@phdthesis{discovery10204584,
           title = {Multi-Object Spectroscopy: 4MOST Instrumentation \& Observational Analysis using CIII]},
            note = {Copyright {\copyright} The Author 2025. Original content in this thesis is licensed under the terms of the Creative Commons Attribution-NonCommercial 4.0 International (CC BY-NC 4.0) Licence (https://creativecommons.org/licenses/by-nc/4.0/). Any third-party copyright material present remains the property of its respective owner(s) and is licensed under its existing terms. Access may initially be restricted at the author's request.},
           month = {February},
          school = {UCL (University College London)},
            year = {2025},
          author = {Cunningham, Mark Hugh},
             url = {https://discovery.ucl.ac.uk/id/eprint/10204584/},
        abstract = {This thesis is an interdisciplinary endeavor spanning the realms of both astronomy
instrumentation and scientific inquiry. Embodying a unique fusion of spectroscopic
instrument development and the analysis of spectroscopic data. This thesis details
the assembly, alignment and integration of the 4MOST Wide Field Corrector
(WFC). 4MOST is a new Multi-Object Spectroscopic (MOS) instrument with a
hexagonal 4.2 square degree field of view, a high-multiplex fibre-fed spectrograph
and a capability to simultaneously obtain spectra of {$\sim$}2400 objects, that will be
mounted at the focus of the 4m-VISTA telescope, Chile. To achieve its science
goals, aligning each lens of the WFC within {$\sim$}100{\ensuremath{\mu}}m of the optical axis posed a
significant challenge. This was addressed through contact metrology methods, supplemented
by pencil beam laser probes. The thesis outlines the opto-mechanical
instrumentation at UCL for aligning the lenses within their cells, detailing the assembly
process and presenting comprehensive results on lens positioning and the
anticipated WFC performance. Using a MOS instrument, the second half of this
thesis investigates the utility of CIII]{\ensuremath{\lambda}}{\ensuremath{\lambda}}1907,1909 emission, usually the brightest
UV line after Ly{\ensuremath{\alpha}}, as a proxy for Ly{\ensuremath{\alpha}} velocity offset in analogues of reionisation
era galaxies. The velocity offset of Ly{\ensuremath{\alpha}} emission from its systemic redshift is an
excellent tracer of conditions that may enable the escape of hydrogen ionising Lyman
continuum (LyC) photons. However at z {$\ge$} 6, Ly{\ensuremath{\alpha}} is often heavily attenuated
by the neutral intergalactic medium. By utilising a sample of 52 star-forming galaxies
selected from the VANDELS survey spanning a redshift of z {$\sim$} 3?4 with robust
detections of the C III] emission line as well as Ly{\ensuremath{\alpha}} we constrain a new correlation
between C III] and Ly{\ensuremath{\alpha}} velocity.}
}