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The X-shooter Spectral Library and stellar population models

PhD ceremony:Ms K. (Kristiina) Verro
When:October 18, 2022
Supervisors:S.C. (Scott) Trager, Prof, prof. dr. R.F. (Reynier) Peletier
Where:Academy building RUG
Faculty:Science and Engineering
The X-shooter Spectral Library and stellar population models

Astronomical objects are generally studied through observation-to-model comparisons. Galaxies are complex islands of stars, gas, dust and dark matter held together by gravity. They come in different shapes and sizes and can contain billions of stars. Galaxies have complicated histories shaped by galaxy interactions and mergers, and the evolution of their stars. The story of the formation and evolution of galaxies is written into the properties of their stars. To disentangle the history of a galaxy from observations, we need to create a set of models to describe the total starlight of a population of stars. 

This thesis looked at stellar population modelling from the stellar spectral library perspective. We aimedto develop the empirical X-shooter Spectral Library (XSL) and create stellar population models based on it. XSL is the most intricate library of spectra of observed stars to date. The full wavelength range of XSL spectra is 350-2480 nm, which covers simultaneously the optical-NIR regions. This is not common amongst empirical stellar spectral libraries, which typically cover a narrower (optical or NIR) range. XSL has a large number of spectra, totalling 830. It is the first empirical stellar library to emphasise stars in their advanced evolutionary stages, while also having good coverage of main sequence stars. With the JWST launched, ESO’s ELT and ESA’s Euclid mission on the horizon, XSL and the associated stellar population models will be useful tools in determining the hidden nature of distant galaxies. All of these telescopes will concentrate on the NIR wavelengths!