes. Observed values were taken from Hyung & Aller (1998). The dereddenedfluxes were derived using an interstellar extinction of C Hβ =0.50 (E B−V=0.34). Fluxes are inunits of 10 −12 erg cm −2 s −1 .Wavelength Ident. Measured Dereddened(nm) Fluxes Fluxes342.68 [Ne V] 25.3 ∗ 118372.60 [O II] 15.17 64.1372.97 [O II] 7.59 32.0386.87 [Ne III] 27.2 111.3436.32 [O III] 7.29 26.6447.15 He I 0.99 3.51468.57 He II 23.5 78.1471.15 [Ar IV] 2.29 7.56474.00 [Ar IV] 2.46 8.05486.10 H β 31.6 99.54500.68 [O III] 522.4 1572519.17 [Ar III] 0.10 0.28519.80 [N I] 1.69 4.81520.03 [N I] 1.17 3.33551.76 [Cl III] 0.64 0.52553.79 [Cl III] 0.23 0.60575.46 [N II] 4.80 12.02575.46 [N II] 4.54 † 11.37587.57 He I 3.10 7.60630.03 [O I] 6.53 14.9631.20 [S III] 0.66 1.50658.33 [N II] 383.7 841658.33 [N II] 263.1 † 576.7671.64 [S II] 1.96 4.21673.08 [S II] 3.13 6.71700.59 [Ar V] 1.39 2.87726.29 [Ar IV] 0.149 0.296732.00 [O II] 3.14 6.196733.03 [O II] 2.63 5.18∗ Taken from Rowlands et al. (1993).† Taken from Perinotto & Corradi (1998) (see text).
3.5. Physical parameters 41Table 3.5–. Electron density. T e=15 000 K is used.Ion IP ⋆ Lines used Obs. N e Other(eV) (nm) ratio (cm −3 ) ref. 1S II 10.4 673.1/671.6 1.59 4260 3100 aO II 13.6 372.6/372.9 2.00 4890 5000 dS III 23.3 33 470/18 700 0.87 871:Cl III 23.8 553.8/551.8 1.15 4900:C III 24.4 190.7/190.9 1.35 4360Ar IV 40.7 472.4/472.5 1.04 4900Ar IV 40.7 471.1/474.0 0.94 5200 4000 bAr V 59.8 13 100/7900 0.62: 34 500:Ne IV 63.4 242.4/242.2 1.11 3400 4000 c1 Values taken from Keenan et al. (1996 a , 1997 b , 1998 c , 1999 d ).: Large uncertainty.⋆ IP: Ionization potential.Fig. 3.2. The difference is mainly due to the flux difference of the 658.3 nm line, about 30%.The observations correspond to different parts of the nebula. However, the 575.5 nm linefluxes are very similar, indicating that the 658.3 line discrepancy maybe ascribed to errors influx determination. The ratio based on Perinotto & Corradi’s (1998) fluxes gives a T e whichbetter agrees with that of O II, that has a similar IP, and therefore was adopted to derive thecurve in Fig. 3.2. The difference in derived T e shows how differences in the fluxes can leadto noticeable differences in the reported temperature.In Fig. 3.2 the values tabulated in Table 3.6 have been plotted with the exception of theNe III T e . Ne III has been excluded because in other studies (Pottasch & Beintema 1999;Bernard Salas et al. 2001, chapter 2) it usually gives a lower T e . Probably this is due to theatomic parameter data. The T e derived from the S III using the line ratio 631.2 nm/33 479nm is not included because the errors are too large. Instead the ratio 631.2/18 700 has beenused. It should also be noticed that the S III ratio is sensitive to the adopted N e and this couldexplain the difference found in both T e . To derive chemical abundances T e corresponding tothe IP of each ion (given by the curve in Fig. 3.2) and N e =4500 cm −3 have been assumed.3.5.2 DiscussionThe N e seems to be constant and this could mean that the ejection of the outer layers is nowat lower rates than it has been before, leading to an homogeneous stratification of the nebula.A trend of T e with IP is found. As previously discussed by Bernard Salas et al. (2001,chapter 2) for NGC 7027, this agrees with a simple picture of a nebula where the highionization states are reached closer to the central star so they give higher temperatures, andthe low states of ionization give lower T e because they are formed further away. It is worthmention that the different values for the optical lines (of N II) given by Hyung & Aller (1998)
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: 3.5. Physical parameters 393.4.3 Op
Page 51 and 52: 3.6. Chemical abundances 43Table 3.
Page 53 and 54: 3.6. Chemical abundances 45Table 3.
Page 55: 3.7. Conclusions 47Acknowledgements
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
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5.6. Comparison between models and
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5.7. Summary and conclusions 103Fig
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5.7. Summary and conclusions 105A s
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6Physical Conditions in PDRs around
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6.2. Observations 109are not promin
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6.4. General parameters of the PNe
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6.4. General parameters of the PNe
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Table 6.3-. Radius, Zanstra tempera
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6.6. Lines fluxes 117Figure 6.2-. S
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6.7. Physical conditions of the PDR
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6.8. PDRs versus Shocks 127Figure 6
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6.10. Atomic, ionized and molecular
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6.10. Atomic, ionized and molecular
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6.11. General discussion 133Table 6
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6.11. General discussion 135Figure
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6.12. Summary and Conclusions 137su
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7Conclusions and future workTHE res
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141• PNe with He/H > 0.14. The st
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143HERSCHEL The launch of this sate
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Nederlandse SamenvattingSTERREN wor
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Nederlandse Samenvatting 147Figuur
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Nederlandse Samenvatting 149PHOTOIO
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Nederlandse Samenvatting 151Figuur
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Nederlandse Samenvatting 153infraro
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English SummarySTARS are born, live
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English Summary 157Figure 2-. Two e
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English Summary 159PHOTOIONIZATIONR
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English Summary 161Figure 5-. Spect
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English Summary 163all) stages of i
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BibliographyAcker A., Marcout J., O
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BIBLIOGRAPHY 167Henry R.B.C., Kwitt
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BIBLIOGRAPHY 169Pottasch S.R., Bern
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List of PublicationsPublications in
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AcknowledgementsI could easily writ
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Acknowledgements 175sense of humor,
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