publication . Doctoral thesis . Thesis . Other literature type . 2017

Unravelling Galaxy Components

Kennedy, Rebecca;
Open Access
  • Published: 22 Jun 2017
  • Country: United Kingdom
Abstract
This thesis aims to understand more about the developmental histories of galaxies and their internal components by studying the wavelength dependence of their spatial structure. I use a large sample of low-redshift galaxies with optical–near-IR imaging from the GAMA survey, which have been fitted with Sersic and Sersic + exponential functions in nine wavebands simultaneously, using software developed by the MegaMorph project.\ud The first section of this thesis examines how the sizes and radial profiles of galaxies vary with wavelength. To quantify the wavelength dependence of effective radius I use the ratio, R, of measurements in two restframe bands. The depen...
Subjects
arXiv: Astrophysics::Cosmology and Extragalactic AstrophysicsAstrophysics::Galaxy Astrophysics
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Doctoral thesis . 2017
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Zenodo
Other literature type . 2017
Provider: Datacite
Zenodo
Other literature type . 2017
Provider: Datacite
112 references, page 1 of 8

1 Introduction 1 1.1 Motivation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 1.2 Galaxy Formation . . . . . . . . . . . . . . . . . . . . . . . . . . 1 1.3 Galaxy Evolution . . . . . . . . . . . . . . . . . . . . . . . . . . 2 1.3.1 Internal processes . . . . . . . . . . . . . . . . . . . . . . 3 1.3.2 Environmental processes . . . . . . . . . . . . . . . . . . 4 1.3.3 Size Evolution . . . . . . . . . . . . . . . . . . . . . . . . 6 1.4 Galaxy Morphology . . . . . . . . . . . . . . . . . . . . . . . . . 7 1.4.1 Measuring structural properties . . . . . . . . . . . . . . 9 1.4.2 Wavelength dependence of structural parameters . . . . . 11 1.4.3 Colour gradients . . . . . . . . . . . . . . . . . . . . . . 12 1.5 Stellar populations . . . . . . . . . . . . . . . . . . . . . . . . . 13 1.5.1 Age-metallicity degeneracy . . . . . . . . . . . . . . . . . 14 1.6 Structure of thesis . . . . . . . . . . . . . . . . . . . . . . . . . 16

2 Data and methods 17 2.1 Galaxy And Mass Assembly (GAMA) . . . . . . . . . . . . . . . 17 2.1.1 Overview . . . . . . . . . . . . . . . . . . . . . . . . . . 17 2.1.2 Data management . . . . . . . . . . . . . . . . . . . . . 18 2.2 MegaMorph . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19 2.3 Sersic modelling and bulge-disc decomposition . . . . . . . . . . 21 2.4 Data used in this thesis . . . . . . . . . . . . . . . . . . . . . . . 27 2.4.1 Two-component ts . . . . . . . . . . . . . . . . . . . . . 29 3.3.2 Luminosity dependence of galaxy structure . . . . . . . . 41 3.3.3 Morphological classi cations . . . . . . . . . . . . . . . . 47 3.3.4 The e ects of dust . . . . . . . . . . . . . . . . . . . . . 48

3.4 Discussion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51 3.4.1 The physical meaning of R and N . . . . . . . . . . . . 51 3.4.2 Comparison of observed trends of R and N with other studies . . . . . . . . . . . . . . . . . . . . . . . . . . . . 54

3.5 Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 57

4 Internal colour gradients of galaxies 60 4.1 Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 60 4.2 Data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 62 4.3 Results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 65 4.3.1 Variation in colour gradient with wavelength . . . . . . . 65 4.3.2 Luminosity dependence of colour gradients . . . . . . . . 66 4.3.3 Origin of bimodality in luminosity dependence of colour gradient . . . . . . . . . . . . . . . . . . . . . . . . . . . 68 4.3.4 Relationship between colour gradients and wavelength dependence of n and Re . . . . . . . . . . . . 71 4.4 Discussion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 72 5.4.2 Comparison of observed trends of component colours with other studies . . . . . . . . . . . . . . . . . 102

5.5 Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 103

6 Stellar Populations 106 6.1 Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 106 6.2 Data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 107 6.3 Results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 107 6.3.1 Do age and metallicity measurements support the distinction between the colour/Sersic index subsamples? . . 108 6.3.2 Bulge & disc age . . . . . . . . . . . . . . . . . . . . . . 110 6.3.3 Bulge & disc metallicity . . . . . . . . . . . . . . . . . . 112 6.4 Discussion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 116

7 Summary and further work 118 7.1 Discussion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 119 7.2 Further work . . . . . . . . . . . . . . . . . . . . . . . . . . . . 123 7.2.1 Are we able to observe separate colour gradients in bulges and discs? . . . . . . . . . . . . . . . . . . . . . . . . . . 123 7.2.2 How does environment impact galaxy formation and evolution? . . . . . . . . . . . . . . . . . . . . . . . . . . . . 124

2.1 GAMA survey area . . . . . . . . . . . . . . . . . . . . . . . . . 18

2.2 G09 SWARP . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21

2.3 SExtractor hot mode . . . . . . . . . . . . . . . . . . . . . . 22

2.4 SExtractor cold mode . . . . . . . . . . . . . . . . . . . . . . 23

2.5 Example segmentation map . . . . . . . . . . . . . . . . . . . . 23

2.6 Example of single-Sersic t . . . . . . . . . . . . . . . . . . . . . 25

2.7 Example of a bulge-disc t . . . . . . . . . . . . . . . . . . . . . 26

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