TRACING ABUNDANCES IN GALAXIES WITH THE SPITZER ...

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Figure 1.2 Example IRS spectrum the Bulge planetary nebula PNG000.7+04.7. The above spectrum results from averaging the fluxes from the two nod positions and scaling the flux in each module to the module with the highest flux (LH). The spectrum consists of low resolution data below 10 µm and high resolution data above 10 µm. Bright lines are labeled. The inset shows a close-up of the spectrum around the H I(7-6) Humphreys-α line at 12.37 µm. 9
etween recapture and photoionization sets the degree of ionization in each part of the nebula. The ion recaptures the electron to an excited level in the process called recombination, and the excited atom decays to lower levels by radiating photons. When a hydrogen ion (H + ) recombines with an electron (leading to an excited H 0 atom), the excited H 0 atom decays to the ground state by emitting a series of photons which generate the H I recombination lines, such as the H I(6-5) Pfund-α line at 7.46 µm and the H I(7-6) Humphreys-α line at 12.37 µm observed in Spitzer spectra of photoionization regions. Figure 1.2 shows a close-up of the Humphreys-α line observed in the spectrum of PNG000.7+04.7. Other elements such as helium also emit recombination lines. 1.2.1 Planetary Nebulae The name “planetary” is a misnomer and was originally derived from the fact that when PNe were studied through small telescopes over two hundred years ago they looked like planets. The name “nebula”, Latin for “cloud” is, however, more appropriate. Huggins & Miller (1864) were the first to look at planetary nebulae through a spectrograph, finding that the spectra of these nebulae differed significantly from those of stars. The planetary nebulae showed only three bright emission lines with little continuum emission in their spectra, and Huggins & Miller (1864) remark “In place of an incandescent solid or liquid body transmitting light of all [wavelengths] through an atmosphere which intercepts by absorption a certain number of them, such as our sun appears to be, we must probably regard these objects, or at least their photo-surfaces, as enormous masses of luminous gas or vapour. For it is alone from matter in the gaseous state that light consisting of certain definite [wavelengths] only, as is the case with the light of these nebulae, is known to be emitted.” This marked the beginning of our understanding of the physical nature 10
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: Boltzmann velocity distribution cha
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 and 42: year lifetime. Spitzer is in an Ear
Page 43 and 44: CHAPTER 2 THE SPITZER IRS INFRARED
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
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Table 3.6 Comparison of the derived
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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
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argon, neon, and sulfur tend to be
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Figure 3.2 Continuum subtracted spe
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Figure 3.3 Profiles of PAH features
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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
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models that show how a binary compa
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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
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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
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S IV) we employ is equal to Te(O +2
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Figure 4.3 M51 H II region Ne III/N
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Figure 4.4 shows a plot of the (Ne
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James Webb Space Telescope (JWST);
Page 127 and 128:
Bernard-Salas, J. & Tielens, A. G.
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Edgar, R. G., Nordhaus, J., Blackma
Page 131 and 132:
Hummer, D. G., Berrington, K. A., E
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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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