The evolution of star-forming galaxies : analysis of infrared observations by AKARI

Sedgwick, Christopher John (2016). The evolution of star-forming galaxies : analysis of infrared observations by AKARI. PhD thesis The Open University.



This thesis presents the results of several projects on the analysis of infrared observations of star-forming galaxies, all of which included observations by the AKARI Space Telescope.

Spectroscopic redshifts have been measured for over 400 galaxies using the fibre spectrograph AAOmega in the AKARI Deep Field South, the first significant spectroscopic campaign in a relatively new, cirrus-free deep field. A local luminosity function of galaxies in this field is also presented, using far-infrared data from AKARI. Various properties are deduced from the atomic emission lines detected, and star-forming spectral energy distribution templates are fitted to these sources using the multi-wavelength data available. The majority of these galaxies are dominated by emission from star formation, and local sources show relatively low dust extinction.

AKARI’s own near-infrared spectroscopic facility was used to observe well-known submillimetre targets in other well-studied deep fields. The most interesting result was the detection of high redshift (z > 3.5) Hα emission lines in two radio galaxies and two submillimetre galaxies shown to be associated with one of them, the highest-redshift Hα detections so far discovered in star-forming galaxies. Both radio galaxies are shown to be quasars, and one is part of a binary quasar. The result from stacking all the Hα targets is also presented.

Two Graphic User Interfaces (GUIs) were written to help with these projects and are described in this thesis.

Finally, the early results of an ongoing experiment to detect gravitational lenses by identifying quasars with enhanced far-infrared luminosity are presented, with about twenty quasars identified in the AKARI all-sky far-infrared survey. Several sources at high redshift appear to show enhanced luminosity, and follow-up optical spectroscopy of seven of these sources shows that three are high-redshift quasars.

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