Abstract:
In this talk I delve into two distinct yet interconnected areas of astronomical research. In the first part, I will walk you through the instrumentation of the 4-metre Multi-Object Spectroscopic Telescope (4MOST) project. Destined for the ESO Paranal Observatory in Chile, 4MOST aims to be a versatile spectroscopic survey facility serving the ESO community. Its innovative design, including a prime focus optical wide-field corrector (WFC), enables the simultaneous capture of 2400 spectra across a ~2.5 degree field of view. The alignment and assembly of the WFC's intricate optical elements pose a significant challenge, requiring meticulous precision. The talk outlines the alignment methodology, incorporating contact metrology and off-axis laser beam systems, to achieve the required accuracy of the WFC optics. Additionally, the presentation provides an update on the instrument's current status.
From building a MOS instrument to using one, in the second part of the talk I will shift our focus to early star-forming galaxies by investigating the potential of the CIII] λλ1907, 1909 doublet emission as a proxy for the heavily attenuated Ly𝛼 λ1215.7 line during the Epoch of Reionisation. Through a comprehensive analysis of star-forming galaxies from the VANDELS survey at z ∼ 3 – 4 using VMOS, we examine the utility of CIII] as a tracer for Lyα properties. The study involves the comparison of equivalent widths and velocity offsets for both emission lines. Our findings reveal intriguing insights, including an anti-correlation between EW(CIII]) and Δ𝑣Ly𝛼 which also displays a dependence on the UV absolute magnitude. We find that for a fixed EW(CIII]), UV-bright Ly𝛼 emitting galaxies show smaller values of Δ𝑣Ly𝛼, which suggests that such galaxies may be undergoing more bursty star-formation compared to the UV-fainter ones, akin to a population of extremely UV-bright galaxies identified at 𝑧 > 10. These finding suggest CIII] may be used as a valuable tool for assessing Ly𝛼 escape at higher redshifts in the JWST era, which would provide unprecedented insights into the dominant contributors of ionising photons towards cosmic reionisation.
