TRACING ABUNDANCES IN GALAXIES WITH THE SPITZER ...

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from Spitzer IRS maps of H II regions. Observations of dust features and emission lines with the Spitzer IRS allow us to probe the physical conditions in a variety of environments — e.g. the planetary nebulae and H II regions discussed in this dissertation. Knowing these physical conditions is important for understanding chemical evolution in galaxies as discussed above. 1.6 In This Dissertation The following chapters present Spitzer IRS data on planetary nebulae and H II regions. Specifically, Chapter 2 presents the case study of abundances in the planetary nebula IC 2448. Chapter 3 discusses abundances and dust in eleven planetary nebulae in the Bulge of the Galaxy. Finally, Chapter 4 gives abundance results for H II regions across the galaxy M51. 29
CHAPTER 2 THE SPITZER IRS INFRARED SPECTRUM AND ABUNDANCES OF THE PLANETARY NEBULA IC 2448 Paper by S. Guiles (the maiden name of S. Gutenkunst), J. Bernard-Salas, S. R. Pottasch, & T. L. Roellig, 2007, ApJ, 660, 1282 2.1 Abstract We present the mid-infrared spectrum of the planetary nebula IC 2448. In order to determine the chemical composition of the nebula, we use the infrared line fluxes from the Spitzer spectrum along with optical line fluxes from the literature and ul- traviolet line fluxes from archival IUE spectra. We determine an extinction of CHβ = 0.27 from hydrogen recombination lines and the radio to Hβ ratio. Forbidden line ratios give an electron density of 1860 cm −3 and an average electron temperature of 12700 K. The use of infrared lines allows us to determine more accurate abundances than previously possible because abundances derived from infrared lines do not vary greatly with the adopted electron temperature and extinction, and additional ionization stages are observed. Elements left mostly unchanged by stellar evolution (Ar, Ne, S, and O) all have subsolar values in IC 2448, indicating that the progenitor star formed out of moderately metal deficient material. Evi- dence from the Spitzer spectrum of IC 2448 supports previous claims that IC 2448 is an old nebula formed from a low mass progenitor star. 2.2 Introduction Determining accurate abundances of planetary nebulae (PNe) is important for understanding how stars and galaxies evolve (Kaler, 1985). PNe abundances of elements made in low and intermediate mass stars (such as helium, carbon, and 30
Page 1 and 2: TRACING ABUNDANCES IN GALAXIES WITH
Page 3 and 4: TRACING ABUNDANCES IN GALAXIES WITH
Page 5 and 6: BIOGRAPHICAL SKETCH Shannon was bor
Page 7 and 8: ACKNOWLEDGEMENTS First and foremost
Page 9 and 10: thank my husband Ryan. The rest of
Page 11 and 12: 3 Chemical Abundances and Dust in P
Page 13 and 14: LIST OF FIGURES 1.1 Diagram of the
Page 15 and 16: ditionally we find that these nebul
Page 17 and 18: seed nuclei relative to the β deca
Page 19 and 20: shape (Carollo et al., 2007). These
Page 21 and 22: Boltzmann velocity distribution cha
Page 23 and 24: etween recapture and photoionizatio
Page 25 and 26: a whole. Additionally, abundances f
Page 27 and 28: at the appropriate temperature and
Page 29 and 30: (a) 3.37 eV 1.40 eV 0.10 eV 0.04 eV
Page 31 and 32: (Iion), the radiative transition ra
Page 33 and 34: lines. For example, changing the ad
Page 35 and 36: Figure 1.4 Starburst99 synthetic sp
Page 37 and 38: Figure 1.5 Example of crystalline s
Page 39 and 40: H H H H H H H H H Anthanthrene C H
Page 41: year lifetime. Spitzer is in an Ear
Page 45 and 46: these elements than previous studie
Page 47 and 48: dust is seen in the spectrum. We se
Page 49 and 50: Figure 2.2 Close-ups of emission li
Page 51 and 52: 2.4 Optical and UV Data We compleme
Page 53 and 54: 2.5 Data Analysis Our goal is to ca
Page 55 and 56: 2.5.2 Electron Density We assume an
Page 57 and 58: Table 2.6 Electron temperatures ass
Page 59 and 60: O, N, and C. The helium ionic abund
Page 61 and 62: Barlow (1994) use UV lines for impo
Page 63 and 64: is a spherical nebula with a low ma
Page 65 and 66: CHAPTER 3 CHEMICAL ABUNDANCES AND D
Page 67 and 68: essential data on important ionizat
Page 69 and 70: are members of the Bulge, (Acker et
Page 71 and 72: Table 3.2 Properties of observed GB
Page 73 and 74: nod-averaged line fluxes. Uncertain
Page 75 and 76: Table 3.3 Multiplicative scaling fa
Page 77 and 78: Table 3.4 Observed infrared line fl
Page 79 and 80: 3.5 Data Analysis 3.5.1 Abundances
Page 81 and 82: Table 3.6 Comparison of the derived
Page 83 and 84: from the most reliable line(s), and
Page 85 and 86: Table 3.7 Electron temperatures and
Page 87 and 88: Table 3.9 Ionic abundances Ion x a
Page 89 and 90: 3.5.2 Crystalline Silicates Crystal
Page 91 and 92: argon, neon, and sulfur tend to be
Page 93 and 94:
Figure 3.2 Continuum subtracted spe
Page 95 and 96:
Figure 3.3 Profiles of PAH features
Page 97 and 98:
mean argon and sulfur abundances ar
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of two smaller than that of Simpson
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towards the Galactic Center. On the
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Table 3.14 Parameters of linear fit
Page 105 and 106:
models that show how a binary compa
Page 107 and 108:
y an outer dense O-rich torus, indi
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CHAPTER 4 ABUNDANCES IN H II REGION
Page 111 and 112:
expect their abundance ratio to rem
Page 113 and 114:
We extract spectra processed throug
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Figure 4.2 IRS spectra of H II regi
Page 117 and 118:
IRS slits from these WIRC observati
Page 119 and 120:
S IV) we employ is equal to Te(O +2
Page 121 and 122:
Figure 4.3 M51 H II region Ne III/N
Page 123 and 124:
Figure 4.4 shows a plot of the (Ne
Page 125 and 126:
James Webb Space Telescope (JWST);
Page 127 and 128:
Bernard-Salas, J. & Tielens, A. G.
Page 129 and 130:
Edgar, R. G., Nordhaus, J., Blackma
Page 131 and 132:
Hummer, D. G., Berrington, K. A., E
Page 133 and 134:
Matsuura, M., Zijlstra, A. A., Mols
Page 135 and 136:
Pradhan, A. K., Montenegro, M., Nah
Page 137:
Vassiliadis, E. & Wood, P. R. 1993,
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