Studying galaxy evolution with modern radio surveys

Thesis

Modern radio surveys are transforming our view of the extragalactic sky, observing both Star Forming Galaxies (SFGs) and Active Galactic Nuclei (AGN) over large fractions of the history of the Universe. This allows us to investigate their evolution. In Chapter 2, I investigate how the relationship between galaxies and their dark matter environments evolves, through studying their angular clustering. Using the VLA 3 GHz COSMOS Survey (Smolcic et al., 2017a,b), I find that AGN reside in more massive haloes than SFGs and that radiatively inefficient AGN tend to reside in more massive haloes than their efficient counterparts. I investigate this further, in Chapter 3, by parameterising the Conditional Luminosity Function (CLF), which links environment to the luminosity distribution of these sources. This is novel at radio frequencies. From this, I study how the typical properties of galaxies vary with environment (or luminosity), again concluding that inefficient AGN reside in the most massive haloes, but that the halo mass supporting AGN and SFGs is smaller at higher redshifts. In Chapter 4, I investigate whether the multi-wavelength source extraction software ProFound (Robotham et al., 2018) can accurately quantify the flux densities of radio sources, irrespective of morphology. This is especially important for modern telescopes with a combination of long and short baselines. I find that Pro- Found is able to outperform commonly used software (PyBDSF and AEGEAN) when complex morphologies are considered and perform competitively when modelling sources with smooth morphologies. Finally, in Chapter 5, I present the deepest low frequency (144 MHz) observations of the XMM-LSS field, using LOFAR. This provides a low frequency catalogue which can be used in conjunction with higher frequency radio surveys. Combining the work of this Thesis will enable greater understanding of the relationship between galaxies and their environments, using future deep extragalactic radio surveys and this is discussed in Chapter 6.

Authors: Hale, C

• DOI: 10.5287/ora-m8jk8y9ax
• Type of award: DPhil
• Level of award: Doctoral
• Awarding institution: University of Oxford
• Keywords: Large Scale Structure; Radio Astronomy
• Subjects: Astrophysics