TRACING ABUNDANCES IN GALAXIES WITH THE SPITZER ...

More documents

Recommendations

Info

Table 3.13 Abundances of PNe and H II regions across the Galaxy. Obtain abundances relative to hydrogen by multiplying the numbers in the Table by 10 x where x is -6 for argon, -4 for neon, -5 for sulfur, and -4 for oxygen. Distance range Ar/H Ne/H S/H O/H (kpc) PNe: This work + others (see §3.6.1) 0–4 4.6 2.7 1.2 4.5 4–8 4.3 1.9 1.2 5.0 8–... 2.7 1.1 0.63 4.2 H II Regions: Simpson et al. (1995) 0–4 ... 2.5 2.7 12 4–8 ... 1.5 1.2 5.6 8–... ... 0.68 0.76 3.6 H II Regions: Martín-Hernández et al. (2002) 0–4 7.9 2.4 1.1 ... 4–8 4.7 2.2 0.89 ... 8–... 2.6 1.2 0.65 ... if the Bulge does not have an abundance gradient, then it formed by dissipationless collapse, where mergers of small protogalactic pieces caused an inhomogeneous collapse over a long period of time and the mergers mixed stars of different ages and metallicities. If the Bulge has only a shallow abundance gradient, then the gravitational potential of the bar in our Galaxy caused concentrated star formation at its center and the stars eventually left the Disk to become (part of) the Bulge (Minniti et al., 1995). Several (mainly optical) studies of GBPNe point toward a slightly more metal- rich Bulge than Disk (Ratag et al., 1992; Cuisinier et al., 2000; Górny et al., 2004; Wang & Liu, 2007). However, Ratag et al. (1992) find that the average abundances of GBPNe cannot be predicted by the abundance gradient observed for GDPNe, hinting that stars in the Bulge are a distinct population from the Disk. Addition- ally, Górny et al. (2004) find that the O/H gradient becomes shallower and may even decrease in the most inner parts of the Disk based on their sample of GDPNe 87
towards the Galactic Center. On the other hand, Exter et al. (2004) find essentially no difference in abundances between their Bulge and Disk PNe samples; however, their results also point to a discontinuation of the Disk metallicity gradient. The large extinction toward the Bulge hinders optical studies of GBPNe. Thus, in this work we seek to confirm the results of the optical studies using mainly infrared data. In order to discover if the abundance trend in the Disk continues in the Bulge, Figure 3.4 shows abundances of argon, neon, sulfur, and oxygen versus galactocentric distance for both the GBPNe and GDPNe (GDPNe data discussed in §3.6.1). We fit lines to the plots of GBPNe and GDPNe abundances versus galactocentric distance in this figure separately (excluding from the fit to the oxygen abundance the four GDPNe that are thought to have depleted oxygen due to hot bottom burning, as discussed in Pottasch & Bernard-Salas 2006), and Table 3.14 gives parameters for these fits. The elemental abundance gradients of the GDPNe range from −0.08 to −0.14 dex/kpc and have uncertainties of 0.03–0.04 dex/kpc. In Figure 3.4 we also over plot the oxygen abundance gradient passing through the fit to the GDPNe abundances at 8 kpc on the plots for the other elements in order to illustrate that the abundances of the GBPNe are not consistent with the abundance versus galactocentric radius trend of GDPNe, whether the abundance data is fit directly to determine the gradient or if the shallower oxygen abundance gradient is assumed. The GBPNe have abundances significantly lower than the abundance in the Bulge predicted by the GDPNe abundance gradients. Unfortunately the uncertainties in our fit to the abundance gradient of GBPNe do not allow us to determine if an abundance gradient is present in the Bulge; thus we cannot conclude anything about the specific method of Bulge formation. The large velocities of objects in the Bulge may smear out any abundance gradient 88
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 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
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
Page 99: of two smaller than that of Simpson
Page 103 and 104: 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
Page 109 and 110: 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
Page 115 and 116: 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,
show all

TRACING ABUNDANCES IN GALAXIES WITH THE SPITZER ...

You also want an ePaper? Increase the reach of your titles

Delete template?

Save as template?