A 3D view of environmental quenching across cosmic time

Amos, Nick and Stott, John (2024) A 3D view of environmental quenching across cosmic time. PhD thesis, Lancaster University.

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Abstract

The study of galaxy evolution is crucial to our understanding of the Uni- verse. It determines how galaxies got from where they started and what their likely end will be. Also crucial is our understanding of how galaxies in denser environments evolve compared to those that are more isolated. A large proportion of the galaxies in the Universe are found in galaxy clusters and so they form a significant population. Significantly, we see at the so called cosmic noon that these galaxies begin to change from largely star-forming to more quiescent systems. This is true both in the field and cluster environment but the significance of the latter on quenching must be understood. In this thesis we investigate star-forming galaxies in clusters at cosmic noon using spatially resolved spectroscopy of the gas content in these galaxies alongside near-infrared photometry. Using these complimentary data we demonstrate that while the cluster environment does not appear to impact these galaxies significantly in some ways compared to their field counterparts, it may be changing their morphology, which in turn may impact their star-formation-rate. We also find that the metallicities of these cluster galaxies deviate from relationships derived from samples of field galaxies, which may indicate the environmental impact of gas exchange between the galaxies and their host cluster but more data is needed to determine if these conclusions are statistically significant. Finally, we report on the serendipitous discovery of a likely Brightest Cluster Galaxy caught in the act of formation. Analysis of the kinematics of two of the four potential merger components indicates that these are likely to merge. Alongside this assessing various combinations of the finalgalaxy stellar masses using these four components demonstrate the final BCG would be well within the mass ranges expected for a BCG at z ∼ 1.4.