eprintid: 10204584 rev_number: 14 eprint_status: archive userid: 699 dir: disk0/10/20/45/84 datestamp: 2025-03-06 15:31:50 lastmod: 2025-03-06 15:31:50 status_changed: 2025-03-06 15:31:50 type: thesis metadata_visibility: show sword_depositor: 699 creators_name: Cunningham, Mark Hugh title: Multi-Object Spectroscopy: 4MOST Instrumentation & Observational Analysis using CIII] ispublished: unpub divisions: UCL divisions: B04 divisions: C06 note: 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. 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 ∼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. date: 2025-02-28 date_type: published oa_status: green full_text_type: other thesis_class: doctoral_open thesis_award: Ph.D language: eng primo: open primo_central: open_green verified: verified_manual elements_id: 2359939 lyricists_name: Cunningham, Mark lyricists_id: MHCUN72 actors_name: Cunningham, Mark actors_name: Stacey, Thomas actors_id: MHCUN72 actors_id: TSSTA20 actors_role: owner actors_role: impersonator full_text_status: public pages: 281 institution: UCL (University College London) department: Physics & Astronomy thesis_type: Doctoral citation: Cunningham, Mark Hugh; (2025) Multi-Object Spectroscopy: 4MOST Instrumentation & Observational Analysis using CIII]. Doctoral thesis (Ph.D), UCL (University College London). Green open access document_url: https://discovery.ucl.ac.uk/id/eprint/10204584/9/Cunningham_10204584_Thesis_pages_moved.pdf