TRACING ABUNDANCES IN GALAXIES WITH THE SPITZER ...

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nitrogen) can be used to test stellar evolution models (Kwok, 2000). Abundances of elements which are not changed during evolution of low and intermediate mass stars (such as neon, argon, sulfur, and in some cases oxygen), can give insight into the chemical content of the gas from which the progenitor star formed (Kwok, 2000); thus abundances of PNe dispersed throughout a galaxy can be used to test galactic evolution models. IC 2448 is an elliptical, average sized PN located at RA = 09 h 07 m 06 s .26, DEC = −69 ◦ 56 ′ 30 ′′ .7 (J2000.0, Kerber et al. (2003)). Optical emission line images of IC 2448 show that diffuse [N II] and [O III] emission pervade the same oval region, which agrees with IC 2448 being an old, evolved nebula (Palen et al., 2002). McCarthy et al. (1990) give further evidence for IC 2448’s advanced age, finding that its evolutionary age is 8400 years and its dynamical age is 7000 years. IC 2448 has an Hα diameter of 10. ′′ 7 x 10. ′′ 0 (Tylenda et al., 2003). Thus at a distance of 2.1 ± 0.6 kpc (Mellema, 2004), IC 2448 has an Hα size of 0.11 x 0.10 pc. Two optical surveys and one optical+ultraviolet survey of PNe include abundance determinations for IC 2448 (Torres-Peimbert & Peimbert, 1977; Milingo et al., 2002a; Kingsburgh & Barlow, 1994). Here we report the first use of mid- infrared line fluxes from IC 2448 to determine its abundances. Using infrared (IR) lines to derive abundances has several advantages over using optical or ultraviolet (UV) lines (Rubin et al., 1988; Pottasch & Beintema, 1999). First, the correction for extinction in the IR is smaller than in the optical and UV, and therefore errors in the extinction coefficient and law affect IR line fluxes less. Second, IR lines are less sensitive to uncertainties in the electron temperature because they come from levels close to the ground level. Finally, some ions have lines in the IR spectrum of IC 2448, but not in the optical or UV spectra. When combined with ionic lines of these elements observed in the optical and UV, we have line fluxes for more ions of 31
these elements than previous studies, reducing the need for ionization correction factors (ICFs) to account for unseen ionization stages. In this paper we use the Spitzer IR spectrum supplemented by the optical and UV spectra to derive ionic and total element abundances of He, Ar, Ne, S, O, N, and C in IC 2448. The next section describes the Spitzer observations and the data reduction. §2.4 gives the optical and UV data. In §2.5 we derive the extinction, electron density, electron temperature, and ionic and total element abundances. §2.6 compares the abundances of IC 2448 with solar and discusses the nature of the progenitor star and we conclude in §2.7. 2.3 Spitzer Observations and Data Reduction IC 2448 was observed with all four modules (Short-Low (SL), Long-Low (LL), Short-High (SH), and Long-High (LH)) of the Infrared Spectrograph (IRS) (Houck et al., 2004) on the Spitzer Space Telescope (Werner et al., 2004) as part of the GTO program ID 45. The AORkeys for IC 2448 are 4112128 (SL, SH, LH observed 2004 July 18), 4112384 (SL, SH, LH off positions observed 2004 July 18), and 12409088 (LL observed 2005 February 17). The data were taken in ‘staring mode’ which acquires spectra at two nod positions along each IRS slit. For the on target AORkeys (4112128 and 12409088), the telescope was pointed at RA = 09 h 07 m 06 s .4, DEC = −69 ◦ 56 ′ 31 ′′ (J2000.0). For the off target AORkey (4112384), the telescope was pointed at RA = 09 h 07 m 06 s .6, DEC = −69 ◦ 58 ′ 29 ′′ (J2000.0). Peak-up imaging was performed for AORkey 4112128, but not for the other AORkeys. The data were processed through version s14.0 of the Spitzer Science Center’s pipeline. We begin our analysis with the unflatfielded (droopres) images to avoid potential problems in the flatfield. Then we run the irsclean 1 program to remove 1 Program available from the Spitzer Science Center’s website at http://ssc.spitzer.caltech.edu 32
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 and 42: year lifetime. Spitzer is in an Ear
Page 43: CHAPTER 2 THE SPITZER IRS INFRARED
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
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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
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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
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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);
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Bernard-Salas, J. & Tielens, A. G.
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Edgar, R. G., Nordhaus, J., Blackma
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Hummer, D. G., Berrington, K. A., E
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Matsuura, M., Zijlstra, A. A., Mols
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Pradhan, A. K., Montenegro, M., Nah
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Vassiliadis, E. & Wood, P. R. 1993,
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