Multi-wavelength extragalactic surveys : star formation of IR-submm elected galaxies

• Main Author: Barrufet de Soto, Laia
• Published: Open University 2018
• Online Access: https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.757656

This Thesis aims to identify and analyse galaxy populations over a range of redshifts in order to evaluate the star formation history over cosmic time. Explicitly focusing on the infrared to submillimetre regime, I carried out a comprehensive multi-wavelength approach at the North and South Ecliptic Poles (NEP/SEP). I explore four different methods to select high-z galaxies identifying a new sample of Dusty Star-Forming Galaxies (DSFGs) producing a legacy catalogue for future spectroscopic studies. These sources are modelled using contemporary spectral fitting algorithms. A detailed comparison of these algorithms concludes that the best results are obtained with the CIGALE package, deriving photometric redshifts and other physical properties. The star formation rate and stellar mass were derived defining their position on the Main Sequence of Galaxies finding a population of DSFGs lying above the MS with high star-formation efficiencies and extreme star-formation possibly due to mergers at early times. A lower redshift counterpart population at radio wavelengths was studied via radio-optical identification and multiwavelength data, calculating photometric redshifts providing better results than simply cross-matching the catalogue with heterogeneous ancillary redshift data. This sub-milliJansky population is then classified by infrared luminosity finding that the stellar mass and gas mass are one order of magnitude higher in more luminous galaxies than in less luminous galaxies. This population is segregated into AGN and DSFGs using a new infrared colour-colour diagrams concluding that using AKARI bands results in better AGN selection than that from WISE. Optical data at the SEP is reduced creating a new catalogue filling a vital gap in the multiwavelength data in this field. This new catalogue is combined with Spitzer and Herschel data identifying a population of Dust Obscured Galaxies at z∼2 the peak of the cosmic star-formation history.