%0 Thesis
%9 Doctoral
%A Cunningham, Mark Hugh
%B Physics & Astronomy
%D 2025
%F discovery:10204584
%I UCL (University College London)
%P 281
%T Multi-Object Spectroscopy: 4MOST Instrumentation & Observational Analysis using CIII]
%U https://discovery.ucl.ac.uk/id/eprint/10204584/
%X 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 ∼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 ∼100μm 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]λλ1907,1909 emission, usually the brightest  UV line after Lyα, as a proxy for Lyα velocity offset in analogues of reionisation  era galaxies. The velocity offset of Lyα 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 ≥ 6, Lyα 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 ∼ 3−4 with robust  detections of the C III] emission line as well as Lyα we constrain a new correlation  between C III] and Lyα velocity.
%Z 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.