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

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108 4 • Long-slit spectrophotometry of multiple knots of Hii galaxies Figure 4.1: False colour image of J1657. This image was obtained using the SDSS explore tools. Circles and squares represent the photometric and spectroscopic SDSS targets, respectively. Note the alignment of the three knots along the parallactic angle. respectively. The observations were made at parallactic angle to avoid effects of differential refraction in the UV. As it can be seen in Figure 4.1, three knots of J1657 are almost perfectly aligned along the parallactic angle. The instrumental configuration, summarized in Table 4.1, covers the whole spectrum from 3400 to 10400 Å (with a gap between 5700 and 5800 Å) providing at the same time a moderate spectral resolution. As in the case of IIZw71, this guarantees the simultaneous measurement of the nebular lines from [Oii] λλ 3727,29 to [Siii] λλ 9069,9532 Å at both ends of the spectrum, in the very same region of the galaxy, with a good signal-to-noise ratio that allows the measurement of the weak lines. Typical values of signal-to-noise ratios are 64 for [Oiii] λ 4363 and 21 for [Sii] λ 4068. Unfortunately, although the spectral range allowed the observation of the Balmer discontinuity, not enough signal-to-noise ratio was achieved to measure this jump with an acceptable accuracy. 4.2.2 WHT observations The long-slit spectrophotometric observations of IIZw71 were obtained using the ISIS double-beam spectrograph mounted on the 4.2m William Herschel Telescope (WHT) of the Isaac Newton Group (ING) at the Roque de los Muchachos Observatory on the Spanish island of La Palma. They were acquired on 2005 July 8 during one single night’s observing run and under photometric conditions, with an average seeing of 0.7 arcsec. The EEV12 and
4.2. Observations and reduction 109 Spectral range Disp. FWHM Spatial res. Exposure Time (Å) (Å px −1 ) (Å) ( ′′ px −1 ) s WHT - ISIS 3670-5070 0.45 1.0 0.2 4× 1200 5500-7800 0.86 3.5 0.2 2× 1200 7600-9900 0.86 3.5 0.2 2× 1200 CAHA - TWIN 3400-5700 1.09 2.8 0.56 5× 1800 5800-10400 2.42 6.9 0.56 5× 1800 Table 4.1: WHT and CAHA instrumental configuration Marconi2 detectors were attached to the blue and red arms of the spectrograph, respectively. The R600B grating was used in the blue covering the wavelength range 3670-5070 Å (centred at λ c = 4370 Å), giving a spectral dispersion of 0.45 Å pixel −1 . On the red arm, the R316R grating was mounted in two different central wavelengths providing a spectral range from 5500 to 7800 Å (λ c = 6650 Å) and from 7600 to 9900 Å (λ c = 8750 Å) with a spectral dispersion of 0.86 Å pixel −1 . To reduce the readout noise of our images, the observations were taken with the ‘SLOW’ CCD speed. The pixel size for this set-up configuration is 0.2 arcsec for both spectral ranges. The slit width was ∼1 arcsec, which, combined with the spectral dispersions, yields spectral resolutions of about 1.0 and 3.5 Å FWHM in the blue and red arms, respectively. The instrumental configuration, summarized in Table 4.1, was planned to cover the whole spectrum from about 3500 to 10000 Å, at the same time providing the required moderate spectral resolution. Unfortunately, the signal-to-noise achieved was by far not as good as in the CAHA observations. The value of signal-to-noise ratio is 10 for [Oiii] λ 4363. To cover all knots along the polar ring at the same exposure, all the spectra were taken at PA= 30 o , an average of 56 o off parallactic angle, and the spectra are thus somehow affected by atmospheric differential refraction. Taking the mean air mass into account during the observations of this object (≈ 1.25) and following the curves by Filippenko (1982), we calculated that the displacement between [Oii] 3727 Å and [Siii] 9069 Å, which are the emission lines the most separated in wavelength, is no greater than 0.9 arcsecs. 4.2.3 Data reduction Several bias and sky flat field frames were taken at the beginning and at the end of the night in both arms. In addition, two lamp flat fields and one calibration lamp exposure were performed at each telescope position. The calibration lamp used was CuNe+CuAr for
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Facultad de Ciencias Departamento d
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A Abigaíl, mi ut A mi familia, por
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La gente del grupo de Astrofísica
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Contents List of Figures List of Ta
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CONTENTS iii B •Physical conditio
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vi LIST OF FIGURES 3.12 Example of
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List of Tables 1.1 Integrated prope
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Chapter 1 Introduction 1.1 Overview
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1.1. Overview 3 Figure 1.1: Sample
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1.1. Overview 5 These massive star
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1.1. Overview 7 Figure 1.3: Color-m
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1.2. Aims and structure of this wor
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12 2 • The star formation history
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40 3 • IFS of a GEHR in NGC 6946
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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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