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Probing Star Formation and Radio Activity Using Faint Galaxy Redshift Surveys Durham E-Theses Probing star formation and radio activity using faint galaxy redshift surveys Davies, Gregory Tudor How to cite: Davies, Gregory Tudor (2008) Probing star formation and radio activity using faint galaxy redshift surveys, Durham theses, Durham University. Available at Durham E-Theses Online: http://etheses.dur.ac.uk/2224/ Use policy The full-text may be used and/or reproduced, and given to third parties in any format or medium, without prior permission or charge, for personal research or study, educational, or not-for-prot purposes provided that: • a full bibliographic reference is made to the original source • a link is made to the metadata record in Durham E-Theses • the full-text is not changed in any way The full-text must not be sold in any format or medium without the formal permission of the copyright holders. Please consult the full Durham E-Theses policy for further details. Academic Support Oce, Durham University, University Oce, Old Elvet, Durham DH1 3HP e-mail: [email protected] Tel: +44 0191 334 6107 http://etheses.dur.ac.uk Probing Star Formation and Radio Activity using Faint Galaxy Redshift Survey by Gregory Tudor Davies A thesis submitted to the University of Durham in accordance with the regulations for admittance to the Degree of Doctor of Philosophy. Department of Physics University of Durham October 2008 The copyright of this thesis rests with the author or the university to which it was submitted. No quotation from it, or information derived from it may be published without the prior written consent of the author or university, and any information derived from it should be acknowledged. 2 6 JAN 2009 Probing Star Formation and Radio Activity using Faint Galaxy Redshift Surveys Gregory Tudor Davies Abstract In this thesis, we study the evolution of radio luminosity functions (RLF) for AGN and star forming galaxies (SFG), the colour-magnitude distributions of radio and X-ray sources at redshift z ~1, the star formation rate density in dwarf galaxies at z ~1 and investigate downsizing. In chapter 1 we give the background to our studies. We describe the Big Bang model before going on to examine different types of galaxies and looking at their star formation rates and the variation of their properties with their environments. We summarise the elements of modern astronomy methodology used throughout this thesis in chapter 2. In this chapter we describe the methods of measuring star formation rates, galaxy environments and luminosity functions. In chapter 3 we match the AEGIS20 radio survey to the DEEP2 optical spectroscopic survey in the extended Groth Strip (EGS) to create a sample of radio-emitting galax• ies that we separate into AGN and SFGs. We derive the RLFs of each of these at two redshift intervals and measure their evolution out to z ~1. We also compare the colour- magnitude distribution of the radio sources to that of the general galaxy population at this redshift and compare these to their local Universe equivalents. We found the evolution of the RLFs to be consistent with pure luminosity evolution with the form L oc (1 + z)a where a = 1.0 ± 0.9 for the AGN and a = 3.7 ± 0.3 for the SFGs. We analyse the variations of these radio sources' properties with their environments in chapter 4. Using the projected nth nearest neighbour method to estimate the density of the envi• ronments, we find a strong trend of SFG numbers dropping with density. The final science chapter is chapter 5 in which we describe the Redshift One LDSS3 Emission-line Survey (ROLES). This survey targets the [Oil] emission line in dwarf galaxies with log(M*/MG )<9.5. We convert the [Oil] luminosity to a star formation rate (SFR) and then proceed to analyse the mass-dependence of the global star forma• tion rate at redshift z ~1. We find that SFR turns over with stellar mass at this redshift. By also comparing to similar studies in the local Universe, we investigate the empirical "downsizing" picture of galaxy evolution. Finally, we present our conclusions and suggestions for future work in chapter 6. Contents 1 Introduction 1 1.1 The Big Bang Model 1 1.1.1 Inflation 4 1.1.2 Nucleosynthesis 7 1.1.3 The Cosmic Microwave Background Radiation 8 1.1.4 Dark Matter and Structure Formation 9 1.1.5 The Cosmological Constant: Dark Energy? 11 1.2 Galaxies: types, properties and their spectra 12 1.2.1 Early Type Galaxies 13 1.2.2 Late Type Galaxies 15 1.2.3 AGN 20 1.2.3.1 The Unified Model 21 1.2.3.2 Radio Emission from AGN 22 1.2.3.3 Sub-classifications of Radio-Loud AGN and Accretion Disks 24 1.2.3.4 X-ray Emission from AGN 25 1.2.3.5 Visible Emission from AGN 26 1.3 Star Formation 26 1.3.1 The Star Formation History of the Universe 26 1.4 Galaxy Environments and their relationship with star formation 29 1.4.1 Galaxy trends with Environment 29 1.4.2 The dependence of SFR on Environment: Nature or Nurture? ... 30 1.5 Motivation for and Structure of this thesis 32 2 The Astronomer's Toolbox 35 2.1 Measuring Star Formation Rates 35 2.1.1 The IMF 36 i 2.1.2 Reddening Corrections 37 2.1.3 HQ 39 2.1.4 [Oil] 41 2.1.5 Far-infrared 41 2.1.6 UV 42 2.1.7 Star Formation and Radio Emission 42 2.1.8 The FIR-Radio Correlation 44 2.1.9 Separating Radio Emission from Star Formation from that from AGN 44 2.2 Measuring Galaxy Environment 46 2.2.1 Issues affecting Environment measures 47 2.2.2 Measures of Environment Density 48 2.3 Measuring the Luminosity Function 50 2.3.1 What is a Luminosity Function? 50 2.3.2 The 1/Vmax method 53 2.4 Galaxy Surveys: Suitability for a Purpose 54 The Evolution of the Radio Luminosity Function and the Colours of Radio Sources at z ~ 1 59 3.1 Introduction 59 3.2 The AEGIS Survey 61 3.2.1 The optical, radio and X-ray surveys 61 3.2.2 Matching the optical and radio surveys 63 3.2.3 Local comparison sample 65 3.3 Separating the Radio Source Populations 66 3.3.1 Colour distribution 66 3.3.2 Separating the two populations 68 3.3.3 Comparison with other measures of AGN activity 73 3.3.3.1 X-ray and FIR 73 3.3.3.2 Optical spectroscopy 76 3.3.3.3 Optical morphologies 77 3.3.3.4 Classification summary 78 3.4 Radio Luminosity Functions 81 3.4.1 Constructing the radio luminosity function 81 3.4.2 The total radio luminosity function 83 ii 3.4.3 AGN and SFG radio luminosity functions 85 3.5 Discussion 88 3.5.1 Comparison with SFRD evolution 89 3.5.2 Star Formation, Radio and X-ray Emission 90 3.5.3 Future Improvements 91 3.6 Conclusions 91 4 The Environments of radio-powered AGN and star forming galaxies at z ~1 93 4.1 Introduction 93 4.2 Analysis 96 4.2.1 Sample Selection 96 4.2.2 Selection completeness Correction 97 4.2.3 Edge Effects 97 4.2.4 A Test of the Environment Density Calculation 98 4.3 Results 99 4.3.1 The Relation between Environment Density and Radio Emission Mechanism 99 4.3.2 The Relation between Environment Density and Galaxy Colour . 101 4.3.3 The Relation between Environment Density and Radio Luminosity 103 4.4 Discussion 105 4.5 Conclusions 108 5 The ROLES Survey HI 5.1 Introduction HI 5.2 Method 113 5.2.1 Survey Design 113 5.2.2 Sample selection & Spectroscopic Observations 114 5.2.3 Spectroscopic data reduction 117 5.2.3.1 Pre-processing 117 5.2.3.2 Sky-subtraction 118 5.2.3.3 Noise estimation 118 5.2.4 Line Detection 121 5.2.4.1 Optimal filtering 121 5.2.4.2 Catalogue cleaning 122 5.2.4.3 Tests of emission line catalogue 124 iii 5.2.4.4 The Final Sample 125 5.2.5 Line identification 125 5.2.5.1 Flux measurement 130 5.3 Analysis & Results 132 5.3.1 L([OII]) to SFR Conversion 132 5.3.2 Spectroscopic completeness 132 5.3.3 Survey volume 134 5.3.3.1 if-band flux limit 135 5.3.3.2 [Oil] flux limit 135 5.3.4 Stellar Masses 137 5.3.5 Star formation rate density 139 5.4 Discussion 141 5.4.1 Comparison with GDDS: Specific Star Formation Rates at z ~ 1 . 141 5.4.2 Star Formation Rate Density as a Function of Mass at z~ 1 145 5.4.3 [Oil] SFR versus total SFR: A study in the local Universe 146 5.4.4 Downsizing 147 5.4.5 Metallicity and Reddening Effects 148 5.5 Conclusions 155 6 Conclusions and Future Work 157 6.1 Radio Luminosity Functions 157 6.2 The Colour-magnitude Distribution of Radio and X-Ray Sources at z ~1 . 158 6.3 The Environments of Radio Sources in DEEP2 159 6.4 The SFRD of Low-Mass galaxies at z ~1 159 6.5 Downsizing 160 6.6 Future Work 161 A Cosmography 163 A.l Hubble's Parameter 163 A.2 Expansion factor, redshift and velocity of recession 163 A.3 The Friedmann Equations 164 A.4 Testing the Flatness of the Universe 166 A.5 The Evolution of the Hubble Parameter 167 A.6 The Comoving Radial Distance Dc 168 A.7 The Angular Diameter Distance DA 168 iv A.8 The Luminosity Distance 169 A.9 The Comoving Volume 170 A.10 The Evolution of the Expansion Factor and of the Energy Density 170 A.10.1 Evolution in a Radiation-dominated Universe 171 A.10.2 Evolution in a Matter-dominated Universe 172 v List of Figures 1.1 The famous Hubble "Tuning Fork Diagram" showing the classification of galaxies.
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