RSN2: Measuring chemical abundances in stellar spectra

Tesi di dottorato

Area Tematica: RSN 2 - Stelle, popolazioni stellari e mezzo interstellare

Referente: Gabriele Cescutti
Titolo: Measuring chemical abundances in stellar spectra
Decorrenza: 26.03.2024


Descrizione:

Galactic Archaeology is a complex and exciting subject. By observing stars in our Galaxy, we can gather precious information on its past assembly process and the present state of its evolution and enrichment.  Moreover, the atmospheres of the oldest stars maintain the fossil signatures of the chemical pollution created by the first stars. These signatures are at the cusp of the efforts that, at the crossing of nuclear physics and stellar evolution models, enable the predictions of stellar nucleosynthesis.  It is a golden age for these studies thanks to GAIA and its spectroscopic follow-ups. 

In this framework, a new multi-fibre spectrograph, HRMOS (https://arxiv.org/pdf/2312.08270.pdf) is planned for VLT, with high-multiplicity (>50 fibers) and operating at R~80,000, providing high-precision parameters and abundances, and isotopic ratios. The project EPOCH (Beyond metallicity: Exploiting the full POtential of CHemical elements) aims at intensively exploiting its data by preparing an automatic pipeline working at a much higher resolution than usual.  

The PhD student will learn how to deal with high-resolution stellar spectra and extract from them the abundances of chemical elements. The PI of the EPOCH project, Laura Magrini, works at the Observatory of Arcetri and a period of exchange is envisaged for the student. 

She/He will also be part of the MINCE (Measuring at intermediate metallicity Neutron Capture elements) survey, an international survey devoted to studying the most elusive elements, from the very heavy thorium to the (relative) light zirconium. 

Thanks to her/his work on spectral synthesis, the Ph.D. candidate will be involved in the study for building up the next generation of instruments at ESO, in particular HRMOS at the VLT, but also CUBES again at the VLT devoted to the UV, and ANDES @ELT, the future 39m telescope. Both instruments will be made with the fundamental contribution of the Trieste and Arcetri Observatories. 

The PhD student is expected to work mainly on the observational and stellar analysis perspective. Still, the chemical abundances obtained will be used on the theoretical side addressing Galactic problems or the evolution of the elements in the Galaxy and in the satellite galaxies of the Milky Way thanks to the expertise within the team.

 

 Figure 1: the logo of EPOCH and the synthetic spectra of a giant star (Teff = 4500 K, log g = 2.5) at a metallicity [Fe/H] = −2.5 and with [Th/Fe]=0.6 ratios at three resolutions. The dashed line indicates the wavelength of the Th II line.