A spatially resolved study of ionized regions in galaxies at different ...

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22 2 • The star formation history of NGC 5471 Figure 2.6: Continuum free Hα image of NGC 5471. The circular aperture of 15 ′′ where the integrated photometry was performed to obtain the total flux is overplotted. The ellipse indicating the core of the region is drawn as reference. others are extrinsic and depend on the properties of the interstellar matter (reddening and extinction law). CHORIZOS can handle SED families for stellar atmospheres and clusters (Starburst99; Leitherer et al., 1999) and uses χ 2 minimization to find all models compatible with the observed data in a (2 intrinsic +2 extrinsic)-dimensional parameter space. It includes a wide list of filters for different systems (Johnson-Cousins, HST/WFPC2, 2MASS, . . . ) and allows for published magnitudes to be used directly. For a set of objects with measured magnitudes m 1 , m 2 , . . . , m M+1 (with independent uncertainties σ 1 , σ 2 , . . . , σ M+1 ), derived independent colors c 1 , c 2 , . . . , c M , and a set of N parameters with M > N, no strict solutions, but only approximate ones, can be found since the problem has more equations or sets of model parameters that produce a given color than model parameters. Hence, the code finds the N-volume of approximate solutions by using χ 2 minimization. The first step of the program is to read the unreddened SED models, extinguish them according to a given extinction law, and obtain the synthetic photometry; the code includes pre-calculated tables for all the models and filters. To run the program, CHORIZOS requires
2.3. Results 23 Aperture R eff F(Hα) L(Hα) Q(H 0 ) M ii EW(Hα) pc 10 −13 erg s −1 cm −2 10 39 erg s −1 10 51 s −1 10 4 M ⊙ Å NGC5471-1 61.1 6.63 ± 0.31 4.1 4.1 13.0 1187 ± 77 NGC5471-2 60.9 3.07 ± 0.14 1.9 1.9 6.1 993 ± 64 NGC5471-3 47.0 0.93 ± 0.04 0.6 0.6 1.9 354 ± 23 NGC5471-4 51.2 1.59 ± 0.07 1.0 1.0 3.2 1103 ± 71 NGC5471-5 46.0 0.79 ± 0.04 0.5 0.5 1.6 788 ± 51 NGC5471-6 58.9 2.42 ± 0.11 1.5 1.5 4.8 919 ± 59 NGC5471-7 63.1 2.34 ± 0.11 1.5 1.4 4.7 872 ± 57 NGC5471-8 43.5 0.72 ± 0.03 0.5 0.4 1.4 756 ± 49 NGC5471-9 34.0 0.38 ± 0.02 0.2 0.2 0.8 1369 ± 90 NGC5471-10 46.2 1.22 ± 0.06 0.8 0.8 2.4 1282 ± 83 NGC5471-11 53.6 0.31 ± 0.01 0.2 0.2 0.6 585 ± 37 NGC 5471 525 36.5 ± 1.70 23 22 73 783 ± 40 Table 2.4: Integrated Hα flux and derived parameters for the eleven regions of NGC 5471. R eff is the effective radius of the polygon. The last row belongs to the integrated values of the whole region. a file with the photometry data and a series of input parameters, such as the model family, understood as the collection of SED from stellar atmosphere models or synthetic stellar populations, and the range of the parameters to be used. Then, CHORIZOS reads the model photometry from the tables calculated previously, interpolates, calculates the likelihood for each grid point, and write the results for each of the four parameters (mode, mean, standard deviation, median, . . . ). The program contains a useful module which reads the results and produces spectra, probability contour plots and additional statistics. In the case of our study, we have used the STARBURST99 models (Leitherer et al., 1999) with the implementation by Smith et al. (2002) which includes a grid of blanketed stellar atmospheres at different metallicities. We fixed two parameters: the known metallicity of NGC 5471 and the type of dust, leaving unconstrained the amount of extinction and the age. Regarding extinction, CHORIZOS works with E(4405 − 5495) and R 5495 , which are the monochromatic equivalent to E(B − V ) and R V respectively, the values 4405 and 5495 referring to the central wavelength (in Å) of the B and V filters. We used the standard type of dust characterized by a value R 5495 = 3.1. The metallicity of the region was assumed to be traced by the oxygen abundance. Recent derivations from detailed spectrophotometric studies give a mean value of 12+log(O/H) of 8.06 ± 0.03 for components A, C and D; a slightly lower abundance of 7.94 ± 0.03 is found for component B (Kennicutt et al., 2003). These values correspond to about 0.25 the solar oxygen abundance, if the value by Asplund et al. (2005) for the solar oxygen abundance is assumed. Therefore we used the
Page 1: Facultad de Ciencias Departamento d
Page 5: A Abigaíl, mi ut A mi familia, por
Page 8 and 9: La gente del grupo de Astrofísica
Page 11 and 12: Contents List of Figures List of Ta
Page 13: CONTENTS iii B •Physical conditio
Page 16 and 17: vi LIST OF FIGURES 3.12 Example of
Page 19 and 20: List of Tables 1.1 Integrated prope
Page 21 and 22: Chapter 1 Introduction 1.1 Overview
Page 23 and 24: 1.1. Overview 3 Figure 1.1: Sample
Page 25 and 26: 1.1. Overview 5 These massive star
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Page 29: 1.2. Aims and structure of this wor
Page 32 and 33: 12 2 • The star formation history
Page 60 and 61: 40 3 • IFS of a GEHR in NGC 6946
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72 3 • IFS of a GEHR in NGC 6946
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β[H 84 3 • IFS of a GEHR in NGC
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106 4 • Long-slit spectrophotomet
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Hδ 116 4 • Long-slit spectrophot
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Table 4.4 continued SDSS J1657 Knot
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150 Conclusions and future work has
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152 Conclusions and future work oth
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154 Conclusions and future work The
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156 Conclusiones Las abundancias to
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158 Conclusiones consistentes con l
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160 Appendix A where c=0.434C. This
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162 Appendix B where R S2 = I(6717
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164 Appendix B Sulphur As in the ca
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166 Appendix B Argon For argon, the
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Appendix C Empirical calibrators In
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C • Empirical calibrators 171 One
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Appendix D Stellar photometry resul
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D • Stellar photometry results of
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190 REFERENCES Bertelli, G., Bressa
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192 REFERENCES Girardi, L. & Bertel
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194 REFERENCES Kunth, D. & Sargent,
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196 REFERENCES Pérez-Montero, E.,
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198 REFERENCES Terlevich, R., Melni
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