thesis - IRS, The Infrared Spectrograph

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16 CHAPTER 2: The ISO–SWS Spectrum of Planetary Nebula NGC 7027The reduction didn’t present any problem except in the first part of band 2c (7 to 12 µm)where the up and down scans deviated significantly from each other, but matched in the restof the band when flatfielding was applied. This doesn’t affect the measured fluxes but couldbe important when reasonable upper limits to some lines are determined, as explained in nextparagraph. This was caused by some detectors (19, 20, 21, 23 and 24) which suffered fromerroneous dark current subtraction. The range 7.3 to 7.6 µm was affected. These detectorswere removed. A reference flat (order one) was defined using the remaining detectors andapplied to the whole band. Flatfielding reduces the mismatch and then all detectors could beused to measured line intensities.It is useful to compute an upper limit to the flux for some unseen lines. For this purpose,outlying data points were removed with the sigclip tool and the spectra were rebinned(sws rebin tool) to a standard resolution. Upper limits for the lines [Cl IV] 11.76 µm, [Na VI]8.61 µm, [K VI] 5.58 and 8.83 µm were calculated using a model of a synthetic Gaussian,with the width corresponding to the resolution, and a height of three times the RMS (deviationfrom the average). These upper limits of unseen lines allow to more accurately apply theionization correction factor for the relevant ions.2.4 Line flux discussionIn Table 2.2 the fluxes measured for the infrared (IR) lines are listed. In total around 80lines were measured. Calibration errors are larger at longer wavelengths but on averageamount to about 20%. Random measurement errors depend on the flux strength: weak lines(I < 5, where I is in 10 −12 erg cm −2 s −1 ) have estimated errors of about 20%, intermediatelines (5 10), have normally lessthan 5% uncertainty. All the lines follow this behavior with the exception of the S III lineat 33.5 µm with a measured intensity of 7.12 10 −12 erg cm −2 s −1 and an uncertainty of19%. This part of the spectrum is the noisiest and weak lines are not seen. Therefore, thisline could be considered an intermediate strength line in this part of the spectrum. Thus theuncertainty in the fluxes of intermediate and strong lines is dominated by the calibration error.NGC 7027’s spectrum is extremely rich as can be seen in Fig. 2.1. The hydrogen andhelium lines are abundant in the whole spectrum but specially in the range 2.4–5.5 µm. Ionswith high stages of ionization are found (i.e. Fe VII, Na VII, Ar VI) in the nebula. Ninemolecular hydrogen lines (H 2 ) have been measured as well and probably originate in theouter part of the nebula where the temperature is lowest. For Ar, K and specially Ne wehave information for the most important stages of ionization implying that the uncertainty inthe ionization correction factor (ICF) used to derive the absolute abundances will be muchreduced. Several stages of ionization of some ions were not observed. Then, an upper limit tothe flux was determined, as described in the previous section. Also noticeable in the spectrumis the strong continuum at the longest wavelength and the features at 3.3, 6.6, 7.7, 8.8 and11.2 µm now known as PAHs as well as a broad PAH plateau from 15 to 20 µm. In thispaper we will concern ourselves only with the emission lines. A detail study of the PAHs andthe plateau can be found in the articles by Peeters et al. (2002), Hony et al. (2001) and VanKerckhoven et al. (2000).
2.4. Line flux discussion 17Table 2.2–. Line fluxes for NGC 7027.λ Ident. Flux † λ Ident. Flux †(µm)(µm)2.406 H 2 , 1→0 Q(1) 3.73 5.580 [K VI] < 8.282.424 H 2 , 1→0 Q(3) 2.35 5.908 H I 6–9 6.532.495 H I 5–17 1.17 5.981 [K IV] 3.602.564 H I 5–15 2.52 6.705 [Cl V] 6.092.613 He I 4–6 1.46 6.910 H 2 , 0→0 S(5) 6.692.626 H I (Brβ) 45.9 6.947 He II 8–9 3.472.671 He I 4–6 1.45 6.985 [Ar II] 30.72.675 H I 5–13 2.24 7.317 [Na III] 13.92.758 H I 5–12 2.84 7.459 H I (Pfα) 28.32.802 H 2 , 1→0 O(3) 2.96 7.503 H I 6–8 8.912.826 He II 7–9 5.43 7.652 [Ne VI] 96.52.905 [Al V] 1.16 7.814 [Fe VII] 2.633.004 H 2 , 1→0 O(4) 0.59 7.901 [Ar V] 47.13.039 H I 5–10 5.70 8.025 H 2 , 0→0 S(4) 2.523.092 He II 6–7 18.8 8.610 [Na VI] < 3.453.095 He II 8-11 1.66 8.761 H I 7–10 2.533.207 [Ca IV] 1.47 8.830 [K VI] < 4.173.234 H 2 , 1→0 O(5) 0.79 8.991 [Ar III] 1223.625 Zn IV? 0.95 9.042 [Na IV] 12.13.740 H I (Pfγ) 11.0 9.525 [Fe VII] 4.853.749 H I 6–17 0.78 9.665 H 2 , 0→0 S(3) 6.823.907 H I 6–15 1.29 9.713 He II 9–10 2.164.020 He I 4–5 1.08 10.510 [S IV] 4294.022 H I 6–14 0.72 11.760 [Cl IV] < 4.164.038 He I 4–5 0.97 12.372 H I 6–7 11.34.052 H I (Brα) 91.6 12.812 [Ne II] 91.64.296 He I 3–5 4.86 13.101 [Ar V] 31.04.377 H I 6–12 1.66 13.520 [Mg V] 38.74.486 [Mg IV] 148 14.321 [Ne V] 13504.529 [Ar VI] 126 15.550 [Ne III] 10904.618 [K III] 4.09 18.713 [S III] 76.04.654 H I (Pfβ) 17.5 19.062 H I 7–8 5.944.672 H I 6-11 2.50 21.800 [Ar III] 3.004.764 He II 7–8 9.43 24.315 [Ne V] 3875.128 H I 6–10 4.51 25.888 [O IV] 7155.510 H 2 , 0→0 S(7) 2.29 33.477 [S III] 7.125.610 [Mg V] 416 34.812 [Si II] 14.936.012 [Ne III] 49.2† In units of 10 −12 erg cm −2 s −1 .
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: 2.3. Data reduction 15Table 2.1-. C
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 and 54: 3.6. Chemical abundances 45Table 3.
Page 55: 3.7. Conclusions 47Acknowledgements
Page 58 and 59: 50 CHAPTER 4: Abundances of Planeta
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66 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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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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