Research at the SAGA Team

The SAGA (Stellar Abundances and Galactic Archaeology) Team conducts research on the areas of stellar evolution and Galactic stellar populations from the observational astrophysics point of view. We use spectroscopy to determine the chemical composition of stars. The SAGA team is exploring novel methodologies to extract complete, precise, and accurate chemical abundances from large samples of stellar spectra. A set of high-quality stellar abundances is the missing piece of the Galactic chemical enrichment puzzle that our team aims to provide.

Below, you can find brief descriptions of the large projects that we are currently working on.

The old Milky Way: a holistic approach to an accurate analysis of metal-poor stars

Project funded by an OPUS-LAP grant co-financed by NCN and the German DFG (2024-2027)

Project members: R. Smiljanic (Polish co-P.I.) and N. Christlieb (German co-P.I.); Deepak and Arthur Alencastro Puls (post-docs based in Poland) and Susmitha Antony (post-doc based in Germany). Former member: André Rodrigo da Silva (PhD student in a 1-year project)

The project is a collaboration between groups at the Nicolaus Copernicus Astronomical Centre of the Polish Academy of Sciences (CAMK, the acronym in Polish), the Centre for Astronomy of the University of Heidelberg (ZAH, the acronym in German). Researchers at the Italian National Institute for Astrophysics (INAF, the acronym in Italian) involved in the CUBES project are also important collaborators.

Our ambition in this project is to conduct an unprecedented, homogeneous analysis of a large set of spectra of very metal-poor stars (defined here as those with metallicity [Fe/H]) ≲ −2.0). The aim is to obtain an accurate and detailed view of their chemical abundances, which will enable a meticulous study of the properties of the first nucleosynthesis sources of stellar origin in the Universe, as well as reconstructing the early chemical evolution of our galaxy.

Furthermore, we propose an original and bold plan to prepare for optimal use of the data to be collected with two new spectrographs that will become available soon: 4MOST (4-metre Multi-Object Spectroscopic Telescope) and CUBES (Cassegrain U-Band Efficient Spectrograph). The work plan is comprehensive and ambitious, including tasks to address the problem from the observational, theoretical, computational, and experimental sides.

The history of C, N, and O in the Galaxy

Project funded by an DAINA grant co-financed by NCN and the Research Council of Lithuania (RCL) (2025-2027)

Project members: R. Smiljanic (Polish co-P.I.) and Š. Mikolaitis (Lithuanian co-P.I.); Heitor Ernandes (Postdoc in Poland). Other members in Lithuania are: Dr. Arnas Drazdauskas, Dr. Markus Ambrosch, Dr. Carlos Viscasillas-Vázquez, PhD Student Barkha Bale, PhD Student Bruno Ćurjurić, and PhD Student Vilius Bagdonas

The project is a collaboration between groups at the Nicolaus Copernicus Astronomical Centre of the Polish Academy of Sciences (CAMK, the acronym in Polish), the Institute of Theoretical Physics and Astronomy, Vilnius University, Lithuania.

The aim of this project is to conduct a comprehensive, homogeneous, and precise analysis of the abundances of carbon, nitrogen, and oxygen (CNO) in a large set of stars belonging to all main Galactic stellar populations. We will use the results to investigate the chemical enrichment history of these elements and explore the effects of evolutionary mixing processes on their abundances in stellar atmospheres.

Combining abundances, ages, and stellar orbits, we will perform a stellar population and radial migration analysis to pinpoint the Galactic region of origin of the stars in the sample. In this way, we can investigate for the first time the local details of the CNO enrichment as a function of the Galactic radius in a large volume of the Milky Way. Moreover, on the stellar evolution side, precise abundances and ages, together with the measurement of activity indicators, will be key to providing a better understanding of the effects of magnetic activity in stellar mixing processes, something still missing.

Together, these efforts will help to clarify with unprecedented detail the intricacies of the history of C, N, and O in the Galaxy, providing important input to improve models of Galactic and stellar evolution.

The Wide-Field Spectroscopic Telescope

Project funded by an Horizon Europe Research Infrastructure financed by European Commission (2025-2027)

Project members at NCAC/PAN, Poland: R. Smiljanic (member of the Steering Committee) and Thibault Boulet (post-doc).

The project is coordinated by the Centre National de la Recherche Scientifique, CNRS (France). There are 11 participant institutes, including the Nicolaus Copernicus Astronomical Centre of the Polish Academy of Sciences (NCAC/PAN, Poland), and seven additional non-funded partner institutes.

The goal of the project is to develop a conceptual design of a the 12-metre wide-field spectroscopic telescope (WST), which will simultaneously operate a multi-object spectrograph (MOS) – capable of observing up to 20 000 astronomical objects at once over a three-square-degree field of view – and an integral field spectrograph (IFS) with a nine square arc minute field-of-view.

The team in Poland is heavily involved in the Science Work Package, co-leading the team responsible for developing the science case on exoplanet, stellar, and Galactic astrophysics. The work includes developing the science cases with high breakthrough potential in more detail, simulating data that will be obtained with WST, investigating the preliminary properties of the targets to be observed, and driving the trade-off process from the science perspective.

The 4-metre Multi-Object Spectrograph Telescope

Project funded through the programme ‘Support for the participation of Polish research teams in international research infrastructure projects’ from the Ministry of Science and Higher Education (MNiSW grant 2026/WK/06; 2026-2031)

Project members at NCAC/PAN, Poland: R. Smiljanic (co-I of the Polish Consortium) and one postdoc (joining soon).

The Polish Consortium of the “4-metre Multi-Object Spectroscopic Telescope” Project (Pol4MOST) was formed in 2022 with the aim to acquiring fund for the participation of four scientists from Polish institutions in the 4MOST project. The four scientists included in the Memorandum of Understanding signed in 2022 are: Boudewijn Roukema, Nicolaus Copernicus University (UMK), Agnieszka Pollo, National Centre for Nuclear Research (NCBJ), Maciej Bilicki, Center for Theoretical Physics, Polish Academy of Sciences (CFT PAN), and Rodolfo Smiljanic, Nicolaus Copernicus Astronomical Center, Polish Academy of Sciences (CAMK PAN).

In June 2026, Pol4MOST was awarded funding from the Ministry of Science and Higher Education to confirm its participation in the 4MOST project. Since then, by the MoU signed with the 4MOST consortium, the four named scientists are partners of the 4MOST project and can additionally indicate one post-doc and any number of PhD students in their group for participation in 4MOST.

Playing CHESS with stars

Project funded by a Sonata Bis grant from NCN (2020-2025; extended to 2026)

Project status: final report in preparation; final publications in preparation!

Former project members: R. Smiljanic (P.I.); Sergen Özdemir and John E. Martínez Fernández (PhD students); Thibault Boulet, Maria Luiza L. Dantas and Hélio D. Perottoni (Post-docs)

This project obtained multi-elemental stellar chemical abundances of unprecedented quality for a sample of about 9900 F-, G-, or K-type stars observed with the UVES spectrograph (Ultraviolet and Visual Echelle Spectrograph). The project aims to reveal the sequence of events that describe the chemical evolution of the Galaxy from the early stages to the present.

To achieve our ambitious goal, we developed a new and innovative system for the large scale analysis of stellar spectroscopic data. This new CHEmical Survey analysis System, CHESS, enabled the extraction of complete, precise, and accurate chemical abundances from large samples of stellar spectra.

An important innovation of this analysis system is the combination of the physical modelling of stellar spectra, done using radiative transfer codes, with data-driven and machine learning methods.

By playing (running) CHESS with (a large sample of) stars, a quality jump in the determination of stellar chemical abundances will be achieved and, as consequence, we will take the understanding of the Galactic chemical enrichment to whole new level.

Near-UV stellar spectroscopy: uncovering the past and building the future

Project funded by an OPUS grant from NCN (2019-2022; extended to 2023)

Project status: final report approved; final publications in preparation.

Former project members: R. Smiljanic (P.I.), André Rodrigo da Silva (PhD student), Riano Giribaldi and Maria Luiza L. Dantas (Post-docs)

This project concentrates in exploring the near-ultraviolet (near-UV) region of the stellar spectra that is observable from the ground (mostly between ∼ 3000 and ∼ 4500 Å). This spectral region is of difficult analysis because of the large number of atomic and molecular lines that are present in the spectra of F-, G-, and K-type stars.

We are working on improving our capabilities of computing synthetic stellar spectra in the near-UV. This improved capability will then be used to investigate different astrophysical problems:

The evolution of abundances of beryllium in metal-poor halo stars;
Abundances of heavy neutron-capture elements in metal-poor stars;
The near-UV photometric colors of globular cluster stars within the multiple-populations framework.

Moreover, we are involved in the CUBES consortium, an international consortium developing a new near-UV spectrograph to be installed at the Very Large Telescope(VLT). Our capabilities of simulating near-UV stellar spectra are useful for defining the desired characteristics of this new instrument.

This project is giving our group improved resources to use near-UV stellar spectra not only to uncover some of the secrets of the past of our Galaxy (the nucleosynthesis of light and heavy elements; the accretion processes in the early Galaxy; and the formation of globular clusters) but also to be part of future developments of instrumentation in the ESO community.

Acknowledgements

The research done at the SAGA Team has been supported by several grants awarded by National Science Center (NCN) over the years.

The WST project is funded by a Horizon Europe Research Infrastructure grant.

Participation at the 4MOST project is funded by a grant awarded by the Polish Ministry of Science and Higher Education (MNiSW grant 2026/WK/06).