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A zoomed in picture of star forming gas in the core of a nearby spiral galaxy. Image Credit: ESO

While the transition from late- to early-type morphology is often treated as a one-way street following the shutdown of star-formation, it is normal for galaxies in hierarchical formation models to oscillate between morphological types. Yet, the short timescales associated with the quenching process at high-z make it difficult to catch galaxies “in the act” of transiting for detailed morpho-kinematic studies. Among the massive z ~ 1 galaxies in extragalactic deep fields we have identified a unique passive galaxy embedded in a faint extended star-forming disk when the Universe was 4 billion years old. The aim of this project is to determine if this galaxy is either in the process of quenching, shutting down star-formation, after violent collapse of gas to the central region, or if we are seeing for the first time the re-growth of a disk around an already quenched compact spheroid. Data from ground-based and space-based telescopes will be used to investigate the true nature of this source, including deep JWST imaging, broad spectral coverage, and spatially resolved emission and absorption spectroscopy.

In this project the student would (1) reduce data from VLT X-Shooter to obtain the gas-phase metallicity of the outer disc; (2) fit stellar population models to estimate stellar age and metallicity of the galaxy bulge;(3) synthesis spectral observations with JWST morphological information providing new constraints on quenching pathways at ‘cosmic noon’; (4) this project can be extended to include comparison results with other observational and theoretical studies on galaxy quenching. The student taking on this project is expected to familiarise themselves with the basic principles spectroscopy and acquire the skills to successfully reduce and analyse data from world-leading facilities.